Cardanol-Based Epoxy Flexibilizers for Inhibition of Composite Propellants

Five epoxy flexibilizers based on cardanol, epichlorohydrin, and several glycols have been synthesized. These have been characterized for epoxide equivalent, number-average molecular weight (M n), and viscosity, and their structures have been established with the help of IR and NMR. The flexibilizing effect of these flexibilizers on the properties of novolac epoxy resin has been studied by preparing different formulations of flexibilizers and Dobeckot E-4 (in different proportions) and curing them with the polyamide hardner EH-411. The resulting cured specimens have been characterized for tensile strength, percent elongation, nonexplosive plasticizer (emolein) absorption, heat resistance, Oxygen Index, brittle temperature, and thermal conductivity. Based on the data for various characteristics, Formulation 7 (Flexibilizer 1:Dobeckot E-4: Hardner EH-411, 1:2:1.5) has been selected for inhibition and static evaluation of composite rocket propellants at ambient, hot, and cold temperatures. The nature of the p-t profiles suggest that Formulation 7 with 30% filler is a potential inhibition system for composite propellants.