Sorptive dilation of polysulfone and poly(ethylene terephthalate) films by high‐pressure carbon dioxide

Abstract

Dilation of polysulfone (PSUL) and crystalline poly(ethylene terephthalate) (PET) films accompanying sorption of carbon dioxide is measured by a cathetometer under high pressure up to 50 atm over the temperature range of 35–65°C. Sorptive dilation isotherms of PSUL are concave and convex to the pressure and concentration axes, respectively, and both isotherms exhibit hysteresis. Each dilation isotherm plotted versus pressure and concentration for the CO2‐PET system shows an inflection point, i.e., a glass transition point, at which the isotherm changes from a nonlinear curve to a straight line. Dilation isotherms of PET below the glass transition point are similar to those of the CO2‐PSUL system, whereas the isotherms above the glass transition point are linear and exhibit no hysteresis. Partial molar volumes of CO2 in these polymers are determined from data of sorptive dilation. On the basis of the extended dual‐mode sorption model and the current data, primitive equations for gas‐sorptive dilation of glassy polymers are proposed.

Effect of CO2 treated polycarbonate membranes on gas transport and sorption properties

“…The gas sorbed into these microvoids would be in Langmuir form. A similar result was reported by Kamiya et al [14] in poly(ethylene terephthalate) (PET) high pressure CO 2 treated membrane. The increases in Langmuir sorption implied that excess free volume of treated membranes would increase with increasing CO 2 density.…”

In situ FTIR measurement of carbon dioxide sorption into poly(ethylene terephthalate) at elevated pressures

“…Similar decreases in solubility were observed by Kamiya et al 20 upon increasing temperature from 35 to 65°C at pressures up to 50 atm and by Hirose et al 39 upon increasing temperature from 25 to 65°C at pressures up to 1 atm. Spectroscopic evidence has shown the existence of a specific interaction between CO 2 and various polymers 28 and confirmed by recent ab initio calculations for PET.…”

“…19 Also, the solubility of CO 2 in PET has been shown to decrease with increasing temperature between 35 and 65°C for a given pressure of 50 atm. 20 In these and other previous studies, the sorption and solubility have only been studied near or above ambient temperatures. At these temperatures, crystallization has been observed when using only modest pressures of CO 2 .…”

Subnanometer hole properties of CO2-exposed polysulfone studied by positron annihilation lifetime spectroscopy

“…The enlargement of the average hole radius with the gas pressure is clearly shown in Figure 7. This is compared with an observed increase of macroscopic elongation measurements as a function of pressure 15 in Figure 7. A quantitative difference is seen between hole radius (R) and macroscopic elongation variations.…”

“…4,14 For highly interactive gases such as CO 2 , large variations in thermal and volumetric properties have been observed. [15][16][17] Typical behavior is the existence of hysteresis during sorption and desorption processes. The effect of temperature on gas sorption, permeability, and selectivity has been studied in detail.…”