Redeposition and densification of pyrolysis products of polymer composites in char layer

Abstract

Under high temperature and pressure of solid rocket motors (SRMs), the pyrolysis will produce a char layer with non-uniform pore structure of Ethylene propylene diene monomer (EPDM) composites, whose compact structure can improve the ablation resistance of the composites. It is of great theoretical and practical significance to study the formation mechanism of the compact structure of the char layer for further studying the ablation mechanism and guiding the development of EPDM composites. To date, the formation mechanism of the compact structure has not been observed with direct evidence. In this work, the in-situ deposition experiment and the deposition ablation experiment for EPDM composites are designed and carried out. The in-situ deposition experiment results show that the pyrolysis gas produced by EPDM composites can generate chemical vapor deposition reaction in the char. The results of the deposition ablation experiment show that the chemical vapor deposition reaction of pyrolysis gas produced by EPDM composites in carbon skeleton surface of the char layer will lead to the densification of its pore structure in the ablation condition of SRMs.