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通过凝胶渗透色谱(GPC)和流变学手段研究了光学稳定剂UV-944、UV-531、UV-9、抗氧剂7910以及甲基丙烯酸缩水甘油酯(GMA)和亚磷酸三苯酯(TPP)六种助剂对聚乳酸(PLA)的的热降解和热稳定性的影响。结果表明:PLA粒料经混炼压片后重均分子量由13.6万下降至10.1万;经过180℃下热处理5h,纯PLA的重均分子量由10.1万下降至3.7万,而填加0.25%(wt)的TPP可使PLA基体的重均分子量由10.1万下降至9.1万;TPP含量为0.25%(wt)样品的储能模量和复数粘度在整个研究时间范围内均保持稳定不变。这些结果表明,TPP的引入有效地阻止了PLA的热降解。UV-944和抗氧剂7910改性PLA样品的重均分子量分别保持在13.3万和12.1万左右,有效地改善了基体的热稳定性。复配助剂UV-944+7910对于PLA基体热稳定性的提高具有协同作用,其效果优于各单一助剂,其它复配助剂均对PLA基体热稳定性的改善效果不佳。
Optical stabilizers UV-944, UV-531, UV-9, antioxidant 7910 and glycidyl methacrylate (GMA) and triphenyl phosphite were studied by gel permeation chromatography (GPC) (TPP) six additives on polylactic acid (PLA) thermal degradation and thermal stability. The results showed that the weight average molecular weight of PLA pellets decreased from 136,000 to 101,000 after mixing and pressing. The weight average molecular weight of pure PLA decreased from 101,000 to 37,000 after heat treatment at 180 ℃ for 5h, while 0.25% wt) of TPP decreased the weight average molecular weight of PLA matrix from 101,000 to 91,000. The storage modulus and complex viscosity of 0.25% (wt) TPP remained stable throughout the study period. These results indicate that the introduction of TPP effectively prevents the thermal degradation of PLA. The weight average molecular weights of UV-944 and antioxidant 7910-modified PLA samples were maintained at about 133,000 and 121,000, respectively, effectively improving the thermal stability of the matrix. The compounding aid UV-944 + 7910 has synergistic effect on the thermal stability of PLA matrix, and its effect is better than that of single additive. All the other compound auxiliaries have not good effect on the thermal stability of PLA matrix.