Influence of melt structure on Form II to I phase transition of Polybutene-1 under shear flow
Influence of melt structure on Form II to I phase transition of Polybutene-1 under shear flow
复制标题
剪切流下熔体结构对聚丁烯-1 II 型至 I 型相变的影响
DOI：
10.1016/j.polymer.2020.122562
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发表时间：
2020
期刊：
影响因子：
4.6
通讯作者：
Chen Jingbo
中科院分区：
文献类型：
--
作者：
Lu Yaguang;Li Han;Wei Hongxing;Wang Binghua;Shen Changyu;Zhang Bin;Chen Jingbo
几十年来，已有研究报道了聚丁烯-1 （PB-1）的化学结构和组成、共混组分和环境对其从II型向I型相变的影响。然而，在聚合物加工方面，如何以简便的方式加速相变仍然是一个具有挑战性的任务。在本研究中，通过毛细管模具简单挤压PB-1的近熔点熔体（NMP熔体）可以实现四倍的相变速率。采用原位小/广角x射线散射（SAXS/WAXS）研究了在名义熔化温度（T m）和平衡熔化温度（T m 0）之间的部分熔化温度（T p）下，非晶熔体内存在的I型纳米晶体的熔化加速了相变。在挤压NMP熔体时，形式II的转变速度比静态NMP熔体更快。在动力学上，半转变时间（τ 1/2）随温度的升高而增加。此外，核心层的τ 1/2比表皮层的τ 1/2大。研究结果表明，熔融幸存的I型纳米晶和剪切流动在加速PB-1的相变过程中起着不可或缺的作用。我们初步认为，在相变过程中，由于剪切流动导致更多的束缚分子分布在取向片层中，而引入额外的内应力取决于I型纳米晶体与II型片层晶体热膨胀系数的不匹配，从而导致I型纳米晶体在相变过程中更高的成核概率。
For decades, the influences of chemical structures and compositions, blend components and ambient environments on phase transition of polybutene-1 (PB-1) from Form II to I have been reported. Nevertheless, in terms of polymer processing, how to expedite the phase transition with a facile way is still a challenging task. In this study, four times the phase transition rate can be achieved by simply extruding the near melting point melt (NMP melt) of PB-1 through a capillary die. The melting survived Form I nanocrystals within the amorphous melt at the partially melting temperature (T p) between the nominal melting temperature (T m) and the equilibrium melting temperature (T m 0) allow accelerating the phase transition which was investigated by means of in situ small/wide angle X-ray scattering (SAXS/WAXS). Upon extruding of NMP melt, Form II transformed even faster than in the quiescent NMP melt. The number of flow-induced oriented crystalline structures (cylindrites) increased by reducing T p. Kinetically, the half-transformation time (τ 1/2) increased with rising T p. Furthermore, τ 1/2 of the core layer is large compared to τ 1/2 of the skin layer. Our results suggest that both melting survived Form I nanocrystals and shear flow play integral roles in accelerating the phase transition of PB-1. We tentatively concluded that the higher nucleation probability of Form I during phase transition can be generated by more tie molecules distributed in the oriented lamellae caused by shear flow and the introducing extra internal stresses depended on the mismatch in the thermal expansion coefficients of Form I nanocrystals and Form II lamellar crystals.