Investigations Of Structure And Properties In Polycarbonate/Poly(Butylene Terephthalate) Blends

The influence of transesterification inbihitors and MMA-co-GMA copolymers on the properties of PBT/PC blends was investigated separately. At the same time, the properties of PBT-b-PC copolymers formed due to transesterification between PBT and PC was studied. The results are as follows:(1) The inhibited transesterification in PBT/PC blends by ammonium polyphosphate (APP), sodium pyrophosphate (SPP) and triphenyl phosphate (TPP) was investigated. The results show that with the increase of blending time, the degree of transesterification reaction increases, which decreases the crystallization ability and induces lower crystallization temperature for the PBT phase. The result of DMA indicates the phase separation takes place for the PBT and PC due to the addition of phosphate compounds. The FTIR. proves the phosphate compounds can’t inhibit the transesterification reaction completely. The impact strength of the blends increases with the addition of inhibitors.(2) The properties of PBT-b-PC copolymers were investigated in detail. X-ray diffraction results shows the PC blocks have not changed the crystal type and growing direction, but decreased the crystallinity. The non-isothermal crystallization results of DSC shows the Tc shifts to lower temperature with the increase of cooling rate. The PC blocks acts as nucleator and improves the crystallization temperature of PBT. PLM results indicate that PC can affect the crystal morphology and decreases the size of spherical crystalline. The TGA results show the thermal decomposition temperature of PBT is improved due to the PC blocks. The dissolution experiment indicates the PBT-co-PC copolymers are much easier to solve than PBT.(3) The compatibilization of MMA-co-GMA on the PBT/PC blends was studied. The chemical reactions between PBT and epoxy groups and the good miscibility between PC and PMMA phase are responsible for the excellent compatibilization effect. The MMA-co-GMA decreases the melting and crystallization temperature of the PBT phase in the PBT/PC blends. DMA result shows the exchange reactions are inhibited due to the compatibilization reactions since the consumption of carboxyl/hydroxyl end groups of PBT phase. MMA-co-GMA copolymers decrease the phase domain size of the PBT/PC blends, and with the increase of GMA content in the MMA-co-GMA copolymers, the blends change from a double continuous phase to a single continuous phase structure. Tensile test indicates that the yield stress, elongation at break and elastic modulus of the PBT/PC blends increase due to the addition of MMA-co-GMA. The impact strength of the blends changes not obviously.