关键词: 聚乳酸, 水解降解, 化学循环, 循环稳定性

Abstract:

The degradation behavior of poly(lactic acid) (PLA) was investigated at a high temperature of 180 °C under the circulating hydrothermal condition, and their weight variation, generation of lactic acid, thermal weight?loss process, and chemical structure were evaluated by mass?loss rate, high performance liquid chromatography, thermogravimetric analysis, Fourier?transform infrared spectroscopy and liquid chromatography?mass spectrometry. The results indicated that the greater the cycle number, the faster the weight loss of PLA. The weight loss process was completed within 40 minutes by a hydrothermal reaction at 180 ° C. The production rate of lactic acid was accelerated with an increase of cycle number, but there was almost no variation in final volume. The PLA conversion rate was not reduced by the chemical cycling process, indicating a good cycle stability. The stability of PLA was enhanced with the progress of hydrothermal process, and the more cycles resulted in a much better stability. In the hydrothermal process, the hydroxyl index and carbonyl index of PLA exhibited an increasing trend with an increase of cycle number, suggesting that the chemical cycle process could accelerate the degradation of PLA.

Key words: poly(lactic acid), hydrolytic degradation, chemical cycle, cycle stability