Effects of poly(vinyl acetate) and poly(vinyl chloride-co-vinyl acetate) low-profile additives on properties of cured unsaturated polyester resins.: I.: Volume shrinkage characteristics and internal pigmentability

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. (C) 2003 Wiley Periodicals, Inc.