气体在聚三氟丙基甲基硅氧烷膜中的渗透性

Gas permeability in polytrifluoropropylmethylsiloxane membrane

为提高有机蒸汽膜的耐溶胀性,选用分子中含有C—F键及不对称结构的橡胶态聚合物聚三氟丙基甲基硅氧烷(PTFPMS),采用溶液浇筑法制备了均质膜,测试了包含全氟烃类在内的10种气体在聚合物膜中的渗透性,并对渗透系数与压力及临界性质之间的关系进行了研究。结果表明,全氟烃类气体的渗透系数较小,低于永久性气体及具有相同碳原子数的烷烃气体;随着压力的增加,CO_2和C_3H_8等吸附性较强的气体渗透系数不断提高;而对于H_2、O_2和N_2等气体,渗透系数变化不大;除H_2、CO_2和全氟烃类外,气体渗透系数随着临界温度的提高而增加;气体分子尺寸大且易被压缩的烷烃气体更容易渗透,渗透系数随着碳原子个数的增加而增大,但对于全氟烃类气体则表现出相反的渗透行为。

In order to improve the swelling resistance of organic vapor membrane,a dense membrane is prepared by solution casting method using polytrifluoropropylmethylsiloxane(PTFPMS） as raw material,which is a rubber polymer with C—F bond and asymmetric structure in the main chain. The permeability of 10 kinds of gases,including perfluorocarbons(PFCs）,in the prepared polymer membrane are determined,and the relationships between the permeability coefficient and pressure as well as critical properties are investigated.The results show that the permeability coefficient of PFCs is lower than that of permanent gases and alkane gases with the same number of carbon atoms.With the increase of pressure,the permeability coefficients of CO2,C3H8 and the gases with stronger adsorptivity will increase continuously,and that of H2,CO2 and N2 have not obvious changes. Except H2,CO2 and PFCs,the permeability coefficients of other gases increase with increase of the critical temperature.The alkane gases that own large molecule size and can be compressed easily will permeate more easily,furthermore,their permeability coefficients increase with the increase of number of their own carbon atoms.But PFCs exhibits opposite permeation behaviors with alkane gases.