保壓過程之模溫控制對於聚乳酸、聚乳酸/洋麻纖維和聚乳酸/蒙脫土射出成形品的高次構造形成之影響

Abstract

通常的塑膠產品僅使用幾週至數年而已，但其分解時間卻長達約900年之久，這樣的產品廢棄後會對地球環境造成相當大的不良影響。且近年來由於石油與礦物等有限的資源日益枯竭，材料價格起伏不定，生質材料與能源漸漸受到重視且有越來越多的相關研究。本研究的目的是要以強化材增強生質材料之性質，使生質材料能做更廣泛的應用。研究中以生質材料聚乳酸分別與強化材洋麻纖維和蒙脫土做混練，再以聚乳酸及其複合物做射出成形且在其保壓階段操控模具溫度，並進行成形樣品的機械性質調查，探討高次構造的影響。 研究結果顯示：聚乳酸需要高溫且長時間的保壓才會有高次結構的產生，但若是高次結構不夠密集，亦無法對拉伸強度有所強化。而在與強化材混練過後的試片方面，由於強化材所預期的分散效果沒有達到，再加上混練時，因為長時間處於高溫下且混練機的強烈剪切作用，造成PLA的劣化使得分子量下降。所以在拉伸強度方面，有混練過的試片其拉伸強度普遍低於純PLA試片。

The plastic productions are usually used just for several weeks to several years, but their degradable time is a very long time, about 900 years. The kind of productions will make largely bad effects on the environment. Lately, finite resources such as oil and minerals, became fewer and fewer, and the price of materials went up and down. More studies will be done about bio-material and bio-energy as more and more attention is paid to them. The purpose of this study is to reinforce the properties of bio-material. Therefore, the bio-material can be applied more generally. This study will blend the bio-material, polylactic acid(PLA), with kenaf fibers, respectively, and montmorillonite(MMT). After that, when PLA and the compositions make injection molding, I will control the mold temperature in the compacting stage. Then, surveying mechanical properties of the molded samples and discussing effects of the superstructure. According to the study result： PLA in the compacting stage needs a long time at high temperature to generate superstructure. If the superstructure is not highly concentrated enough, it will not reinforce the tensile strength of PLA. About the PLA samples with blending reinforcement, their tensile strength is lower than the PLA samples. Because of that, decentralization of reinforcement was not achieved. Furthermore, a long period of time at high temperature with shear effect in the blending machine caused the degradation and molecular weight decrease of PLA.