黏土含量在聚乳酸/蒙脫土奈米複合材料的微細發泡射出成型機械/熱/流變性質之影響

本實驗主要探討聚乳酸/蒙脫土奈米複合材料，利用傳統射出成型與超臨界流體微細發泡射出成型製成符合美國材料試驗協會(ASTM)的標準試片，藉由改變蒙脫土的含量(0、1、3、5、7、9 wt%)探討對機械性質(拉伸、衝擊、DMA)、物理性質(熱傳導係數)、熱性質(DSC、TGA)、氣泡微結構(SEM)、奈米結構(XRD、TEM)以及流變性質之影響。研究結果顯示，傳統射出和超臨界流體微細發泡射出在機械性質方面，聚乳酸隨著蒙脫土含量的增加，其抗拉強度與衝擊強度皆呈現下降的趨勢。在XRD測試方面，當聚乳酸添加適量蒙脫土後，其結晶度有增大的趨勢。在TEM測試方面，可以看出蒙脫土為片狀的材料，而與聚乳酸基材結合後，隨著蒙脫土含量的增加，從脫層型的材料結構轉變成插層型的材料結構。在氣泡微結構方面，得知氣泡大小會隨著蒙脫土含量的增加而有變小的趨勢，並提高了氣泡密度。熱性質方面，隨著蒙脫土含量的增加，可有效提升複合材料的熔融溫度(Tm)、熱裂解溫度(Td)。在熱傳導係數方面，超臨界流體微細發泡射出成型之熱傳導係數比傳統射出成型之熱傳導係數低，隨著蒙脫土含量的增加，可提高材料之熱傳導係數。流變性質方面，發現隨著蒙脫土含量的增加會降低材料之黏度係數。抗拉強度和黏度係數的降低是因為聚乳酸/蒙脫土奈米複合材料裂解之緣故。

關鍵字

聚乳酸；蒙脫土；超臨界流體微細發泡射出成型；熱傳導係數；流變

並列摘要

This study investigated the effect of clay loading on the Poly-Lactic-Acid(PLA) nanocomposites. PLA/Montmorillonites(MMT) nanocomposites were diluted from masterbatch and clay content were 1, 3, 5, 7, 9 wt% respectively. The PLA/MMT nanocomposites were then molded by conventional and microcellular injection molding process. The effects of clay loading on the mechanical, thermal, foaming and rheological properties were investigated. The results showed that addition of Montmorillonites(MMT) decreased the tensile/impact strength of PLA/Clay nanocomposites. The nanocomposite structures were examined by X-ray diffraction(XRD) and Transmission Electron Microscope(TEM). The XRD results showed that with the addition of clay which increased the crystallinity of the PLA/MMT nanocomposites. The thermal properties results showed with the addition of clay which increased melting temperature, degradation temperature and thermal conductivity of the nanocomposites. The clay helps the nanocomposites on having small size cell on the foamed nanocomposites. For the rheological test, with the addition of clay which decreased the viscosity of the nanocomposites. The decreased tensile strength and viscosity is caused by the degradation of the PLA/MMT nanocomposites.