Effects of Silicon Substitution in the Main Chain Network Segments of Polycyanurates
AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIR/SPACE AND MISSILE PROPULSION DIV/PROPUL MATERIALS APPLICATIONS BR
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This presentation summarizes the study of the effects of silicon substitution in both network segments dicyanates and junctions tricyanates. It appears that silicon substitution does result in increased free volume, a lower fully cured Tg, and , when compared at the same degree of conversion, lower density, lower packing fraction, and higher coefficient of thermal expansion. In at least some cases, the increased molar volume leads to lower water uptake, apparently by decreasing the overall density of cyanurate groups in the material. Incorporation of silicon in both network segments and at network junctions facilitates attainment of a higher degree of conversion under a given set of cure conditions, and appears to lower the activation energy for cure. This effect can offset or even overcome the effects of increased free volume.
- Organic Chemistry
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