Desorptionof Carbon Dioxidein 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 six 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+Aexp-(t-t0)/τ,the other was Y=Y0+A（t-t0）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 calculated with the desorption equation.The result suggested that the diffusion coefficient of CO2 was about 10-7cm2/s and it depended on the amount of CO2 in polymer,temperature and the treated pressure.