摘要
摘要 從熱力學的角度來看，隨著老化時間增加薄膜趨於緻密屬於一種自發行為，薄膜的氣體透過量隨著老化程度增加而降低是無法避免的，因此本研究探討PMMA薄膜的物理老化行為對薄膜氣體分離性能的影響。本研究利用DMA、DSC、Cahn、GPA等儀器量測薄膜的α-轉移溫度、β-轉移溫度、氣體溶解係數、氣體透過係數，探討分子鏈運動性改變對薄膜內自由體積之影響，進而分析物理性老化對薄膜分離行為之影響，最後經由經驗方程式推導評估薄膜老化行為。 由玻璃轉移溫度和β-轉移溫度往高溫偏移可以發現，隨著老化時間增加薄膜內部自由體積的變化可能為影響氣體透過薄膜的主要原因。分析PALS與薄膜氣體分離測試結果，可知薄膜在老化過程自由體積的大小與數量均逐漸變小。 薄膜老化過程中影響自由體積的主要因素為薄膜內高分子鏈鬆弛的程度，時間效應與溫度效應對高分子鏈鬆弛程度具有等效性。固定溫度隨著老化時間增加，薄膜內高分子鏈鬆弛程度增加，使得膜內自由體積減少，造成氣體透過係數下降。在固定量測時間內，隨著儲存溫度上升，可能由於薄膜內高分子鏈鬆弛程度增加，使得膜內自由體積減少，造成氣體透過係數下降。 將不同溫度效應下得到的氣體透過係數與時間的關係，利用溫度與時間具有等效性的概念經由curve fitting可得評估薄膜老化行為的經驗方程式。
並列摘要
Abstract The effect of physical aging on gas separation performance of PMMA membrane was investigated in this study. Physical aging is inherent thermodynamic nature of the glassy polymeric membrane because it is a spontaneous process that non-equilibrium state tends to approach equilibrium state slowly. The effect of physical aging on the β-transition temperature, glass transition temperature, gas solubility, free volume distribution ,and gas permeability parameters of dense membranes were characterized by DMA、DSC、Cahn 、PALS and GPA. The experiment data were used to illustrate the behavior of physical aging in the polymer membrane. At last we are going to find an equation by which makes permeability and aging time to be connected. The glass transition temperature is increased with the increasing aging time can be explained by the glass transition temperature is depends on the free volume. The decreasing of free volume during aging inhibited the chain mobility of the polymer and increased the glass transition temperature of the membrane, and the changes of free volume become smaller. The free volume is depends on degree of chain entanglement, chain rigidity, and the structure of the polymer. The permeability decreased with increasing time is because the increase in the chain relaxation or the increase in the temperature, and temperature effect is another important factor in the physical aging the membrane. Different stored temperatures also make different kind of aging behavior. Using curve fitting experiment to get an equationby which makes permeability and aging time to be connected. At last we modify the equation by which is from temperature effect, and make the equation close to the real data.