Microhardness of condensation polymers and copolymers .1. Coreactive blends of polyethylene terephthalate and polycarbonates

The microhardness of coreactive blends of polyethylene terephthalate (PET) and bisphenol A polycarbonate (PC) was investigated over the whole range of compositions. The occurrence of one single glass transition temperature (T-g) step in the differential scanning calorimetry (DSC) curves indicated that intensive chemical interactions had taken place during melt blending, resulting in formation of copolycondensates with dominating random sequential order. The parallel decrease of microhardness (H) and of T-g with increasing PET content in the blends has been ascribed to the formation of new copolymer molecules enriched in the component characterized by lower H and T-g values. It is emphasized that such noncrystallizable copolymers offer the possibility to evaluate the intrinsic contribution of the repeating units to the H and T-g characteristics of copolymers with various compositions and sequential orders.