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  • 1995-1999
  • 1985-1989  (708)
  • 1905-1909
  • 1986  (708)
  • Chemical Engineering  (708)
  • 1
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 9-14 
    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: Polyolefins functionalized with diethylmaleate were mixed with poly(vinylchloride) (PVC) in different compositions. Intermolecular interactions involving the carbonyl groups of the side chains of the functionalized polyolefins and methine hydrogens of PVC were investigated by means of infrared spectroscopy. The major flexibility of the ester groups attached to the backbone chains, with respect to polyesters, seems to increase the capability of such groups to interact with groups of more polar polymers, thus allowing prediction of easier miscibility, which however also depends on the starting polyolefin structure and function-alization degree.
    Additional Material: 4 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 15-27 
    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: Non-aqueous dispersions of poly(vinyl acetate) stabilized by a surface layer of poly(2-ethylhexyl methacrylate) (PEHMA) were prepared. We modified the recipe for particle synthesis, using as a stabilizer a copolymer of EHMA containing a small amount of either phenanthrene (Phe) or pyrene (Py) groups. These fluorescent labels permit us to assess different aspects of stabilizer chain morphology and dynamics. In the particles labeled with Phe groups, the ability of oxygen to quench Phe fluorescence is used as a monitor of O2 sorption at the stabilizer-particle interface. In these experiments, information about the location of the labels and the PEHMA polymer is obtained. In the particles labeled with Py, pyrene self-quenching and excimer formation serves as a sensor of conformational and mobility changes in the PEHMA polymer upon anchoring in the particle.
    Additional Material: 8 Ill.
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  • 3
    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 phase morphology and polymer chain orientation in polyethylene-polycarbonte blends is investigated. A blend with a dispersed polyethylene phase was found to exhibit phase growth under quiescent conditions. Addition of a styrene-(ethylene/butene) block copolymer controls the phase morphology and prevents phase growth. Melt spun tapes and tubular film have been prepared from polyethylene-polycarbonate blends. Orientation of the crystallo-graphic axes of the polyethylene and the chain axis of the polycarbonate were determined by infrared dichroism. The addition of polycarbonate to polyethylene is found to decrease chain orientation at the same drawdown stress.
    Additional Material: 10 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), 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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  • 5
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 3-8 
    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 systematic study of static and kinetic phase behavior of deuterated polystyrene/poly(vinylmethylether) blends is presented in this paper. The static properties are studied by the small angle neutron scattering techniques and the kinetics of phase decomposition are studied by the temperature jump light scattering; technique. This procedure provides detailed information about phase behavior with regard to both thermodynamics and kinetics.
    Additional Material: 12 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 34-44 
    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: Commercial high density polyethylene and polyamide-6 (PA) resins were melt blended in the Brabender Plasticorder twin-screw extruder. The blends containing zero to 30 wt percent of polyamide-6 were examined in dynamic and steady state shear at 150, 200, and 250°C. The Theological test results are discussed in terms of morphology of the samples as observed under scanning electron microscope. Microscopy of the extrudates has shown a temperature dependent movement of the polyamide in the capillary during the extrusion and that fibrillation of the PA phase in the extensional field occurred at all temperatures.
    Additional Material: 18 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 103-110 
    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 theoretical model proposed for simulation of the injection molding of partially crystalline thermoplastics can predict fill time, velocity, temperature and pressure distributions, the distribution of shear and normal stresses, crystallinity, amorphous birefringence, and tensile moduli. In this paper, experimental data will be compared to the predictions of the model.
    Additional Material: 22 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 28-33 
    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: Rheological data have been collected both in shear and non-isothermal elongational flow on three different types of blends, made from one low density polyethylene sample and three linear low density polyethylene samples.In addition to the flow curves, data are presented on the extrudate-swell phenomenon, on the instability arising in capillary flow and on the tensile behavior in the molten state.
    Additional Material: 15 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 74-81 
    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 of nominally identical high impact polystyrene resins having different and well-characterized rubber particle size distributions is discussed. A numerical model for craze termination is presented and its predictions are compared with experimental data. An alternative explanation for the observed effect of particle size on fracture energy is considered.
    Additional Material: 14 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 63-73 
    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: Morphology and mechanical properties of (amine terminated butadiene acrylonitrile rubber/diglycidyl ether of bis-phenol-A epoxy resin) blends of different compositions, cured in wide range of temperatures, are described. Curing at low temperature promoted formation of homogeneous materials with poor fracture resistance. On the contrary, at high temperature tough heterogeneous blends were obtained. Such blends showed phase inversion above 20 percent of rubber. The volume fraction of precipitated phase, determined on SEM micrographs, was higher than the amount of added rubber. A fracture mechanism to account for this is proposed. Extensive voiding and interface damage were observed in the low temperature cured materials. Such phenomena did not contribute to the fracture energy.
    Additional Material: 25 Ill.
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  • 11
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 111-115 
    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 key to successfully implementing polymer blends in end-use applications includes an understanding of performance requirements and the physical property balance of the blend, as well as the provision of financial incentive to the fabricator, The economic gain is calculated for two cases where blends were introduced to displace another material: a blend which gives higher productivity for blown film applications and a blend which allows for increased flow and a gage reduction for an injection molding application. As the resin cost usually accounts for more than seventy percent of the final product cost, the resin or blend cost affects the economic gain (if any) from the fabricator's point of view. Therefore, successful commercial implementation of a new resin or blend depends on its relative cost and benefit to other commercially available materials.
    Additional Material: 3 Ill.
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  • 12
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 1405-1409 
    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 recent years there has been increasing recognition of the importance of melt elasticity in polymer processing. A new instrument has been developed that determines the elastic properties of polymers in the melt state by measuring both the stress relaxation and strain recovery characteristics as a function of applied rate of strain, temperature, and magnitude of applied strain. Data on several different polymers will be presented together with examples of the significance of melt elasticity in such processing operations as thermoforming, blow molding, and film forming. A material parameter that is very important in the processing of polymers such as polystyrene and poly(methylmethacrylate) is the transition above the glass transition, Tg, referred to as the liquid-liquid transition, TII. At this transition there is an abrupt change in the elasticity of the melt. Processing above or below this transition produces products with very different end use properties.
    Additional Material: 7 Ill.
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  • 13
    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 interfacial tensions of immiscible binary blends of poly(dimethyl siloxane) (PDMS) and polybutadiene (PBD) have been determined as a function of molecular weight and temperature. The technique employed for these measurements takes advantage of recent advances in the determination and analysis of pendant fluid drop profiles. The experimental data are compared to the predictions of square gradient theories and theories based on the diffusion equation approach as developed by Helfand and co-workers. Qualitative agreement is obtained with both types of theory when the Flory-Huggins interaction parameter is taken to be comprised of two terms: a temperature independent term of entropic origin; and an enthalpic term that is inversely dependent upon the temperature.
    Additional Material: 10 Ill.
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  • 14
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 1429-1433 
    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: Interrelationships between reaction conditions and material properties of thermosetting and high Tg polymers are discussed from the point of view of a generalized time-temperature-transformation (TTT) diagram.
    Additional Material: 2 Ill.
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  • 15
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 1451-1456 
    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 glass transition temperatures (Tg) and dynamic mechanical properties of random copolymers of styrene-4-vinylpyridine quaternized with iodoalkanes are presented for vinylpyridine contents up to ten percent and pendant alkyl chains up to ten carbons in length. Two linear relationships, between ion content and glass transition temperature and between pendant alkyl chain length and the Tg, are observed. An equation is presented that can be used to predict the Tg for such copolymers based on their ion contents and alkyl chain lengths.
    Additional Material: 5 Ill.
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  • 16
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986) 
    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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  • 17
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 1469-1477 
    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: Polyetheretherketone (PEEK) is a relatively new high temperature engineering thermoplastic. The stability of neat and fiberglass reinforced PEEK towards air, KClO4, and TiH1.65/KClO4 blend was studied by the surface sensitive technique of X-ray photoelectron spectroscopy (XPS) and bulk technique of thermogravimetric (TG) analysis. Both of these examinations revealed no oxidation in the presence of air or KClO4 at temperatures of 60 or 120°C. In addition, no reduction of PEEK was observed in the presence of a reducing agent such as TiH1.65. The TG results also showed no air oxidation between 120 and 500°C.
