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  • 1
    ISSN: 0935-9648
    Keywords: Chemistry ; Polymer and Materials Science
    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
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0935-9648
    Keywords: Chemistry ; Polymer and Materials Science
    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
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1042-7147
    Keywords: emulsion ; copolymerization ; tribromophenyl maleimide ; styrene ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Emulsion copolymerization of Tribromophenyl Maleimide (TBPMI) and styrene was conducted by semi-batch and batch processes. The effects of monomer composition and copolymerization method on copolymerization rate, molecular weight and molecular weight distribution, latex particle size and size distribution, glass transition temperature (Tg), thermal stability and mechanical properties were investigated. A kinetic study has shown that the rate of copolymerization in the batch process increased with increasing TBPMI content in the monomer feed. For the semi-batch polymerized samples, molecular weight decreased and molecular weight distribution increased with increasing TBPMI content in the monomer feed. For the batch polymerized samples, molecular weight also decreased but no obvious tendency was observed for the molecular weight distribution when TBPMI content increased. Compared with the batch copolymers, the semi-batch copolymers have a higher molecular weight at the same initial monomer mixture composition. Latex particle size decreased, while particle size distribution slightly increased with increasing TBPMI content in both semi-batch and batch latices. The semi-batch samples exhibit only a single Tg, the value of which increses linearly with increasing TBPMI content. For the batch copolymers, two Tgs were found, reflecting a mixture of styrene-rich and TBPMI-rich copolymer chains. TGA results indicate that the thermal stability of the semi-batch copolymers increased with increasing TBPMI concentration. Young's and flexural moduli increased, while tensile and flexural strengths decreased by increasing the TBPMI content for both the semi-batch and batch specimens. The semi-batch specimens have higher tensile and flexural strenghts than the batch ones.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0721-3115
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A threshold particle velocity criteria derived by E.R. Fitzgerald for the beginning of crystal lattice breakup and disintegration has been applied to shocked explosives and an inert material. In shocked explosives, reactions leading to detonation occur above a certain “threshold” magnitude. The computed crystal lattice breakup shock pressures compare rather well with observed experimental “threshold” shock pressures for six high explosives. The six explosives are: Comp-B3, Comp-B, TNT, PBX-9404, Tetryl, and H-6.In addition, the crystal lattice breakup criteria provides an explanation for the observed lowering of the detonation “threshold” shock pressure as the explosives are made more porous or less dense.Finally, the shock pressures, at which output from thermocouples embedded in shocked materials (PBX-9404 and Plexiglass) increases dramatically, compare favorably with predictions based on crystal lattice disintegration criteria.Consequently, it is tentatively concluded that crystal lattice breakup, or self-sustained phonon fission as Fitzgerald calls it, is responsible for the initiation of detonation in shocked explosives and enhanced thermocouple output in shocked materials. It is also postulated that the lattice breakup phenomena is also responsible for phase changes, increased chemical reactivity, and anomalous electrical activity which are observed in certain inert materials under relatively low level shock loading.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: poly(N-substituted maleimide-co-styrene) copolymer films were electropolymerized onto copper substrates as possible candidates for electronic applications. The N-substituted moieties that were investigated include phenyi, 3-carboxyphenyl, and 4-carboxyphenyl. Uniform coatings of 25 μm or more thickness were successfully applied using each of the three N-substituted maleimides. The thickness was controlled by manipulating the monomer concentration, current density, and reaction time. Not only did the 3- and 4-carboxyphenylmaleimide (CMI)/styrene copolymers have high glass transition temperatures (220°C) and fairly good thermal stability (≈ 430°C), but they also have rather low dielectric constants (2.55 for 4-CMI/styrene), comparable to those of polyimides. Polymerization of the coatings was observed by in-situ Fourier transform infrared spectroscopy (FTIRS), using a special cell that made the observation of the polymer structure development possible. It was found by FTIRS that all three monomers, when used with styrene, produced