Solubility and diffusivity measurements in nitrogen–poly(vinyl acetate) and nitrogen–toluene–poly(vinyl acetate) systems with the differential pressure decay technique

Abstract

ABSTRACT:In creating thin films of polymers by solution processing, a common problem is the undesirable formation of bubbles during the drying process. Practical experience shows that bubbles can be created well below the boiling point of the solvent. Also, it has been observed that the degassing of the polymer solutions results in reduced bubble formation, and this indicates a relationship between the presence of air and bubble formation. This work is based on the hypothesis that if the solubility of air in the polymer solution increases with the solvent concentration, then the solution can become supersaturated with air as the concentration of the solvent is reduced during the drying process. To test this hypothesis, knowledge of the thermodynamics of the mixture is required. This study concentrated on the system of poly(vinyl acetate), toluene, and nitrogen. A thermodynamic model to predict phase behavior of this system was developed. The solubility of nitrogen in poly(vinyl acetate) and poly(vinyl acetate)-toluene as a function of the toluene composition over wide ranges of temperatures and pressures was measured with the pressure decay technique. The group-contribution lattice-fluid equation of state was employed to correlate the thermodynamic behavior of the binary and ternary systems. In addition, experiments were conducted to measure the diffusion coefficients of the nitrogen in poly(vinyl acetate).

Predicting the solubility of gases, vapors, and supercritical fluids in amorphous polymers from electron density using convolutional neural networks

“…The dataset comprises 14 808 experimental or derived data points from 257 sources, 17,64–318 featuring 102 polymers and 79 solvents/gases, which together form 497 polymer–gas pairs. A total of 256 unique chemical compounds were considered, accounting for different repeating units of the same polymer, with 2462 unique conformers.…”

Mechanism of bubble formation in the drying of polymer films

“…To model the drying, knowledge of the vapor‐liquid equilibria of the binary and ternary mixtures is necessary. In a previous publication1 solubility and diffusion data for the relevant systems were obtained by the pressure decay method over ranges of temperature and concentration. The solubility data were correlated using the group‐contribution, lattice‐fluid equation of state (GCLF‐EoS) 2.…”

“…(2) determines D 02 and ξ 23 . By applying the free‐volume parameters for poly(vinyl acetate) from Table I and diffusivity data from Pourdarvish et al,1 these two parameters are calculated as: where, D and D are the diffusion coefficients at different temperatures. As a check on the experimental data, the parameter ξ 23 was also estimated from the Sugden group‐contribution method 8.…”

“…(2) determines D 02 and n 23 . By applying the free-volume parameters for poly(vinyl acetate) from Table I and diffusivity data from Pourdarvish et al, 1 these two parameters are calculated as:…”