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  • 1985-1989  (11,831)
  • 1960-1964  (2,803)
  • Life and Medical Sciences  (9,926)
  • Chemical Engineering  (4,708)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989) 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1-1 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 29-35 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A recently developed analytical technique, modulus profiling, conveniently allows the mechanical properties of elastomers to be mapped with spatial resclutions approaching 0.05 mm. Thus, spatial heterogeneities in modulus caused by processing and aging phenomena can be easily monitored. This paper describes some typical results from polymer aging studies, which Indicate the insights available from this technique. These include application of modulus profiling to understanding (1) mechanical property deterioration of Viton in an elevated temperature, gamma-radiation environment, (2) recent continuous stress-relaxation results, and (3) the role of ozone for non mechanically-stressed materials in high energy radiation environments.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Thermal and mechanical studies on many linear polyesters have revealed their behavior in crystalline, liquid crystalline, and amorphous phases. Their phase behavior in binary compositions has also been studied by a range of additional techniques and in combinations including the polycarbonate of bisphenol-A. Regions of amorphous compatibility and incompatibility have been identified and measures made of transition temperature changes with composition. The conditions for transreaction have also been determined and the properties measured for the resultant new copolymers.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989) 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 100-106 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The present paper describes the evaluation of nonlinear thermally induced residual stresses in the cooling of polymer melt during injection molding of plastic components. The computational methodology adopted is based on the transfinite element approach, which is a hybrid scheme as it combines transform methods and classical Galerkin schemes with finite element formulations to preserve the modeling versatility. The applicability of the proposed formulations for understanding the physics and the nature of the nonlinear thermally induced stresses in the solidifying process of a sample amorphous polystyrene specimen demonstrates the basic capabilities and potential of the methodology. Results obtained agree qualitatively well with earlier research studies and experimental findings relevant to thermally induced residual stresses in the injection molding of plastic components.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 127-133 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A method to obtain microscopic and macroscopic coatings with improved resistance to debonding is described. The procedure, based on polymer-metal complexes, involved the adsorption on inorganic substrates of a poly(vinyl alcohol)-copper II chelate that is also able to catalyze the polymerization of monomers or prepolymers with grafting. The molecular structure of the complex, its adsorption on inorganic surfaces, and the mechanism of the polymerization induced by the supported catalyst are summarized. Much emphasis is placed on application of this technology to the realization of encapsulated filler and pigment and of coatings with improved adherence and solvent resistance. In the field of composite materials, it is demonstrated from several examples that the encapsulation of the filler can be a way to block chemical interactions between filler and matrix, to promote filler dispersion, and to improve mechanical properties.
    Additional Material: 7 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 334-338 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: As a result of increased interest from industry in using dielectric cure monitoring, a need has arisen for simplifying frequency, cure, and temperature dependent data so that control decisions can be readily made. Techniques utilizing data covering several decades of frequency now exist for separating ionic conduction levels from dipole and electrode polarization responses. Ionic conduction levels are particularly useful since they can be correlated to both viscosity and extent of cure. In addition to being a function of extent of cure, dielectric properties are also influenced by temperature. This dependence often makes the dielectric response more difficult to interpret. This paper investigates two methods for overcoming the temperature dependence of the dielectric response during nonisothermal cure. The first method utilizes recent WLF modeling techniques and extends them with the end result of extracting Tg in real time during cure. The second technique involves measuring the temperature dependence of uncured and cured material. Utilizing the correlation between log ionic conductivity and extent of cure, which has been noted by previous researchers, the normalized conductivity can be converted to a cure index. Several examples including epoxy, polyurethane, and a UV cured photoresist are presented, showing data before normalization and after both Tg and cure index determination.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 359-365 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Poly(ethylene terephthalate) (PET) and bisphenol-a-polycarbonate (PC) are known to form a miscible blend whereas ternary blends of PET, PC, and polypropylene (PP) form two phases. This is based on the considerations of various chemical events which may occur in these systems. The role of ester-carbonate interchange reactions during melt mixing and fabricating is found to be unimportant. Differential scanning calorimetric analysis of the ternary blends shows that there appears to occur an exothermic transition in the heating mode of the instrument. This exothermic event was found to be suppressed considerably by incorporating suitable additives into the system. Degradation reactions studied by thermogravimetric analysis and a dilute solution viscometric technique reveal that there exists some kind of interaction among the components even with the immiscible PP component.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 397-404 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Interpenetrating polymer networks of polyurethane and unsaturated polyester were prepared by reaction injection molding (RIM) and transfer molding. The structures of the molded samples were analyzed by electron microscopy and dynamic mechanical analysis. It was found that polymer morphology and dynamic mechanical properties depend strongly on the molding temperature, reaction rate and reaction sequence. Simplified structure models based on Takayanagi's model and sample morphology can predict the storage modulus reasonably well but not the tanδ.
    Additional Material: 14 Ill.
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  • 11
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 432-432 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 448-455 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The plasticating or melting behavior of polymer pellets sliding on a hot metal surface was investigated. An analytical model was developed for predicting the melting rate and the shear stress of an incompletely compacted solid bed of pellets in terms of the rheological and thermodynamic properties of the polymer, the pellet size, the degree of compaction, and the operating conditions. This investigation extends the results of the previous investigators obtained for a fully compacted solid bed of polymers to an incompletely compacted solid bed of polymers, closely representing the initial stage of the plasticating mechanism inside a screw extruder. Experimental verification of the analytical model developed here was made by testing six different commercial polymers.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 456-462 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Vitrification occurs during the reaction injection molding (RIM) of epoxy resin, and the curing reaction rate is reduced as the Tg of the reacting mixture exceeds or approaches the local reaction temperature inside the mold cavity. The effect will be manifested in the distribution of the glass transition temperature across the thickness direction of the molded product. The reaction kinetic equation which includes the vitrification term in the form of the WLF equation is used in the computer simulation of the epoxy RIM process and the effect of the vitrification is shown by comparing with models with no vitrification considerations.
    Additional Material: 8 Ill.
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  • 14
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 479-487 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The performance of screws of advanced design in injection molding has been investigated with respect to four different objectives: (1) improvement of distributive mixing; (2) improvement of dispersive mixing; (3) increase of plasticating capacity; and (4) reduction of inhomogeneity of melt temperature.The screws used are three zone screws with different compression ratios, screws with pineapple or Maddock/Egan mixing elements, with one or two channel barrier sections, with static mixers mounted in the valve or in the nozzle, or with combinations of these different elements. The best mixing quality is obtained with multi-channel Maddock sections. The highest plasticating capacity and, consequently, the shortest cycle times are achieved with the barrier screws. Temperature measurements show that these screws improve melt homogeneity considerably with a relatively small loss of plasticating time. In all cases, increasing the back pressure gives inferior results compared with improvement of the screw design.
    Additional Material: 14 Ill.
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  • 15
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 505-512 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The impact fracture energy (Gc) for a polypropylene homopolymer and a copolymer with and without calcium carbonate fillers was measured over a range of temperatures between -40°C and 40°C using fracture mechanics principles. The fillers studied were Omyacarb (∼2.7 μm) and Winnofil (∼75 nm) and 10% by weight was added to the matrix material. These fillers did not have any appreciable effect on Gc of the copolymer-based composites. However, the Omyacarb fillers improved Gc of the homopolymer at low temperatures (≤20°C) due to enhanced microplastic flow as observed on the fracture surfaces. The fillers increased the stiffness of both the homopolymer and copolymer. It would appear that up to 10% of cheap calcium carbonate fillers could be added to the more expensive polypropylene to reduce the production cost without any significant loss of impact fracture energy.
    Additional Material: 15 Ill.
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  • 16
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 499-504 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A novel sliding plate rheometer has been developed that is suitable for use with molten plastics, concentrated polymer solutions, raw elastomers, and other viscoelastic or thixotropic materials. It can generate steady shear rates from 0.05 to 500 s-1 and can also be used to measure linear viscoelastic properties. In addition, it can be used to measure a broad spectrum of nonlinear viscoelastic properties such as the nonlinear relaxation modulus and the shear stress growth coefficient. In order to measure these nonlinear properties it is necessary to generate large, uniform, transient deformations Involving high strain rates. Rotational and capillary melt rheometers are not capable of generating this type of deformation, and until now it was not convenient to use sliding plate rheometers for this type of application. However, the recent development of a reliable and robust shear stress transducer makes it very convenient to use the sliding plate geometry to carry out all of these tests. The new rheometer is described, and examples of the types of data it can generate are shown.
    Additional Material: 8 Ill.
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  • 17
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 308-314 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: During the sheet molding compound (SMC) compression molding process, a premeasured polymer charge is placed between the heated halves of a mold which are then brought together to squeeze the polymer and fill the mold, after which pressure is maintained while the part cures. The cure stage constitutes the larger part of the molding cycle and thus affords the largest potential for cycle time reduction. In general, cure times in SMC processing are set longer than necessary, since the inherent material and process variation make it difficult to predict cure times with more than 10 to 20% accuracy. Accurate methods to detect the end of cure would be very beneficial and would permit opening the mold as soon as the material has cured, avoiding unnecessary waste of time. In this paper, several techniques that show promise for monitoring the state of cure are reviewed and experimental results given. Their relative advantages and accuracies are compared. In particular, the use of linear variable displacement transducers, pressure transducers, and thermocouples is discussed. We also show how the measurements compare to theoretical predictions of the state of cure.
