Temperature, conversion, and phase separation profiles during mold cure of a modified vinyl-ester resin

Abstract

In this work, morphological differences over the thickness of modified vinyl-ester (VE) samples are studied. A thermodynamic analysis based in the Flory-Rehner theory is proposed to evaluate the spinodal decomposition temperature evolution during the reaction. This model takes into account changes in (styrene-co-VE) copolymer composition and binary interaction parameters with conversion. Then, from the energy and mass balance equations, temperature and conversion profiles over the thickness as a function of reaction time are calculated. Combining these profiles with the proposed thermodynamic model, spinodal decomposition conversion graphs are constructed. To verify model predictions, a synthesized VE resin was modified with 7.5 wt% of poly(butadiene-co-acrylonitrile) vinyl terminated (VTBN) elastomer and then cured in molds of 3, 7, 12, and 20 mm thickness at 80°C. Fracture surfaces were observed by scanning electron microscopy showing morphological differences over thickness, which can be explained from the results obtained from the simulation.