alternating copolymers. © 1993 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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: 2- or 4-carboxyphenyl methacrylamide (2- or 4-CPM) was successfully electrocopolymerized with either methylmethacrylate (MMA) or N-phenylmaleimide (NPMI) to form a thick thermoplastic matrix with high glass-transition temperature (200-300°C), on Hercules AS-4 graphite fibers. The dependence of the diffusion of active species through the coating upon the solvent/water ratio in the cell was estimated from the electrochemical diffusion behavior of hexacyanoferrate (III) ions. A higher solvent/water ratio helped to increase polymer weight gain by increasing the solvent swelling and increasing the diffusion coefficient of active species. A highly solvent-swollen polymer layer promoted the rate of polymer weight gain. The copolymer composition of 4-CPM/MMA and 4-CPM/NPMI polymers was random, and the effects of variables were consistent with free-radical polymerization kinetics. The electropolymerization rates of 4-CPM/MMA and 4-CPM/NPMI were increased by increasing current density and monomer concentration. For a slight temperature increase (from 28-45°), electropolymerization rate and polymer weight gain increased dramatically for the 4-CPM/NPMI system. © 1993 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A new in situ polymerization method is discussed wherein monomers of the major component are polymerized in the presence of a preformed thermotropic liquid crystalline polymer (LCP). Poly(p-oxybenzoate-co-p-phenyleneisophthalate) (HIQ) was chosen for this study. HIQ is well known to have a narrow process window and to be difficult to process reproducibly, both drawbacks for a commercial product. An in situ polymerization of the HIQ monomers in the presence of a fully polymerized LCP, such as poly(4-oxybenzoate-co-6-oxy-2-naphthoate) (CO) results in the “CO-HIQ” in situ blend. The in situ blend exhibited reduced biphasic morphology and was more homogeneous than was HIQ. The glass fiber-filled CO-HIQ resin also featured improved melt flow and more reproducible mechanical properties than those of HIQ. The in situ blends were characterized by optical microscopy, 1H-NMR, and melt rheology. The effect of the LCP level on the morphology of the in situ blend is discussed. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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  • 8
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A Novel polymeric coupling agent was synthesized through the reaction of polycarbonate (PC) and 3-glycidoxypropyltrimethoxysilane (GPS) in the presence of a quaternary ammonium salt. The reaction in the solid state gave a GPS-modified PC, which had a bimodel molecular weight distribution. The solutions of the GPS-modified PC were effective primers for promoting the adhesion of a siliceous abrasion-resistant coating to the PC substrate. © 1995 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A technique for estimating Mc, the molecular weight between crosslinks, of amine-cured epoxy resins is described. The technique is based upon the stoichiometry of the curing reaction and the amount of primary amino and epoxy groups remaining in the polymer at a given time. The Mc values so calculated are shown to be consistent with Mc results obtained from separate measurements of swelling and the polymer-solvent interaction parameter χ1 for the range of polymer concentration in which both measurements could be obtained. A means of estimating the relative reaction rates of the primary and secondary amino groups with the epoxy groups is given. Under proper curing conditions the amine-epoxy reaction goes very nearly to completion. The presence or absence of an exotherm has no noticeable effect on the course of the reaction between bisphenol A-epichlorohydrin (Epon 828) and methylene dianiline.
    Additional Material: 5 Ill.
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  • 10
    ISSN: 0887-6266
    Keywords: surface segregation ; segment asymmetry ; polymer blends ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We reexamine the influence of statistical segment length asymmetry on the surface segregation of homopolymer blends in a mean field thread model of polymer melts. By developing numerical self-consistent field solutions of the Edwards-Helfand equations, we demonstrate that the component with the smaller value of the parameter β2 = a2/(6ν) (a is the statistical segment length and ν is the segment volume) is enriched at a neutral, impenetrable surface. Qualitatively, this finding is in agreement with our earlier analytical work and with experiment. However, in contrast to our earlier work, we find that the absolute magnitude of the segregation is a sensitive function of the chain lengths of the two species and of the compressibility of the system. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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