    Additional Material: 15 Ill.
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  • 18
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 339-346 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The parallel-plate test fixture on a Rheometrics viscometer was electrically isolated so that the rheological and dielectric properties of a thermoset polymer system could be simultaneously measured. This enabled the relationship between the dielectric properties and the rheological properties to be directly examined. A close relationship was established between the dielectric properties (dipole relaxation time and specific conductivity) and the pre-gelation bulk viscosity. This relationship suggested that models similar in form to those used to describe the change in viscosity might be used to describe the changing dielectric properties. The limitations and advantages of two such models, which attempt to describe the time-temperature behavior of the dielectric properties, were then tested for use with a typical aerospace epoxy resin system.
    Additional Material: 8 Ill.
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  • 19
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989) 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
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  • 20
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 586-592 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: We investigated the miscibility of polybutadienes with butadiene-styrene copolymers of varying styrene content. The methods of optical microscopy, differential scanning calorimetry, and small angle light scattering (SALS) were used. All polymers/copolymers used in this study have equivalent butadiene microstructures. Copolymers with high styrene levels are immiscible with polybutadiene. The tendency to miscibility increases with decreasing styrene content. An upper critical solution temperature is observed with the 23 percent styrene copolymer.
    Additional Material: 12 Ill.
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  • 21
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 405-414 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Poly(ether-ether-ketone) (PEEK) is a newly developed engineering thermoplastic with potentially vast application in advanced composites due to its exceptional performance. It is thus desired to understand the relationship between physical processing, microstructure and fracture in this semicrystalline polymer. Both oriented and unoriented PEEK were mechanically characterized using static test of three-point bend specimens. The molecular chain orientation was imposed using a rolltrusion technique. The effects of thickness, strain rate, Initial crack length ratio, and orientation on fracture toughness (Kc) are investigated. The crystallinity is also examined by density measurement. The degree of orientation is determined qualitatively by wide-angle X-ray scattering diffraction patterns and quantitatively by further measurement using an image analysis system. Fractographic analysis, using scanning electron microscopy, provides precise information about the mode of fracture, Results indicate that both the modulus and the fracture toughness are remarkedly increased in the direction of drawing (T-type) as opposed to the transverse direction (L-type).
    Additional Material: 15 Ill.
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  • 22
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 420-425 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Herein is more detail to microscopic aspects of electron transport through a conductor-filled polymer than has yet been considered in the literature (irrespective of quantum mechanical tunneling and thermal expansion). Some of these details only clarify earlier theories, but others lead to new discoveries such as the cubic conduction path coordination number z = 18 (contrasted with the classical geometric coordination number of z = 6). New also are simplified derivations of the high and low fill asymptotes of the master equation for conductance as a function of fill fraction in the effective medium theory of conductor-filled polymers.
    Additional Material: 6 Ill.
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  • 23
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Several recent calculations of the stress field around crazes in glassy polymers have been based on experimentally obtained craze opening displacements. Although various techniques for performing these calculations have been presented (i.e., Fourier transform, boundary integral, and finite element methods), all are based on the solution of the same ill-conditioned boundary value problem. Specific boundary conditions required to calculate the stresses around a craze lead to a large change in the stress field with small changes in the craze profile which are within the reported experimental tolerance.
    Additional Material: 5 Ill.
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  • 24
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 433-440 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The flow of Newtonian and non-Newtonian fluids which obeys a power law relationship between shear stress and shear rate has been modeled in the melt conveying section of a self-wiping co-rotating twin-screw extruder using a finite element analysis of an unwound channel section. Predictions of throughput against pressure gradient are compared with experimentally obtained results for maize grits which is represented as a power law material. Rheological data applicable to extrusion simulation were obtained from capillary rheometry. Comparisons are reasonable with predicted characteristic showing similar behavior.
    Additional Material: 6 Ill.
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  • 25
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The emulsifying activity of a poly(hydrogenated butadiene-b-methyl methacrylate) (HPB-b-PMMA) copolymer is investigated in incompatible blends of a low density polyethylene and poly(styrene-co-acrylonitrile) resins (mainly ABS) prepared in the melt state on a two-roll mill. Optical and scanning electron microscopy observations clearly demonstrate that a moderate amount of copolymer (5 wt %) very significantly decreases the particle size and enhances interfacial adhesion. The block copolymer is also responsible for a strong improvement in both the ductility and Charpy impact resistance of PE/ABS blends.
    Additional Material: 7 Ill.
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  • 26
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 564-572 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: To improve the powder processing behavior of ultrahigh-molecular-weight polyethylene, a conductive iron filler was distributed within the polymer in a segregated network. The filler level was kept at a minimum of 10 volume percent, which was sufficient to coat completely all the polymer particle surfaces. This filler level was low enough to avoid modifying the resin properties to a significant extent. Compaction of these filled samples showed a slower densification, under pressure, similar level of final densification at 80% densification parameter, and a doubling of plateau pressure value to 200 MPa in comparison with the unfilled polymer. The filler was found to reduce drastically the postcompaction relaxation time from 24 h to 6 h. The magnitude of the axial (compaction direction) relaxation was unchanged, but the radial relaxation was one quarter of that for the unfilled polymer. Sintering behavior showed improved densification because of lower dimensional changes during sintering resulting in 80% relative sintered density, higher than the 75% percent value for the unfilled polymer, but yielded a 20% lower sintered strength, An alternative process of rapid sintering by induction heating was explored, its feasibility demonstrated, and a recommendation is made to make powder processing of this polymer commercially attractive.
    Additional Material: 9 Ill.
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  • 27
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 874-877 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The application of X-Ray lithography in mass production of devices is only economically viable if resist materials of highest sensitivity can be provided. Chemical amplification is the key concept to achieve such performance. It is outlined for a highly sensitive three component positive tone X-Ray resist, consisting of a Novolak binder matrix, a starter compound, which - on X-Ray exposure - yields an acid, which catalytically decomposes a dissolution inhibitor. Resist performance is discussed in terms of reaction kinetics and their implications on resist response, simulation, and handling procedures.
    Additional Material: 4 Ill.
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  • 28
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989) 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
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  • 29
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 898-901 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Many styrylpyridinium compounds (SPC), which are very stable in the dark, were prepared and evaluated as photobleachable dyes for contrast enhanced lithography (CEL). The photobleaching characteristics of water-soluble contrast enhancing materials composed of SPC and water-soluble polymer depend on the structure of the SPC and the kind of polymers used. The technique using SPC-based CEL proved to be very effective for the resist pattern profiles.
    Additional Material: 7 Ill.
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  • 30
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 916-919 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Dissolution inhibition mechanisms of naphthoquinone diazides in novolak based positive photoresists were investigated from three different aspects: • Dipolar interaction.• Interfacial chemical reactions.• Chemical structures of naphthoquinone diazides.The results suggest that there exists a hydrogen bonding interaction between the compounds with the matrix novolak resin and that naphthoquinone diazides would crosslink the resin in contact with an alkaline developer, both of which contribute to dissolution inhibition mechanisms. However, there seems to exist another dissolution inhibition mechanism; namely, 1,2-naphthoquinone diazide does not inhibit dissolution of the matrix novolak resin at all while a clear dissolution inhibition effect Is observed for its derivatives containing sulfonyl groups. In the present paper, three dissolution inhibition mechanisms of naphthoquinone diazides will be proposed.
    Additional Material: 4 Ill.
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  • 31
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 625-631 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A commercial liquid crystalline polymer (LCP) sample was characterized both in shear and in nonisothermal elongational flow over a wide range of temperatures (240-350°C). The LCP sample employed was a copolyesteramide of 2,6 hydroxynaphthoic acid, terephthalic acid, and aminophenol manufactured by Celanese and commercially known as Vectra B950. The viscosity decreases dramatically at temperatures above the crystal-nematic transition of the polymer. At lower temperatures, the extrusion of the sample is mainly due to plastic flow. Die-swell values are very small and contraction of the extrudate is also revealed, but the sample shows high elasticity. The polymer is not spinnable at very low temperatures, and the melt strength rapidly decreases with increasing temperature.
    Additional Material: 12 Ill.
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  • 32
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 639-644 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Calculation of gas permeation in food packaging structures can be done using a steady-state analysis employing the permeability coefficient. While this approach is adequate for some applications, for many others a time-dependent transport analysis must be considered to make quantitative predictions of shelf life. The limitation of the simple permeability analysis for multilayer structures is illustrated for Saran-coated polycarbonate and poly(ethylene terephthalate) soda cans. These more detailed calculations on package structures can be done using standard computer library routines to include both the effect of gas sorption and diffusion.
    Additional Material: 7 Ill.
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  • 33
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1097-1102 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Nonisothermal differential scanning calorimetry (DSC) measurements were used to estimate the kinetic parameters for the curing reaction of a commercial unsaturated polyester resin. The reaction rate expression was derived from a mechanistic kinetic model based on the concept of free radical polymerization, accounting also for the diffusion controlled reaction. The total heat of reaction was evaluated in experiments run at very low scan speeds and using high amount of initiator. The kinetic parameters were found to show no dependency on the heating rate nor on the initiator concentration. Dynamic DSC measurements provide reliable kinetic data over a broad range of temperatures that is mostly significant for process simulations.
