A MORPHOLOGICAL-STUDY ON THE PLASTICIZATION OF POLY(VINYL CHLORIDE) BY DIETHYLHEXYL SUCCINATE AND DIBUTYL PHTHALATE

The effects of different plasticizers on the structural features of PV C were investigated. Particular emphasis was on the fine structure as denoted by small-angle X-ray scattering (SAXS). The influence of plast icizer content on the mechanical response was followed by dynamic mech anical spectroscopy. The particular plasticizers investigated principa lly were diethylhexyl succinate and dibutyl phthalate, although other phthalate plasticizers were investigated including dibutyl succinate a nd dibutyl sebacate. It was noted that structural features at the 100- to 200-angstrom level were systematically influenced by the type and amount of plasticizer and in particular by its solubility parameter. T o account for the observed behavior, a model was proposed which specul ates that the absorption of plasticizer is nonuniform within the syste m and in particular within the local regions where crystallites exist. The level of swelling of plasticizer into the amorphous regions at so me distance from the crystallites is different (and greater) than that in disordered regions near the crystallites. This degree of differenc e in swelling, however, is dependent upon the solubility parameter of the plasticizer. This model, which is in general support of an earlier model, also helps to account for the large difference in temperature- dependent dynamic mechanical behavior introduced by the different plas ticizer species.