Thermal and Ablation Properties of Poly(urethane-isocyanurate)/Polyhedral Oligomeric Silsesquioxane Composites

This study investigated the thermal stability and ablation resistance of poly(urethaneisocyanurate)/polyhedral oligomeric silsesquioxane (PU-PIR/POSS) composites that were prepared by a one-step PU reaction using hydroxyl-terminated polybutadiene (HTPB) prepolymer, reactive or nonreactive POSS diol, and polymeric diphenylmethane diisocyanate (PMDI). The ablation properties were examined using an oxyacetylene torch, and the ablation rate and relative ablation resistivity were evaluated. The results showed that the crosslinked PIR structures in PU-PIR made a positive contribution to the thermal stability and ablation resistance. POSS is a highly ablative-resistant material owing to its unique nanosized silica-forming ability during an ablation test. On the other hand, the incorporation of POSS into PU-PIR to form the PU-PIR/POSS composites did not result in improved ablation resistance. This was attributed to the interruption of the thermally stable PIR formation during the reaction; however, it compensated for the adverse effect of the decreasing PIR concentration in the composites by their silica-forming ability during the ablation test, maintaining the same ablation resistivity as PU-PIR.