The effect of a comonomer, methyl methacrylate (MMA), on volume shrinkage and residual styrene content of an unsaturated polyester (UP) resin with low profile additives (LPAs) cured at low temperature was investigated by an integrated reaction kinetics-morphology-property analysis. MMA affects the volume shrinkage and residual styrene content differently depending on MMA to styrene (St) C=C bond molar ratio. At low MMA/St ratio, residual styrene decreases and the volume shrinkage of the resin system remains unchanged. At high MMA/St ratio, residual styrene can be substantially reduced, but the resin system suffers poor volume shrinkage control. Reactivity of the comonomer MMA and its compatibility to other components in the resin system can explain the observed results. A series of Seemann composites resin infusion molding process (SCRIMP) were conducted to study the relationship among materials, processing, and properties of molded composites in low temperature curing processes. (C) 2003 Elsevier Science Ltd. All rights reserved.