聚羥基丁酯/聚乳酸摻合物的相容性與生物分解行為

Studies on Compatibility and Biodegradability of PHB/PLA Blends

劉義峋(Yi-Hsun Liu)

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(2011年)

https://doi.org/10.6846/TKU.2011.00925

摘要

高分子材料擁有良好的機械性質與材料的易加工性，大幅降低生產成本，以上的優點，使得高分子材料在日常生活中大量的被使用而增加了生活的便利性。其中，脂肪族熱塑性聚酯類的聚乳酸(Poly(lactic acid), PLA)與聚羥基丁酯(Poly(3-hydroxybutyrate), PHB)由於可以被微生物分泌的酵素所分解而被稱為是對環境友善的生物可分解高分子。為了使聚乳酸有較好的機械性質，部分研究選擇添加塑化劑，但是塑化劑本身不見得可以被微生物所分泌的酵素分解，因此本研究欲以聚羥基丁酯與聚乳酸作摻合，藉此改善聚乳酸在機械性質上韌硬的缺點，除了克服以上的問題外，增加相容性也是本實驗需要克服的難關，並期望聚羥基丁酯的加入，不會造成聚乳酸被環境分解時的困難。
經由實驗結果顯示，降低PHB的分子量與PLA作摻合能夠獲得良好的相容性，降低摻合物在機械性質上因相分離所會面臨的缺點。此外，由於PHB的分子量下降，使之不易結晶的特性，在拉力試驗中，PLA/PHB組成比例為80/20時，可以將斷裂伸長率從PLA的7.1 %增加至226 %，足足增加了30倍！
此外，在生物分解實驗中，藉由添加少量的PHB (5 wt%)可以降低PLA在Streptomyces sp. 76T-1中所需要的分解時間，從原先的72小時降低至64小時左右；可是當PHB含量繼續增加到10 wt%時會降低PLA的分解速率 ;當PHB含量增加至20 wt%，由於薄膜在水相中產生的孔洞可促進酵素進入薄膜中，使薄膜崩解，增加酵素與PLA的接觸面積，使PLA能夠持續的被分解。

關鍵字

聚羥基丁酯 ； 聚乳酸 ； 摻合物 ； 相容性 ； 酵素分解

並列摘要

Biodegradable polymers have recently attracted great attension because environmental pollution. PLA and PHB is a aliphatic thermoplastic polyester and a biodegradation plastic. In this study, we blended PLA with PHB. We hope it could have a good miscibility and increase the mechanical properties. Then we measure the physical properties and mechanical properties. Finally, we degrade the PHB/PLA blends by streptomyces 76T-1 to investigate the degradability of PHB/PLA blends. Because the miscibility was increased by reduceing the molecular weight of PHB, we blend PLA with PHB by mixer at 180oC for 20 min to obtain the low molecular weight PHB blend with PLA. We could increase the crystallinity of PLA by adding the low molecular weight PHB.The elongation at break was increased from 7% to 226% by blending 20 wt% PHB. We use Streptomyces sp. 76T-1 to degrade PLA and PHB/PLA blends. After degradating test in 72 hour, PLA could be degradating completely. Adding 5 wt% low molecular weight PHB could accelerate the degradating rate, because the low crystallinity of PLA after adding 5 wt% PHB. But adding PHB more then 10 wt% could slow down the degradating rate. After degradating test, we found that the crystallinity was changed by the environment temperature not by degrading of Streptomyces sp. 76T-1. In the other word, the crystallinity have not changing in the degrade behavior.

並列關鍵字

PLA ； PHB ； Blends ； Enzymatic degradation ； Streptomyces

參考文獻

1. W. Masaji, K. Fusako, Numerical simulation for enzymatic degradation of poly(vinyl alcohol). Polymer Degradation and Stability, 2003. 81: p. 393-399.

2. R.-J. Mueller, Biological degradation of synthetic polyesters—Enzymes as potential catalysts for polyester recycling. Process Biochemistry, 2006. 41: p. 2124-2128.

3. Edward M. Petrie, Biodegradable Polymers in Adhesive Systems, (June 1, 2007)

4. R. K. Kulkarni, K. G. Pani, C. Neuman, F. Leonard, Polylactic acid for surgical implants. Arch. Surg., 1966. 93: p. 839-843.

5. S. S. Ray, M. Bousmina, Biodegradable polymers and their layered silicate nanocomposites: In greening the 21st century materials world. Progress in Materials Science, 2005. 50: p. 962–1079.