Blending low content of poly[(R)-3-hydroxybutyrate-co-4-hydroxybutyrate] (P34HB ≤8 wt %) with poly(L-lactide) (PLLA) has proven effective in enhancing heat resistance of PLLA fibers. Unfortunately, the enhancement is relatively limited with boiling water shrinkage of PLLA/P34HB blend fibers reduced to 9.9% at most. In this study, a series of PLLA/poly[(R)-3-hydroxybutyrate] (PHB) blend fibers with low PHB content (≤8 wt %) was prepared with sound spinnability. Surprisingly, the PLLA/PHB blend fibers showed much lower boiling water shrinkage than the PLLA/P34HB blend fibers with the same blend ratio. In particular, the boiling water shrinkage was dropped from ca. 80% for neat PLLA fibers to 9.9% for the PLA/P34HB blend fibers and further to 3.8% for the PLA/PHB blend fibers with 8 wt % P34HB or PHB added. Such an exceptionally improved heat resistance of the PLLA/PHB blend fibers could be closely related to an increase in crystallinity (X_c,PLLA) of the PLLA phase. Specifically, the mobility of the PLLA segments was promoted in the presence of PHB, along with notably improved orientation of the PLLA phase in the PLLA/PHB blend fibers. More importantly, investigation on crystallization behaviors revealed that the PHB phase served as an effective nucleating agent to accelerate the overall crystallization of PLLA. By contrast, the P34HB phase only acted as spherulite growth-accelerating and/or nucleation-assisting agents. These findings help provide a facile and effective strategy to improve heat resistance of PLLA fibers more significantly.

中文翻译：

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具有优异耐热性的聚丙交酯/聚[(R)-3-羟基丁酸酯] (PHB) 共混纤维：PHB 对结晶的影响

将低含量的聚[( R )-3-羟基丁酸酯-co -4-羟基丁酸酯] (P34HB ≤8 wt%) 与聚 (L-丙交酯) (PLLA) 混合已证明可有效提高 PLLA 纤维的耐热性。不幸的是，增强相对有限，PLLA/P34HB 混纺纤维的沸水收缩率最多降至 9.9%。在这项研究中，一系列 PLLA/poly[( R)-3-羟基丁酸酯] (PHB) 混合纤维具有低 PHB 含量（≤8 wt%），具有良好的可纺性。令人惊讶的是，PLLA/PHB 混纺纤维的沸水收缩率比具有相同混纺比的 PLLA/P34HB 混纺纤维低得多。特别是，沸水收缩率从 ca 下降。纯 PLLA 纤维为 80%，PLA/P34HB 混合纤维为 9.9%，添加 8 wt% P34HB 或 PHB 的 PLA/PHB 混合纤维为 3.8%。PLLA/PHB 共混纤维的这种特别改善的耐热性可能与结晶度的增加密切相关（X _c,PLLA) 的 PLLA 阶段。具体而言，在 PHB 存在的情况下，PLLA 链段的流动性得到提升，同时 PLLA/PHB 共混纤维中 PLLA 相的取向显着改善。更重要的是，对结晶行为的研究表明，PHB 相是一种有效的成核剂，可加速 PLLA 的整体结晶。相比之下，P34HB 相仅充当球晶生长加速剂和/或成核辅助剂。这些发现有助于提供一种简便有效的策略来更显着地提高 PLLA 纤维的耐热性。