Novolac epoxy resins have recently been reported for inhibition of hydroxy terminated polybutadiene (HTPB) based composite propellants and their elongation has been improved by the incorporation of some flexibilizers. In the present investigation, curing behaviour of a novolac epoxy resin (Dobeckot E4) by hardeners (polyamide EH 411 and polyamine H 758) in conjunction with a polysulphide flexibilizer has been studied using infrared (IR) spectroscopy. It is observed that the rate of curing of Dobeckot E4 by hardeners such as hardener EH411 and hardener H 758, is higher as compared to polysulphide flexibilizer LP-33. Further, rate of curing of epoxy resin by hardeners such as EH411 and H758 enhances in the presence of flexibilizer LP-33. The curing studies by infrared (IR) spectroscopy suggest that har4deners EH411/H758 react with epoxy ring of epoxy resin and as a result, epoxy ring opens while curing. Similarly, - SH group of polysulphide flexibilizer LP-33, reacts with the epoxy ring of resin and opens it as curing progresses and thus enhances the rate of curing of epoxy resin in conjunction with hardeners EH411/H758. This is also supported by the gel time and exotherm peak temperature data.
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