CO₂ plasticization and physical aging of perfluorocyclobutyl polymer selective layers

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• 作者：Jinxiang Zhou ; Adam T. Haldeman ; Earl H. Wagener ; Scott M. Husson
• 关键词：Carbon capture ; Free volume ; Glassy polymer ; Thermal annealing ; Thermal history
• 刊名：Journal of Membrane Science
• 出版年：15 March, 2014
• 年：2014
• 卷：454
• 期：Complete
• 页码：398-406
• 全文大小：592 K

文摘

Carbon dioxide plasticization and physical aging are two phenomena that occur in glassy polymers that limit their effectiveness as selective layers in composite gas separation membranes. These two phenomena become more significant in polymeric thin films, which presents challenges for the long-term, stable operation of thin-film composite membranes. The objective of this work was to study CO₂ plasticization and physical aging of perfluorocyclobutyl (PFCB) polymer thin film selective layers (<100 nm), which are new to the membrane art. Specifically, measurements on PFCB polymer selective layers were conducted to evaluate the influence of film processing conditions (PFCB concentration and coating speed), aging time, and heat treatments on CO₂ plasticization pressure. Findings indicate that PFCB layer thickness plays an important role on plasticization resistance when the thickness is less than 40 nm. However, when the thickness is greater than 40 nm, concentration of the coating solution also played an important role. Using concentrations above the overlap concentration yielded films with higher plasticization pressure compared to films with similar thickness prepared from dilute solution. Findings also show that films annealed at higher temperature exhibited higher plasticization pressure. Long-term CO₂ exposure studies indicated that CO₂ plasticization lessens the impact that physical aging has on permeability loss during the early stage of use, but at longer times, CO₂ plasticization accelerates physical aging. Overall, results presented in this work contribute new understanding of plasticization and physical aging, and may be used to guide further improvements in polymer performance for CO₂ separations.