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  • 11
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 315-324 
    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: Using dielectric techniques to monitor thermoset properties on-line during processing requires a mathematical relationship between the experimentally obtained signals and the physical state of the polymer. Such a relationship accounting for the dielectric response during both isothermal and dynamic cure experiments is developed in this study. Ionic conductivity changes with cure were described using the Keinle-Race expression, while an approach taken by Lane, Bachmann, and Seferis for modeling dipolar relaxation during isothermal cure was extended to nonisothermal cure conditions. Both of these approaches were combined in this study, providing a complete description of the dielectric changes occurring in thermosetting systems resulting from cure. Experimental results for a model epoxy/amine system were predicted with the developed methodology for isothermal cure at 140°C, 150°C, 160°C, and 170°C and cure under dynamic heating conditions at 1°C per minute.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 937-941 
    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: Polyamic acids synthesized from di-trifluoromethyl methane bis(phthalic anhydride) and 4,4'-diaminophyenyl sulfone (F-1) and 4,4'-diaminophenyl ether (F-4) were found to have excellent negative E-beam resist properties. The best materials contain about 90 percent imidized structural units having sensitivities of 1.5 to 2.5 μC cm-2 and contrast of 1.0 to 1.3. Polyamic acid of pyromellitic dianhydride and 4,4'-diaminophenyl sulfone (P-1) imidized to 97 percent exhibits useful positive E-beam resist properties. Radiation induces imidization and chain scission to alter the solubility of the resist polymers resulting in the formation of latent images.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 583-591 
    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 analytical methodology was developed capable of describing interrelations between thermal processing and polymer structure for thermoplastic based composite laminates. Specifically, this modeling methodology was used to describe experimental results generated with a specially designed match die quench mold by processing both neat PEEK polymer and carbon fiber reinforced laminate samples at different cooling rates. The developed model accurately predicted temperature profiles for PEEK laminates of different thicknesses, under normal as well as extreme quenching conditions of 114°C/s. surface cooling rates that are possible to generate with the quench mold. In general, the modeling methodology is capable of predicting a part's thermal profile during processing in terms of the composite's microscopic intrinsic properties (fiber and matrix), composition, and lamina orientation. Furthermore, by coupling to the thermal profile description, a previously developed crystallization kinetics model for PEEK polymer and its carbon reinforced composite, a quantitative description of structural development during processing was obtained. Thus, with this analytical methodology, a skin-core crystallinity profile, where the crystallinity varies with part-thickness as a result of uneven cooling experienced during processing, was predicted both for the neat PEEK polymer and its carbon reinforced laminate forms. Finally, the developed methodology clearly established the interplay of both microscopic heat transfer and kinetics of crystallization/solidification of the matrix that must be accounted for in predicting the final structure of a carbon fiber reinforced laminate that will, in turn, govern microscopic and macroscopic performance.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 634-639 
    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: Neat poly(ether-ether-ketone) (PEEK) and carbon fiber reinforced PEEK (APC-2) specimens were prepared using a variety of cooling rates to achieve a range of crystallinities. Amorphous specimens were exposed to a variety of fluids to determine the penetrant types which are able to strongly influence the material. This allowed the estimation of the solubility parameter and hydrogen bonding index for PEEK to be 9.5 and 3.1, respectively. Methylene chloride was used to investigate the kinetics of penetrant sorption. The data demonstrated Case II behavior, with the initial crystallinity having a pronounced effect on both the kinetic and equilibrium data. Accordingly, a model was proposed capable of describing the sorption level and penetration depth as a function of time given the sample crystallinity and sorption temperature. With Case II behavior there was no difference in the sorption kinetics of neat and fiber reinforced PEEK. Finally, the dynamic mechanical properties measured during sorption were found to be dependent on the sorption process.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 8 (1987), S. 271-282 
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A systematic study of thermo-mechanical properties of high speed spun poly(ethylene terephthalate) fibers was undertaken as part of a broad quantitative process - structure - property examination of semicrystalline polymers through appropriate composite models. Calorimetric experiments on a series of fibers spun at different speeds show that crystallinity increases with takeup speed rapidly below 4500 m/min but at a slower rate above that speed. The glass transition, cold crystallization, and melting temperatures were also found to increase with speed. A similar increase is exhibited by both the refractive index of these fibers along the fiber axis and the fiber birefringence. Comparison of birefringence measurements with those predicted from a composite two-phase optical model led to the conclusion that form birefringence may be a significant contributor to the overall birefringence and that it may not be ignored in calculations of orientation functions with this experimental technique.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 7 (1986), S. 158-169 
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The processing, structure and properties of polyetheretherketone (PEEK) semicrystalline thermoplastic as matrix polymer for high performance composites has been investigated in this work. In processing PEEK samples with different crystallinities, a specially designed mold capable of cooling the polymer in excess of 115°C/s from its melt temperature was constructed. In addition, during processing studies, a reaction of PEEK in the presence of copper was discovered. Analysis of the samples in terms of their crystallinity values also provided a new method for measuring crystallinity of the matrix in the composite. Crystallization of low crystalline samples at room temperature in the presence of methylene chloride was also confirmed for the first time with polarized microscopy. However, at the same time, the excellent hygrothermal resistance of PEEK was also confirmed. Finally, dynamic mechanical and stress-strain experiments with samples of different crystallinities elucidated the dependence of these properties to crystallinity. However, this study also elucidated that under normal processing conditions for high performance composites, PEEK properties may not be strongly affected by different levels of crystallinity.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 9 (1988), S. 36-41 
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Dynamic fiber wettability measurements are performed on T-300 carbon and Teflon fibers immersed in hexa methyl disiloxane (HMDS) silicone oil and a difunctional liquid epoxy resin, neopentyl diglycidyl ether (NPDGE). Specifically, four types of these carbon fibers, which are used to reinforce high performance composites, are studied. Decreases in the wetting force are observed for progressive immersions of all carbon fibers in the silicone oil but not observed with Teflon fibers, indicating adsorption may be occurring on the carbon surface. Perimeters determined from these wetting measurements on carbon fibers are larger than those calculated, assuming the fibers to be smooth cylinders. Scanning electron micrographs suggest this difference is attributable to surface crenulations. All carbon fibers immersed in the epoxy resin show non-zero contact angles.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 6 (1985), S. 47-53 
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This study focuses on the processing-structure-property relations for salicylic acid modified high performance epoxy matrix systems for carbon fiber composites. Differential scanning calorimetry and dynamic mechanical data have shown that as the concentration of salicylic acid increases, the degree of cure first increases, reaches a maximum, and then decreases steadily. Analysis of the results indicated that small amounts of salicyclic acid accelerates the amine-epoxide reactions resulting into crosslinked networks with increased degree of cure; increasing amounts, however, give rise to networks with reduced crosslinking by reducing the net available diaminodiphenyl sulfone (DDS) content in the system by a reaction of the DDS with salicylic acid. Overall, this study has demonstrated that salicyclic acid modification offers the potential for monitoring and controlling amine-epoxide reactions that may influence the application and usage of epoxy matrices in composite systems.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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