Additive Effect on the Cure Behavior of a Trifunctional Cyanate Ester Resin

摘要

A comparison between the cure behavior of a trifunctional cyanate ester resin (PT30) and a difunctional system (L10) has been investigated by differential scanning calorimetry (DSC). Triazine systems are of interest for applications in air craft cabin interiors due to moderate price, low toxicity, low heat release rate and high char yield. The monomers were cured in the presence of small amounts of a phosphonate ester fire retardant with the objective of increasing the fire resistance of the network. The thermal and thermo-oxidative stability of the PT30 network was investigated by isothermal thermogravimetric analysis (TGA). The thermal stability was comparable to high performance polymers such as poly(benzobisoxazole) and high temperature polyimide thermosets with regards to an overall activation energy for the decomposition process. The overall cure kinetics for the trifunctional system was investigated by a general first order expression with respect to the cyanate ester concentration as well as an integrated rate equation. An overall activation energy of 59.0 kJ/mol was calculated. Addition of the phosphonate ester resulted in an increase in the activation energy (69.9 kJ/mol) with a concentration of 21% by weight of additive. The collision frequency factor increased nearly two fold from a value of 2.4 × 10~3 (1/sec), 0% additive to 1.3 × 10~5 (1/sec), 21% additive. The effect on the cure kinetics of the phosphonate ester on a difunctional cyanate ester was also investigated. With the addition of 4% by weight of additive the overall activation energy increased from 33.1 kJ/mol to 56.7 kJ/mol. The collision frequency factor increased from 2.0 × 10~1 (1/sec) to 1.6 × 10~5 (1/sec) with the addition of the flame retardant. It is believed that the impurities in the phosphonate ester flame retardant are acting as a catalyst thus lowering the gel point of the networks.