Evaluation of the effects of biobased plasticizers on the thermal and mechanical properties of poly(vinyl chloride)

Blends were prepared of poly(vinyl chloride) (PVC) with four different plasticizers; esters of aconitic, citric, and phthalic acids; and other ingredients used in commercial flexible PVC products. The thermal and mechanical properties of the fresh products and of the products after 6 months of aging were measured. Young's modulus of the PVC blends was reduced about 10-fold by an increase in the plasticizer level from 15 to 30 phr from the semirigid to the flexible range according to the ASTM classification, but a 40-phr level was required for PVC to retain its flexibility beyond 6 months. At the 40-phr level, tributyl aconitate performed better than diisononyl phthalate (DINP) or tributyl citrate, in terms of lowering Young's modulus, both in the fresh materials and those aged for 6 months. The effects of the four plasticizers on the glass-transition temperature (T-g) were similar, with T, close to ambient temperature at the 30- and 40-phr levels in freshly prepared samples and at 40-60 degrees C in those aged for 6 months. The thermal stability of the PVC plasticized with DINP was superior among the group. Overall, tributyl aconitate appeared to be a good candidate for use in consumer products where the alleged toxicity of DINP may be an issue. (c) 2006 Wiley Periodicals, Inc.