Du Mengxue, Jariyavidyanont Katalee, Kühnert Ines, Boldt Regine, Androsch René
Interdisciplinary Center for Transfer-oriented Research in Natural Sciences, Martin Luther University Halle-Wittenberg, 06099 Halle/Saale, Germany.
Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Str. 6, 01069 Dresden, Germany.
Polymers (Basel). 2021 Apr 13;13(8):1266. doi: 10.3390/polym13081266.
The concept of specific work of flow has been applied for the analysis of critical shearing conditions for the formation of crystal nuclei in poly (l-lactic acid) (PLLA). Systematic variation in both time and rate of shearing the melt in a parallel-plate rheometer revealed that these parameters are interconvertible regarding the shear-induced formation of crystal nuclei; that is, low shear rate can be compensated for by increasing the shear time and vice versa. This result supports the view that critical shearing conditions can be expressed by a single quantity, providing additional options for tailoring polymer processing routes when enhanced nuclei formation is desired/unwanted. Analysis of PLLA of different mass-average molar masses of 70, 90, 120, and 576 kDa confirmed improved shear-induced crystal nucleation for materials of higher molar mass, with critical specific works of flow, above which shear-induced nuclei formation occurs, of 550, 60, 25, and 5 kPa, respectively.
流动比功的概念已被应用于分析聚（L-乳酸）（PLLA）中晶核形成的临界剪切条件。在平行板流变仪中对熔体进行剪切时，时间和剪切速率的系统变化表明，就剪切诱导的晶核形成而言，这些参数是可以相互转换的；也就是说，低剪切速率可以通过增加剪切时间来补偿，反之亦然。这一结果支持了这样一种观点，即临界剪切条件可以用一个单一的量来表示，当需要/不需要增强成核时，为定制聚合物加工路线提供了更多选择。对质量平均摩尔质量分别为70、90、120和576 kDa的不同PLLA进行分析，证实了较高摩尔质量的材料具有更好的剪切诱导结晶成核能力，其发生剪切诱导成核的临界流动比功分别为550、60、25和5 kPa。