    Additional Material: 10 Ill.
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  • 18
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 1478-1482 
    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 miscibility of the polycarbonate of bisphenol A with the polyhydroxyether of bisphenol A was analyzed using differential scanning calorimetry and the, results are compared with the torque data obtained using a Brabender Plasticorder. The possibility of interchange reactions was analyzed by means of the observation of the melt-viscosity variation versus processing time in the mixer-bowl. These reactions form graft-copolymers that develop into crosslinked copolymers at higher residence times. It was also shown that the speed of these reactions depends on the processing temperature. The variation produced on the glass-transition temperature because of branching was also analyzed.
    Additional Material: 6 Ill.
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  • 19
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 1552-1562 
    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-purpose finite element program has been used to simulate the flow of nonshear-thinning, highly elastic polymer solutions (Boger fluids). In particular, the creeping flow through an abrupt 4:1 circular and planar contraction is studied, as well as the flow at the exit of a capillary die for the determination of extrudate swell. Experimentally measured normal stress and viscosity data are included in a simple rheological model, based on the viscometric simplification of the CEF constitutive equation. Vortex size and intensity in the die entry and extrudate swell at the die exit increase rapidly, with elasticity level, in general agreement with experimental findings. It is shown that despite the limitations of the model, the viscometric approximation can be used to study the effect of normal stresses in cases where a main flow direction can unambiguously be defined. In die exit Flows, it can also provide an upper limit for the determination of extrudate swell, while Tanner's theory of elastic recovery provides the lower limit.
    Additional Material: 14 Ill.
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  • 20
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 1533-1542 
    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 transport property of chloroform in undeformed and stress-whitened polypropylenes was studied. The rate of penetration of liquid chloroform in whitened samples prepared by uniaxial stretching was slower than that of the undeformed material. In the whitened region, the process appeared to be Fickian diffusion, while in the undeformed material, it was a combination of Fickian and Case-II. The diffusivity (at 50°C) in the whitened region increased about 8 times as the strain rate of stretching decreased from 0.67 to 0.033/min. The temperature dependence of diffusivity (ε = 0.67/min) showed an activation energy of 10.16 Kcal/mole. The whitening effect was greatly reduced as chloroform was absorbed; the final residual whitening after desorption increased with the rate of stretching as determined by transmission densitometry. For the undeformed polypropylene, Case-II type of matrix relaxation contributed significantly to the total flux. The transport process was relaxation controlled at the surface: it gradually changed to Fickian diffusion behavior toward the middle plane. The flux contribution of relaxation across the thickness increased with the sorption time, and that of diffusion decreased. These observations seem to indicate that cold drawing impeded the deformation by swelling stress from occurring at the penetration front.
    Additional Material: 15 Ill.
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  • 21
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 468-478 
    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 the application of plastic pipes for fluid transport and for the protection of underground electrical cables, it is desirable to improve mechanical properties, particularly in the hoop direction. The use of orientable reinforcing particles such as chopped glass fibers could make possible such an improvement if the orientation of the fibers could be controlled. While conventional pipe extrusion dies tend to promote axial fiber orientation, the use of an expanding channel die has been proposed to produce a preferential hoop orientation of fibers. In this paper, a theoretical model of the flow of a fiber suspension through an expanding channel die that predicts the fiber orientation distribution at the die exit is described. The effects of Theological properties and die geometry on the final fiber orientation distribution are predicted. The results of an experimental study of fiber orientation in pipe extruded using an expanding channel die are shown to be in agreement with the theoretical predictions.
    Additional Material: 12 Ill.
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  • 22
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 534-542 
    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 effect of pressure on the densification of amorphous polymers in the Injection-molding process is examined. Density distributions in molded polystyrene slabs were measured for several well-defined molding histories. In all cases the density of the molded part was spatially inhomogeneous, and its distribution in the slab was closely related to the pressure and temperature histories that prevailed in the molding cavity during the process cycle. The density profile in the gapwise direction followed a characteristic “parabolic” pattern with a minimum at the midplane of the slab. A simple phenomenological model, based on the pressure-induced densification effect, was constructed to explain the observed density profiles, and close agreement with experimental data was found. Annealing of the molded article at a high temperature (〈Tg) caused the density to decrease overall and become more uniform across the part. This is generally consistent with volume-recovery data for the densified material, which were generated independently in a controlled pressure-densification experiment.
    Additional Material: 16 Ill.
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  • 23
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 543-553 
    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 systematic design of the classical “coat hanger” die is proposed and tested experimentally. The objectives of the design are 1. distribution of the polymer over the width of the die before it reaches the final lip section for thickness adjustment, 2. invariance of distribution to flow rate, 3. invariance to changes in polymer viscosity, and 4. uniform average residence time. The die design is based on a flow model which assumes power-law viscosity, steady shear flow In each cross-section, uniform temperature, and separation of the flows into a manifold component and a component in a slit section of uniform height. The design corrects for an oversimplification of the pressure gradient that was applied in previous studies; and it differs from previous designs by suggesting a rectangular cross-section for the manifold. Applications to side-fed dies for extrusion blow molding and to a sheet extrusion die achieved uniform distribution and did not require any additional flow corrections (such as choker bars or flexible lips). With the new design, the lip region of the die can freely be used for thickness control, fine tuning, or further shaping of the extrudate.
    Additional Material: 16 Ill.
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  • 24
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 662-672 
    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 rheological behavior of sulfonated polyisobutylene based elastomeric ionomers has been studied. The effects of molecular architecture, type of cation, and addition of excess neutralization agent were investigated. The effect of temperature was studied to a limited extent. In a specific case, the influence of an ionic plasticizer, zinc stearate was also examined. It was found that in these telechelic ionomers where the ionic groups are located exclusively at the chain ends, significant Ionic interactions may persist even at 180°C. The zinc-neutralized ionomers had the lowest viscosity as compared to the corresponding potassium- or calcium-neutralized ionomers. The covalent character of zinc is believed responsible for this behavior. Other factors being constant, the triarm based ionomers are more viscous than the monofunctional ionomers. A mixture of monofunctional ionomers with the triarm, species is a model for dangling chain ends, and results in a slight lowering of the viscosity under the conditions studied. Zinc stearate acts as an ionic plasticizer. Upon the addition of 15 percent by weight of zinc-stearate to the ionomer, the low shear rate viscosity drops by several orders of magnitude and renders the ionomer thermally processable at moderate temperatures.
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  • 25
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 673-681 
    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 experimental investigation was conducted into elucidating the mechanism of foam devolatilization. For the investigation, we have constructed two separate apparatuses of Plexiglas - one simulating the partially filled flow channel in a single-screw devolatilizer, and the other simulating the partially filled, closed-chamber (often referred to as the “C-chamber),” in a twin-screw devolatilizer. The test fluids employed were aqueous solutions of polyacrylamide having various concentrations. During the preparation of the test fluids, we controlled the amount of air entrapped in the liquid phase by varying the level of vacuum applied. The entrapped air stayed as fine gas bubbles dispersed in the polymer solution, and mixtures of the polymer solution and air bubbles were subjected to devolatilization experiments. In the use of a single-screw devolatilizer, we have observed that: 1. The streamlines show circulatory flow patterns forming a singular point at a position slightly below the free surface, where small gas bubbles are trapped initially and become stationary, and 2. The small gas bubbles trapped at the stationary position coalesce later to form large gas bubbles, which then move slowly toward the free surface and are removed under vacuum from the system. In the use of twin-screw devolatilizers, we have found that the degree of fill, the rotational direction of the screws, and the degree of intermeshing, (i. e., partially or fully intermeshing) greatly influence the amount of free surface available for the removal of volatiles, as well as the flow patterns in the liquid pool, and thus the devolatilization efficiency.
    Additional Material: 19 Ill.
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  • 26
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 690-694 
    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: Drawing of a semicrystalline polymer causes a molecular transformation from a spherulitic-to-fibrillar morphology. Shrinkage, which is a characteristic property of polymeric fibers, reverses, to a large extent, the extension that takes place during the deformational process of drawing. This paper focuses on the shrinkage behavior of various drawn semicrystalline polymers and the results are used as further evidence for the feasibility of a phase-transition model whose mechanism can be generally termed “strain-induced recrystallization.”
