The optimum conditions for crosslinking rigid poly(vinyl chloride) with trimethylolpropane trimethacrylate (TMPTMA) and peroxide have been examined. The extent of crosslinking was measured by determining gel content by Soxhlet extraction in tetrahydrofuran. Mechanical properties were measured at 130 degrees C and dynamic viscoelastic measurements were carried out to detect changes in the glass transition temperature (T-g). It was found that 15 phr of TMPTMA and 0.3 phr of peroxide were optimum concentrations for maximizing the extent of crosslinking, tensile strength, and T-g. The lower molding temperature of 170 degrees C was preferred to minimize thermal degradation. (c) 2006 Wiley Periodicals, Inc.