利用放線菌分解聚乳酸奈米複合材料之研究

Studies on the Degradation of PLA/Clay Nanocomposites by Streptomyces 76T-1

蔡嘉儒(Chia-Ju Tsai)

指導教授 ： 董崇民

淡江大學/工學院/化學工程與材料工程學系碩士班/碩士(2010年)

https://doi.org/10.6846/TKU.2010.00990

摘要

由於環境汙染日益嚴重，因此生物可分解高分子逐漸受到大家的重視。聚乳酸(Poly(lactic acid)，PLA) 是一種脂肪族熱塑性聚酯類生物可分解塑膠，由於它的生物可分解性以及對於環境的友善性，因此受到廣泛的注意。本研究首先以疏水性的插層劑(二胺基聚異丙醚，POP-diamine)來提高蒙脫土(Na+-MMT)的層間距，希望藉此提高蒙脫土的分散性，並測量聚乳酸/蒙脫土複合材料的物理性質及機械性值，另外以市售改質蒙脫土(C30B)做為比較；最後，將製作出來的聚乳酸奈米複合材料以放線菌進行分解實驗，探討蒙脫土的添加對聚乳酸生物可分解性質的影響。
結果顯示經由二胺基聚異丙醚可成功的將蒙脫土的層間距由1.24 nm撐開至4.64 nm，但與聚乳酸經由混煉熱壓成膜厚，層間距卻又下降至2.26 nm，推測是由於二胺基聚異丙醚從蒙脫土層間遷移至聚乳酸基材之中。市售的改質蒙脫土與聚乳酸在經由混煉熱壓成膜之後，可成功的將層間距撐開至3.60 nm，顯示出可成功的製備出插層型奈米複合材料。添加入市售改質蒙脫土後，可提升聚乳酸的陽氏模數，使得聚乳酸變得更為硬脆；添加入利用二胺基聚異丙醚所插層的蒙脫土之後，使得聚乳酸的斷裂伸長率增加至13%，使得聚乳酸更具有韌性。不管是添加了市售的改質蒙脫土或是自行改質的蒙脫土，均可使聚乳酸的起始重量損失溫度以及最大重量損失溫度提升，可增加聚乳酸的熱穩定性。經由Streptomyces sp. 76T-1放線菌的分解實驗之後，可發現聚乳酸在72小時之內就可被分解完，在添加入市售改質蒙脫土之後，可加速聚乳酸分解速率。但添加了自行插層的蒙脫土之後，聚乳酸的分解性變得很差，推測是因為二胺基聚異丙醚會酵素對聚乳酸的分解速率，在經過72小時的分解之後，仍殘留有40 wt%的聚乳酸。另外在分解過後，可發現聚乳酸的結晶度以及分子量均未產生明顯的變化。為了解結晶度是否會影響放線菌對聚乳酸的分解行為，我們製作出高結晶度的聚乳酸(結晶度37%)。由於高結晶度聚乳酸的結構較為緻密，因此在經由72小時分解之後，仍可維持80%的重量不被分解。從SEM圖中可看到，放線菌會先分解聚乳酸的無定型區，然後再分解結晶區。在本次實驗中，分解過後的結晶度以及分子量均無明顯的變化，因此推測出放線菌Streptomyces sp. 76T-1是經由表面侵蝕的作用力來分解聚乳酸。

關鍵字

聚乳酸 ； 酵素分解 ； 蒙脫土 ； 放線菌

並列摘要

Biodegradable polymers have recently attracted great attension because environmental pollution. PLA is a aliphatic thermoplastic polyester and a biodegradation plastic. In this study, we use hydrophobic intercalation agent (POP-diamine) to ezpansion the inter-lamellar space of Na+-MMT. We hope it could increase the disperse of montmorillonite. Then we measure the physical properties and mechanical properties, and compare with commercial modified montmorillonite (C30B).Finally, we degrade the PLA nanocomposites by streptomyces 76T-1 to investigate the degradability of PLA nanocomposites. We could expand the inter-lamellar space from 1.24 nm to 4.64 nm by using POP-diamine as intercalation agent. But after meting blending, the inter-lamellar space would reduce to 2.26 nm. The reason is the POP-diamine would move to PLA matrix after melting blending. We could prepare intercalation-nanocomposite by melting blending with C30B. When adding C30B, we could increase the modulus of PLA.And when adding the POP-MMT, we could increase the elonation at break. By adding the montmorillonite, we could increase the thermal ability of PLA. We use Streptomyces sp. 76T-1 to degrade PLA. After degradating test in 72 hour, PLA could be degradating completely. Adding cloisite 30B could accelerate the degradating rate. But POP-diamine could slow down the degradating rate. After degradating test in 72 hour, we still have 40%wt PLA. After degradating test, we found that the crystallinity and molecular weight have not changing. For understanding the relation between degradation rate and crstallinity, we made hight crystallinity PLA (crystalinity 37 %). After degradating test in 72 hour, we still have 80 wt% PLA. In the result of SEM, we found that Streptomyces sp. 76T-1 degrade the amorphous firstly, then crystalline. By the results of thickness test and molecular weight test in this paper, we assume that Streptomyces sp. 76T-1 degrade PLA by surface erosion.

並列關鍵字

PLA ； Enzymatic degradation ； Montmorillonite ； Streptomyces

參考文獻

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