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  • 27
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    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 682-689 
    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 theoretical study of the one-directional coextrusion flow of two molten polymers between parallel plates has been carried out using a non-isothermal power-law model. A numerical method has been used to solve simultaneously the momentum and energy balance equations, in order to obtain the evolutions of the interface position, the pressure gradient, and the temperature profiles all along the flow. The theoretical results are in good agreement with experimental values measured on an industrial coextrusion line.
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  • 28
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 695-700 
    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 National Center for Small-Angle Scattering Research (NCSASR) is a user dedicated national facility at the Oak Ridge National Laboratory. It is sponsored by the National Science Foundation under an interagency agreement with the Department of Energy. The facilities of the Center include the NSF funded. 30-m small-angle neutron scattering (SANS) instrument at the High Flux Isotope Reactor, as well as part-time use of four other small-angle x-ray and SANS instruments. One of the most active areas of SANS research has been polymer science and over half the proposals received by the Center have been in this area. Approximately 20 percent of the beam time has been allocated to users in the chemical industry for the study of polymer structure, and this paper reviews some highlights of this work in the areas of chain configuration in bulk polymers and solutions, the structure of blends and networks and investigations of core-shell latexes. In addition some of the first time-dependent experiments performed on the 30-m facility are described.
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  • 29
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 717-724 
    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 model describing the expansion of a polyurethane (PU) foam in a closed mold is developed. An energy balance is stated, together with constitutive equations for the vaporization rate of the foaming agent and the polymerization kinetics. A numerical solution is obtained for an experimentally-characterized PU formulation. It is shown that in order to avoid premature gelling or undesirable density distributions, the wall temperature must be close to the initial one. The relative fraction of skin in the foam may be increased by decreasing the part thickness or by adding less catalyst or more blowing agent to the formulation. Factors affecting cream, rise, and process times are discussed.
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  • 30
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 725-729 
    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 incremental response ΔG(t) obtained by superposing a deformation, Δγ, on a large deformation, γ1, has been determined in step shear experiments for a polyisobutylene solution and for a poly(methylmethacrylate) glass in torsion. For both systems ΔG(t) at γ1 was found to be smaller than the linear viscoelastic modulus, G(t), at zero prestrain. ΔG(t) was found to increase with increasing time, te, after imposition of the large deformation. It was also observed that the “apparent relaxation spectrum” associated with ΔG(t) narrows and shifts to shorter times when compared to the spectrum associated with the linear viscoelastic modulus, ΔG(t). The results for the solution art-well described by the nonlinear constitutive equation of the BKZ elastic fluid theory. It is found that ΔG(t) for the glass falls between the behavior predicted by the BKZ theory and the linear viscoelastic behavior.
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  • 31
    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 extent of molecular demixing of poly[cross-(ethyl acrylate)]-inter-poly[cross-(methyl methacrylate)] interpenetrating polymer networks (PEA/PMMA IPNs), of mid-range composition was investigated by decrosslinking and/or annealing using dynamic mechanical spectroscopy. A single broad transition characteristic of extensive but incomplete molecular mixing was observed for the PEA/PMMA IPN. The presence of crosslinking in both phases of an IPN enhances the mutual miscibility of the polymers. Through the use of a labile crosslinker, acrylic acid anhydride (AAA), polymer networks may be decross-linked, allowing the chains to separate and form two distinct phases. Annealing further sharpens the transitions, and phase separation becomes most pronounced when decrosslinking is followed by annealing.
    Additional Material: 8 Ill.
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  • 32
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 736-745 
    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 extensive experimental study of the effect of processing and resin variables on the light transmission of polypropylene tubular blown film is reported. The resin variables investigated include melt flow rate (average molecular weight), molecular weight distribution, and the addition of a nucleating agent. Processing variables studied include blow-up and draw down ratios, and frost line height (cooling rate). Increasing the draw down and blowup ratios and decreasing the frost line height generally lead to increased light transmission. Decreasing the resin melt flow rate, narrowing the molecular weight distribution, and the addition of a nucleating agent also improve light transmission. The overall light transmission properties of the films are dominated by their surface roughness characteristics, while the internal morphology of the films plays a secondary role. The changes in light transmission of the films in response to changes in processing or resin variables were traced to their effect on the surface texture and internal morphology.
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  • 33
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 760-767 
    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 use of the J method to characterize fracture is described, and it is noted that smaller specimens may be used to obtain plane strain values than in conventional linear elastic fracture mechanics (LEFM) tests. Various methods of computing J are described, and the extrapolations necessary to define crack initiation are discussed. The various schemes and size criteria are then explored for a polypropylene copolymer, and it is found that the recommended ASTM procedure using energy works well. The method is then used to characterize several toughened polymers, and some discussion of the slope of the resistance curve is given.
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  • 34
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 746-759 
    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 generally accepted kinetic mechanism for free radical copolymerization was simplified by various assumptions and restrictions to give several realistic and easily evaluated models for the simulation of industrial molding. Six assumptions, including conversion-dependent rate coefficients and constant comonomer concentration ratios, were used to obtain a simplified model. Special cases of this simplified model were obtained by the following additional constraints: (1) Restriction C, consecutive inhibition and radical generation reactions; (2) Restriction I, constant initiator decomposition rate; (3) Restriction Z, zero termination rate for free radicals; and (4) Restriction K or P, all rate coefficients independent of conversion or only polymerization rate coefficient dependent on conversion. For various combinations of these restrictions, the time and concentration variables in the simplified model are separated and solved; the separate solutions are then combined in various ways to give models capable of predicting a wide variety of behavior. Many of these models have analytical solutions that greatly facilitate the evaluation of rate constants. Models based on restrictions KCI, PCI, and PCZ are shown to give good agreement with isothermal DSC data plotted as reaction rate versus time and, in a more sensitive test, as reaction rate divided by monomer concentration versus fractional conversion. Because of their predictive ability and ease of evaluating constants. Models PCI and PCZ are recommended for simulating industrial processing; they are particularly well suited for simulating compression molding of sheet molding compound.
    Additional Material: 5 Ill.
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  • 35
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986) 
    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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  • 36
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 768-775 
    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 strength and durability in wet environment of aluminum/epoxy/aluminum joints are investigated as a function of structural changes of γ aminopropyltriethoxy silane (γ-APS) primer at the interface. Both dry and wet strengths exhibit strong dependencies on both the thickness and the extent of drying of γ-APS prior to joint formation. Generally, dry strength decreases with increasing thickness of γ-APS primer, and increases with dehydration of γ-APS at any given thickness. Strength retention of the joints after exposure to water at 55°C also improves dramatically when the adsorbed γ-APS is extensively dried. These results are analogous to earlier observations with α-Al2O3/polyethylene joint system. In aluminum joints, porous oxide substrate facilitates the mechanical interlocking mechanism, and its interplay with both the thickness and the extent of cure of γ-APS is analyzed by characterizing the fractured surfaces using scanning electron microscopy (SEM) electron spectroscopy for chemical analysis (ESCA).
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  • 37
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    Polymer Engineering and Science 26 (1986), S. 931-939 
    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 silicone elastomer RTV-142 is often used as a particle-getter material inside electronics packages. The adhesion mechanism that forms the bond between the particle and the cured adhesive has been investigated. One expects, theoretically, that polymer chains exhibit a temperature-dependent mobility. This is consistent with the hypothesis that the flow of polymer chain segments around asperities on the foreign particles causes adhesion. Calculations of the surface energy of an idealized polymer system are presented which support the concept of a free-energetically driven flow of chain segments into pores and around asperities. Polymer surface-chain mobility is investigated experimentally by the scanning electron microscope analysis of a fractured, cut, and particle-decorated surface. Surface appearance changes were noted as a function of temperature. Scanning electron micrographs indicate that polymer chain movement is temperature dependent. Such findings support the proposed adhesion mechanism.
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  • 38
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    Polymer Engineering and Science 26 (1986), S. 940-946 
    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 electrical conductivity and the dissipation factor of silicone rubber vulcanized by the condensation reaction of α,ω-dihydroxypolysiloxane with ethoxysilane, using dibutyltin dilaurate as a catalyst, were studied. Rubber specimens, with different amounts of catalyst, were prepared using various vulcanization times and then heat treated in dry or wet atmospheres containing oxygen and nitrogen. The electrical properties of these specimens were measured at 20 to 200°C in dry air. The amounts of residual catalysts and unreacted ethoxy groups were analyzed by colorimetric and gas chromatographic methods. Factors influencing the specimen electrical properties were discussed in terms of preparation conditions and amount of residual compounds.
