Effect of lewis acids on cure kinetics and mechanical properties of hydroxyterminated polybutadiene polymers

The effect of two Lewis acids, viz. BF 3 and AlCl 3 on the cure reaction of hydroxy‐terminated polybutadiene: toluene diisocyanate systems has been studied in order to evaluate them as possible pot‐life extenders in solid propellant formulations. The enthalpy of the cure exotherm, evaluated from DSC curves, did not show any dependence on the concentration of the two acids. The kinetic parameters for the cure reaction showed an increase in both cases indicating the effectiveness of the acids as reaction retardants. However, BF 3 is not a suitable candidate for pot‐life extension, because of its adverse effect on the elongation at break of the cured HTPB samples. The coefficient of thermal expansion is unaffected by the two additives, probably because of their negligible influence on the cross‐link density of the cured network.