ABSTRACT: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 110°C, 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.
ABSTRACT:Three series of self-synthesized poly(vinyl acetate)-based low-profile additives (LPAs) with different chemical structures and molecular weights, including poly-(vinyl acetate), poly(vinyl chloride-co-vinyl acetate), and poly(vinyl chloride-co-vinyl acetate-co-maleic anhydride), were studied. Their effects on the volume shrinkage characteristics and internal pigmentability for low-shrink unsaturated polyester (UP) resins during cure were investigated. The experimental results were examined with an integrated approach involving measurements of the static phase characteristics of the ternary styrene/UP/LPA system, the reaction kinetics, the cured sample morphology, and microvoid formation by using differential scanning calorimetry, scanning electron microscopy, optical microscopy, and image analysis. Based on the Takayanagi mechanical model, factors leading to both good volume shrinkage control and acceptable internal pigmentability for the molded parts were explored.
ABSTRACT: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 volume shrinkage characteristics and internal pigmentability for low-shrink unsaturated polyester (UP) resins during curing were investigated by an integrated approach of static phase characteristics of the ternary styrene (ST)/UP/LPA system, reaction kinetics, cured-sample morphology, microvoid formation, and property measurements. The relative volume fraction of microvoids generated during the cure was controlled by the stiffness of the UP resin used, the compatibility of the uncured ST/UP/LPA systems, and the glass-transition temperature of the LPAs used. On the basis of the Takayanagi mechanical model, the LPA mechanism on volume shrinkage control, which accounted for phase separation and microvoid formation, and factors leading to both a good volume shrinkage control and acceptable internal pigmentability for the molded parts are discussed.
ABSTRACT:Three series of self-synthesized poly(vinyl acetate)-based low-profile additives (LPAs), including poly-(vinyl acetate), poly(vinyl chloride-co-vinyl acetate), and poly(vinyl chloride-co-vinyl acetate-co-maleic anhydride), with different chemical structures and molecular weights were studied. Their effects on the glass-transition temperatures and mechanical properties for thermoset polymer blends made from styrene, unsaturated polyester, and LPAs were investigated by an integrated approach of the static phase characteristics, cured sample morphology, reaction kinetics, and property measurements. Based on Takayanagi mechanical models, the factors that control the glass-transition temperature in each phase region of the cured samples and the mechanical properties are discussed.
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