Phase morphology of polyblends of amorphous polycarbonate and semi-crystalline polyethylene terephthalate

Phase morphology, state of compatibility and various properties of blends of polycarbonate (PC) with bottle-grade and fibre-grade polyethylene terephthalate (BPET and FPET, respectively) were investigated. It was found that these blends have two-phase separated morphology with partial miscibility. Scanning electron micrographs revealed separated domains of PC-rich and PET-rich zones. PC domains appear spherical increasing in size from 2 mum for PC20/FPET80 up to about 5 mum for PC60/FPET40 blend. Further increase in PC content up to 80% caused phase inversion in which FPET appears as finely dispersed domains in continuous PC matrix. T-g of PC-rich phase decreased from 153 degreesC for pure PC down to 140 degreesC for PC20/BPET80. Similar trend was observed in PC/FPET blends. Also, T-g of BPET-rich blend increases from 90 degreesC for pure BPET up to 98 degreesC for PC60/BPET40. Melting temperature of PET remains practically unchanged with partial compatibility of the blends. Tensile modulus, yield strength and impact resistance of the blends conform to an additive blend properties. Blends show good chemical resistance properties. Viscosity ratio of PC to PET was about 4 to 6, suggesting ease of PC/PET processing in manufacturing process.