This research considers a two‐step chain extension reaction in the presence of two chain extenders, Joncryl and Pyromellitic dianhydride (PMDA), as a solution for poor melt properties of poly (lactic acid) (PLA). The aim of adding PMDA is to increase the carboxyl groups via the anhydride ring‐opening reaction so that the reaction between PLA and Joncryl could be facilitated since the reactivity between the epoxy and carboxyl group is more than epoxy and hydroxyl group. The reactions are confirmed by measuring the acid value, and a two‐step reaction mechanism is suggested. Shear and elongational rheological properties of the samples are investigated; furthermore, gel permeation chromatography analyses and tensile tests are exploited for studying the molecular weight and tensile properties, respectively. The results show that the chain extension reactions lead to an increase in the storage modulus, complex viscosity, and molecular weight. Also, the PLA chains which are extended utilizing both chain extenders simultaneously evince a synergistic improvement in the shear and elongational rheological properties due to longer segments between branching points on the structure.

中文翻译：

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Joncryl和PMDA两步扩链对聚乳酸流变性能的影响

这项研究考虑了在存在两种扩链剂琼脂基和均苯四酸二酐（PMDA）的情况下进行的两步扩链反应，作为解决聚乳酸（PLA）熔融性能差的解决方案。添加PMDA的目的是通过酸酐的开环反应增加羧基，从而可以促进PLA和Joncryl之间的反应，因为环氧和羧基之间的反应性大于环氧和羟基。通过测量酸值可以确认反应，并提出了两步反应机理。研究了样品的剪切和伸长流变特性。此外，利用凝胶渗透色谱分析和拉伸试验分别研究分子量和拉伸性能。结果表明，扩链反应导致储能模量，复数粘度和分子量的增加。同样，同时利用两个扩链剂延伸的PLA链由于在结构上的支化点之间较长的链段而需要在剪切和伸长流变性质上的协同改善。