聚乳酸和聚乳酸/淀粉复合材料在温暖潮湿环境中的水解降解与热氧化降解的区别

Materials Pub Date : 2024-07-25 DOI:10.3390/ma17153683
Victoria Goetjes, Jan-Christoph Zarges, Hans-Peter Heim
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引用次数: 0

摘要

要将聚乳酸(PLA)和聚乳酸/淀粉复合材料应用于玩具等技术部件,就必须了解它们在水热环境中的相关应用条件下的降解行为。为此,我们使用双螺杆挤出机生产了聚乳酸和原生马铃薯淀粉复合材料,然后将其加工成测试试样,在不同的温度(23、50、70、90 °C)和湿度(10、50、75、90%)条件下进行了为期一周的老化处理。随后进行机械表征(拉伸试验),并使用凝胶渗透色谱法(GPC)、热重分析法(TGA)、傅立叶变换红外光谱法(FTIR)和核磁共振光谱法(NMR)鉴定降解情况。随着温度和湿度的升高,聚乳酸出现了明显的降解,由于结晶度增加,加入 50 wt.% 的淀粉可以减少或减缓这种降解。水解被认为是聚乳酸和聚乳酸/淀粉复合材料的主要降解机制,尤其是在玻璃化温度以上,热氧化降解也起着辅助作用。水解降解和热氧化降解都会导致拉伸强度等机械性能降低。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Differentiation between Hydrolytic and Thermo-Oxidative Degradation of Poly(lactic acid) and Poly(lactic acid)/Starch Composites in Warm and Humid Environments
For the application of poly(lactic acid) (PLA) and PLA/starch composites in technical components such as toys, it is essential to know their degradation behavior under relevant application conditions in a hydrothermal environment. For this purpose, composites made from PLA and native potato starch were produced using twin-screw extruders and then processed into test specimens, which were then subjected to various one-week ageing processes with varying temperatures (23, 50, 70, 90 °C) and humidity levels (10, 50, 75, 90%). This was followed by mechanical characterization (tensile test) and identification of degradation using Gel Permeation Chromatography (GPC), Thermogravimetric Analysis (TGA), Fourier Transform Infrared Spectroscopy (FTIR), and Nuclear Magnetic Resonance spectroscopy (NMR). With increasing temperature and humidity, there was a clear degradation of the PLA, which could be reduced or slowed down by adding 50 wt.% starch, due to increased crystallinity. Hydrolysis was identified as the main degradation mechanism for PLA and PLA/starch composites, especially above the glass transition temperature, with thermo-oxidative degradation also playing a subordinate role. Both hydrolytic degradation and thermo-oxidative degradation led to a reduction in mechanical properties such as tensile strength.
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