MICROHARDNESS OF CONDENSATION POLYMERS AND COPOLYMERS - 2 - POLY(ESTER ETHER CARBONATE) THERMOPLASTIC TERPOLYMERS

The number of phases, transition temperatures, and microhardness of a series of poly(ester ether carbonate) (PEEC) multiblock terpolymers wi th poly(butylene terephthalate) (PET) hard segments have been investig ated as a function of ether/carbonate (EC) soft-segment composition at constant PET content. The polymerization degree of PET and the intrin sic viscosity of the terpolymers were determined by viscosimetry. The degree of crystallinity, long spacing, glass transitions T-g, and melt ing temperature were derived by means of x-ray diffraction, dynamic me chanical thermal analysis (DMTA), and differential scanning calorimetr y (DSC) measurements. Surface mechanical properties were studied by mi croindentation tests. It was found that the terpolymer consists of two amorphous (EC and PET) phases and one crystalline (PET) phase. The T- g value of PET does not depend on the chemical composition of the soft segments, in the contrast to the T-g of the soft-segment amorphous ph ase. Introduction of polycarbonate moities in the soft segments induce s an increase of T-g by 50 degrees C without formation of an additiona l (third) amorphous phase. The reduced crystallizability of PET hard s egments (by;a factor of 3) is explained by this decrease of flexibilit y of the soft segments, which also causes a twofold reduction in the m icrohardness values. The dominating contribution of crystallinity to t he microhardness is shown. However, the much lower measured overall mi crohardness in contrast to the one calculated by means of the additive law is explained by the plasticizing effect of the soft amorphous pha se, This assumption is in agreement with the structure model derived f rom the small-angle x-ray (SAXS) and wide-angle x-ray (WAXS) data.