Phase separation in semicrystalline blends of poly(phenylene sulfide) and poly(ethylene terephthalate). II. Effect of poly(phenylene sulfide) homopolymer solubilization of PPS-graft-PET copolymer on morphology and crystallization behavior

The morphology and crystallization behavior of poly(phenylene sulfide) (PPS ) and poly(ethylene terephthalate) (PET) blends compatibilized with graft c opolymers were investigated. PPS-blend-PET compositions were prepared in wh ich the viscosity of the PPS phase was varied to assess the morphological i mplications. The dispersed-phase particle size was influenced by the combin ed effects of the ratio of dispersed-phase viscosity to continuous-phase vi scosity and reduced interfacial tension due to the addition of PPS-graft-PE T copolymers to the blends. In the absence of graft; copolymer, the finest dispersion of PET in a continuous phase of PPS was achieved when the viscos ity ratio between blend components was nearly equal. As expected, PET parti cle sizes increased as the viscosity ratio diverged from unity. When graft copolymers were added to the blends, fine dispersions of PET were achieved despite large differences in the viscosities of PPS and PET homopolymers. T he interfacial activity of the PPS-graft-PET copolymer appeared to be relat ed to the molecular weight ratio of the PPS homopolymer to the PPS segment of the graft copolymer (M-H/M-A). With increasing solubilization of the PPS graft copolymer segment by the PPS homopolymer, the particle size of the P ET dispersed phase decreased. In crystallization studies, the presence of t he PPS phase increased the crystallization temperature of PET. The magnitud e of the increase in the PET crystallization temperature coincided with the viscosity ratio and extent of the PPS homopolymer solubilization in the gr aft, copolymer. (C) 2000 John Wiley & Sons, Inc.