Thermal and ablative properties of rocket insulator compound based on EPDM

The thermal and ablative properties of insulator compound based on EPDM have been investigated by exposing the compound to the ablative environment produced by a plasma arc jet in the laboratory. The effect of individual fillers has also been studied. The rate of erosion and mass loss decrease and the heat of ablation increases with increase in asbestos loading in the rubber composite. This is due to reduction in thermal conductivity and enhanced heat stability of the vulcanizate. Similar results have been observed for cork-filled composite. An increase in char formation at high loading improves the ablation properties of cork-filled vulcanizates. Fe 2O 3-filled composite shows peculiar behaviour in the sense that there is an initial increase in rate of erosion and rate of mass loss and a decrease in the heat of ablation at low loading of Fe 2O 3, because Fe 2O 3 catalyses the decomposition of the vulcanizates. But at relatively higher loading, ablative properties improve marginally as Fe 2O 3 acts as a protective layer at the boundary and reduces the material loss during ablation. However, the ablative properties of the insulator compound containing all three components, namely, asbestos, cork and Fe 2O 3, exhibit great improvement. A mechanism of ablation of the insulator compound has been suggested.