聚丁二酸丁二醇酯/纖維素奈米微晶/環氧大豆油生物可降解摻合物

Abstract

聚丁二酸丁二醇酯 (Polybutylene succinate, PBS) 是一個石油提煉的生物可降解的高分子，被視為塑膠包材新興的材料。為了增加生物降解性及機械強度，本研究選用纖維素奈米微晶 (Cellulose nanocrystal, CNC) 與PBS混摻，但因為纖維素易形成應力集中點導致機械性質下降，需要添加增塑劑提升摻合物的延伸率。本研究選用環氧大豆油 (Epoxidized soybean oil, ESO)作為增塑劑。 在溶劑鑄造 (Solvent casting) 的製程中，PBS混摻ESO後的延伸率上升，這歸因於PBS結晶度的下降及微結構中長週期序列的改變。在DSC及DMA也可發現ESO能夠讓PBS的玻璃轉移溫度下降。這兩項變化與增塑劑的功能有直接的關係，代表ESO可作為此摻合物有效的增塑劑。另外在生物降解性方面，添加CNC的摻合物的降解速率相對於PBS是四倍，證明此摻合物不會對環境產生極大的危害。 在混煉 (Compounding) 製程中，由於機械性質會受混煉條件影響，經由極限黏度及拉伸試驗發現最適合摻合物的混煉時間為一分鐘。在此混煉條件下，機械性質、熱性質及微結構的變化皆與溶劑鑄造製程中相符合並且保留了PBS原有的機械性質，再利用預先混合的方式使CNC和ESO混合，增加CNC的分散性進而提升摻合物的阻氣性質。總結來說，摻合物的性質具有再現性，並且保有良好的機械性質、熱穩定性及生物降解性。

Polybutylene succinate (PBS) is one of the fossil-based biodegradable polymer, which is regarded as the emerging material for plastic packaging. Cellulose nanocrystal (CNC) is chosen to be incorporated with PBS for enhancement of biodegradability and mechanical strength. Unfortunately, the brittle cellulose particles form stress concentration points easily that sabotage the elongation of the composite. Therefore, epoxidized soybean oil (ESO) is employed as the plasticizer, which is required for the composite. The composite is processed by two techniques: solvent casting and compounding. In the case of solvent casting, the elongation of the composite raises siginificantly with the addition of ESO, which attributes to the remarkable declination of the crystallinity and the alternation of the microstructure. In addition, the glass transition temperature of PBS drops with the addition of ESO according to the data of DMA and DSC. These two circumstances are closely related to the functions of plasticizer, proving that ESO can be an efficient plasticizer of the composite. The biodegradability of the composite is also found to be four times greater than the neat PBS in the biodegradation test, indicating that the composite is able to be decomposed faster in nature without being hazardous to the environment. In the case of compounding, the molecular weight and intrinsic viscosity of PBS decrease with the increasing time of compounding due to the impact of thermal degradation and the shear force of the compounder, which determines that the optimized condition of compounding is one minute. The microstructure, thermal stability and mechanical properties of composite processed by compounder show a similar tendency compared to solvent casting. Moreover, the pre-mix of CNC and ESO serves as a conducive approach to the dispersion of CNC in the matrix of PBS, resulting in the better gas barrier properties. In conclusion, the composite which retains outstanding mechanical properties and advantages of biodegradable plastic is reproducible.