    Additional Material: 5 Ill.
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  • 34
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1103-1106 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The solid state hydrolysis of a copolyester based on a mixture of 1,4-cyclohexanedimethanol and ethylene glycol condensed with terephthalic acid was studied at 100°C and 57 to 96 kPa water vapor partial pressure (55% to 95% relative humidity). The equilibrium water sorption in weight percent (C∞) was found to be \documentclass{article}\pagestyle{empty}\begin{document}$$ C_\infty = 1.45 \times \,10^{ - 5} (P_{H_2 O} )^{1.2} $$\end{document} where PH2O is the water vapor partial pressure in kPa. For specimens 0.32-cm thick, it took about 24 h to reach 0.9C∞. The intrinsic viscosity (IV) was measured and used to calculate the relative change in molecular weight (M̄w) from the relationship IV ∝ (M̄w)0.7. The decrease in molecular weight was linear with time, and the rate of decrease was found to be proportional to C∞; the empirical correlation is \documentclass{article}\pagestyle{empty}\begin{document}$$ k = 0.026 \times C_\infty $$\end{document} where the rate constant, k, is in day-1. A decrease of 50% in M̄w was observed after 22 days at 95% relative humidity.
    Additional Material: 5 Ill.
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  • 35
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989) 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
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  • 36
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 887-890 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A new positive-working photosensitive system of silicon polymer, containing silylether groups in the main chain and a photo-induced acid precursor was investigated. The silicon polymer is hydrolized by a photogenerated acid and degraded to low molecular weight compounds. Thus the effect of solubility inhibition of the polymer is diminished. The higher photosensitivity of this system as compared with 1,2-quinone diazide compounds is due to the catalytic reaction of the acid on the hydrolysis of the silicon polymer. The chemical structure around silylether groups in the polymer, in particular more hydrophilic and less steric structures, affects the rate of hydrolysis and thus the photosensitivity. Among various types of photo-induced acid precursors examined, e.g., s-triazine and 1,3,4-oxadiazole compounds substituted by trihalomethyl groups were effective.
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  • 37
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A finite element technique has been developed for coupled reaction and heat transfer analysis in which mass diffusion is negligible. The temperature unknowns are located at nodal points, while the reaction variables (species concentrations, reaction rates) are at the Gauss points in each element. With a mechanistic kinetic model, the SMC (sheet molding compound) cure in 2-D and 3-D geometries was analyzed. The results for plate-and-rib configurations show the progression of cure and heat transfer and the influence of geometry on the progression. The analysis for a flat sheet of SMC in a mold with localized heating using bubblers indicates the thermal interaction between the mold and the curing SMC. Temperature and reaction profiles are given for each case.
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  • 38
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1309-1309 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 39
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1340-1367 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Studies of strength development at polymer-polymer interfaces are examined and applications to welding of similar and dissimilar polymers are considered. The fracture properties of the weld, namely, fracture stress, σ, fracture energy, GIc, fatigue crack propagation rate da/dN, and microscopic aspects of the deformation process are determined using compact tension, wedge cleavage, and double cantilever beam healing experiments. The mechanical properties are related to the structure of the interface via microscopic deformation mechanisms involving disentanglement and bond rupture. The time dependent structure of the welding interface is determined in terms of the molecular dynamics of the polymer chains, the chemical compatibility, and the fractal nature of diffuse interfaces. Several experimental methods are used to probe the weld structure and compare with theoretical scaling laws, Results are given for symmetric amorphous welds, incompatible and compatible asymmetric amorphous welds, incompatible semicrystalline and polymer-metal welds. The relevance of interface healing studies to thermal, friction, solvent and ultrasonic welds is discussed.
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  • 40
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1387-1395 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The integrity of a pipeline system is determined by its weakest links. Joints may be such places. Heat fusion is the most common joining method for distribution gas piping. There are procedural, thermal, and mechanical aspects of making fusion joints. Procedural aspects, such as heater calibration and cleanliness, can be assured only by rigorous training and certification of the operators. Thermal and mechanical aspects consist of specifying joining conditions such as the heater temperature, heating time, and joining pressure. In the absence of procedural errors, the strength of a fusion joint should depend on the pipe material, pipe dimensions, and the thermal and mechanical joining conditions.The measured parameters that are measures of strength are impact energy and location of failure in the tensile impact test. A parameter, termed the joining parameter, was found to characterize the joining conditions. This parameter is a function of bead volume, melt volume at the end of the heating phase, and pipe wall thickness. Of the mechanical test parameters, the impact energy was found to correlate best with the joining parameter.
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  • 41
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1413-1418 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A variety of thermoplastic fully imidized poly(imide siloxane) segmented copolymers with useful thermal and mechanical properties have been prepared. Other interesting properties described are the materials' hydrophobic character, surface domination, UV stability, and atomic oxygen plasma resistance.
    Additional Material: 7 Ill.
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  • 42
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    Polymer Engineering and Science 29 (1989), S. 1446-1455 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This study deals with the cold compaction of polyether-etherketone (PEEK) and nickel powder blends. Four different types of PEEK powders which are commercially available from Imperial Chemical Industries (ICI) were utilized for this investigation. These PEEK powders included fine and coarse size powders of a low viscosity grade (150PF and 150P) and similar powders of a high viscosity grade (450PF and 450P). Each of the four different PEEK powders were blended with about 10 vol-% nickel powder (Novamet) using a dry mixing technique. These PEEK/nickel powder blends were then successfully compacted at room temperature. Green strengths as high as 39.5 MPa and 26.3 MPa were measured on nickel filled 150 grade and 450 grade compacts, respectively. The higher strength values of the nickel filled compacts compared to their respective unfilled ones were attributed to a higher degree of mechanical interlocking and plastic deformation, which was induced in the polymer particles during compaction by the hard nickel filler. These composites also exhibited lower viscoelastic recoveries than their respective unfilled compacts. Electrical resistivities as low as 0.06 ohm-cm were achieved by compacting 150P/nickel powder blends. This resistivity value agreed well with the calculated value predicted from the literature.
    Additional Material: 15 Ill.
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  • 43
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1456-1465 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This study deals with the characterization and cold compaction of polyetheretherketone (PEEK) powders. Four different types of PEEK powders which are commercially available from Imperial Chemical Industries (ICI) were characterized for density, crystallinity, particle size, particle size distribution, and particle morphology. Fine and coarse size powders of a low viscosity grade (150PF and 150P) and similar powders of a high viscosity grade (450PF and 450P) were processed. Compaction was successful at room temperature using the 150 grade powders but not with the 450 grade powders. Compressibility curves were obtained at room temperature for the 150 grade powders and their post-compaction viscoelastic recoveries were measured. The coarse and fine size 150 grade powders reached relative plateau densities of 95.8% and 95.1%, respectively, when compacted at pressures exceeding 300 MPa. These high densification values at room temperature were associated with minimal post-compaction viscoelastic recoveries and as-compacted strengths as high as 8.9 MPa. A modified densification parameter (DP*) was developed based on the plastic deformation of the crystalline regions alone. This new dimensionless parameter, DP*, demonstrated a better fit of all the compaction data. The transverse rupture strength and the green density data are presented and explained in terms of this DP*.
    Additional Material: 12 Ill.
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  • 44
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989) 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 45
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1528-1533 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A study was conducted of blends of poly(vinyl chloride) (PVC) with a poly(methyl methacrylate co imide). The latter polymer was found to be miscible in PVC and to raise the glass transition temperature of the blend. Blends of all compositions could be oriented, but the processing temperature increased in proportion with Tg. For a given blend composition, orientation increased with increasing stretch ratio and strain rate and with decreasing stretch temperature. Increasing copolyimide content and increasing orientation generally lead to improved mechanical properties, though the blends containing high levels of copolyimide exhibited low ductilities.
    Additional Material: 14 Ill.
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  • 46
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    Polymer Engineering and Science 29 (1989), S. 1574-1578 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The optical properties of polyetherimide resin as described by the complex index of refraction, N = n - ik, are derived by Kramers-Kronig analysis of experimental absorption and reflectance data obtained in the range 40 μm ≥ λ ≥105 nm. Potential uses of this polymer as a printed circuit board material and as a packaging medium for microelectronic circuitry and the relevance of optical data in laser-assisted processing schemes used in these and other applications are briefly discussed.
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  • 47
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    Polymer Engineering and Science 29 (1989), S. 214-226 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Shear modification treatment represents a special shearing history affecting mainly the elastic behavior of polymer melts. This process has been attributed to reversible physical changes in the entanglement structure of the polymer chain network. Shear modification studies were performed for two well-characterized low-density polyethylene (LDPE) grades differing in molecular weight distribution and degree of long chain branching. The shear working of the material was carried out using a specially designed shearing unit producing definable amounts of pure shear in a continuous process. Measurements of the dynamic storage modulus, G′, steady-state shear compliance; Je, extrudate swell, melt flow index, and the extensional behavior (Rheotens test) indicate that primarily properties associated with the elasticity of the melt are reduced in value. The observed reduction is found to correlate with the mean specific energy dissipated during sample preparation. Comparing the two LDPE grades showed that higher degrees of modification can be obtained at lower energy input levels for the more highly branched grade. Reversibility tests were performed and complete recovery of the initial material behavior was observed. Comparison of measurement results for samples prepared using the shearing unit presented here and a Brabender Plasticorder indicates that the degree of modification depends not only on the molecular structure of the polymer but also on the manner in which the shearing history is imposed upon the material.
