Formation of stretched fibrils and nanohybrid shish-kebabs in isotactic polypropylene-based nanocomposites by application of a dynamic oscillatory shear
Formation of stretched fibrils and nanohybrid shish-kebabs in isotactic polypropylene-based nanocomposites by application of a dynamic oscillatory shear
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通过应用动态振荡剪切在等规聚丙烯纳米复合材料中形成拉伸原纤维和纳米杂化羊肉串
DOI：
10.1016/j.cej.2018.04.197
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发表时间：
2018-09-15
影响因子：
15.1
通讯作者：
Kuang, Tairong
中科院分区：
文献类型：
--
作者：
Li, Lengwan;Li, Wei;Kuang, Tairong
高分子材料从微观到纳米的层次结构对其物理性能有显著影响。通过加工控制聚合物中分层结构的形成仍然是一个挑战。本文提出了一种绿色、便捷的聚合物加工方法，利用新开发的环振荡推拉成型（LOPPM）方法制备具有层次超结构的等规聚丙烯(iPP)/聚四氟乙烯（PTFE）纳米复合材料。通过充分利用强振荡剪切的优势，原位生成的聚四氟乙烯原纤维被细化为纳米级且排列良好，作为中心纤维，诱导形成具有iPP晶片（kebabs）的纳米杂交羊肉串（NHSK）上层结构。利用分子动力学模拟进一步研究了NHSK超结构的结构演化。与无原纤维或具有柔性原纤维的系统相比，拉伸后的原纤维可以促进串生长成具有更紧凑和有序的分子链结构的大结构域。排列良好的原纤维和NHSK上层结构对提高性能起着至关重要的作用。所制备的含3 wt% PTFE的iPP/PTFE纳米复合材料与常规注塑复合材料相比，冲击强度和弯曲强度分别提高了197.9%和36.0%。同时，LOPPM iPP/PTFE纳米复合材料在恶劣环境（超过150℃）下具有优异的抗热变形性能，同时具有疏水性表面。这些发现提供了一个简单的策略，以生产高性能聚合物从审慎控制的样品制剂。
The hierarchical structures from micro-to nano-scale in polymeric materials can dramatically affect their physical properties. Controlling the formation of hierarchical structures in polymers through processing remains a challenge. We present here a green and convenient polymer processing approach to prepare isotactic polypropylene (iPP)/polytetrafluoroethylene (PTFE) nanocomposites with hierarchical superstructures via recently developed loop oscillating push-pull molding (LOPPM) method. By taking full advantage of intense oscillatory shear, the in situ generated PTFE fibrils are refined into nanoscale and well aligned, serving as the central shish to induce the formation of nanohybrid shish-kebab (NHSK) superstructure with iPP crystalline lamellae (kebabs). The structure evolution of NHSK superstructures was further examined using molecular dynamics simulations. The stretched fibrils can promote the kebabs growing into large domains with a more compact and ordered molecular chain configuration, compared to that in systems without fibrils or with flexible fibrils. The well-aligned fibrils and NHSK superstructure play a crucial role in enhancing properties. The prepared iPP/PTFE nanocomposites containing 3 wt% PTFE achieved 197.9% and 36.0% improvement in impact and flexural strength, respectively, as compared with the conventional injection-molded composites. Meanwhile, the LOPPM iPP/PTFE nanocomposites exhibits excellent resistance to thermal deformation under harsh environment (over 150 degrees C) while fabricates a hydrophobic surface. These findings provide a facile strategy to produce high-performance polymers from judiciously controlled sample preparations.