Abstract Bio-based and bio-degradable poly( l -lactide), PLLA, suffers from low crystallization rate. The synergetic effect of fibril-like nucleator (N1,N1′-(ethane-1,2-diyl)bis(N2-phenyloxalamide)) (OXA) and shear flow on speeding up the melt crystallization of the PLLA is the first time reported in this work. The synergetic effect was investigated by using a rheometer. Neither fibril-like OXA nor shear flow showed obvious accelerating effect at 155 °C on the crystallization of PLLA leading to limited crystallinity (Xc) within 70–100 min. In contrast, a crystallinity of more than 40% and an onset crystallization time (tonset) of less than 3 min were achieved by tailoring the shear conditions. The critical shear condition for the fast crystallization of the PLLA/OXA systems at 155 °C is 0.4 rad/s for 10–15 s. A lower shear temperature (e.g., 150 °C in comparison with 155 °C) would increase the crystallization rate much further. Mechanism study revealed that the OXA fibril network and a certain extent of PLLA chain orientation that induced by the shear flow while subsequently stabilized by the OXA fibrils are responsible for the significantly enhanced nucleation and overall melt crystallization kinetics. In addition, the shear flow and fibril-like OXA nucleators not only facilitated the crystallization of PLLA α-form crystals but also promoted the formation of α′- (or δ) and β-form crystals.

中文翻译：

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原纤维状成核剂和剪切流对聚（l-丙交酯）熔体结晶的强协同作用

摘要 生物基和可生物降解的聚（l-丙交酯）PLLA 结晶速率低。首次报道了原纤维状成核剂（N1，N1'-（乙烷-1，2-二基）双（N2-苯基草酰胺））（OXA）和剪切流对加速PLLA熔体结晶的协同作用在这项工作中。使用流变仪研究了协同效应。在 155°C 时，原纤维状 OXA 和剪切流均未对 PLLA 的结晶显示出明显的加速作用，导致 70-100 分钟内结晶度（Xc）有限。相比之下，通过调整剪切条件实现了超过 40% 的结晶度和小于 3 分钟的起始结晶时间（tonset）。PLLA/OXA 系统在 155°C 下快速结晶的临界剪切条件为 0.4 rad/s，持续 10-15 秒。较低的剪切温度（例如，150 °C 与 155 °C 相比）将进一步提高结晶速率。机理研究表明，OXA 原纤维网络和由剪切流诱导并随后由 OXA 原纤维稳定的一定程度的 PLLA 链取向是显着增强的成核和整体熔体结晶动力学的原因。此外，剪切流和原纤维状 OXA 成核剂不仅促进了 PLLA α 型晶体的结晶，而且促进了 α'-（或 δ）和 β 型晶体的形成。机理研究表明，OXA 原纤维网络和由剪切流诱导并随后由 OXA 原纤维稳定的一定程度的 PLLA 链取向是显着增强的成核和整体熔体结晶动力学的原因。此外，剪切流和原纤维状 OXA 成核剂不仅促进了 PLLA α 型晶体的结晶，而且促进了 α'-（或 δ）和 β 型晶体的形成。机理研究表明，OXA 原纤维网络和由剪切流诱导并随后由 OXA 原纤维稳定的一定程度的 PLLA 链取向是显着增强的成核和整体熔体结晶动力学的原因。此外，剪切流和原纤维状 OXA 成核剂不仅促进了 PLLA α 型晶体的结晶，而且促进了 α'-（或 δ）和 β 型晶体的形成。