Thermal and ablation resistance of syntactic foamed EPDM-based heat shielding materials

EPDM/aramid fibers ablatives represent the state of the art of Elastomeric Heat Shielding Materials (EHSMs) for Solid Rocket Motors (SRMs). EPDM exhibits the lowest density among elastomers maximizing the payload of a SRM. Due to necessity to further maximize the payload of a rocket, density reducer fillers, such as glass or phenolic microballoons, can be considered in the material formulation of the SRM insulation liner. However, the open literature on EPDM based EHSMs combined with these density reducers is extremely limited because these formulations are generally proprietary of companies manufacturing SRMs. In our paper we studied the heat capacity, thermal and dimensional stability, mechanical properties, and ablation resistance of EPDM based EHSMs combined with glass microspheres at different percentages. Moreover, Perlite, an affordable density reducer additive commonly used in concrete applications, was also evaluated and compared with glass microballoons.