The phase diagram of a ternary system of PVDF

dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) was determined in terms of a pseudo binary system with the same polymer concentration and different DBP content in diluent mixture. The experimental results showed that as the DBP content increased in diluent mixture

the phase separation changed from liquid-liquid phase separation to solid-liquid phase separation

and both the cloudy point for L-L phase separation and crystallization temperature shifted to lower temperature. Molar excess free energy of mixing △GE implying the estimated interaction between PVDF and diluent mixture was characterized to explain the features in the phase diagram. The effects of DBP content in diluent mixture on crystallization behavior and phase separated structure were investigated. The crystallization of PVDF in system with L-L phase separation was perfect

but the crystallinity was lower relative to the system with only S-L phase separation. The phase separated structures can be controlled successfully by varying the DBP content in diluent mixture as the cooling conditions kept constant.