Effect of composition of SAN copolymer on the miscibility of PVC/ABS blends

A series of ABS graft copolymers and SAN copolymers with different acrylonitrile (AN) contents were synthesized with emulsion copolymerization technique. By melt blending these copolymers with PVC resin and di-isooctyl phthalate (DOP), PVC/ABS, PVC/SAN, PVC/ABS/DOP and PVC/SAN/DOP blends were prepared. The miscibility and morphology of the blends were investigated by using dynamic mechanical analysis (DMA), TEM and SEM. It is found that in all cases PVC and ABS are immiscible for SAN copolymer with different AN contents. When AN content is less than 23.4% in SAN copolymers, a single tan delta peak over room temperature in DMA detection is found because of the introduction of DOP in the PCV/ABS blends, but the morphological observations show that the PVC and SAN copolymer are immiscible and the phase domain size of the blends intensively depends on the AN content of SAN copolymers in ABS graft copolymers. When the AN content of SAN copolymer is 23.4 % the size of phase domain in the blends is the smallest.