The rheological behavior and thermal properties of a poly(butyl acrylate-co-2-ethylhexyl acrylate) [P(BA-EHA)]-grafted vinyl chloride (VC) composite resin [P(BA-EHA)/poly(vinyl chloride) (PVC)] and its materials were investigated. The rheological behavior, thermal stability, and Vicat softening temperature (VST) of P(BA-EHA)/PVC were measured with capillary rheometry, thermal analysis, and VST testing, respectively. The effects of the P(BAEHA) content and the polymerization temperature of grafted VC on the rheological behavior of the composite resin were examined. The weight loss of the composite resin and its extracted remainder via heating were analyzed. The influence of the content and crosslinking degree of P(BAEHA) and the polymerization temperature of the grafted VC on VST of the materials was determined. The results indicated the pseudoplastic-flow nature of the composite resin. The flow property of the modified PVC resin was improved because of the incorporation of the acrylate polymer. The molecular weight of PVC greatly influenced the flow behavior and VST of the composite resin and its materials. The flowability of the composite resin markedly increased, and the VST of its materials decreased as the polymerization temperature of the grafted VC increased. The initial degradation temperature of the composite resin increased as the P(BA-EHA) content increased. The VST of the samples was enhanced a little as the content of the crosslinking agent increased in P(BA-EHA). As expected, the composite resin, with good impact resistance, had better heating stability and flowability than pure PVC, whereas the VST of the material decreased little with increasing P(BA-EHA) content. Therefore, P(BA-EHA)/PVC resins prepared by seeded emulsion polymerization have excellent potential for widespread applications. (C) 2004 Wiley Periodicals, Inc.