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  • 48
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989) 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 49
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1637-1637 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 50
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1628-1635 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The compressive and tensile properties of polyester mortar were studied under various curing conditions, temperature, and strain rate. The curing temperature was varied from room temperature to 80°C. The behavior of polyester mortar was studied using a uniform sand with strain rate and temperature varied between 0.01 to 6 percent strain per minute and 22°C and 120°C, respectively. The strength, failure strain, modulus and stress-strain relationships of polyester mortar are influenced by the curing method, testing temperature, and strain rate to varying degrees. The influence of test variables on the mechanical properties of polyester mortar are quantified. Pretreating the aggregates with a silane coupling agent further enhances the compressive and tensile strength of the mortar. The compressive modulus and splitting tensile strength of polyester mortar are related to the compressive strength. A constitutive model is used to predict the compressive stress-strain behavior of polyester mortar.
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  • 51
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    Polymer Engineering and Science 29 (1989), S. 1667-1676 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Under the right conditions, high strengths are shown to be achievable in vibration welded polycarbonate to polyetherimide Joints. While welding of thermoplastic interfaces of the same material can be understood in terms of interchain diffusion at elevated temperatures, this mechanism is severely limited in the case of dissimilar materials. Scanning electron microscopy is used to show that part of the bond strength in such dissimilar materials results from mechanical interlocking of the two polymers, which is caused by viscous mixing. The effects of the weld parameters on the weld morphology are considered in detail.
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  • 52
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    Polymer Engineering and Science 29 (1989), S. 1689-1698 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Ultrasonic welding is one of the most popular techniques for joining thermoplastics because it is fast, economical, and easily automated. In near-field ultrasonic welding, the distance between the horn and the joint interface is 6 mm or less. This study investigated the near-field ultrasonic welding of amorphous (acrylonitrile-butadiene-styrene and polystyrene) and semicrystalline (polyethylene and polypropylene) polymers. High frequency ultrasonic wave propagation and attenuation measurements were made in order to estimate the dynamic mechanical moduli of the polymers. The estimated moduli were entered into a lumped parameter model in order to predict heating rates and energy dissipation. Experimental results showed that variations in the welding pressure had little effect on energy dissipation or joint strength; Increasing the amplitude of vibration increased the energy dissipation and the weld strength. For the semicrystalline polymers, increasing the weld time improved strength up to weld times greater than 1.5 s, where strength leveled off. For the amorphous polymers, the weld strength increased with Increasing weld time up to times of 0.8 s; for longer weld times, the power required was too high, causing overloading of the welder. Monitoring of the energy dissipation and static displacement or collapse provided valuable information on weld quality.
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  • 53
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    Polymer Engineering and Science 29 (1989), S. 1733-1737 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The hydrolytic stability of a new commercial polycarbonate (Calibre 300, Dow Chemical USA) was investigated and compared with that of other commercial polycarbonates. The tests were conducted between 56% and 95% relative humidity (R. H.) at 100°C. Also performed were water immersion tests at 80 and 100°C. The water diffusivity was found to be 8.7 × 10-7 cm2/s at 100°C with an activation energy of 7.9 kcal/mole. These values are similar to other glassy polymers. The equilibrium water sorption, C∞, was found to increase with temperature and R.H. The isotherm at 100°C was determined to be: C∞ = 0.005945 [R.H.]. When samples immersed in a water bath at 100°C were transferred into room-temperature water, visible aqueous microcavities were formed due to the condition of super-saturation, and under stress may become crack initiation sites. For the polycarbonate investigated here, it was found that the decrease in weight-average molecular weight (M̄)w was a first-order process under a constant R.H. and temperature, and that hydrolytic embrittlement, i. e., (M̄)w 〈34,000, was reached after ca. 188, 143, 99, and 66 days under 56%, 73%, 87%, and 95% R.H., respectively, at 100°C. A comparison with reported hydrolytic stability data for other polycarbonates showed large differences in their stability which are believed to be due to the extent of end-group capping (over 95% in Calibre 300) and resin purity: both phenolic end-groups and some additives (i.e., fire retardants, thermal stabilizers) are known to accelerate hydrolytic degradation.
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  • 54
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    Polymer Engineering and Science 29 (1989), S. 1766-1773 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Moldability and mechanical properties of polyethylene terephthalate (PET) under normal molding conditions were found to improve significantly when it was blended with bisphenol-A-polycarbonate (PC) and polypropylene (PP) to form ternary polymer blend systems. DSC results of these blends revealed that the PET and PC components formed a miscible blend while PP being incompatible with them, formed a separate phase. PP was also found to form a sleeve around the PET-PC miscible phase and, thereby, showed a skin-core type of morphology. Variations of mechanical properties with varying amounts of PP was measured keeping the ratio of PET and PC constant. Tensile and flexural properties of the blends decrease with the amount of PP. Notched impact strength increases up to a certain level of PP and then decreases, while the unnotched values decrease gradually. The effect of annealing on the mechanical properties of these blends have been discussed on the basis of the increased crystallinity of some of the components.
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  • 55
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1786-1795 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The possible multimodal sorption mechanisms in glassy amorphous poly-ether-ether-ketone (PEEK) are presented. By varying the penetrant-polymer affinity, experimental temperature, and external solvent activity, a broad range of sorption behaviors from ideal Fickian diffusion to limiting relaxation controlled kinetics is observed. In particular, water, methylene chloride, and n-heptane sorption kinetics are analyzed and interpreted on the basis of the multiple transport mechanisms. Low uptake liquid n-heptane sorption follows ordinary Fickian diffusion. Analogously, water vapor at low activity, is sorbed in small amounts in the same limiting mode while, at higher activities, the moderately higher penetrant uptakes induce slow relaxation coupled with ideal Fickian diffusion. The highly interacting methylene chloride leads to ideal Fickian diffusion only at very low activities, while anomalous non-ideal Fickian diffusion and limiting Case II and diffusion controlled swelling are observed at moderate and at high solvent activities, respectively. Limiting Case II sorption of methylene chloride in PEEK has been observed only at a very low temperature (-32°C). The optical microscopy observations of cryogenically fractured samples contacted with liquid methylene chloride at 5, 20 and 36°C revealed the presence of a sharp front moving linearly with the square root of time. Solvent induced crystallization in methylene chloride swollen samples was detected by means of differential scanning calorimetry (DSC) and wide angle X-ray scattering (WAXS). Finally, sorption from liquid methylene chloride/n-heptane solutions with varying compositions are presented. The progressive increase of the more high sorbing methylene chloride concentration in the solutions, leads to the same wide variety of sorption behavior observed in the methylene chloride vapor sorptions. The gas chromatographic (GC) analysis indicated that the presence of methylene chloride enhanced the n-heptane sorption in the polymer.
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  • 56
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1649-1654 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Welding represents one of the key stages in the manufacture of injection molded or blow molded plastics products. One process frequently employed is heated-tool butt welding. However, the high seam quality associated with this process can only be attained through reliable process control and optimized welding parameters. This paper presents a simple new method for determining these parameters. Mathematical and physical descriptions of the individual process stages and a computer-controlled heated-tool butt welding machine serve as the basis for determining the parameters.
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  • 57
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1661-1666 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A measuring method is presented for process monitoring and process analysis of linear vibration welding of thermoplastics. The method works by recording and evaluating time-dependent signals that describe the process - such as the frequency-dependent signals of the displacement of the two parts being joined, the tangential force in the welding plane - and the nonperiodic signals of the welding process, i.e. the normal force in the welding plane and the melting or joining displacement of the parts being joined. It is possible to determine the energy input into the welding zone as a function of the selected machine parameters and the process sequence over time.
    Additional Material: 12 Ill.
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  • 58
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    Polymer Engineering and Science 29 (1989), S. 1699-1704 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In far-field ultrasonic welding of plastic parts the distance between the ultrasonic horn and the joint is greater than 6 mm. This study investigated the farfield ultrasonic welding of amorphous (acrylo butadiene styrene and polystyrene) and semicrystalline (polyethylene and polypropylene) polymers. Far-field welding worked well for amorphous polymers. Weld strength improved substantially with increasing amplitude of vibration at the joint interface. Increasing the weld pressure and/or the weld time also resulted in higher weld strengths. Far-field ultrasonic welding was not successful for semicrystalline polymers. The parts melted and deformed at the horn/part interface with little or no melting at the joint interface. A model for wave propagation in viscoelastic materials, which was developed to predict the vibration amplitude experienced at the joint interface, indicates that increasing the length of the samples to a half a wavelength should improve the far-field welding of semicrystalline polymers by maximizing the amplitude of vibration at the joint interface.
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  • 59
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989) 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 60
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1746-1758 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A methodological survey of preparation of microspheres and microcapsules by suspension cross-linking is presented. Thus, basic features of suspension cross-linking, i.e., the formation of small droplets of a polymer solution (or melt) in an immiscible liquid followed by hardening of these droplets by covalent cross-linking, are discussed. Typical microspherical and microcapsular products manufactured by suspension cross-linking of naturally occurring and preformed synthetic polymers, including agarose and cellulose beads, albumin microspheres and microcapsules, polystyrene beads and epoxy resin microcapsules, are described. Manufacturing parameters controlling microsphere/microcapsule characteristics are also briefly outlined.
