Effect of multi-walled carbon nanotubes on thermal stability and ablation properties of EPDM insulation materials for solid rocket motors

Multi-walled carbon nanotubes (MWCNTs) have excellent physicochemical properties and can be used as fillers to improve the performance of insulation materials. However, there is currently no proper understanding of the mechanism by which MWCNTs improve the ablation performance of insulation materials. Here, we prepare two formulations of ethylene propylene diene monomer (EPDM) insulation materials with and without MWCNTs and study their thermal stability and ablation characteristics via thermogravimetric analysis, high temperature char layer residue experiments, oxyacetylene ablation tests, and other analytical methods along with scanning electron microscopy and energy dispersive X-ray spectroscopy. The intrinsic mechanism by which MWCNTs improve the ablation performance of insulation materials is revealed from the perspectives of char layer formation, consumption, and micro-morphology. The addition of MWCNTs increased the carbon residue rate after thermal decomposition and can suppress the consumption reaction of the char layer under high-temperature conditions. Microscopic morphological analyses show that the insulation material containing MWCNTs has a denser char layer surface and a network-like structure inside, which improve the ability of the char layer to resist erosion by gas flow. The combination of these factors improves the ablation performance of EPDM. Our findings regarding the MWCNT reinforcement mechanism can guide the design of new insulation materials.