低聚物含量对聚乳酸熔纺成形工艺的影响

Influence of oligomer content on melt spinning process of poly(lactic acid)

为确定聚乳酸(PLA)中低聚物的成分并研究其含量对PLA熔纺成形工艺的影响,采用在线取样的方法对同批次不同低聚物含量的PLA切片进行对比分析。通过傅里叶红外光谱仪(FT-IR)、核磁共振氢谱仪(1H NMR)、差式扫描量热仪(DSC)、热失重分析仪(TG)和复丝强力仪对PLA切片的化学结构、熔融和结晶行为、热稳定性以及纤维力学性能进行了测试表征。结果表明:PLA中低聚物的成分为丙交酯和低聚合度的PLA;低聚物的存在降低了PLA切片的玻璃化转变温度、熔融峰温度以及结晶度,增加了半结晶时间,但并未改变其成核方式;去除低聚物后PLA的起始分解温度从134.1℃升高到320.7℃,降解活化能从114.5 kJ/mol增加到354.2 kJ/mol;经热牵伸2.3倍后所得纤维断裂伸长率为17.1%,断裂强度高达4.1 cN/dtex。

Two kinds of PLA with different oligomer contents were used to investigate the specific components of oligomer and the influence of its content on the melt spinning process of PLA. The chemical structure, melting and crystallization behavior and thermal stability of PLA, as well as the mechanical properties of its fibers were studied by using FT-IR, 1H NMR, DSC, TG and yarn strength tester, respectively. Results show that the components of oligomer are lactide and PLA with low degree of polymerization. The presence of oligomer makes the glass transition temperature and melt temperature and crystallinity decreased and the half crystallization time of PLA increased. However, the nucleation mode does not change. Besides, the initial degradation temperature of PLA is increased from 134. 1 ℃ to 320.7 ℃ , and the activation energy during the main stage of degradation is increased from 114.5 kJ/mol 354.2 kJ/mol when oligomers are removed. Moreover, the strength-at-break of PLA fibers reaches 4.1 cN/dtex while the elongation-at-break maintains at 17.1% when drafted by 2.3 times.