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  • 61
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989) 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 62
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1325-1331 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In structures composed of polymer matrix composite materials, components must be joined such that the overall structure retains its structural integrity while it is performing its, intended function which can include both mechanical loads (static and dynamic) and environmental loads (temperature and humidity). The use of composite materials in complex structures almost always reduces the number of components in the structures compared to the use of metallic alloys for the same structure. Thus, using composite materials not only results in great savings in weight, but also through a reduced number of joining operations, results in significant savings in assembly, inspection, parts storage, and movement, resulting in increased reliability and lower cost. Yet joining is still required. Joining metallic structures is a mature technology involving riveting, bolting, welding, glueing, brazing, soldering, and other methods. However, for most polymer matrix composites only adhesive bonding and mechanical fastening can be utilized. Attention has been given recently, however, to localized welding of thermoplastic polymer matrix composites, and this will be discussed briefly later. Inherently, adhesive bonding is preferable to mechanical fastening because of the continuous connection, whereas in drilling holes for bolts or rivets, fibers or other reinforcements are cut, and large stress concentrations occar at each discrete fastener hole. The following is a review of much of the literature dealing with adhesive bonding of polymer matrix composite structures. It is Intended not only to be a review, but also a background for detailed study of the referenced and other documents, and a catalyst for future research.
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  • 63
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    Polymer Engineering and Science 29 (1989), S. 1488-1491 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Gelation phenomenon in thermoset polymers is an area of extreme importance from the processing point of view. Gel point (GP) has traditionally been detected using rheological and mechanical techniques. We wish to report the use of dielectric and especially calorimetric techniques for detecting GP. Using a particular thermoset system, we have compared the calorimetric, dielectric, and mechanical techniques and shown how to define GP in terms of time and temperature. As a matter of convenience, we have briefly defined the gelation phenomenon in thermosets, its significance and measurement, and a critical evaluation of the techniques for detecting GP.
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  • 64
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    Polymer Engineering and Science 29 (1989), S. 1516-1523 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A study of orientation development in polystyrene film by biaxial stretching is described. Stretch ratios up to 7.2 × 7.2 were used. Mechanical properties of polystyrene films were correlated with the level of molecular orientation developed by uniaxial or biaxial stretching. Sensitivity of the mechanical properties to change due to development of orientation varied as follows: Yield strength 〈 Young's modulus 〈 Tensile strength 〈 Elongation to break. Brittle to ductile transition phenomena were observed at certain orientation values in the orientation triangle diagram. The transition occurs when f1B × f2B ∼ 0.0025 for biaxially oriented and f1B ∼ 0.015 in the machine direction for uniaxially oriented films. SEM photomicrographs show that the fracture surfaces of ductile failures exhibit many fibrils while brittle failures exhibit no fibrils.
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  • 65
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    Polymer Engineering and Science 29 (1989) 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 66
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    Polymer Engineering and Science 29 (1989), S. 1579-1587 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A general kinetic model was developed to simulate the grafting of monomers such as unsaturated carboxylic acids and silanes to ethylene polymers. The polymers considered were ethylene-co-vinyl acetate (EVA), ethylene-co-butyl acrylate (EBA), and low-density polyethylene (LDPE). Grafting was assumed to proceed by a free-radical mechanism involving chain transfer. Organic peroxides having a strong tendency for hydrogen abstraction were selected as the source of primary radicals. The model simulated the grafting reaction as taking place in a single screw extruder. The residence time distribution in the extruder was experimentally determined by tracer analysis, according to which the extruder was a plug-flow reactor connected to two mixed reactors in parallel. The model is able to predict the extent of grafting in terms of predefined parameters. Comparison of model predictions with available experimental data showed slight deviations, the possible causes of which are discussed. However, the kinetic behavior expected on the basis of the input parameters was observed, and, as such, the model allowed study of the effect of process variables on grafting kinetics and provided insight into the reaction mechanism.
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  • 67
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    Polymer Engineering and Science 29 (1989), S. 1598-1603 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This paper describes characterizations performed on two types of polyethylene T-Joints as well as the starting resin from which they were manufactured. It was found that the melt flow rate of material taken from the two types of joints differed from that of the starting resin and differed from each other by as much as a factor of two. Investigation of the environmental stress-crack resistance (ESCR) and uniaxial creep behavior of material from the two joints revealed further significant differences in behavior between the two joints. These observations lead to the conclusion that subtle differences in the processing conditions can result in significant differences in the long-term mechanical behavior.
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  • 68
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    Polymer Engineering and Science 29 (1989), S. 1614-1617 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The tensile strength of solid-filled rubbers is predicted by the statistical model proposed in this paper, by which the maximum area fraction of the solid filler in a representative cube is calculated. The minimum net cross-section area of the rubber matrix is thus obtained, and this is used to calculate the reduction in strength of the compound in comparison to that of the unfilled rubber. The prediction is then tested by experiments using hydroxyl-terminated polybutadiene (HTPB) filled with glass spheres. After curing, tensile specimens were cut from sheets and exposed to humidity-controlled environments so as to debond the filler particles from the rubber matrix, and were tested in tension. The experimental results were found consistent with the predictions.
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  • 69
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    Polymer Engineering and Science 29 (1989), S. 1683-1688 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In vibration welding of thermoplastics, frictional work done by vibrating two parts under pressure, along their common interface, is used to generate heat to effect a weld. Past work on welding characterized the effects of weld parameters such as the weld frequency, the weld pressure, and the weld time, on the welding process and weld strength, and showed that the most important parameter affecting weld strength Is the weld penetration - the decrease in the distance between the parts being welded that is caused by lateral outflow of material in the molten film. However, those weld studies were based on specimens of constant nominal thickness (6.35 mm, 0.25 in). This paper is concerned with the effects of specimen thickness on the weld process and weld strength.
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  • 70
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    Polymer Engineering and Science 29 (1989), S. 1722-1729 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A transient two-dimensional thermal model for resistance welding of thermoplastic composites is presented. A parametric study is conducted that yields insight into the welding process enabling some critical process and material parameters to be identified. Time to melt is predicted by the model and is successfully compared to experimental observations. Local heating and meltthrough can also be explained by the transient thermal model in agreement with experimental observations. Mode I fracture toughness of unidirectional graphite reinforced poly(etheretherketone) resistance welded double cantilever beam specimens are conducted under various process conditions. Experimental results indicate that under optimum process conditions, the interlaminar fracture toughness of the bulk compression-molded thermoplastic composite material can be achieved using resistance heating as a joining technique.
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  • 71
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Although fibers are subject to complex deformations during processing and end use, most research has concentrated on tensile properties. We have extended our studies to include the ultimate torsional properties, i.e., the breaking twist angle (BTA), and the flexural fatigue life of single fibers. We now have sufficient data on diverse fiber types that we may compare their mechanical properties. Thus, in this paper we report the mechanical properties of the different starting, untreated, fibers, tested under fiducial conditions. We then develop and consider some interrelationships between these selected single fiber physical properties.
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  • 72
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    Polymer Engineering and Science 29 (1989), S. 1774-1785 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: We have analyzed step growth polymerization in a flat film with finite mass transfer resistance. We have shown rigorously that the molecular weight distribution (MWD) at equilibrium is given by the Flory distribution, and under reaction the form of the MWD does not change if the feed is either pure monomer or in equilibrium initially. Extensive computations have shown that it is possible to split the film into growing interfacial and shrinking bulk regions. It is possible to obtain similarity transformations of concentrations of condensation product, and polymer as time invariant profiles. Based on this finding, we have determined a solution for step growth polymerization with finite mass transfer in films. The results lie within 5% of the “exact” numerical computations, for all possible variations of parameters.
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  • 73
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Thermal analysis of oriented polymers involves several transitional processes which may be coupled in a complex way. The disorientation process that occurs during heating is often accompanied by dimensional shrinkage which may occur in both amorphous and crystalline oriented polymers. From differential scanning calorimetry (DSC) measurements it has been determined that shrinkage is an exothermic process. In amorphous atactic polystyrene (PS), hot drawn uniaxially, the shrinkage occurs just above Tg. In triaxially oriented polyethylene (PE) and isotactic polypropylene (iPP), shrinkage and melting take place concomitantly, producing multiple melting peaks. In rolltruded (and also in biaxially oriented) poly(ethyleneterephthalate) (PET) films, shrinkage and crystallization are found to be coupled and to occur between Tg and Tm upon heating. If the enthalpy contribution due to shrinkage is ignored, it follows that crystallinities determined by DSC are incorrect. In this study, the influence of shrinkage upon transitional changes in oriented polymers is investigated in a systematic manner.
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  • 74
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    Polymer Engineering and Science 29 (1989), S. 1534-1543 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: We offer a detailed study on the anisotropic optical properties in uni and simultaneous biaxially stretched Poly(ethylene terephthalate) (PET) films. Cast amorphous sheets of PET were stretched to a series of extension ratios in two mutually perpendicular directions at 80, 90, and 100°C. Additionally, 0selected films were subsequently “heat-set” by annealing with their width and lengths constrained. The principal refractive indices at sodium D wavelength of these, asstretched and heat-set films were obtained using a modified Abbe refractometer. The changes in the principal refractive indices with the processing history were correlated with the orientation of PET chains and phenyl plane normals, which were determined independently by wide angle X-ray (WAXS) pole figure technique.
