Cure behavior of ethylene propylene diene terpolymer insulation for large composite rocket motor casing

Abstract Two potential formulations of sulfur cured ethylene propylene diene terpolymer (EPDM) insulation were characterized against the proven insulation based on nitrile rubber (NBR) in the earlier study. Unlike the proven insulation, the cure behavior exhibited by sulfur cured EPDM is quite different in that, the rheometer curves exhibit marching behavior even at elevated temperature for longer duration (160°C for 7 h; most severe condition). This warranted extensive cure study at different temperatures for varying durations in order to determine the optimum cure condition. The methodology adopted to find out the optimum cure condition and corroboration of the same in terms of instrumental techniques (differential scanning calorimetry, thermogravimetric analysis, and Fourier transform infrared), which are quite interesting, are discussed in this article.