Nonisothermal cure kinetics and diffusion effect of liquid‐crystalline epoxy sulfonyl bis(1,4‐phenylene)bis[4‐(2,3‐epoxypropyloxy)benzoate] resin with aromatic diamine

Abstract

AbstractThe curing kinetics of the liquid‐crystalline epoxy resin sulfonyl bis(1,4‐phenylene)bis[4‐(2,3‐epoxypropyloxy)benzoate] with 4,4′‐diaminodiphenylsulfone was investigated by nonisothermal differential scanning calorimetry. The relationship between the apparent activation energy (Ea) and the conversion was determined, and the effects of the molecular structure and the order of liquid crystallinity on Ea are discussed in detail. Some parameters were evaluated with the autocatalytic kinetic model of the Šesták–Berggren (S–B) equation. The results show that there were some deviations of these simulation curves from the experimental curves at high heating rates and in the late stage of the curing reaction. The diffusion effect in the nonisothermal curing reaction is discussed, and a diffusion factor was proposed and introduced into the S–B equation. Then, a modified S–B equation was created, as follows: ${{d\alpha } \over {dt}} = K\alpha ^m (1 - \alpha )^n \times {1 \over {1 + \exp \left[ {C\left( {\alpha - \alpha _c } \right)} \right]}}$, where α is the conversion, t is the time, m and n are reaction orders, K is rate constant, C is the diffusion coefficient, and αc is the critical conversion. The theoretical simulation curves agreed very well with the experimental data as determined with the modified S–B equation, which may be more useful for describing and predicting the nonisothermal curing reaction kinetics of epoxy resin. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012