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  • 75
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    Polymer Engineering and Science 29 (1989), S. 1642-1648 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In order to achieve high fatigue strengths in heated-tool butt welds in plastic pipes used in gas and water supply lines, it is essential that optimum welding parameters be selected. In this paper, the different process phases are described by means of dimensionless characteristic parameters that have been obtained by applying similarity principles to heated-tool butt welding. On the basis of strength studies conducted on welded Joints, it is shown that the best weld quality is attained when the welding parameters are selected such that identical sheaf deformations result in the joint zones of small and large pipes. Laws for scaling data from small-pipe to large-pipe welds are then based on the values of these nondimensional numbers.
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  • 76
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    Journal of Morphology 199 (1989), S. 165-174 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: During ontogeny, the apical and basal components of dicamptodontid teeth exhibit three major developmental stages: nonpedicellate, subpedicellate, and pedicellate. Premetamorphic larvae tend to have nonpedicellate teeth, incompletely or recently metamorphosed individuals tend to have subpedicellate teeth, and fully transformed adults usually have pedicellate teeth. In concert with this transition, cusp morphology is modified from a larval monocuspid, to an incipiently bicuspid, to definitive adult bicuspid, and finally to an adult monocuspid condition. Thus, the larval and adult monocuspid conditions are ontogenetically distinct. The morphology of the larval monocuspid, adult bicuspid, and adult monocuspid conditions differs between Dicamptodon and Rhyacotriton. However, the incipient bicuspid condition in these two genera is very similar in appearance, suggesting that Dicamptodon and Rhyacotriton may be more closely related to each other than to the family Ambystomatidae in which they both sometimes are placed. The method of establishing ontogenetic trajectories seems to be preferable to comparisons based on adult structure, since similarities in the morphology of adults often is owing to convergent or parallel evolution.
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  • 77
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    Journal of Morphology 199 (1989), S. 207-221 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Comparative morphological analysis of the female reproductive tract in macroglossine bats was undertaken to test the hypothesis that nectarivory arose at least twice within Old World fruit bats. Given that features of the female reproductive tract are not directly involved in adaptations for feeding, this data set should provide a test of the monophyly of macroglossine bats. A cladistic analysis of variation in the structure of the ovaries, oviducts, uterus, and external genitalia supports the hypothesis that Megaloglossus has developed a nectar-feeding habit independent of other macroglossine genera. Most of the variation in female reproductive organs among pteropodids is found in the development of derived external and internal features of the uterus. Fusion of uterine cornua, expansion of the common uterine body, and elaboration of the cervical region are found in a group which includes species of Pteropus, Dobsonia, Nyctimene, and the macroglossines (excluding Megaloglossus). Results of this study are concordant with independent data sets, thus providing a phylogenetic framework to evaluate critically structural and functional design in the evolution of pteropodid feeding mechanisms.
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  • 78
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    Journal of Morphology 200 (1989), S. 269-300 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Descriptive data are provided for ontogeny of bone to metamorphosis in the myobatrachine species Uperoleia trachyderma; in pre- and postmetamorphic specimens of U. lithomoda, Crinia signifera, and Pseudophryne bibroni; and in postmetamorphic specimens of U. laevigata. Data derived from postmetamorphic U. laevigata indicate that dermal and endochondral elements ossify independently of each other in Uperoleia. Crinia signifera does not show the same degree of independence of ossification of dermal and endochondral elements as Uperoleia, whereas dermal and endochondral elements are not independent in P. bibroni. Ten (or possibly eleven) features are identified as being influenced by heterochrony within Uperoleia, confirming that the genus represents a highly pedomorphic lineage, four elements are influenced by heterochrony in Crinia, but only two in Pseudophryne.
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  • 79
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    Journal of Morphology 200 (1989), S. 301-319 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Investigation of eight developmental stages by means of serial sections and subsequent graphic or wax model reconstructions, as well as by means of cleared-and-stained and dissected material, revealed that the ethmoidal endocranium in Pipa pipa consists in early states of a single horizontal ethmoid plate lacking labial cartilages. Later in the course of development, structures comparable with those in other anurans appear, though modified and of reduced size. These adult structures arise from the new cartilaginous tissue located above the former larval ethmoid plate, whereas the latter entirely disappear. This phenomenon can be observed also in P. carvalhoi and in Xenopus laevis; hence, it supposedly occurs in all pipids. On the other hand, in anuran larvae, which develop cornua trabecularum in the ethmoidal region, these persist in adults as part of the nasal septum. Positional and developmental differences suggest that, although the ethmoid plate and the cornua trabecularum arise from the same region of the cranial neural crest, they are not fully corresponding structures. Comparison with adults of other pipid genera confirmed the conclusion of some earlier investigators that P. pipa is the most specialized among pipids.
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  • 80
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The Harderian gland of the musk shrew Suncus murinus is elongated anteroposteriorly from in front of the eye to behind the ear. The gland is divided into two portions: an anterior portion (A portion) and a posterior portion (P portion). The single secretory duct of the gland emerges from the anterior end of the P portion, receives several secretory ducts of the A portion during the course along it, runs around the ventral aspect of the eyeball, and finally opens into the anterior corner of conjunctival sacs. The two portions of the gland show a fundamentally similar histological structure, having a poorly developed intraglandular duct system and wide tubular alveoli. The quantity of lipid vacuoles and stromal connective tissue in the A portion is greater than in the P portion. The lipid vacuoles in both portions are surrounded by unit membranes, but their contents appear different.The lacrimal gland of the musk shrew is located along the ventral side of the P portion of the Harderian gland. The lacrimal duct emerges from its anterior end, runs around the ventral and anterior aspects of the ear, crosses the A portion of the Harderian gapos; and, and finally opens at the posterior corner of conjunctival sacs. The lobules of the lacrimal gland comprise a branched duct system and terminal acini with two types of secretory cells: (1) acidic cells positive both for the periodic acid-Schiff reaction (PAS) and for Alcian blue (AB) and (2) neutral cells positive for PAS and negative for AB. Both cell types tend to make separate acini, but when present in the same acinus, the acidic cells occupy relatively peripheral positions in the acinus. Both cell types lack intercellular canaliculi.On the basis of the present study as well as previous descriptions in the literature, the author suggests that the mammalian lacrimal glands can be divided into two sets: (1) a Glandula lacrimalis superior with multiple secretory ducts associated with the upper eyelid and (2) a Glandula lacrimalis inferior with a single secretory duct opening into the lateral corner of the conjunctival sacs. These glands have a fundamentally similar histological structure; but in the rabbit, which possesses both sets of lacrimal glands, they are different. On the other hand, the secretory cells of lacrimal glands generally have no intercellular secretory canaliculi, which are characteristically present between the serous secretory cells of the salivary glands.
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  • 81
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The leg musculature from 11, 14, and 17 day chick embryos was analyzed histochemically to investigate the temporal and spatial distribution of various types of sulfated glycosaminoglycans present during skeletal muscle development. Types of glycans were identified by selective degradation with specific glycosidases and nitrous acid coupled with Alcian blue staining procedures for sulfated polyanions and with [35S]sulfate autoradiography. On day 11, radiolabeled chondroitin sulfate glycosaminoglycans are localized extracellularly in both the myogenic and connective tissue cell populations. By day 17, incorporation of [35S]sulfate into chondroitin sulfate is substantially reduced, although Alcian blue-stained chondroitin sulfate molecules are still detectable. With increasing age and developmental state of the tissues, radiolabeled and stained dermatan sulfate and heparan sulfate progressively increase in relative quantity compared to chondroitin sulfate both in muscle and in associated connective tissue elements. These changes in glycosaminoglycans correlate well with similar changes previously determined biochemically and further document the alterations in extracellular matrix components during embryonic skeletal myogenesis.
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  • 82
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    Journal of Morphology 201 (1989), S. 119-129 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The aquiferous system of representatives of the orders Dictyocer-atida, Dendroceratida, and Verongida has been studied to note its relevance to the systematics of the groups. The volume of the choanocyte chamber, the size and shape of the choanocytes, the number of choanocytes per chamber, the relative development of the mesohyl, and the features of endopinacocytes are estimated from scanning and transmission electron microscopic observations of representatives of most families of the three orders. Although the Dysideidae have a reticulate skeleton and were classified in the order Dictyoceratida, they are actually closer to the Aplysillidae (Dendroceratida) than to dictyoceratids. The anatomy and cytology of the Halisarcidae differ profoundly from those of these three orders and are clearly more closely related to nonkeratose sponges. Some changes in classification lead to a pattern with highly homogeneous orders that clearly differ in their anatomic and cytologic features, which does not support the hypothesis of a common origin of the “keratose” sponges.
