PLA的酸性降解及其机理分析

目的研究PLA在酸性条件下降解及其机理。方法通过在酸性水溶液中降解不同时间,得到一系列不同相对分子质量的PLA,利用黏度法、凝胶色谱以及红外光谱对PLA的降解机理进行研究。结果 PLA的数均分子量随降解时间的增加逐渐减小,失重率和降解率逐渐升高,在降解23 d后,产物的数均分子量从4050降至2490,失重率从9.9%升至75.1%,降解率从98.3%提高至99.0%。降解过程中,PLA的相对分子质量分布系数基本保持不变,一直维持在1.25左右。结论在降解过程中,酯键的断裂是PLA初步降解的主要方式,H+浓度的升高有利于催化酯键的断裂,加剧PLA降解。     

Degradation behaviors,thermostability and mechanical properties of poly （ethylene terephthalate）/polylactic acid blends

It is difficult for polyethylene terephthalate （PET） to degrade,which caused severe pollution.In this work,polylactic acid （PLA） was introduced to improve the degradation of PET.PET/PLA was synthesized by extrusion blending.The thermal,crystalline and mechanical properties of blends were investigated with TGA,DSC,WAXD and universal testing machine.The degradation of the blends in soil,acid and alkaline buffer solutions was assessed,respectively.It was found that the introduction of a little PLA promoted crystallization of PET during injection molding process.The starting decomposition temperature lowered from 412.1 ℃ of pure PET to 330.4 ℃ at 50% PLA content,tensile and bending strength of blends gradually decreased with the PLA content increasing,while the degradation rate improved.Alkaline environment was most beneficial for blends to degrade.The degradation mechanism was discussed.