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  • 39
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    Polymer Engineering and Science 26 (1986), S. 957-961 
    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 approximation method is proposed to predict the Mow rate-pressure drop relation for isothermal laminar flow of any time-independent fluid in wire coating extrusion. A geometric parameter method proposed earlier is used in predict the pressure-driven flow in the annulus. The method is demonstrated for Newtonian, power law, and Ellis fluids. The accuracy of the method is shown by comparing the predictions with the theoretical and experimental results of Han and Rao. An expression for wire coating thickness is also given.
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  • 40
    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 properties of poly(vinyl chlorlde)/ehlorinated poly(vinyl chloride) (61.6 percent C1) blends, prepared by melt and solution blending, were measured by various tests. Based on the chlorinated poly(vinyl chloride) (CPVC) composition, percent chlorine, and mole percent CC12 groups, these blends were expected to show intermediate properties between miscible and immiscible systems. Indicative of miscible behavior were the single glass transition temperatures over the entire composition range for both melt and solution blended mixtures. A single phase was also indicated by transmission electron microscopy. However, the yield stress showed a minimum value less than either of the pure components in the 50 to 75 percent CPVC range, which is characteristic of two-phased systems. Specific volume, glass transition temperature, and heat distortion temperature were linear with binary composition. The storage modulus showed a small maximum, suggesting a weak interaction between the two miscible polymers. Heats of melting for the residual PVC crystallinity were also less than expected from linear additivity. At 160°C and 210°C, the logarithm of the complex viscosity was essentially linear with volume fraction of CPVC, except for a very slight decrease in the 50 to 75 percent CPVC range, which may have been a result of lower crystallinity. At 140°C, the complex viscosity of the CPVC was less than that of PVC owing to the higher crystallinity of the latter. The viscosities were similar at 160°C, but at 210°C, where most of the crystallites had melted, the complex viscosity of the CPVC was higher because of its higher glass transition temperature.
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  • 41
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    Polymer Engineering and Science 26 (1986), S. 969-974 
    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: Twin-screw extruders are used very effectively, when partially filled, for mixing and surface renewal of high-viscosity fluids. The rate of energy input, often sufficiently high to be a major design consideration, determines the drive power, the heat input to the fluid, and the cooling requirements. Operating limitations may be fixed by thermal degradation of the material being processed. A simple model for the rate of energy dissipation in twin-screw extruders predicts that the power input is proportional to the square of the screw speed. Measurements were made of shaft torque and screw speed for polyisobutylene passing through a large twin-screw extruder having co-rotating shafts. The experimental procedure avoids the problems of changes in holdup and temperature that accompany changes in screw speed under steady state conditions. The power input was found to be proportional to the screw speed raised to the exponent 1.90. This result was attributed to slightly pseudoplastic behavior of the fluid in the radial clearances.
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  • 42
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    Polymer Engineering and Science 26 (1986), S. 975-981 
    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 steady state structure of non-isothermal free radical solution polymerization in a continuous stirred tank reactor is analyzed. With mean residence time as a bifurcation parameter, five regions of steady states are identified. The effect of reactor operating conditions on the structure and the stability of steady state is discussed.
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  • 43
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    Polymer Engineering and Science 26 (1986), S. 1021-1032 
    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 review aims to encompass various situations where optical microscopy - particularly observation and measurement of birefringence - can be used to deduce the nature of intermolecular correlations in polymers. The necessary background dealing with light propagation in anisotropic media is summarized in practical terms. The review is especially concerned with illustrating how unjustified assumptions and ambiguous terminology can cause erroneous interpretation of results. Many references cited are themselves reviews or even textbooks; they afford detailed access to the wide and diffuse literature that full coverage of this subject demands, but would constitute an unwieldly bibliography if listed as individual publications.
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  • 44
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    Polymer Engineering and Science 26 (1986), S. 92-102 
    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 realistic simulation of the injection molding process should be capable of describing moldability parameters, such as pressure drop in the delivery system and cavity and melt-front progression during cavity filling, as well as predicting the characteristics of the final product, such as residual stresses and crystallinity distributions. After a brief review of the existing models for the mathematical modeling of the injection molding process, a new model, that meets the above requirements, is proposed.
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  • 45
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986) 
    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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  • 46
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    Polymer Engineering and Science 26 (1986), S. 2-2 
    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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  • 47
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    Polymer Engineering and Science 26 (1986), S. 54-62 
    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 analysis is made of the thermodynamic and kinetic factors affecting phase separation in blends of di-, tri- and tetrafunctional epoxy resins, cured with either diamino-diphenylsulphone (DOS) or with dicyanodiamide (Dicy), and modified with either poly(ethersulphone) (PES) or carboxyl-terminated butadiene acrylonitrile (CTBN) rubber. The applicability and limitations of the solubility parameter approach in predicting compatibility in reactive blends are considered.
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  • 48
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    Polymer Engineering and Science 26 (1986), S. 82-91 
    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: Set of procedures employing melt viscoelasticity functions for selecting components and composition of the binary polyblends and estimating minor phase domain size is introduced and illustrated with examples. The procedures intended for Computer Aided Manufacture of the polyblends (CAMOBLE) are based on shear stress dependent viscoelasticity ratios, and the selection of the composition exploits stress dependent synergism of the viscoelasticity functions. Also used is auxilary procedure for composition selection is based on verified blending laws accounting for interaction and shear effects. Evaluation of the performance characteristics (“mechanical properties”) is illustrated with a modified Kerner model.
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  • 49
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    Polymer Engineering and Science 26 (1986), S. 116-119 
    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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    Polymer Engineering and Science 26 (1986), S. 144-151 
    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 dynamic responses of a 2-1/2 inch single screw plasticating extruder and extrusion line were investigated. Step changes in screw speed, take-up speed, back pressure, and processing materials were used to determine the transient responses of barrel pressures, die pressure, melt temperature, and extrudate thickness. Dynamic responses of the entire extrusion line can be explained by the flow mechanism of the extruder and the logical properties of the polymer used. A capillary rheometer was also used to determine if it could simulate pressure responses in the extruder for screw speed changes. Results showed that capillary rheometer was helpful in estimating the short term pressure responses in the die.
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  • 51
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    Polymer Engineering and Science 26 (1986), S. 127-132 
    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 effect of free radical desorption is studied by using a mathematical model of particle size distribution in continuous emulsion polymerization. By comparing the theoretical prediction with experimental data, the value of Do for the vinyl acetate (VAc) system is best chosen as 0.19 × 10-7 cm2/h. The effect of radical desorption as well as mean residence time on the absolute particle size distribution, total concentration of polymer particles, conversion, and average number of radicals per polymer particle are analyzed by the model proposed.
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  • 52
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    Polymer Engineering and Science 26 (1986), S. 139-143 
    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: Polystyrene particles were coated by electroless deposition of copper, nickel or copper and nickel. The metal-coated polystyrene particles were molded at high temperature and pressure into plaques, in which the metallic shell continuity was preserved and a continuous conducting metal network was formed. Very high conductivities at low metal concentrations (less than 1 percent v/v) are obtained by this procedure. The resistivity, dielectric constant, and dissipation factor of these metal containing composites are presented as functions of the metal concentration, frequency, and temperature. The metal containing composites exhibit reasonable flexural properties.
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  • 53
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    Polymer Engineering and Science 26 (1986), S. 133-138 
    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 response to difficulties encountered in measuring and reproducing the flow properties of Boger fluids (dilute solutions of polyarcylamide in corn syrup), Choplin, et al. proposed it particular variety of lubricant (Emkarox) and also solutions of polyacrylamide (Pusher 700) in mixtures of glycerine and water as better model fluids for molten polymers than the original Boger fluid. In response to this work it is argued that the model fluid systems proposed by Choplin, et al., although interesting in concept, have insufficient elasticity and hence are of limited potential for use in investigative work in polymer fluid mechanics. Of all the highly elastic constant viscosity fluids available, the polyisobutylene-polybutene system is the most attractive. Both the properties of this organic Boger fluid and the original Boger fluid, are entirely consistent with simple fluid theory.