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  • 83
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    Journal of Morphology 201 (1989), S. 161-178 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The wall of the asymmetrical saclike lungs of the fishes Polypterus and Erpetoichthys consists of several functionally different tissue layers. Their lumen is lined by a surface epithelium composed of (1) highly attenuated cells, termed pneumocytes I; (2) pneumocytes II with lamellar bodies, presumably indicating surfactant production; (3) mucous cells; and (4) ciliated cells. Underlying the pneumocytes I is a dense capillary net. The thin continuous endothelium of this net, together with the pneumocytes I, constitute the very thin blood-air barrier. The basement membrane of epithelium and endothelium fuse in the area of the blood-air barrier (thickness 210 m̈m). Secretory and ciliary cells form longitudinal rows in the epithelium. Below the zone with a gas-exchanging tissue, a layer of connective tissue containing collagen and special elastic fibers occurs. The blood vessels that give rise to or drain the superficial capillary plexus are located in this connective tissue. The outermost layer of the lung consists of muscle cells, a narrow inner zone with smooth muscle cells, and an outer, broader zone with cross-striated muscle cells. The lung is innervated by myelinated and nonmyelinated nerve fibers. The morphology of the gas-exchange tissue in the lungs of these primitive bony fish is fundamentally very similar to that of the lungs of tetrapod vertebrates. The morphologic observations are in close agreement with physiologic data, disclosing well-developed respiratory capacities. Structural simplicity can be regarded as a model from which the lungs of the higher vertebrates derived. In addition to respiratory function, the lungs seem also to have hydrostatic tasks.
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  • 84
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    Journal of Morphology 201 (1989), S. 179-186 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Effect of turning of the egg during incubation on development of the area vasculosa of the chick embryo was investigated. The size of the area vasculosa was determined by two methods: direct measurement with calipers and measurement of a template cut from the eggshell by use of an automatic surface area recorder. The effects of turning and additionally the effects of lowered temperature (36°C) on both growth of the area vasculosa by day 7 and embryo growth by day 14 of incubation were investigated. The effects of turning during a critical period for turning, from 3 to 7 days of incubation, were also recorded. Generally, failure to turn eggs retarded growth of the area vasculosa. Turning during the critical period stimulated the extent of growth of the area vasculosa by day 7 of incubation and of subsequent embryonic growth by day 14. Incubation at low temperature resulted both in reduced expansion of the area vasculosa and retarded embryonic growth in a pattern similar to that observed for unturned eggs. It is suggested that turning stimulates development of blood vessels in the area vasculosa via localized increases in blood pressure. The effect of a reduced area vasculosa is considered to retard embryonic development through restricted nutrient uptake from the yolk. The prevailing hypothesis that turning prevents deleterious membrane adhesions is questioned in light of these observations. It is suggested that the physiological basis for the need for turning lies in maximizing the growth rate of the area vasculosa to maximize yolk use and embryonic growth rate.
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  • 85
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    Journal of Morphology 200 (1989), S. 123-130 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Recessive mutant gene c in axolotls results in a failure of the heart to function because of abnormal embryonic induction processes. The myocardium in this mutant lacks organized sarcomeric myofibrils. The present study was undertaken to determine if developmental abnormalities were evident in other areas of the heart besides the myocardium. A detailed comparative survey of the structure of developing normal and mutant hearts, including the endocardium, its cellular derivatives, and the extracellular matrix, known as cardiac jelly, showed that in the mutant there are fewer than the normal number of endocardial cells lining the heart lumen, the number of mesenchyme cells is reduced, and the cardiac jelly area is greatly enlarged in the posterior part of the truncus adjacent to the ventricle.
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  • 86
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    Journal of Morphology 200 (1989), S. 163-174 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Plethodontid salamanders have unique nasolabial grooves that may function as “capillary tubes” to convey chemicals to the vomeronasal organ when these animals nose-tap. 3H-proline was placed at the base of these grooves in Plethodon cinereus, and autoradiography revealed large concentrations of radioactive material in the vomeronasal organs. There was no significant accumulation of radioactive material in the main olfactory epithelium. Salamanders with blocked nasolabial grooves lacked significant accumulation of material in their nasolabial grooves or vomeronasal epithelia, although some salamanders had radioactive material in the posterior portion of their vomeronasal organ that had entered through the internal nares. Anteriorly placed vomeronasal organs situated adjacent to the posterior limits of the nasolabial grooves may insure that nose-tapping primarily stimulates the vomeronasal sensory epithelium.
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  • 87
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 200 (1989) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 88
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    Journal of Morphology 200 (1989), S. 231-245 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A new mechanical model for function of the pharyngeal jaw apparatus in generalized perciform fishes is developed from work with the family Haemulidae. The model is based on anatomical observations, patterns of muscle activity during feeding (electromyography), and the actions of directly stimulated muscles. The primary working stroke of the pharyngeal apparatus involves simultaneous upper jaw depression and retraction against a stabilized and elevating lower jaw. The working stroke is characterized by overlapping activity in most branchial muscles and is resolved into three phases. Four muscles (obliquus dorsalis 3, levator posterior, levator externus 3/4, and obliquus posterior) that act to depress the upper jaws become active in the first phase. Next, the retractor dorsalis, the only upper jaw retracting muscle, becomes active. Finally, there is activity in several muscles (transversus ventrales, pharyngocleithralis externus, pharyngohyoideus, and protractor pectoralis) that attach to the lower jaws. The combined effect of these muscles is to elevate and stabilize the lower jaws against the depressing and retracting upper jaws.The model identifies a novel mechanism of upper jaw depression, here proposed to be the primary component of the perciform pharyngeal jaw bite. The key to this mechanism is the joint between the epibranchial and toothed pharyngobranchial of arches 3 and 4. Dorsal rotation of epibranchials 3 and 4 about the insertion of the obliquus posterior depresses the lateral border of pharyngobranchials 3 and 4 (upper jaw). The obliquus dorsalis 3 muscle crosses the epibranchial-pharyngo-branchial joint in arches 3 and 4, and several additional muscles effect epibranchial rotation. Five upper jaw muscles cause upper jaw depression upon electrical stimulation: the obliquus dorsalis 3, levator posterior, levator externus 3/4, obliquus posterior, and transversus dorsalis. This result directly contradicts previous interpretations of function for the first three muscles. The presence of strong depression of the upper pharyngeal jaws explains the ability of many generalized perciform fishes to crush hard prey in their pharyngeal apparatus.
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  • 89
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    Journal of Morphology 200 (1989), S. 255-267 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Changes in body morphology during growth and reproduction in the hydromedusa Eleutheria dichotoma are described in terms of variations in eight different characters: umbrella diameter, total surface area, tentacle area, umbrella area, tentacle knob diameter, number of embryos, and diameter and area of buds. Sexually (sex) and vegetatively (veg) reproducing medusae differ significantly in their body morphometrics. Statistically significant allometric relations exist between umbrella diameter and (1) central area (sex and veg); (2) tentacle area (veg); (3) total area (veg); (4) tentacle knob diameter (veg); (5) bud diameter; and (6) number of embryos. A significant correlation between umbrella diameter and area is also found in undetached buds. During sexual reproduction, umbrella area shows positive allometry and loses its correlations to total area, tentacle area, and tentacle knob diameter. Linear and nonlinear bivariate allometric coefficients allow estimation of total body size from only one or two easily measurable attributes, e.g., umbrella and tentacle knob diameter. Curve fitting by the classic allometric equation (y = bxc) is only negligibly worse than that obtained with a “full” equation (y = a + c), and statistical confidence is better.Chemical analyses for carbon and nitrogen content allow estimation of biomass from the projection area of the body surface. The relation factors are 1.06 μgC mm-2 (sex) and 1.14 μgC mm-2 (veg) for carbon and 0.293 μgN mm-2 (sex) and 0.287 μgN mm-2 (veg) for nitrogen. The C:N ratios are 3.6 and 4.0 for sexual and vegetative medusae, respectively. The use of allometric regression formulas to calculate surface areas and to relate these to carbon content provides quick estimations of body size in a microscopic animal.
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  • 90
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    Journal of Morphology 202 (1989), S. 13-28 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The neuronal organization of the accessory olfactory bulb (AOB), which receives sensory information from the vomeronasal organ, was described in a squamate reptile (Podarcis hispanica) by means of light microscopy. Using the Golgi-impregnation method, seven neuronal types could be distinguished:Periglomerular cells constitute a morphologically heterogeneous population of small neurons located between and around the glomeruli.The mitral cells are diffusely distributed in the AOB. Their cell bodies are usually located within the mitral cell layer, but some of them could be also observed in the plexiform layers. Mitral cells were classified into three subgroups on the basis of their sizes and dendritic tree morphologies. Thus, the “outer mitral cells” have the biggest cell bodies, and their distal secondary dendrites are mainly distributed rostrocaudally in the external plexiform layer. The “inner mitral cells” have large cell bodies, and their secondary dendrites are distributed dorsoventrally and are located deeper than those of the other two subgroups. The third type, the “small mitral cells,” is the smallest one among mitral cells in the AOB, and from their cell bodies, only two main dendritic trunks arise.The granule cells are composed of several categories based on their different cell body locations and dendritic tree morphologies. Thus, the “superficial granule cells” are located exclusively in the external plexiform layer and have small dendritic fields. The “middle granule cells” have fusiform cell bodies - situated in the internal plexiform layer - and present a wide dendritic projection area. Finally, the “deep granule cells” are distributed throughout the granule cell layer and include a great variety of dendritic tree morphologies.The distribution and morphological features of all neuronal types constituting the AOB of Podarcis were compared with those reported on other vertebrates. The results suggest that the lamination pattern and neuronal organization of the AOB in lizards are more similar to that of mammals than to that of the remaining vertebrates.
