THE CRYSTALLIZATION OF POLY(BUTYLENE TERE PHTHALATE)(PBT) AND POLYCARBONATE (PC) IN THE POLYMER BLEND PBT PC/

The crystallization behavior of PBT as well as PC is changed in the co ntrolled-processed blend due to intermolecular interactions between th e different macromolecules in molten state. If the kinetics of the cry stallization process prevents a crystallization-induced separation, th e partial miscibility of the amorphous phases, measured by the glass t ransition temperatures, will lead to a decrease of the crystallinity o f PBT. The crystallinity, normalized to the concentration of PBT in th e blend, is independent from the concentration of PC at low cooling ra tes. At high cooling rates, PBT is crystallizing stepwise in the blend PBT/PC 40/60 wt.-%. The crystallization temperature in the anisotherm ic crystallization process is increased at low contents of PC due to a changed nucleation mechanism. The half-time of crystallization is inc reasing in blends with an increasing PC-content in isothermic crystall ization experiments. The normally amorphous PC crystallizes considerab ly fast in presence of PBT in PC-rich blends. The crystallization or c hange in the state of order of PC was measured in situ by X-ray diffra ction. Calorimetric experiments confirm this result and allow a quanti tative estimation of the PC-crystallinity, which amounts to some 20% i n the blend PBT/PC 5/95 wt.-%.