Achieving a low electrical percolation threshold and superior mechanical performance in poly(L-lactide)/thermoplastic polyurethane/carbon nanotubes composites via tailoring phase morphology with the aid of stereocomplex crystallites
Achieving a low electrical percolation threshold and superior mechanical performance in poly(L-lactide)/thermoplastic polyurethane/carbon nanotubes composites via tailoring phase morphology with the aid of stereocomplex crystallites
复制标题
通过借助立体复合微晶调整相形态，实现聚（L-丙交酯）/热塑性聚氨酯/碳纳米管复合材料的低电渗流阈值和优异的机械性能
DOI：
10.1039/c6ra27401c
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发表时间：
2017-01-01
期刊：
影响因子：
3.9
通讯作者：
Fu, Qiang
中科院分区：
文献类型：
--
作者：
Liu, Zhenwei;Bai, Hongwei;Fu, Qiang
导电纳米填料在共连续聚合物共混物中的选择性定位为大大降低导电聚合物复合材料的电渗流阈值提供了一种有效的方法。然而，实现非常低的逾渗阈值仍然是一个很大的挑战，因为选择性填充相的完全连续性的临界含量通常很高。本文以聚乳酸/热塑性聚氨酯/碳纳米管（PLLA/TPU/CNTs）复合材料为例，通过在PLLA熔体中构建立体复合物（SC）微晶，有效调控共混物基体的相变行为，实现了一种简便、通用的制备高导电PLLA基复合材料的策略，该复合材料具有极低的逾渗阈值和优异的刚韧性平衡。为此，通过在190 °C下熔融混合将少量能够与PLLA链共结晶以形成SC微晶的聚（D-丙交酯）（PDLA）掺入复合材料中。这些SC微晶可以用作物理交联点以显著增加PLLA熔体粘度，并随后在低得多的CNT填充的TPU相含量下在PLLA/TPU共混物基质中诱导共连续结构的形成。结果，所获得的复合材料不仅显示出显着降低的逾渗阈值（0.3重量%），但也表现出平衡的冲击韧性和机械强度。重要的是，促进共混基质中CNT填充相的完全连续性的策略是低成本和可扩展的，为高导电性PLLA基复合材料的设计和工程开辟了新的途径。
Selective localization of conductive nanofillers in one phase of co-continuous polymer blends provides an efficient method to greatly reduce the electrical percolation threshold of conductive polymer composites. However, it is still a big challenge to achieve very low percolation thresholds because the critical content for the complete continuity of the selectively filled phase is generally high. In this contribution, taking poly(L-lactide)/thermoplastic polyurethane/carbon nanotubes (PLLA/TPU/CNTs) composite as an example, we demonstrate a facile and versatile strategy for the fabrication of highly conductive PLLA-based composites with very low percolation threshold as well as excellent stiffness–toughness balance via constructing stereocomplex (SC) crystallites in PLLA melt to effectively tailor the phase transition behavior of the blend matrices. To do this, small amounts of poly(D-lactide) (PDLA) capable of co-crystallizing with the PLLA chains to form SC crystallites were incorporated into the composites by melt mixing at 190 °C. These SC crystallites can serve as physical cross-linking points to significantly increase PLLA melt-viscosity and subsequently induce the formation of co-continuous structure in the PLLA/TPU blend matrix at a much lower content of the CNTs-filled TPU phase. As a result, the obtained composites not only show a dramatically reduced percolation threshold (0.3 wt%) but also exhibit a balanced impact toughness and mechanical strength. Importantly, the strategy to promote the complete continuity of the CNTs-filled phase in blend matrix is low-cost and scalable, opening up a new avenue for the design and engineering of highly conductive PLLA-based composites.