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  • 91
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    Journal of Morphology 202 (1989), S. 69-88 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Iridescent butterfly scales are structurally colored, relying upon the interaction of light with detailed architecture to produce their color. In some iridescent scales, the reflective elements are contained within the body of the scale and come in two basic forms, lattices that produce diffraction colors (analogous to those produced by opal), and stacks of laminae that produce thin-film interference colors (analogous to those produced by soap or oil films). Both structures are remarkably complex and precise, yet each is only part of the total edifice built by the cell that makes the scale.To understand better how a cell can produce lattices or thin-film laminae, I studied the development of iridescent scales from two lycaenid butterflies. The presence of diffraction and thin-film scales in the same family (and in some cases on the same individual) suggests that the two types must be developmentally related; yet these results yield no clear explanation as to how. The diffraction lattice appears to be shaped within the boundaries of the scale cell by means of a convoluted series of membranes in which the smooth endoplasmic reticulum plays an important part. The thin-film interference laminae appear to result from the condensation of a network of filaments and tubes secreted outside the boundaries of the cell. This paper outlines the developmental histories of both types of scale and discusses the developmental implications of the mechanisms by which they form.
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  • 92
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Wing folding spicules, elytral binding patches, and elytral locking devices of adult male and female seed weevils, Smicronyx fulvus LeConte and S. sordidus LeConte, involved in stridulation are described. Sound is produced by both sexes of the two species when the plectrum, paired conical teeth located along the anterior margin of the dorsally elevated seventh sternite, is struck against an elongate file, the pars stridens, on the under surface of the apical portion of each elytron. A second plectrum, on the sixth tergite, is well-developed in males of both species and is used by males to produce sound before and during mating.Sex-specific and species-specific differences in the sound produced is attributed to structural variation in the pars stridens and the elytra. The pars stridens determines frequencies, while the elytra may further modify the sound. The frequency range for male S. fulvus is 1,000 cycles per second (cps) through 13,000 cps and for male S. sordidus is 2,500 cps through 13,000 cps. The frequency range for female S. fulvus is 2,000 cps through 11,500 cps and for female S. sordidus is 900 cps through 11,500 cps.
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  • 93
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    Journal of Morphology 202 (1989), S. 53-68 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A study of neuromast ontogeny and lateral line canal formation in Oreochromis aureus and Cichlasoma nigrofasciatum reveals the existence of two classes of neuromasts: those that arise just before hatching (presumptive canal neuromasts, dorsal superficial neuromasts, gap neuromasts, and caudal fin neuromasts) and pairs of neuromasts that arise on each lateral line scale lateral to each canal segment at the same time as canal formation. In the anterior trunk canal segment, each presumptive canal neuromast is accompanied by a dorsoventrally oriented superficial neuromast forming an orthogonal neuromast pair. It is suggested that each of these dorsoventrally oriented superficial neuromasts is homologous to the transverse superficial neuromast row described by Münz (Zoomorphology 93:73-86, '79) in other cichlids. It is further suggested that the longitudinal lines described by Münz (Zoomorphology 93:73-86, '79) are derived from the pair of superficial neuromasts that arise during canal formation. Distinct changes in neuromast topography are documented. Neuromast formation, scale formation, and lateral line canal formation are three distinct and sequential processes. The distribution of neuromasts is correlated with myomere configuration; there is always one presumptive canal neuromast on each myomere. A single scale forms beneath each presumptive canal neuromast. Canal segment formation is initiated with the enclosure of each presumptive canal neuromast by an epithelial bridge which later ossifies. The distinction of these three processes raises questions as to the causal relationships among them.
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  • 94
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    Journal of Morphology 199 (1989), S. 299-311 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Gonadal differentiation in premetamorphic Bombina orientalis is described and staged. The pattern of events during differentiation in Bombina differs in several respects from that previously described in other anurans. The Bombina gonad initially develops on the ventral surface of the vena cava, where there is no pre-existent somatic genital ridge prior to the arrival of the germ cells. The sexually undifferentiated gonad does not have a distinct cortex and medulla; instead, medullary cells ingress from the mesonephric blastema during sexual differentiation. Formation of a testis or an ovary appears to depend on the ability (or lack of ability) of the medulla to invade the germ cell-containing cortex. In the germ line, sexual differetiation can be recognized by a premeiotic increase in oogonial cell volume.
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  • 95
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1569-1573 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The gel melting temperature and crystallization kinetics of ultra-high molecular weight polyethylene (UHMW-PE)/decalin systems were investigated. Two methods were used to determine gel melting temperature; thermomechanical analysis (TMA) with a penetration probe and differential scanning calorimetry (DSC). The melting points determined from TMA and DSC were in good agreement, indicating that the crystallization of UHME-PE is an essential step for gelation. The gel melting temperature increases with UHMW-PE concentration. The change in gel melting temperature with composition results from interaction of the components in the amorphous phase. The gelation and crystallization rates increase with decreasing UHMW-PE concentration.
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  • 96
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    Polymer Engineering and Science 29 (1989), S. 1553-1559 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The cure of an epoxy-anhydride resin system used in pultrusion was characterized to develop an understanding of the cure behavior and to determine potential process controls parameters. Isothermal cures of neat resin formulations were monitored by differential scanning calorimetry (DSC), torsional braid analysis (TBA), and microdielectrometry (MDE). The processing conditions define a time/ temperature region in which monitoring would be applicable. Both DSC and MDE were found to yield useful information in this region, however, the events typically monitored by TBA either did not occur or occurred too quickly to be monitored. Significant ionic conductivity was observed in the fully cured resins at temperatures above the glass transition temperature and could possibly be used as a control parameter. This study revealed an apparent change in reaction mechanism with increasing cure temperature. DSC showed a change in activation energy with extent of reaction and a decrease in heat of reaction at the higher isothermal cure temperatures. The formation of a different network structure was indicated by a decreasing glass transition temperature of the cured resin with increasing cure temperature by both DSC and TBA.
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  • 97
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    Polymer Engineering and Science 29 (1989), S. 1604-1610 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An investigation of the effect of physical aging on excess enthalpy of compatible polymer blends was carried out. Poly(methyl methacrylate) (PMMA) and poly(styrene-co-acrylonitrile) (SAN) were chosen for this study. Blends of different ratios of PMMA and SAN were physically aged at different times and temperatures below their glass transition (Tg) and then subjected to enthalpy relaxation measurement in a differential scanning calorimeter (DSC). An improved procedure was developed and, employed to analyze the data. The error associated with the calculation of the normalized deviation in enthalpy, known as the “Φ” function, was below 4%. The relaxation was observed to proceed faster at higher aging temperature. It was also found that at higher aging temperatures of Tg - 20 and Tg- 35°C, enthalpy relaxation in SAN-rich blends proceeds faster than in PMMA rich blends, while at the low aging temperature of Tg- 50°C the rate of relaxation becomes independent of the composition.
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  • 98
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    Polymer Engineering and Science 29 (1989), S. 1638-1641 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Die-drawing techniques recently developed at Leeds University make it possible to produce oriented polymer tubes with both axial draw and hoopwise expansion. These products have increased axial stiffness, improved barrier properties, and excellent resistance to chemical reagents. Normally mechanical methods are used to join such tubes in order to preserve their orientation: however we show that electrofusion techniques produce joints of strengths such that in tensile tests, failure always occurs in the fittings, not at the joint interfaces. Optical and electron microscopy reveal different zones in the welds and indicate that only 20 percent of the wall thickness is affected by the electrofusion process. The pipe studied was biaxially drawn medium density polyethylene of outside diameter 63 mm with draw ratios of 4 in the axial direction and 2, inner hoop. Optimum welding conditions were determined using socket and saddle electrofusion fittings. The joints did not fail in a standard crush test. Careful control of welding parameters is essential in butt fusion welding when the maximum weld strength exceeds that of the undrawn polymer.
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  • 99
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The lungs of the New Caldeonian gecko Rhacodactylus leachianus were examined by means of gross dissection and light and electron microscopy. This tropical species, which is the largest living gecko, possesses two simple, single-chambered lungs. Right and left lungs are of similar size and shape. The lung volume (27.2 ml · 100 g-1) is similar to that of the tokay (Gekko gecko) but differs in that the gas exchange tissue is approximately homogeneously distributed, and the parenchymal units (ediculae) are very large, ∼2 mm in diameter. The parenchymal depth varies according to the location in the lung, being deepest near the middle of the lung and shallowest caudally. Scanning and transmission electron microscopy reveal an unusual distribution of ciliated cells in patches on the edicular walls as well as on the trabeculae. Secretory cell are very numerous, particularly in the bronchial epithelium, where they greatly outnumber the ciliated cells. The secretory cells form a morphological continuum characterized by small secretory droplets apically and large vacuoles basally. This continuum includes cells resembling type II pneumocytes but which are devoid of lamellar bodies. Type I pneumocytes similar to those of other reptiles cover the respiratory capillaries, where they form a thin, air-blood barrier together with the capillary endothelial cells and the fused basement laminae. The innervation, musculature, and vascular distribution in R. leachianus are also characterized. Apparent simplification of the lungs in this taxon may be related to features of its sluggish habits, whereas peculiarities of cell tissue composition may reflect demands of its mesic habitat.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
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  • 100
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 199 (1989) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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