聚(4-甲基-1-戊烯)薄膜內結晶型態、自由體積與氣體傳輸性質關聯性之探討

Correlationship between crystalline conformation, free volume and gas transport properties of poly(4-methyl-1-pentene) membrane

吳宣潁(Hsuan-Ying Wu)

指導教授 ： 胡蒨傑 ； 賴君義

中原大學/工學院/化學工程研究所/碩士(2012年)

https://doi.org/10.6840/cycu201200601

摘要

本研究以乾式相轉換法製備出聚四甲基-1-戊烯 (Poly(4-methyl-l-pentene), TPX)氣體分離膜，再經由恆溫再結晶於不同時間下進行熱處理製備不同結晶度的TPX薄膜，並探討其結晶型態、自由體積性質以及氣體傳輸性質的關聯。研究中發現一極特殊之現象，TPX薄膜之氣體透過係數隨結晶度增加而上升，其氧/氮選擇比也隨之上升後持平，此與一般高分子薄膜氣體分離現象相反。為了深入探討此現象，本研究結合正電子湮滅壽命譜儀(Positron annihilation lifetime spectroscopy, PALS) 、廣角X射線繞射儀(Wide angle X-ray diffraction, WAXD)及小角度X射線散射儀(Small angle X-ray scattering, SAXS)分析薄膜內之自由體積、結晶型態、晶板結構之變化。並藉由微差式掃描熱卡計分析儀(Differential Scanning Calorimetry)、熱重分析儀(Thermogravimetry Analysis)、動態機械黏彈分析儀(Dynamic Mechanical Analysis)等儀器用於分析薄膜物性。結果顯示，結晶度隨熱處理時間增加而增加，並且熱處理造成晶型的轉換，其氣體透過係數增加的原因與自由體積有很明顯的關聯性。PALS結果指出當結晶度增加，在結晶區和束縛之無定形區(Rigid amorphous fraction, RAF)內量測到的自由體積R3a及在可移動之無定形區(Mobile amorphous fraction, MAF)區域內量測到的R3b皆隨結晶度之增加而增加，使氣體更易通過而提升透過係數。另外，I3a的增加代表了較小的自由體積孔洞數量的增加，也提供了更多具有選擇性的孔洞，因此提高選擇比。SAXS分析證明晶層-無定形層交互排列堆疊中的la (無定形層)的厚度比起lc (結晶層)明顯增加了許多，RAF區域高分子鏈受到熱處理排列成結晶，高分子鏈被拉伸而產生具有一些提供氣體透過以及提升選擇比的自由體積(R3a)， MAF區域的高分子鏈也因排列成結晶區域被拉扯，使得R3b變大，可提升其氣體透過。

關鍵字

正子 ； 聚(4-甲基-1-戊烯) ； 薄膜 ； 結晶度 ； 氣體傳輸

並列摘要

In this study, poly(4-methyl-l-pentene) (TPX) gas separation membranes were fabricated by the dry-phase inversion method. The TPX membranes were isothermally recrystallized through annealing for a period of time to prepare TPX membranes with different crystallinities. The correlation between crystalline structure, free-volume properties and gas transport behavior of the TPX membranes were investigated.
The oxygen gas permeability increased while the selectivity of O2/N2 first increased then remained constant with the increase in crystallinity. This phenomenon was opposite to the results of other crystalline polymeric membranes. To discuss this phenomenon, the positron annihilation lifetime spectroscopy (PALS), wide angle X-ray diffraction (WAXD) and small angle X-ray scattering (SAXS) were used to analyze the free¬¬-volume properties, the types of crystalline phase, and the lamellar structure of the TPX membranes. Furthermore, the physical characteristics of the TPX membranes were evaluated by differential scanning calorimetry (DSC), thermogravimetry analysis (TGA) and dynamic mechanical analysis (DMA). Results indicated that the crystallinty increased with increasing recrystallization time, and the crystal phase was changed by the recrystallization process. PALS data demonstrated that R3a (the free volume size in crystalline region and rigid amorphous fraction, RAF) and R4 (the free volume size in mobile amorphous fraction, MAF) increased with increasing crystallinity. This result led to the increase in gas permeability. The increase in I3 (related to the amount of the smaller free volume holes) resulted in the increase in selectivity. From SAXS analysis, we indicated that the thickness of the amorphous layer (la) in the alternating packing of the amorphous-crystalline region increased much more than the thickness of the crystalline layer (lc). The polymer chains in RAF and MAF were stretched and oriented to form crystals because of the recrystallization treatment. These behaviors led to the increase in R3a, R3b and gas permeability.

並列關鍵字

(Poly(4-methyl-l-pentene) ； positron ； membrane ； crystallinity ； gas transport

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