Polyester–Polycarbonate blends. III. Polyesters based on 1,4-cyclohexanedimethanol/terephthalic acid/isophthalic acid



Melt blends of polycarbonate with Kodel, a homopolyester formed from 1,4-cyclohexanedimethanol and terephthalic acid, and with Kodar, a copolyester formed by replacing some of the terephthalic acid with isophthalic acid, were prepared and their transitional behavior were examined by thermal analysis and dynamic mechanical testing. Blends formed with either polyester were found to have a single Tg over the entire compositional range. Single composition-dependent α- and β-relaxation temperatures were also observed for blends made with either polyester at all compositions. From these data it is concluded that both Kodel and Kodar blends with polycarbonate form miscible amorphous phases. The role of ester–carbonate interchange reactions during melt mixing was experimentally examined and found to be unimportant, from which it is concluded that the observed miscible phase formation is due to physical interactions between the blend components.