Abstract：
In this study, we irradiated amorphous (A) and semi-crystalline (SC) poly(lactic acid) (PLA) with different UV-C doses up to 2214 kJ/m2. We achieved an average crystallinity of 43 % by heat treatment, which was unaffected by UV-C irradiation. Modulated differential scanning calorimetry showed that crystal polymorphs and the ratio of rigid amorphous and mobile amorphous phases were also unaffected. Using gel permeation chromatography analysis, we showed that the degradation mechanism was noncatalytic random scission, and the initial molar mass was reduced by >90 % at a dose of 2214 kJ/m2 for both A- and SC-PLA samples. Our Raman spectroscopy results indicated that the probability of the formation of oxygen-containing groups increases with increasing UV-C doses. Since we found that the mechanical properties of PLA films can be tailored with UV-C light, we proposed a method to predict the overall tensile curve as a function of the UV-C dose. We also proposed a modified Cross-WLF model to describe the effect of UV-C irradiation on viscosity up to 55 % molar mass reduction. The models allow us to estimate the limits of recyclability and reusability of sterilised PLA products.
摘要：
在这项研究中,我们用高达2214kJ/m2的不同UV-C剂量辐照无定形(A)和半结晶(SC)聚乳酸(PLA)。我们通过热处理实现了43%的平均结晶度，其不受UV-C照射的影响。调制差示扫描量热法表明，晶体多晶型物以及刚性非晶相和流动非晶相的比例也不受影响。采用凝胶渗透色谱分析,我们发现降解机理是非催化随机断裂，并且对于A-和SC-PLA样品,初始摩尔质量在2214kJ/m2的剂量下降低>90%。我们的拉曼光谱结果表明，含氧基团形成的可能性随着UV-C剂量的增加而增加。由于我们发现PLA薄膜的机械性能可以用UV-C光定制，我们提出了一种方法来预测整体拉伸曲线作为UV-C剂量的函数。我们还提出了一种改进的Cross-WLF模型来描述UV-C辐照对粘度的影响，摩尔质量降低高达55％。这些模型使我们能够估计灭菌PLA产品的可回收性和可重复使用性的限制。
