Characterization of thermoset cure behavior by differential scanning calorimetry. Part II: Effects of low‐profile additives

Abstract An autocatalyzed second‐order kinetic model was adopted to compare the isothermal and dynamic cure behavior of low‐profile polyester resins in terms of kinetic parameters such as degree of cure, cure rate, half‐life, onset cure temperature, reaction order, and Arrhenius parameters. The reaction orders of low‐profile unsaturated polyesters appear to be almost independent of isothermal cure temperatures. The ultimate conversion, conversion at peak maximum, onset cure temperature, and Arrhenius parameters of polyesters are only slightly affected by the concentration and type of low‐profile additives in the resins. Low‐profile additives, in general, tend to retard the cure rate and suppress the exothermicity of polyester resins because of dilution effects. For low‐profile additives such as poly(vinyl acetate) and polyurethane, which are “quite” compatible with polyesters before cure, the overall reaction rates of the resins are substantially enhanced over those of less compatible additives. However, the ultimate conversion of low‐profile polyesters is found to be slightly greater than that of neat polyester, in most cases.