A lightweight rubber foaming insulation reinforced by carbon nanotubes and carbon fibers for solid rocket motors

The development of lightweight insulation materials has become one of the effective ways to improve the performance of solid rocket motors (SRMs). In this paper, porous structure was introduced into ethylene propylene diene monomer (EPDM) insulation materials through rubber foaming technology to prepare lightweight insulation materials. The influence of foaming agent content and pre-curing temperature on morphology and properties of EPDM rubber foams were investigated. With the increase in pre-curing temperature, the cell size decreases significantly and the cell becomes more uniform, resulting in an increase in mechanical properties. As the foaming agent content increases, the cell density increases gradually without significant change in cell diameter. Meanwhile, the mechanical properties of insulation materials gradually decrease. EPDM rubber foams have optimum ablation resistance when the pre-curing temperature is 120 °C and the content of foaming agent is 6phr. Its charring ablation rate is 0.186 mm/s, only increasing by 16% compared with that of basic formula. On this basis, carbon nanotubes (CNTs) and carbon fibers (CF) were added to reinforce EPDM rubber foams. The tensile strength of the reinforced formula increases by 36.4% compared to the foaming formula, which is 19.2% lower than that of the basic formula. The charring rate of the reinforced formula decreases by 35.5% compared to the foaming formula, which is only 5.3% higher than that of the basic formula.