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Extension of the pot life for hydroxyl‐terminated polybutadiene (HTPB) based propellant binder systems was attempted through employing a bicurative system comprising of toluene‐di‐isocyanate (TDI) and isophorone‐di‐isocyanate (IPDI). Pot life characteristics were studied through evaluating curing kinetics for the HTPB‐bicurative binder formulations. Curing kinetics were studied through viscosity buildup during the cure reaction and estimation of the rate constants for viscosity build‐up. Introduction of IPDI slowed down the curing process, but at the same time, has not adversely affected the mechanical characteristics. One of the discouraging factors in adopting IPDI as curative is the poor interface characteristics between liner and insulator of the solid propellant grains, and it has been proposed that the root cause for the same is the permeation of IPDI through the insulator. Quantification of such permeation was attempted from the numerical values for cross‐link density evaluated for various binder compositions. Remedy for poor interface characteristics is suggested in this study.

A microstructure analysis is carried out to optimize the process parameters of a randomly oriented discrete length hybrid carbon fiber reinforced carbon matrix composite. The composite is fabricated by moulding of a slurry into a preform, followed by hot-pressing and carbonization. Heating rates of 0.1, 0.2, 0.3, 0.5, 1, and 3.3°C/min and pressures of 5, 10, 15, and 20 MPa are applied during hot-pressing. Matrix precursor to reinforcement weight ratios of 70:30, 50:50, and 30:70 are also considered. A microstructure analysis of the carbon/ carbon compacts is performed for each variant. Higher heating rates give bloated compacts whereas low heating rates give bloating-free, fine microstructure compacts. The compacts fabricated at higher pressure have displayed side oozing of molten pitch and discrete length carbon fibers. The microstructure of the compacts fabricated at low pressure shows a lack of densification. The compacts with low matrix precursor to reinforcement weight ratios have insufficient bonding agent to bind the reinforcement whereas the higher matrix precursor to reinforcement weight ratio results in a plaster-like structure. Based on the microstructure analysis, a heating rate of 0.2°C/min, pressure of 15 MPa, and a matrix precursor to reinforcement ratio of 50:50 are found to be optimum w.r.t attaining bloating-free densification and processing time.