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  • 54
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    Polymer Engineering and Science 26 (1986), S. 152-161 
    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 dynamic response of a 2.5 inch plasticating extruder and the extrusion line are modeled using high density polyethylene and acrylics us extrudate. Screw speed, back pressure valve position, and material changes are used as forcing functions. Three fundamental transfer functions in the Laplace domain: a first order, a second order, and a lead-lag, are developed to simulate the short term and long term responses of temperatures, pressures, and extrudate thickness. A kinetic-elastic model which can predict rheological properties of non-Newtonian, viscoelastic materials is also applied to the pressure responses of the extrusion process. This model can fit the experimental data well but due to the complexity involved in its parameter setting, more modifications are required before it can be applied for the control of extrusion process.
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  • 55
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986) 
    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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  • 56
    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: Both ethylamine and ammonia in aqueous solutions catalyze the hydrolysis of tetraethylorthosilicate to precipitate silica filler within poly(dimethylsiloxane) elastomers. The rate of filler precipitation can vary in a complex manner, possibly due to loss of colloidal silica and, in the case of the ethylamine solutions, deswelling of the networks. Increase in catalyst concentration increases the precipitation rate, and increase in amount of filler precipitated dramatically increases the modulus and ultimate strength of the networks, thus demonstrating the desired reinforcing effects.
    Additional Material: 4 Ill.
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  • 57
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    Polymer Engineering and Science 26 (1986), S. 171-186 
    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-purpose finite element program has been used to simulate the flow of polymers through wire-coating dies. The analysis includes Newtonian and power-law fluids. The effect of normal stresses was examined through a simple viscoelastic constitutive equation, Nonisothermal wire coating was studied to obtain the temperature field within the melt. The effect of a slip condition at the solid boundaries was also examined. The determination of the coating melt free surface was carried out through an iterative procedure. The finite element solution provides details about the existence and extent of recirculation regions, about hot spots due to viscous dissipation, and also captures the stress singularities present at the impact of the melt with the wire and at the exit from the die. Pressure distribution, maximum temperature rise, haul-off wire tension, maximum wire tension, and stresses at the wire surface and die wall are also presented.
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  • 58
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    Polymer Engineering and Science 26 (1986), S. 189-189 
    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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  • 59
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    Polymer Engineering and Science 26 (1986), S. 162-166 
    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: Gamma radiation and high-energy electrons were used to crosslink two types of polybutadiene (PBD), the first having random cis-trans-vinyl contents and the second consisting primarily of blocks of cis units and blocks of trans. The resulting elastomers were studied in elongation in the unswollen stale, generally at 5°C, and in swelling equilibrium in a thermodynamically good solvent. Stress-strain isotherms obtained for the random-PBD networks did not show upturns in the reduced stress [f*] at high elongations, which is consistent with their non-crystallizability. The stereoblock polymers were found to be crystalline, with melting points ranging from 14 to 65°C. Attempts to achieve strain-induced crystallization in the stereoblock networks by judicious choice of temperature were unsuccessful as judged by the absence of any significant upturns in [f*]. Values of the elasticity constants 2C1 and 2C2, and the molecular weight between crosslinks were similar to those obtained from the linear portions of the isotherms previously reported for high-cis and high-trans PBD, which readily undergo strain-induced crystallization.
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  • 60
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    Polymer Engineering and Science 26 (1986), S. 205-213 
    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 feedforward plus feedback control method (FFC) and an adaptive feedforward plus feedback control method (AFFC) were proposed in this study to control the extrudate thickness of polymer extrusion. They were tested by step changes of screw speed and feedstock, and square wave type of screw speed changes. It is found that these feedforward control methods worked very well for various load disturbances but they required a good process model and accurate on-line measurements of manipulated variables and load variables. The feedback function was necessary to compensate the over- or under-corrections of the feedforward controllers and to handle other disturbances which were not considered in the feedforward model.
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  • 61
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    Polymer Engineering and Science 26 (1986), S. 197-204 
    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: On-line computer control of extrudate thickness was carried out using a 2-1/2 Inch single screw plasticating extruder. Predried poly(methyl methacrylate) (PMMA) was extruded through a slit die. Two feedback control methods, a conventional PI controller and a Smith predictor dead time compensation, were tried for both set point changes (i. e., extrudate thickness changes) and load changes (i. e., screw speed changes). Results showed that both the PI feedback control and the Smith predictor were satisfactory for long term set point changes but not for load changes. Since the Smith predictor may compensate the process dead time, it would be useful for regulating short term set point changes such as barrel temperature settings.
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  • 62
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    Polymer Engineering and Science 26 (1986), S. 190-196 
    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 ultimate properties of a molded article arc directly related In the microstructure of the article and are consequently influenced by the thermomechanical history experienced by the melt during processing. The mold filling behavior of thermopalastic polymer melts has been analyzed quantitatively by means of a computer simulation. The mathematical model is based on the equations of continuity, motion, and energy, along with appropriate constitutive relations and relevant initial and boundary conditions. The governing system of equations is solved numerically by means of a Marker-and-Cell computational scheme. One to the significant implications for microstructure development, the fountain effect at the advancing free surface is explicitly taken into consideration in the simulation. The model yields data on filling time and melt front position as well as velocity, temperature, pressure, and shear stress distributions within the mold cavity. The rearrangement of the velocity and temperature profiles in the vicinity of the melt front are considered in detail. Experimental studies have also been undertaken in order to verify the predictions of the computer Simulation.
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  • 63
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    Polymer Engineering and Science 26 (1986), S. 225-232 
    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: There has been considerable controversy over whether one can extract the primary normal stress difference (N1) for polymer melts from hole pressure (PH) and exit pressure (Pex) data. In this paper values of PH and Pex are obtained for three polymer melts in the same slit-die apparatus under the same operating conditions. It is found that there is a good correlation between values of N1 obtained by means of a cone-and-plate rheometer and those obtained by means of PH data and the Higashitani-Pritchard theory. On the other hand, values of N1 obtained by means of Pex data for polystyrene were two to five times higher than those obtained by means of the cone-and-plate device. For the lower molecular weight low density polyethylene (LDPE) sample, values of Pex were found to be both positive and negative. For the higher molecular weight LDPE sample, values of Pex were found not to increase monotonically with with σw. Hence, it was difficult to obtain unequivocal values of N1 for LDPE.
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  • 64
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    Polymer Engineering and Science 26 (1986), S. 233-238 
    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: Dimensional changes in complex profile extrusions are classified as overall size and local shape changes which can be related naturally and systematically to changes in operating conditions. The theoretical basis and supporting experimental data for simultaneous, independent control of certain classes of extrudate dimensions are presented for the following strategies: (1) size control by manipulating line speed relative to extruder output rate, (2) shape control by manipulating extrudate swell through adjustments in stock temperature, and (3) shape control by manipulating local die flow by adjusting the die temperature set point.
    Additional Material: 7 Ill.
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  • 65
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    Polymer Engineering and Science 26 (1986), S. 243-254 
    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 the Injection molding process, nonuniform heat transfer between the polymer and the mold caused by flow during the cavity filling stage can lead to spatial variations in the cavity surface temperature. This can result in an increase in cycle time or poor part quality. An investigation of the flow-induced, nonuniform, cavity surface temperature is reported here. A flow model for a thin, rectangular, end-gated cavity and a model for the steady-state temperature distribution in a simple mold are developed. These are applied to some thermosetting and thermoplastic systems. For both filled and unfilled thermosets, it is found that a simple plug flow model gives a good approximation for the heat transfer during flow. For thermoplastics, however, the full flow solution must be used. For the cases considered in this study, the steady-state temperature variation along the cavity surface is less for the thermoplastics than for the thermosets.
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  • 66
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    Polymer Engineering and Science 26 (1986), S. 214-224 
    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: It is of importance to estimate the pressure drop of polymeric materials in a converging die with an abrupt change in geometry for many polymer processes. In the present study, experiments have been conducted with an extruder and conical dies of four different converging angles for two different polymeric melts under various processing conditions. As part of the analysis, numerical calculations have been carried out using a finite element method (FEM) for a power-law fluid model, A simple formula for estimating pressure drops has also been derived based on a power-law fluid model with normal-stress effects incorporated. In particular, the formula with the normal-stress term excluded underpredicts pressure drops systematically at high flow rates, giving very similar results to those by the FEM calculation. When the normal-stress term is included, the formula is in bettor agreement with the experimental data, confirming that the normal stress effect is important at high flow rates. Other formulae in the literature have been also compared with the present experimental data.
