Antiplasticization in the Slightly Plasticized Poly(vinyl chloride)

The dynamic mechanical moduli of slightly (0—16wt%) plasticized poly(vinyl chloride) were measured by the method of free damped oscillation in the temperature range from −180 to +100°C. The added plasticizers are tricresyl phosphate (TCP), butyl benzyl phthalate (BBP), dioctyl phthalate (DOP), dibutyl sebacate (DBS) and dioctyl sebacate (DOS). Two dispersion regions (α and β) are observed in the case of poly(vinyl chloride) and they are influenced by addition of plasticizers. The α-dispersion shifts to the lower temperature side and broadens with increasing plasticizer content. These effects are mainly dependent upon the plasticizer species, and of the above plasticizers their plasticizing ability decreases in the order of DOS> DBS> DOP> BBP> TCP. The β-dispersion, whose activation energy was estimated to be 14.3 kcal/mol, first begins to disappear from the higher temperature side with increasing plasticizer content and ultimately vanishes. This effect scarcely depends upon the plasticizer species.Young’s moduli of these samples were measured at −20— +40°C from observing the tensile stress relaxation. The modulus vs. plasticizer content curve shows a maximum. This is an example of “antiplasticization.” The ability of additives to provoke antiplasticization decreases in the reverse order of plasticizing ability, that is, in the order of TCP> BBP> DOP> DBS> DOS.