Gravimetric study of high‐pressure sorption of gases in polymers

Abstract

A gravimetric method for determining precisely the solubility of gases in polymers at high pressure is described. The solubilities of N2 and CO2 in low‐density polyethylene (LDPE); CO2 in polycarbonate (PC); and N2, CH4, C2H6, and CO2 in polysulfone (PSUL) have been measured as a function of pressure up to 50 atm. Most of the measured sorption isotherms agreed closely with published data, but reproducible and time‐dependent hysteresis in the sorption of CO2, C2H6, and CH4 in glassy polymers, PC, and PSUL, was observed in this study for the first time. Like the well known conditioning effect of high‐pressure CO2 on the sorption capacity of glassy polymers, these hysteresis phenomena are believed to be due to the plasticizing effect of sorbed gases. On the basis of the current data, the dual‐mode sorption model including the plasticization by sorbed gas is discussed and a primitive equation for the concentration of sorbed gases in a quasiequilibrium state of sorption or desorption is proposed.

Effect of Temperature and Mechanical Stress on Barrier Properties of Polymeric Films Used for Food Packaging

“…An increased O 2 /CO 2 permselectivity is obtained for the following films exposed to stress cycles: This loss in selectivity is generally interpreted as plasticization: a weakening effect on the polymer introduced by the strongly sorbing CO 2 [25].…”

Transport Properties of Gases in Polymers: Experimental Methods

“…According to Equation (15), the value of t/l 2 for which the ratio M(t)/M ∞ is equal to 1/2 is expressed by the following equation [9]: (18) This is equivalent to the next relation (19), which gives the coefficient of diffusion [5, [8][9][10]14]: (19) In Figures 2 and 3, a theoretical curve of gas sorption in a polymer matrix and an experimental test of CO 2 desorption in a low-density polyethylene are respectively plotted.…”

“…The principle is to quantify the weight variation of a polymer sample submitted to a gas, with an electronic balance for example. Introduced into a high-pressure (HP) cell, this balance allows to obtain tests at a pressure of 6 MPa and temperatures of about 80°C [18,19]. Some evolutions of this technique allow to perform measurements at a pressure of 12 MPa and a temperature up to 350°C with a resolution of 10 µg, for an initial weight of polymer sample of about 1 g [20,21].…”

Gas Permeation in Semicrystalline Polyethylene as Studied by Molecular Simulation and Elastic Model

“…Several techniques like gravimetry [1][2][3][4], permeation cell [5,6] and NMR [7] have been adopted to measure solubility and diffusion coefficients. From a theoretical point of view, these two quantities are usually described and calculated through the concept of free volume [8][9][10], the dual-mode transport model [11][12][13][14], and molecular theories [15][16][17][18].…”