Effects of poly(methyl methacrylate)-based low-profile additives on the properties of cured unsaturated polyester resins. I. Miscibility, curing behavior, and glass-transition temperatures

The effects of three series of self-synthesized poly(methyl methacrylate) (PMMA)-based low-profile additives (LPAs), including PMMA, poly(methyl methacrylateco-butyl acrylate), and poly(methyl methacrylate-co-butyl acrylate-co-maleic anhydride), with different chemical structures and MWs on the miscibility, cured-sample morphology, curing kinetics, and glass-transition temperatures for styrene (ST) /unsaturated polyester (UP) resin/LPA ternary systems were investigated by group contribution methods, scanning electron microscopy, differential scanning calorimetry (DSC), and dynamic mechanical analysis, respectively. Before curing at room temperature, the degree of phase separation for the ST/UP/LPA systems was generally explainable by the calculated polarity difference per unit volume between the UP resin and LPA. During curing at 110degreesC, the compatibility of the ST/UP/LPA systems, as revealed by cured-sample morphology, was judged from the relative magnitude of the DSC peak reaction rate and the broadness of the peak. On the basis of Takayanagi's mechanical models, the effects of LPA on the final cure conversion and the glass-transition temperature in the major continuous phase of ST-crosslinked polyester for the ST/UP/LPA systems was also examined.