Thermal behavior of core-shell rubber/styrene monomer gels

The thermal behavior of core-shell rubber (CSR)/styrene monomer mixtures wa s studied using subambient differential scanning calorimetry (DSC). Interac tion between the styrene and CSR material was observed as a depression of t he freezing and melting points of the styrene monomer and as a shift in the glass transition temperature of the rubbery phase in the CSR materials. Th e depression of the freezing point of the styrene in the CSR/styrene mixtur es was related to the size of the critical nuclei required for crystallizat ion. The heat of crystallization was found to decrease linearly with decrea sing styrene content, but calculations showed that not all of the styrene p resent in the mixtures crystallized upon cooling, confirming that there was an interaction between the CSR material and the styrene monomer. At temper atures below the glass transition temperature of the system, the mixtures c ontain a pure styrene crystalline phase and an amorphous CSR/styrene phase. The styrene was found to act as a plasticizer, reducing the glass transiti on temperature of the rubbery core material. The variation of the glass tra nsition temperature of the CSR/styrene systems was determined with respect to the composition of the amorphous phase. (C) 2000 John Wiley & Sons, Inc.