Vapor−Liquid Equilibria of Water, Methanol, and Methyl Acetate in Poly(vinyl acetate) and Partially and Fully Hydrolyzed Poly(vinyl alcohol)

Abstract

A general procedure has been developed to predict the vapor−liquid equilibria (VLE) of solvent/copolymer systems with the Panayiotou and Vera equation of state (PV-EOS), using binary interaction parameters deduced from homopolymer VLE data. Mixing rules are proposed for the PV-EOS pure-component parameters and homopolymer−solvent binary interaction parameters in order to predict solvent solubilities in copolymer systems. This methodology has been evaluated with VLE data acquired in this study for water, methanol, and methyl acetate in poly(vinyl acetate), poly(vinyl alcohol), and a copolymer comprised of these two homopolymers containing 88% (molar) poly(vinyl alcohol) repeat units. The predictions from the PV-EOS of the copolymer VLE are in excellent agreement with our experimental data.

Solvent‐induced crystal formation in polymers: Experimental studies and theoretical modeling of poly(vinyl alcohol) based on free‐volume concepts

“…The poly(vinyl) alcohol‐water system was used to illustrate the adequacy of the model. The details of the diffusion and solubility behavior in PVOH have been published previously . The free‐volume parameters used to describe the concentration and temperature dependencies of the mutual diffusion coefficient and polymer chain mobility are listed in Table .…”

Diffusion of solvents in poly(vinyl acetate) and partially and fully hydrolyzed poly(vinyl alcohol)

“…In most cases the available data were regressed for values of D 0 and ξ but in a few cases a value for E was also needed to obtain good correlations. The Flory–Huggins interaction parameter χ was calculated from the solubility data of Palamara et al . All the input data and the regressed parameters are given in Table .…”

“…As discussed by Palamara et al ., crystallinity in the PVAc − PVOH system is an important issue as it affects the solubility and should be expected to affect the diffusivity. There is general consensus that the solvents do not enter the crystalline phase, although the definition of what is a true crystal phase and what is the intermediate phase between a crystal and the truly amorphous phase is questionable.…”

“…The solubility and diffusivity of water, methanol and methyl acetate are of particular interest in the use and production of these polymers. Palamara et al 1 have provided extensive data on the solubility for these systems. In this paper the diffusivities of the same solvents in the same polymers are reported and analyzed.…”

“…Some researchers have reported, for example, that water will not change the crystal structure of PVOH 2 while others have found spectroscopic and X-ray diffraction evidence that there is some dissolution of PVOH in the presence of water. 3,4 Palamara et al 1 suggest that these differences are due to variation in the pretreatment of the PVOH before the measurements. As a result it was recommended that a harsh annealing procedure be used in preparing the polymers for study.…”