Curing kinetics of pre-crosslinked carboxyl-terminated butadiene acrylonitrile (CTBN) modified epoxy blends

The purpose of this study is to investigate the curing kinetics of neat and pre-crosslinked or non-crosslinked carboxyl-terminated butadiene acrylonitrile liquid rubber (CTBN) toughened epoxies cured with isophorone diamine (IPDA) using non-isothermal and isothermal differential scanning calorimetry. The results show that CTBN has a complex effect on the curing process of epoxy/IPDA systems. The carboxyl groups of CTBN can accelerate the curing reactions, while the phase-separated CTBN particles and the dilution of curing ingredients caused by CTBN addition can hinder the curing reactions, resulting in an increase in activation energy. Interestingly, the activation energy of pre-crosslinked CTBN/epoxy systems decreases compared to their non-crosslinked counterparts because of the enhanced curing effect of the benzoic acid produced by benzoyl peroxide (BPO). An autocatalytic Kamal's model is successfully used to describe the curing process of epoxy systems studied.