AbstractPolycarbonate blends with poly(ε‐caprolactone) were prepared by both melt‐blending and solution‐blending techniques, and the properties of these blends were studied by thermal analytical and dynamic mechanical testing methods. Each blend composition was found to have a single glass transition temperature, and the temperature location of this transition was found to be a function only of blend composition and to be independent of the blending technique employed. This behavior led to the conclusions that these two polymers form blends containing a single amorphous phase comprised of the two materials and that this miscible phase results primarily from physical rather than chemical interactions between the two polymers. A reversible liquid‐liquid‐type phase separation was found to occur when the blend system was heated to high melt temperatures. The temperature required for phase separation, the lower critical solution temperature, was found to vary with blend composition and component molecular weight in the manner expected from thermodynamic considerations. The level of crystallinity of poly(ε‐caprolactone) was affected by the presence of the polycarbonate. The polycarbonate also crystallized to an appreciable extent in many
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