- 學位論文
PEI/PI摻合薄膜及其衍生之碳分子篩薄膜氣體分離行為之研究
Investigation on gas separation performance of PEI/PI blend membrane and carbon molecular sieve membrane derived from PEI/PI blend
摘要
本研究使用Polyimide與Polyetherimide為前驅物，希望藉由摻合的方式來調控前驅物之自由體積尺寸，進而控制複合碳分子篩薄膜（CMSM）的孔洞尺寸，並嘗試利用本實驗室所發展之自由正電子壽命（τ2）與孔洞尺寸關係式對前驅物與複合碳分子篩薄膜進行孔洞分析。 研究中利用DMA與SEM鑑定無支撐材摻合薄膜的相容性，使用正子湮滅技術分析無支撐材薄膜前驅物及CMSM的自由體積尺寸與孔洞尺寸，利用ATR-FTIR與XPS分析碳化前後薄膜的化學組成差異，並在35℃下進行，N2、O2與CO2氣體透過測試。 研究結果指出，無支撐材薄膜為相容摻合薄膜，且表面與截面為均相且無缺陷，而利用τ2數據計算出之自由體積半徑與孔洞尺寸會隨著PEI的添加量上升而下降，這表示我們成功利用摻合的方式去調控前驅物的微結構進而控制CMSM的微結構，在ATR-FTIR與XPS的鑑定中發現，碳化前後前驅物的化學組成有明顯的差異，官能基會裂解成氣體的形式離開薄膜，且元素組成大部分轉成碳元素，在碳化過後，複合碳分子篩薄膜的氣體透過有大幅提升，相較於無支撐材摻合薄膜，整體氧氣氣體透過係數提升40倍以上，二氧化碳氣體透過係數提升35倍以上。
並列摘要
In this study, polyimide (PI) and polyetherimide (PEI) were used as precursors for preparing supported carbon molecular sieve membranes (CMSMs). It was expected that the free volume in the precursors could be tuned by blending the two precursors to control the pore size in CMSMs. It was attempted to estimate the free volume and the pore size in the precursors and the CMSMs by using the equation developed in our laboratory, which expresses the relation between the free positron lifetime (τ2) and the pore size. The miscibility of the freestanding blend membrane precursors was determined by SEM and DMA. Positron annihilation spectroscopy (PAS) was used to analyze the free volume size in the freestanding blend membrane and the pore size in the supported CMSM. The chemical compositions of the membrane before and after carbonization were characterized with the use of ATR-FTIR and XPS. Permeation tests with N2, O2, CO2 were carried at 35℃. Results show that the freestanding blend membranes were miscible and had a defect-free surface and cross-sectional morphologies. The free volume and pore size radii, which were calculated by the τ2 equation, decreased when the PEI content increased. This indicated that the microstructure of the precursors by the blend method could be tuned successfully, and the microstructure of the supported CMSM could also be controlled. From ATR-FTIR and XPS results, it was found that the chemical compositions of the membrane before and after carbonization were quite different. The functional groups were pyrolyzed and released from the membranes. The composition of membranes were transformed to carbon. After carbonization, the gas permeability of the supported CMSM was evidently increased. Compared to the freestanding blend membrane, the CMSM permeability for oxygen and carbon dioxide was increased by more than 40 and 35 times, respectively.