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首页> 外文期刊>Physical chemistry chemical physics: PCCP >Relaxation behavior of shear-induced crystallization precursors in isotactic polypropylene containing sorbitol-based nucleating agents with different nucleating abilities
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Relaxation behavior of shear-induced crystallization precursors in isotactic polypropylene containing sorbitol-based nucleating agents with different nucleating abilities

机译：剪切诱导的结晶前体在含有不同成核能力的山梨醇基成核剂的等规聚丙烯中的弛豫行为

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摘要

The nature of shear-induced crystallization precursors, especially their relaxation behaviour, is an important issue in polymer chemical physics. In our work, relaxation behavior of shear-induced crystallization precursors in isotactic polypropylene containing various sorbitol-based nucleating agents (NAs) with different nucleating abilities was investigated by using both rheological and in situ small angle X-ray scattering (SAXS) methods. Rheological crystallization kinetics results showed that the amount of shear-induced precursors, calculated separately from the total nuclei, decayed exponentially with relaxation time in both pure and nucleated iPP. By fitting the decay of shear-induced precursors with relaxation time, the relaxation rate of precursors in nucleated iPP was found to be slower than that in pure iPP. Interestingly, it further decreased with the increase in the nucleating ability of sorbitol-based NAs. Meanwhile, the life-time of precursors was prolonged in nucleated iPP with increasing nucleating ability. Similar results were also testified by in situ SAXS measurements. By investigating the life-times at different temperatures, the activation energy for the relaxation of precursors was calculated and found to increase with stronger nucleating abilities. Our results demonstrated that sorbitol-based NAs could stabilize the iPP precursors and the effect of stabilization enhanced with the increase in nucleating ability. We believe that our work can not only help better reveal the relaxation behavior of shear-induced precursors but also provides a new perspective for understanding the role of NAs in real processing.
机译：剪切诱导的结晶前体的性质，特别是其弛豫行为，是聚合物化学物理学中的重要问题。在我们的工作中，通过使用流变和原位小角度X射线散射（SAXS）方法研究了剪切诱导的结晶前体在含有各种具有不同成核能力的山梨醇基成核剂（NAs）的等规聚丙烯中的弛豫行为。流变结晶动力学结果表明，在纯iPP和有核iPP中，从总核中分别计算出的剪切诱导前体的数量随驰豫时间呈指数衰减。通过将剪切诱导的前体的衰减与弛豫时间拟合，发现有核iPP中前体的弛豫速率比纯iPP中的慢。有趣的是，随着基于山梨糖醇的NA的成核能力的增加，其进一步降低。同时，随着成核能力的提高，有核iPP中前驱体的寿命延长。通过原位SAXS测量也证明了相似的结果。通过研究在不同温度下的寿命，可以计算出前体弛豫的活化能，并发现其随着成核能力的增强而增加。我们的结果表明，基于山梨糖醇的NAs可以稳定iPP前体，并且随着成核能力的提高，稳定作用得到增强。我们相信，我们的工作不仅可以帮助更好地揭示剪切诱导前体的弛豫行为，而且可以为理解NA在实际加工中的作用提供新的视角。

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