Thermal Stability and Ablation Behavior of Modified Polydimethylsiloxane-Based Polyurethane Composites Reinforced with Polyhedral Oligomeric Silsesquioxane.

Series of polydimethylsiloxane (PDMS)-based polyurethane (PU)/polyhedral oligomeric silsesquioxane (POSS) composites are prepared using ether or polyether modified diol/polyol PDMS prepolymers, isophorone diisocyanate (IPDI) and either non-reactive or reactive POSS. The effect of POSS incorporated chemically or physically, number of ethylene oxide units and crosslinking on PDMS based PU is investigated in terms of thermal stability and ablation properties. The ablation property is measured using an oxyacetylene torch test, and the ablation rate is evaluated. The results show that POSS molecules make a considerable influence on the ablative resistance, because they act as protective silica forming precursors under oxyacetylene condition. POSS molecules, especially methyl POSS, in PU matrix leads to the formation of densely accumulated spherical silica layers on the top of the ablated surface, resulting in improved ablation resistance.