Polylactide (PLA) is a representative material in biodegradable polymers, but its application is limited due to the brittleness and poor toughness. In order to investigate the basic brittleness mechanism of PLA, the morphology and formation of spherulite defects in PLA, including ring line cracks with width around 0.3 nm and micropores with diameters of 0.8-1.2μm, were studied by polarizing microscope and atomic force microscope. The effects of cooling rate, sample thickness, PLA molecular weight, isothermal crystallization temperature and spherulite growth maturity on PLA spherulite defects were discussed. Both ring line cracks and micropores are caused by internal stress caused during PLA melt cooling process, and their morphology would be changed by internal stress distribution with various factors mentioned above. The inhibition of crystal defects will potentially improve the mechanical properties of PLA, thus these results will provide useful references for the toughening modification of PLA.

聚丙交酯（PLA）是生物可降解聚合物的代表材料，但由于其脆性和韧性差，其应用受到限制。为了研究PLA的基本脆性机理，通过偏光显微镜和原子力显微镜研究了PLA的球晶缺陷的形貌和形成，包括宽度约0.3 nm的环形裂纹和直径0.8-1.2μm的微孔。讨论了冷却速率，样品厚度，PLA分子量，等温结晶温度和球晶生长成熟度对PLA球晶缺陷的影响。环形裂纹和微孔都是由PLA熔体冷却过程中产生的内部应力引起的，它们的形态会因上述各种因素而受到内部应力分布的影响。