Abstract Poly (lactic acid) (PLA) has properties suitable for many applications. However, PLA's properties are affected by environmental conditions. In this study, the glass-rubber transition temperatures (Tg) of PLA films were measured during immersion (i.e., in-situ) in pure alcohols and alcohol aqueous solutions using a dynamic mechanical analysis technique. The Tg of PLA decreased when immersed in alcohols. For pure aliphatic alcohols, the Tg reduction became smaller as the number of carbons (C1–C10) in the alcohol main chains increased. The Fox equation and the Hansen solubility parameters (HSP)/Flory-Huggins (FH) model were used to explain the Tg reduction. The relationships explained the interactions between PLA and pure alcohols with small molecules (C1–C8), but bigger pure alcohols (C9–C10) did not fit the prediction. The chemical isomerism in pure propanol (i.e., propan-1-ol and propan-2-ol) did not affect the Tg reduction. The Tg reduction in propan-2-ol aqueous solutions was concentration dependent although the partition coefficients based on the HSP and the FH parameters did not fit this relationship. The in-situ immersion of PLA in alcohol solutions could be used to evaluate the change in Tg from the Tg of dry PLA.

中文翻译：

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聚乳酸薄膜在醇溶液中热机械性能的原位变化

摘要 聚乳酸 (PLA) 具有适用于多种应用的特性。然而，PLA 的性能受环境条件的影响。在这项研究中，PLA 薄膜的玻璃-橡胶转变温度 (Tg) 在浸入（即原位）纯醇和醇水溶液期间使用动态力学分析技术进行测量。当浸入醇中时，PLA 的 Tg 降低。对于纯脂肪醇，随着醇主链中碳原子数（C1-C10）的增加，Tg 降低量变小。Fox 方程和 Hansen 溶解度参数 (HSP)/Flory-Huggins (FH) 模型用于解释 Tg 降低。该关系解释了 PLA 和纯醇与小分子 (C1-C8) 之间的相互作用，但较大的纯醇 (C9-C10) 不符合预测。纯丙醇（即丙-1-醇和丙-2-醇）中的化学异构不影响Tg 降低。尽管基于 HSP 和 FH 参数的分配系数不符合这种关系，但 2-丙醇水溶液中的 Tg 降低与浓度有关。PLA 在醇溶液中的原位浸渍可用于评估 Tg 相对于干 PLA 的 Tg 的变化。