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  • 67
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    Polymer Engineering and Science 26 (1986), S. 239-242 
    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: Polytetrafluoroethylene (PTFE) was solid state extruded to fiber form at temperatures between 250 and 300°C and at pressures between 7000 and 15,000 psi. The PTFE fibers had a diameter of 0.0502 inches and the reduction ratio for extrusion was 55.8. The fibers were tested for mechanical strength, and examined with a scanning electron microscope, which revealed a fibrous structure at high magnifications. The melting point of the fibers was 342°C by differential scanning calorimetry. The tensile properties were enhanced with an increase in processing temperature and pressure, the highest properties resulting from an extrusion temperature of 300°C and pressures greater than 10,000 psi. A tensile strength of 5500 psi and a secant modulus of 250,000 psi were obtained.
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  • 68
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986) 
    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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  • 69
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    Polymer Engineering and Science 26 (1986), S. 255-267 
    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 cell model describing the diffusion-induced growth of closely spaced single bubbles developed in an earlier publication is now used as the microscopic building block of an analysis of low-pressure structural foam molding. Heat transfer, solidification, and bulk flow of the foam in the mold cavity are included in this macroscopic analysis. An experimental method is described whereby the bulk density of an expanding thermoplastic polymeric foam is measured as a function of time when the expanding foam is prepared by the short shot injection molding process. Instantaneous and final bulk foam density data obtained for various values of the controlling process parameters are compared with the predictions of the model. These predictions are found to be in qualitative agreement with the experimental measurements reported here. However, quantitative differences exist between the two. These differences are explained mainly by the omission of melt elasticity and bubble coalescence in the model.
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  • 70
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    Polymer Engineering and Science 26 (1986), S. 285-289 
    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: Draw ratios have been measured for samples of polyethylene and trons-polyisoprene, crystallized at various temperatures and at various degrees of orientation. The values obtained range from unity, i. e., no drawing is observed, up to values of about 15X for materials crystallized in the oriented state and then drawn in a perpendicular direction. The results are in rough accord with a simple molecular network model in which network strands are incorporated into crystallites with a number of reversals of direction (folds), and the remainder of a strand between network junctions is randomly arranged. The reduction in draw ratio with increasing temperature of crystallization and with increasing orientation at the time of crystallization is then accounted for in terms of a reduction in the number of reversals (folds) per molecular strand. Differences in natural draw ratio for different polymers are attributed to variations in characteristic sequence length within a crystallite and in the number of folds per network strand.
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  • 71
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    Polymer Engineering and Science 26 (1986), S. 274-284 
    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 effect of ductility on fatigue behavior was studied using two DGEBA-based (diglycidyl ether of bisphenol A) epoxies: a ductile Epon 815/Versamid 140 and a brittle Epon 828/Epon Z. Failure modes were different although normalized stress-life relations were similar for both resins. Two competing failure mechanisms were identified: viscoelastic creep, and nucleation and coalescence into a main crack of microcracks. No signs of crazing or fibrillation were detected. The plastic elongation during fatigue was larger in Epon 815/Versamid 140. Fracture sources showed cracked material surrounded by a region of stable growth of the main crack. In the brittle Epon 828/Epon Z cracked material was scarce and the crack initiation region was clean, especially at high stress levels. Discontinuous crack growth bands and striations were seen in the stable crack growth regions. During unstable propagation the crack advanced at different levels joined by deep cleavage steps. Branching of the main crack occurred only in the brittle resin at the final stage of propagation.
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  • 72
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    Polymer Engineering and Science 26 (1986), S. 296-296 
    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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  • 73
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    Polymer Engineering and Science 26 (1986), S. 269-273 
    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: Torsional and tension-torsion creep studies have been performed on cellulose acetate butyrate at 65°C. The aging shift factor, μ, at this temperature has been determined to be 0.85. This is somewhat higher than 0.75 which was suggested as a maximum value for cellulose acetate butyrate (5). Axial stresses cause the torsional retardation times to become shorter. The change in retardation time is mainly determined by the magnitude of the axial stress and not by the length of time during which the axial stress is applied. Torsional stresses cause the axial retardation times to shift in a similar manner. The shifting of retardation times follows a maximum shear stress criterion.
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  • 74
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    Polymer Engineering and Science 26 (1986), S. 290-296 
    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: Physical aging of a network epoxy resin in both the dry and water plasticized state has been investigated using calorimetric methods. Enthalpic retardation (recovery) towards equilibrium below the glass transition temperature (TK) has been qualitatively and quantitatively evaluated over a wide temperature range by following the enthalpy recovered (Er) on re-heating through to and beyond the glass transition. Results indicate that water, acting as a plasticizer, accelerates aging at any given temperature. However, by using the respective Tg as a point of reference, a simple comparison of the kinetics of aging in the dry and plasticized state suggests that in the temperature range studied there are no significant differences. These observations, together with observed dilational and relaxational effects of water which appears to erase all accumulated aging effects in dry aged material, are commented upon and their importance in the' context of transport-phenomena and moisture sorption-desorption cycles are discussed.
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  • 75
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    Polymer Engineering and Science 26 (1986), S. 297-303 
    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: Rates of crystallization, stress-optical coefficients, and melting points were determined for unelongated and elongated polysebacate model networks. For the unelongated networks, the maximum rate of crystallization was found to occur at approximately 0°C. For the elongated networks, the stress-optical coefficients documented the extent to which strain-induced crystallization was facilitated by increase in elongation and decrease in temperature. Measurements of stress relaxation due to crystallization at constant elongation indicated that the dimensionality of crystallization growth decreased from 3.0 to 2.5 as the temperature increased Melting points increased significantly with increase in elongation as predicted by theory. Fiber (non-equilibrium) shrinkage temperatures, as expected, showed no correlation with the melting points.
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  • 76
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    Polymer Engineering and Science 26 (1986), S. 304-309 
    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: Networks were prepared from a sample of 1,4-polybutacliene having an extremely high cis content (98.5 mol percent) and from other samples having relatively high trans contents (72 to 80 mol percent). The cross-linking techniques employed were gamma irradiation, ultraviolet irradiation, and peroxide thermolysis. The resulting elastomers were studied in elongation in the unswollen state at several temperatures, to their rupture points, and in swelling equilibrium in a good solvent. Values of the elasticity constant 2C1 obtained from the stress-strain isotherms at low and moderate elongations gave values of the molecular weight M, between cross-links in at least approximate agreement with those obtained from the swelling equilibrium data. The other elasticity constant 2C2 generally had relatively large values, suggesting inhomogeneous cross-linking, but approached zero for small Mc as expected from reduced configurational interpenetration. At high elongations, the reduced stress for the high-cis polymer showed marked upturns due to strain-induced crystallization.
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  • 77
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    Polymer Engineering and Science 26 (1986), S. 310-317 
    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: Residual stresses, generally present in solid polymers, arise as a result of temperature gradients during solidification. These stresses influence the mechanical behavior of polymers and therefore it is important to measure them; most conventional methods are destructive. In the present work, a non-destructive photoelastic technique is discussed and applied to circular rods of poly(methyl methacrylate) (PMMA). This technique involves the measurement of the distribution of total birefringence across a diameter; the residual stress distribution is obtained numerically from the birefringence distribution. The influence of the birefringence caused by molecular orientation is also investigated. This technique is also applied to a glass rod, in which case the molecular birefringence is minimum. It is seen that the residual stresses obtained in this case are consistent with equilibrium considerations.
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  • 78
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    Polymer Engineering and Science 26 (1986), S. 326-331 
    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 explores the concept of continuously extruding reacting polyurethane foams. The control of the process is hampered by the fact that the state of the conversion of the extrudate is not directly observable. We present the general concept, describe an experimental apparatus, present a mathematical model of the process, and report on some initial experimentation. In the experimental work, low density (0.5 g/cc) polyurethane foam was extruded in a cylindrical cross section at a rate of 250 g/min. Maximum run time was thirty minutes. In all cases, the experiment had to be stopped due to problems in the process. Problems requiring further investigation were identified: channelling of uncured liquid foam around the solid cured foam, poor skin quality due to adhesion of the foam to the wall, and the general lack of observability of the conversion field.
