添加蒙特石及球磨處理對聚乳酸-澱粉複合材料之影響

Abstract

本試驗以聚乳酸(poly(lactic acid), PLA)及澱粉為材料，聚乙二醇(poly(ethylene glycol, PEG)為塑化劑，添加不同含量之天然或有機修飾蒙特石(montmorillonite)作為填料，經由球磨處理後熱壓製備複合膜，並探討球磨處理、蒙特石種類及蒙特石添加量對聚乳酸-澱粉複合材料性質的影響。以掃描式電子顯微鏡觀察複合材料中澱粉之顆粒形態、界面及分散情形，穿透式電子顯微鏡觀察蒙特石分散情形，X光繞射及小角度X光散射分析複合膜之蒙特石分布形態及結晶結構。結果顯示，球磨處理能使蒙特石失去整齊排列結構並分散於複合材料中；澱粉顆粒在球磨過程中變形程度則受到蒙特石的添加以及蒙特石層間是否有有機分子修飾的影響。此外，由於聚乙二醇傾向吸附在蒙特石晶層表面，蒙特石在材料中的形態、添加量及是否有有機分子修飾會決定聚乙二醇在材料中的分布。複合膜中聚乳酸的結晶結構並不會受到蒙特石添加或球磨處理影響。測定複合材料之機械性質與水氣通透性(water vapor permeability, WVP)得知，機械性質與水氣通透性與複合材料中澱粉、蒙特石及聚乙二醇之形態及分布有相關性，其中以添加3%有機修飾蒙特石、球磨處理4 hr之聚乳酸-澱粉複合材料之楊氏模數提升及水氣通透效果降低最為顯著，但其斷裂延伸率及拉伸強度則降低最多。

Different amounts of montmorillonite (MMT) or organomodified montmorillonite (OMMT) were incorporated into a poly(lactic Acid)-starch (PLA-starch) composite film by means of ball milling and hot pressed, which used poly(ethylene glycol) (PEG) as the plasticizer. The effects of ball milling conditions, types of MMT and MMT contents on the morphology and properties of PLA-starch composite were discussed. Scanning electron microscopy (SEM) was used to study the morphology, surface and distribution of starch granules in the composite films. The distribution of MMT in the composite films was investigated by transmission electron microscopy (TEM). X-ray diffraction (XRD) and small angle X-ray scattering (SAXS) was used to analyze the morphology of MMT and the crystalline structure of the composite films. The results shows that the dispersion of clay minerals could be improved by the ball milling treatment, while the effects of ball milling treatment on the morphology and the dispersion of starch were influenced by the addition of MMT and OMMT. Besides, due to that PEG tending to be adsorbed on the surface of MMT, the morphology, type and content of MMT dominated the distribution of PEG in the composite films. The mechanical and water vapor permeability (WVP) properties of the composite films were influenced by the morphologies and distributions of starch, MMT and PEG. The best composite films in terms of Young’s modulus and WVP could be obtained by adding 3% OMMT and 4 hr ball milling or adding 1.5% OMMT and 8 hr ball milling, but the tensile strength and elongation of the composite films decreased the most.