Poly(lactic acid) (PLA) is one of the most important alternatives to fossil-fuel based polymers due to its biodegradability and good properties. However, the growing production along with the increasing resistance to degradation of the newer grades could lead to waste management problem. The application of mechanical recycling, which could be the best valorization method for biodegradation-resistant PLA residues, is limited by the degradation of the polymer, which decreases its performance, so it is interesting to develop simple and acceptable methods to improve the recycled plastic. The aim of this work is to study the effect of thermal treatments of PLA residues (with two levels of degradation) on the structure and properties of recycled PLA. During thermal treatments, both polycondensation and degradation reactions take place, and the net result depends on the degradation level of the residue and the time and temperature of the treatment. In adequate conditions, polycondensation reactions increase the molecular weight of the residue and lead to significant improvements of the mechanical and thermal properties of the recycled plastic. These results suggest that thermal treatments represent a simple, cost-effective and environmentally friendly method to improve the recyclability of PLA and, hence, the environmental impact of this plastic.

聚乳酸（PLA）具有生物降解性和良好的性能，因此是化石燃料基聚合物最重要的替代品之一。但是，随着产量的增长以及对较新等级产品的抗降解能力的提高，可能会导致废物管理问题。机械回收的应用可能是抵抗生物降解的PLA残留物的最佳增值方法，但受到聚合物降解（降低其性能）的限制，因此，开发简单且可接受的方法来改善回收塑料是很有趣的。这项工作的目的是研究热处理的PLA残留物（具有两个降解水平）对再生PLA的结构和性能的影响。在热处理过程中，会发生缩聚和降解反应，最终结果取决于残留物的降解程度以及处理的时间和温度。在适当的条件下，缩聚反应会增加残留物的分子量，并显着改善回收塑料的机械和热性能。这些结果表明，热处理代表了一种简单，具有成本效益且对环境友好的方法，可以提高PLA的可回收性，从而改善这种塑料的环境影响。