Relationships Among Molecular Structure, Processing, Water Uptake, and Moisture-Induced Degradation in Cyanate Ester Resins
AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE
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Polycyanurates also known as cyanate ester resins offer numerous advantages in composite structures for aerospace, energy, and electronics applications, and are often considered as higher-performance replacements for epoxy resins. Though generally low, the moisture uptake and stability in hot water of polycyanurates varies significantly as a function of monomer type and processing conditions. It is therefore important to understand the fundamental mechanisms responsible for water uptake and the resultant implications for the rational design of cyanate ester molecular structure and selection of appropriate processing parameters. Moisture uptake studies of polycyanurates, including ternary copolymerized blends, monomer chemistries incorporating silicon, and new monomer architectures based on phloroglucinol all revealed a strong correlation with nominal polycyanurate number density. The same trend was apparent in analysis of many commercial cyanate ester products. Dynamic TMA studies revealed a strong negative effect of the presence of catalyst on the retention of Tg in the commercial product Primaset registered trademark LECy, similar to effects observed for other cyanate ester resins. The use of less active metal chelate catalysts was shown to reduce the loss in Tg.
- Polymer Chemistry