Investigation of the Diffusion of Di-n-hexyl Phthalate in Rubbery Poly(vinyl Chloride) Using Electrical Impednace Spectroscopy

Document Type

Article

Publication Date

5-25-1992

Department

Polymers and High Performance Materials

Abstract

Electrical impedance spectroscopy was used to monitor the diffusion of the plasticizer di-n-hexyl phthalate in poly(vinyl chloride) films above the glass transition temperature. In the isothermal experiment, the initial plasticizer concentration was greatest at the film surfaces and lowest in the middle and then readjusted toward a more uniform profile across the film thickness as the system moved toward equilibrium at constant plasticizer content. Curves of the imaginary part of the complex impedance vs frequency, at constant temperature, show peaks that shift to higher frequencies with increasing diffusion time. The frequency at peak maximum increased linearly with diffusion time at constant temperature. Plots of imaginary vs real parts of the complex impedance appear as well-defined depressed semicircles from which a distribution-of-relaxation-times parameter can be extracted. Altogether, the results reflect an average increase in polymer chain segmental mobility as well as a decrease in microstructural heterogeneity owing to a redistribution of the free volume throughout the sample as the plasticizer advances from the surfaces toward the middle of the film.

Publication Title

Macromolecules

Volume

25

Issue

11

First Page

2869

Last Page

2874

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