Effects of Solvent Molecular Structure on Diffusion through Plasticized Poly(vinyl chloride) Films

Diffusion of organic
solvents in plasticized poly­(vinyl chloride)
(PVC) films is industrially significant for inkjet-printed PVC graphic
displays, but comprehensive research on the mechanism of solvent diffusion
in such systems is lacking. This study employs two easy-to-implement
experimental techniques for diffusion measurement and reports on both
the steady-state and non-steady-state diffusivities of 20 industrially
relevant organic solvents, spanning five chemical moieties, in a commercial
PVC base film. To better understand the trends in diffusivity values
with solvent properties, the diffusivity was compared to multiple
kinetic mobility and thermodynamic diffusion models. Kinetic mobility
parameters representing molecular size and shape were found to be
good predictors of diffusivity in this study. In contrast, the thermodynamic
Hansen solubility parameters from the solvent and PVC were shown to
be a less robust predictor of the diffusivities. Molecular weight,
van der Waals volume, and vapor pressure were identified as the best
performing predictors that also have distinct merits for guiding industrial
practices and furthering theoretical understandings. Ultimately, the
results from this study are useful in predicting the performance of
solvents for industrial inkjet printing and in understanding the underlying
microscopic transport mechanisms.