Kinetics of water vapor diffusion in plasticized poly(vinyl chloride)
摘要
Kinetics of water vapor diffusion in poly(vinyl chloride) (PVC) plasticized with di-(2-ethylhexyl)phthalate and epoxidized linseed oil and without plasticizer were monitored as a function of plasticization level and diffusion temperature. Water absorption by the polymer was monitored using thermogravimetric analysis at temperatures between 303 and 343 K. Water diffusion coefficients were obtained by comparison of experimental data with series solution of Fick’s equation for diffusion kinetics in a uniform cylindrical solid. The deduced diffusion coefficients ranged from 2.10 × 10–7 cm2 s−1, in PVC with Tg = 274.2 K at 303 K, to 21.0 × 10–7 cm2 s−1, in PVC with Tg = 266.0 K at 343 K. Temperature dependence of coefficients of water vapor diffusion in PVC was obtained for several levels of plasticization. The activation energies of water vapor diffusion ranging from 20.4 kJ mol−1 to 43.5 kJ mol−1 were obtained. The activation energy decreased with the increase in the concentration of plasticizer and consequent decrease in the PVC glass transition temperature. Linear compensation effect was established for water vapor diffusion in PVC, and water diffusion activation entropies values were deduced.
Graphical Abstract