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  • 79
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    Polymer Engineering and Science 26 (1986) 
    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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  • 80
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    Polymer Engineering and Science 26 (1986), S. 332-336 
    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 melt flow behaviour of polypropylene filled with organoantimony compounds, triphenylstibinedibromide and its derivatives with tribromo-, trichloro-, and pentachloro-phenols, as flame retardants has been studied in the temperature range of 180 to 220°C, and at shear rates of 29.5 to 588.8's-1, using a capillary rheometer. A decrease in the melt viscosity at all shear rates and temperatures was noticed on addition of these flame retardants, The melt viscosity further decreased upon increasing the concentration (from 5 to 20 phr) of the flame retardants. The die swell was measured in order to determine the melt elasticity of the filled systems. The minimum melt viscosity of filled propylene was observed approximately where the maximum die swell (melt elasticity) occurred.
    Additional Material: 5 Ill.
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  • 81
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 318-325 
    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 large deformation behavior of nylon-6 when subjected to constant loading rate tests has been investigated experimentally. Three types of loadings - tension, torsion, and combined tension-torsion - have been used and the strain histories for each type analyzed. It is shown that a piecewise power law in time can adequately describe the strain histories up to equivalent strains as high as 30 percent for all cases. This piecewise power law shows well-defined transitions from one mode to the other while each mode is characterized by a power law exponent valid for all types of loading. On the basis of experimental results, it is also possible to establish the functional form of various kernels involved in the Green-Rivlin representation of the non-linear viscoelastic behavior of nylon-6. This method of finding kernels is much simpler than the conventional method of carrying out a large number of multi-step creep tests. A comparison is also made between the results of the present work and the well-known Findley equation, particularly with respect to the instantaneous strain response of materials.
    Additional Material: 5 Ill.
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  • 82
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 337-337 
    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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  • 83
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 346-353 
    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: Dielectric data from an epoxy resin system were used as the foundation for dielectric modeling of the curing process. This resin system (DGEBA-polyamide) was chosen as an easily processible model system. Dielectric average relaxation times, defined as the reciprocal of the angular frequency at which the loss component of the dielectric constant reaches a maximum, were determined for a 40°C isothermal cure. The changes in the average relaxation time through the cure exhibited similar behavior to those for viscosity, which inspired the correlation of the two properties. The dielectric relaxation time was modeled using a six-parameter model analogous to that used for viscosity. The model parameters were in turn associated with both intrinsic properties of the system and reaction kinetics describing the cure. The possibility of extending the relaxation time model for use with single-frequency data by means of a time-frequency correlation was also investigated. Combined, these two modeling methodologies provide a powerful constitutive approach for describing dielectric properties of thermosetting polymers during cure.
    Additional Material: 7 Ill.
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  • 84
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 354-357 
    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 isothermal cure of a diglycidyl ether of Bisphenol-A (DGEBA) epoxy resin with diaminodiphenylsulfone has been characterized by microdielectrometry and differential scanning calorimetry. The cure temperatures ranged from 410 to 460K. The behavior of the relaxed (or static) dielectric permittivity vs. cure time and temperature was determined from the microdielectrometry data. The DSC data was fit to an autocatalyzed reaction kinetics model, which was then used to predict reactive group concentrations as a function of cure time and temperature. The temperature dependence of the relaxed permittivity at constant chemical conversion was examined in the context of the Onsager theory for the relaxed permittivity of a system of independent dipoles. This analysis indicated that the dipoles in the resin are not independent, as assumed by the Onsager theory, and that the behavior is similar to that observed in polyethers. An empirical modification to the Onsager theory was used in conjunction with the kinetic model to estimate dipole moments for the epoxide, primary amine, and reacted (secondary and tertiary) amine groups. The relative and absolute values of the dipole moments were in good agreement with estimates based on the structures, leading to the conclusion that the observed decrease of the relaxed permittivity during cure of this epoxy/amine system is due to the changing concentrations of polar reactive groups.
    Additional Material: 7 Ill.
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  • 85
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 338-345 
    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: Dynamic dielectric analysis (DDA) has been used to study curing polymer systems and thermoplastics. Measurements have been made over a frequency range of six decades. This wide range of frequencies increases the amount of information which can be obtained. The data is analyzed in terms of the frequency dependence of the complex permittivity ε*, specific conductivity σ(ohm-1 cm-1), and the relaxation time τ, parameters which are characteristic of the cure state of the material and independent of the size of the sample. Dynamic dielectric measurements have been used to monitor polymer processing in UDEL-P1700, LARC-160, polyphenyl quinoxaline (PPQ), and Epon 828 cured with Agent U. Dynamic dielectric measurements have been correlated with viscosity for the polysulfone thermoplastic UDEL-P1700 and with viscosity and ultrasonic measurements on the DGEBA type epoxy Epon 828 cured with Agent U. The experimental results suggest that when ionic processes dominate the dielectric response, the intensive property σ is a good monitor of the resin's viscosity. The results show that the dielectric relaxation time τ can be used to monitor the state of the system and the extent and rate of the reaction. Solvent evolution can also be easily observed.
    Additional Material: 16 Ill.
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  • 86
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 358-361 
    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 report the use of microdielectrometry for monitoring the cure of the matrix resins in epoxy-glass and epoxy-graphite composites. The multi-ply laminates are cured in a press using ramped temperatures. The microdielectrometer sensor is embedded in a cavity made by cutting a hole in each of the inner plies. For a brominated-epoxy glass-reinforced prepreg ramped to final cure temperatures as high as 200°C and at pressures up to 60 psi, a reproducible pattern of cure events is observed beginning with the flow of resin onto the sensor electrodes and ending with the characteristic stabilizing of the loss factor late in cure. The apparent dielectric properties (permittivity and loss factor) show good reproducibility for identically prepared samples, but their characteristics differ from those observed in neat resin. A ten-fold increase in resin conductivity is noted when cures of glass-reinforced prepreg are compared to cures of neat resin flaked off the prepreg. Special techniques are required in sample preparation when monitoring the cure of prepregs containing conductive fibers such as graphite.
    Additional Material: 5 Ill.
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  • 87
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986) 
    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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  • 88
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 362-366 
    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: Variation of molar mix ratio of the Epon 828/Diamino-diphenyl sulfone (DDS) system was found to have significant influences on pre-cure and post-cure properties. Microdielectrometry showed that dielectric constant varies from about 9 to above 30 depending on DDS content before cure. Times to the 10 kHz loss peak during cures at 177°C were found to decrease with increasing DDS content. Above a ratio of 2/1 and below 1/2, due to the low molecular weight of the reaction products, loss peaks did not occur. Ionic conduction was shown to have a strong correlation with calorimetric kinetic cure data. The influence of both excess amine and excess DDS was to produce cured material with high ionic conduction levels indicative of loose networks. Deviations from ideal stoichiometry as small as 1.1/1 produced noticable differences in the finally cured network.
    Additional Material: 7 Ill.
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  • 89
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 367-372 
    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 investigated the use of acoustic waveguide techniques to measure the cure and stress state of epoxy resins and composites. It is anticipated that the waveguides, which are incorporated within the structure, will also be valuable for nondestructive (NDE) evaluation of stress, strain, and damage caused to the structure during its life time. While dielectric techniques are commonly used to monitor the cure of composites, they suffer because metal electrodes intrude into the structure and poor signal-to-noise ratios may be encountered with graphite composites. Acoustic waveguides can be made compatible with the host structure and after the cure monitoring function is over, remain in the structure for NDE of flaws and voids, as well as to monitor other parameters. This paper presents results on experiments to monitor the cure and stress state of resins and composites with a 1.5 mm diameter polyester-fiberglass acoustic waveguide in curing resin. A 1000 to 1 change in the peak value of a 71 kHz acoustic signal was found. Other parameters now being investigated are: frequency of transmission and phase change, transit time, waveguide size and shape, and acoustic wave attenuation characteristics.
    Additional Material: 6 Ill.
