Determination and Use of Phase Diagrams for Rubber- or Thermoplastic-Modified Poly(cyanurate) Networks
Résumé
Blends of two cyanate ester monomers [4,4'-dicyanato-1,1-diphenylethane (DPEDC) or 4,4'-dicyanato-2,2-diphenylpropane (DCBA)] with several initially miscible reinforcing additives were studied as a function of cyanate conversion. The phase diagrams (temperature vs. conversion for the different transitions: phase separation,
gelation, and vitrification) provide a good overview of the systems and allow easy comparisons. DCBA is a better solvent than DPEDC. Rubber systems based on butadiene-acrylonitrile have an upper critical solubility temperature (UCST) behavior, whereas poly (ether sulfone)s (PESs) induce a lower critical solubility temperature (LCST) behavior. The acrylonitrile content of the rubbers and the molar mass of the PES additives also have a great influence on their miscibility. During an isothermal cure, phase separation always occurs before vitrification; in rubber it generally occurs before gelation, and in PES it occurs together with gelation. The temperature and viscosity at which phase separation occurs are critical for the final morphology. Reactive additives accelerate the curing
process and modify this morphology by inducing a complex matrix-particle interface, and a substructure inside the dispersed particles; these modifications produce the best toughening effects.
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Determination & use of phase diagrams for rubber- or TP-modified poly(cyanurate) networks Cao 1996.pdf (2.12 Mo)
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