Effects of carbon nanotubes on char structure and heat transfer in ethylene propylene diene monomer composites at high temperature

Abstract Owing to their high thermal conductivities, the direct addition of carbon nanotubes (CNTs) as fillers for ablative insulation materials inevitably has a deleterious effect on the performance of the obtained composites. However, this paper found that CNTs could reduce the thermal conductivity of the char layer skeleton of ethylene propylene diene monomer (EPDM) composites at high temperature. In this study, the ablation characteristics of EPDM composites with CNTs were tested using an ablation test motor. The results show that CNTs can reduce the ablation rates and the thermal conductivity of the char layer skeleton of the composites at high temperature. CNTs promote vapor deposition of pyrolysis gases, and a layer of pyrolytic carbon is formed on the surface of CNTs. As a result, the structure of the char layer becomes denser, and the thermal conductivity of the char layer skeleton decreases.