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  • 90
    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 melt strength method is analyzed in terms of its ability to predict the axial stress levels found in tubular film extrusion of low density polyethylene. For certain values of the capillary L/D, the level of axial stresses and average Newtonian viscosity found in the filament stretching and film blowing are comparable at the same draw ratio. The elongation to break of the finished film was found to be primarily determined by the axial stress during the film blowing, at constant frost line height.
    Additional Material: 9 Ill.
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  • 91
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 381-387 
    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 polymerization of the phenolformaldehyde matrix material of porous glass fiber composites is of vital importance in the production of the composite; it also has an, essential effect on the strength properties of the composite, which correlate directly with the degree of polymerization. With a certain material combination, the optimal strength properties can be obtained by a suitable thermal treatment, which depends on the kinetics of the polymerization process. In this study we found that the highest strength values of the composite are obtained by making the polymerization (curing) rapid at a very high temperature using resins with a high degree of polymerization and a high dry matter content. As regards the structure of the composite, the factors that affect the polymerization process arc density, resin content, and thickness. The results obtained with this kind of a composite are valid within a density region of 600 to 1500 kg/m3. At lower densities, the polymerization process changes, since thermal convection plays a greater role, and at higher densities the insulating effect of porosity begins to decrease.
    Additional Material: 9 Ill.
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  • 92
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 373-379 
    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 thermosetting resins and composites made from them begin to be used in critical applications, it becomes necessary to monitor and analyze the cure of the resin within the confines of the processing equipment. Such measurements have been carried out using a dielectric technique called dielectrometry or dielectric analysis. Conventional dielectrometry has certain limitations associated with the use of parallel plate geometry for electrodes. For in situ measurement of cure, intrusiveness of electrodes is a problem which may require placement of electrodes in non-strategic areas. Since electrode spacing changes during cure, it is difficult to deduce permittivity and loss factor from the data. At lower frequencies the capacitive currents are small and signal-to-noise ratios are small, therefore, measurement at low frequencies (〉100 Hz) typically require large electrode sizes. One approach to overcome the problems described above is the development of microdielectrometry. A solid state integrated circuit chip, 2 by 4 mm in size, is used as the sensor. The miniature sensor can measure the properties of a dielectric on its surface, therefore it need not intrude into the composite part. Transistors which are built into the integrated circuit are used to amplify the signal to make low frequency (〉1 Hz) measurements feasible. The electrode geometry does not change, therefore loss factor and permittivity data can be deduced in real-time. During cure of the resin or composite material, permittivity and loss factor are measured continuously at a series of preselected frequencies. Real-time-data is plotted on a strip chart and is also stored in a cassette for later analysis. Temperature of the curing material is measured either by a diode on the sensor or by externally placed thermocouples. Results on an aromatic amine cured epoxy resin and a dicyandiamide cured epoxy resin prepreg are presented in this report. The data obtained by microdielectrometry is compared and correlated to results obtained using differential scanning calorimetry, infrared analysis, and dynamic mechanical analysis. Results show that microdielectrometry can be used to follow the cure of epoxy resins and absolute measurements of permittivity and loss factor can be made to provide information on the mechanisms that produce the observed changes. Data at 1 Hz can be obtained but for certain lossy systems at typical cure temperatures, the data is often out of range of the instrument, thus restricting use to 10 Hz and higher frequencies. At very high loss factors (〉100) a “blocking” phenomenon is observed due to charge pile up at electrode surfaces which results in erroneously high permittivity values.
    Additional Material: 8 Ill.
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  • 93
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 393-404 
    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: A mathematical model has been developed to simulate the pultrusion process, namely the profiles of temperature and the degree of cure in both the axial and radial directions in a pultrusion die of cylindrical shape. For the study, the equations of continuity and energy transport, coupled with a kinetic expression for the curing reaction, were solved numerically, using a finite difference method. For the kinetic expression, we used an empirical expression of the form dα/dt = (k1 + k2αm)(1 - α)n to describe the curing behavior of both unsaturated polyester and epoxy resins. Differential scanning calorimetry (DSC) was used to investigate the curing behavior of the following systems: unsaturated polyester resin/glass fiber, epoxy resin/glass fiber, and epoxy resin/carbon fiber. The results of DSC runs were used to determine the kinetic parameters, which enabled us to predict the effects on the pultrusion characteristics of the following variables: (1) the type of initiator; (2) the type of fiber reinforcement; (3) the type of resin; and (4) the pulling speed and hence the residence time.
    Additional Material: 22 Ill.
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  • 94
    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 approach to high-density, high-modulus binders for explosives is to blend low-density, high-modulus polymers with high-density, low-modulus polymers. Improved properties, which these pairs theoretically should have, are discussed. Two attempts to achieve miscibility between a high-density fluoropolymer (Kel-F 800) and high-modulus thermoplastics (Lucite 130 and Phenoxy PKHJ) were unsuccessful. These blends are immiscible and their physical properties are additive or only slightly enhanced. Anelastic properties of the blends indicate phase separation by the presence of two glass transitions, one associated with each phase.
    Additional Material: 11 Ill.
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  • 95
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 1514-1523 
    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: Differential Scanning Calorimetry (DSC) is used to study the curing behavior of epoxy systems. For non-catalyzed diamine-epoxy systems, the reaction enthalpy ΔH and the glass transition temperature Tg are evaluated and related to the structure of the hardener. A method is developed to determine the activation energy. The effect of variations in the amine-to-epoxy ratio r on Tg is also examined. A maximum value is observed for r = 1. Then, the influence of benzyldimethylamine as catalyst in an anhydride/DGEBA system and in three diamine/DGEBA systems is reported. In the cases of DDS and DDA curing agent the maximum value of Tg is shifted, to r = 0, 6. The results are explained by different reaction mechanisms.
    Additional Material: 14 Ill.
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  • 96
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    Polymer Engineering and Science 26 (1986), S. 418-426 
    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 this paper it is shown that the formation and subsequent breakup of threadlike particles are important disperging mechanisms and largely govern the morphology resulting from a polymer blending process. Experiments on the breakup of Newtonian threads surrounded by a second Newtonian fluid have been carried out and good agreement with Tomotika's theory is achieved. Experiments on the breakup of viscoelastic fluid threads showed the influence of shear thinning and stretch thickening effects of the fluids used. To investigate the influence of non-Newtonian behavior of molten polymers on capillary instabilities, experiments were carried out on the breakup of molten polymer threads embedded in a second polymer melt. Surprisingly an absence of shear thinning and stretch thickening effects was noticed and good agreement with Tomotika's theory was obtained. Finally, the stability of threads of fluids exhibiting a yield stress was studied. A criterion predicting the stability of such threads was established and verified experimentally. On the basis of this criterion a possible explanation is given for the stability of a certain class of co-continuous morphologies.
    Additional Material: 18 Ill.
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  • 97
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 427-431 
    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 objective of a chemoviscosity model of a thermosetting resin is to describe the change of viscosity for a temperature-time program. A model is most advantageously developed by starting with a viscosity-temperature relationship and then relating the parameters of this equation to the rate of polymerization. Thus, the chemoviscosity is related directly to the polymerization kinetics of the thermosetting resin and, thereby, to its chemical composition. Viscosity-temperature relationships based on free-volume theory such as the Williams-Landel-Ferry equation and the Vogel equation appear to fit the chemoviscosity of an amine-cured epoxy resin more precisely than relation ships based on resin flow as an activated process.
    Additional Material: 10 Ill.
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  • 98
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 432-440 
    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: Over the past decade great strides have been made in the measurement, modeling and application of the rheology or viscosity history of curing thermosets. This paper will review the work that lead to the formulation of a simple predictive model to simulate the viscosity path of curing epoxies and to the use of the model in the understanding of the epoxy lamination process. Subsequent work by others that has clearly refined, extended, and simplified the method will be discussed.
    Additional Material: 25 Ill.
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  • 99
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 441-445 
    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: Viscoelastic properties in terms of complex viscosity |η*| and storage modulus G' have been studied for highly filled polymer composites. The viscous response and elastic response to changes in the frequency of dynamic oscillations have been fitted through an appropriate Theological model. A relationship between |η*| and G' is shown to exist, and the model parameters determined through the correlation have been shown to be useful in estimating the viscoelastic properties of commercially important ferrite-filled polymeric systems with loading in the range of 87-94 weight-percent.
    Additional Material: 8 Ill.
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  • 100
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986) 
    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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