生物可分解性聚合物摻和系統之結晶行為研究

A Study of Crystallization Behavior in PLA Compounded System

李孟良(Meng-Liand Lee)

指導教授 ： 芮祥鵬

國立臺北科技大學/工程學院/有機高分子研究所/碩士(2005年)

摘要

本實驗利用meso-聚乳酸(PDLLA)及L-聚乳酸(PLLA)加入不同比例之滑石粉(Talc)與二氧化鈦(TiO2)混鋉出含有不同比例(5%、10%、20%、30%)之聚合物，並與meso-聚乳酸(PDLLA)及L-聚乳酸(PLLA)之均聚物比較於不同等溫結晶溫度結晶完成樣品之結晶熱力學、動力學性質。
首先利用微差掃描熱卡計(DSC)將含有不同比例(5%、10%、20%、30%)滑石粉與二氧化鈦之聚合物與meso-聚乳酸(PDLLA)及L-聚乳酸(PLLA)之均聚物於不同等溫結晶溫度(Tc)結晶，根據Hoffman-Weeks方程式得到樣品之平衡熔點(Tm0)，發現到不論有無添加滑石粉(Talc)之聚合物，其平衡熔點(Tm0)皆會約略相同。而利用樣品於各等溫結晶溫度(Tc)下結晶之熔融曲線，可計算出樣品於該結晶溫度的結晶度，發現到樣品於中過冷度時，因遠離樣品的玻璃轉換溫度(Tg)與熔點(Tm)，故結晶度會到一極大值，再利用樣品的結晶放熱曲線計算出樣品完成比例與結晶時間的關係，將此曲線利用Avrami方程式加以分析，可得到樣品之結晶速率(G1/2)及Avrami指數(n)，而由結晶速率(G1/2)可得知含有不同比例(5%、10%、20%、30%)滑石粉與二氧化鈦之聚合物及meso-聚乳酸(PDLLA)及L-聚乳酸(PLLA)之均聚物會隨著等溫結晶溫度(Tc)的上升，其結晶速率(G1/2)會先上升而後降低，由此可證明結晶的成核成長機制，且可得知隨著不同比例(5%、10%、20%、30%)滑石粉含量增加之聚合物，其結晶速率(G1/2)也會隨之上升，且由摻混不同比例滑石粉(Talc)之聚合物，比較在相同結晶溫度(1150C、1250C)下之結晶速率(G1/2)，發現到添加10%Talc後，結晶速率(G1/2)增加趨於平緩，但其隨著不同比例(5%、10%、20%、30%)二氧化鈦含量增加之聚合物則不然。接著利用Lauritizen-Hoffman方程式可得到樣品之regimeIII轉換成regimeII臨界溫度，發現到有添加滑石粉(Talc)之聚合物，其臨界溫度比均聚物約略上升，並利用偏光顯微鏡(POM)觀察其成核數量，在相互印証之下，可得知其有添加滑石粉(Talc)之聚合物之臨界溫度比均聚物約略上升，最後，在小角度X光散射實驗中，可得知不論有無添加滑石粉(Talc)皆不會影響到其結晶厚度，再藉由Thompson-Gibbs方程式可得知，添加不同比例滑石粉(Talc)之聚合物其熔點(Tm)變化，主要是受到鏈褶曲表面自由能σe變化之影響。

關鍵字

meso-聚乳酸(PDLLA) ； L-聚乳酸(PLLA) ； 滑石粉(Talc)

並列摘要

In this study, differential scanning calorimetry (DSC), polarized optical microscopy (POM) and small angle X-Ray scattering system (SAXS) were employed to study the crystallization/melting behavior of PDLLA、PLLA、PDLLA/Talc compounds、PDLLA/TiO2 compounds and PLLA/Talc compounds.
With Avrami analysis, the crystallization rate constant for PDLLA、PLLA、PDLLA/Talc compounds、PDLLA/TiO2 compounds and PLLA/Talc compounds were evaluated. The equilibrium melting point was obtained using the Hoffman-Weeks method. It was found that the equilibrium melting point of PDLLA/Talc compounds and PLLA/Talc compounds was the same with that of PDLLA and PLLA respectively. The crystallization rate (G1/2) increased first and then decreased when the temperature increased. The addition of Talc showed a significant enhancement to the increase of crystallization rate and the downward shift of the optimum crystallization temperature. However, the overall crystallinity was found to be independent on the addition of Talc. Finally, the transition temperature between regimeIII and regimeII, obtained using the Lauritizen-Hoffman method, was found to be higher for PDLLA/Talc and PLLA/Talc compounds than those of pure PDLLA and PLLA systems.
With SAXS, insignificant difference was found in the long period length, L, for system compounded with and without Talc. However, it was found that the melting points of PDLLA/Talc compound and PLLA/Talc compound were higher than those of PDLLA and PLLA respectively. Based on previous results and Thomson-Gibbs theory, the higher melting temperature induced by addition of Talc is due to the higher folding surface free energy(σe) in a Polymer/Talc system. The addition of Talc might suppress the chain mobility to result in a higherσe as mentioned above.

並列關鍵字

meso-Polylactide acid(PDLLA) ； L-Polylactide acid(PLLA) ； Talc

參考文獻

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