Physical aging embrittles poly(lactide acid) (PLA), an eco‐friendly, biocompatible, and biodegradable polymer. Freshly hot pressed polylactic acid has a large rupturing strain, breaking at small deformation after aging for several hours at room temperature. The application of poststretching onto PLA, however, can increase its toughness and mechanical stability, as shown by Shengqiang Cai and colleagues in the article on page 3488. (DOI: 10.1002/pol.20200526)

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封面图片，第58卷，第24期

物理老化会使聚丙交酯酸（PLA）变脆，这是一种生态友好，具有生物相容性且可生物降解的聚合物。新鲜热压的聚乳酸具有大的破裂应变，在室温下老化数小时后以小的变形破裂。但是，将后拉伸应用到PLA上可以提高其韧性和机械稳定性，如蔡胜强及其同事在3488页上的文章中所示。（DOI：10.1002 / pol.20200526）