利用聚胺酯增韌聚乳酸之研究

Abstract

本研究以六種不同之聚酯型二元醇與己二異氰酸酯(HDI)反應合成聚胺酯，並將合成後之聚胺酯與聚乳酸進行混摻，藉以改善聚乳酸之韌性及延展性，並藉由改變二元醇之種類及分子量，探討混摻物之機械性質、熱性質、混摻相容性、結晶性質及拉伸斷裂面之型態，藉以瞭解聚胺酯增韌聚乳酸的結果與機制。由微差掃瞄熱卡計分析(DSC)之結果，發現混摻物有兩個Tg存在，且分別很接近原本PU與PLA之Tg，顯示其為不相容混摻系統。即使只在PLA中混摻10%之PU，斷裂伸長率仍有明顯之上升，且抗張強度亦有所提升，顯示PU對PLA有良好之增韌效果。但若PU的含量比例超過30%以上，PLA與PU間的巨觀相分離會更明顯，因此混摻物的機械性質會大幅下降。PU的結晶度與結晶速率為影響混摻物機械性質的重要因素，PU的結晶性越好，則拉伸過程中應力硬化的效果越明顯，因此混摻物的機械性質越佳。本研究以最簡便的熔融混摻法，成功地利用可分解的聚酯型聚胺酯增韌聚乳酸，且不影響聚乳酸原有之抗張強度與耐熱性，可望大幅提升聚乳酸的應用性，為極具潛力之生物可分解材料。

To toughen polylactic acid (PLA), biodegradable polyurethanes (PUs) synthesized from different types and molecular weights of polyol were melt-blended with the PLA. Mechanical properties, thermal properties, crystalline properties, morphology of fracture surfaces, and toughening mechanism of the blends were compared and discussed. The blends were characterized as an immiscible system for their individual glass transition temperatures in the differential scanning calorimeter (DSC) test. The elongation at break was significantly increased even though only 10% PU was added to the PLA, indicating the toughening effect of the PU on the PLA. The tensile strength was also increased when 10% PU added. But the tensile strength and elongation at break were lower for the PU content more than 30% because of the macro-phase separation. The mechanical properties of the PLA/PU blends were influenced by the crystallinity and crystallization speed of the PU. The blends were more flexible and tough materials and necking formation was observed during the tensile test.