Thermal insulation and char layer mechanical properties of a novel ethylene propylene diene monomer composite reinforced with carbon nanotubes coated via chemical vapour deposition

Currently, carbon nanotubes (CNTs) are used as popular fillers for enhancing the composite insulation materials in solid rocket motors (SRMs). While the mechanical properties of the char layer are enhanced by their use, the thermal insulation performance is reduced. This study proposes to solve this problem by pre-coating CNTs. The surface of CNTs was coated with a carbon layer using chemical vapour deposition (CVD), resulting in an ethylene propylene diene monomer (EPDM) composite insulation material reinforced with coated-CNTs. Furthermore, the ablation experiments were examined using oxyacetylene ablation test (OAT). The experimental results show that, compared with that of the CNTs formulation, the thermal conductivity of the coated-CNTs formulation is significantly reduced. On the other hand, for the coated-CNTs formulation, the temperature response time of the back of the material is increased, while the heating rate and maximum temperature are greatly reduced. In addition, the char layer of the coated-CNTs formulation has better compression resistance compared with that of the CNTs formulation. It is concluded that the coated-CNTs not only improve the thermal insulation performance by reducing the thermal conductivity of the material, but also promote the particle erosion resistance of the insulation material by enhancing the strength of the char layer.