Desorption of Carbon Dioxide in Supercritical Co₂-Swollen Polymers

A study was undertaken to investigate the desorption of CO₂ in the six polymers, namely, LDPE, PP, PA6, EVA, PS and PU. The sir polymers were treated in supercritical CO₂. The temperature of supercritical CO₂ was 40℃, pressure was from 8.0 to 14.0MPa. The weight change of polymers after treatment was fitted with two functions. One function was Y=Y₀ +A \exp \left\-\left(t-t_0\right) / \tau\right\, the other was Y=Y₀ +A\left(t-t_0\right)^1 / 2. The result indicated that the weight change of polymers after treatment in mass with time showed a dependence on the logarithm of time. The desorption equation of CO₂ in polymers was given in accordance with Fickian diffusion law. The diffusion coefficient of CO₂ was calculable with the desorption equation. The result suggestal that the diffusion coefficient of CO₂ was about 10^-7 cm²/s and it depended on the amount of CO₂ in polymer, temperature and the treated pressure.