Ultralow percolation threshold and enhanced electromagnetic interference shielding in poly(L-lactide)/multi-walled carbon nanotube nanocomposites with electrically conductive segregated networks
Ultralow percolation threshold and enhanced electromagnetic interference shielding in poly(L-lactide)/multi-walled carbon nanotube nanocomposites with electrically conductive segregated networks
复制标题
DOI：
10.1039/c7tc02948a
复制
发表时间：
2017-09
影响因子：
6.4
通讯作者：
Kai Zhang;Gen-Hui Li;La-Mei Feng;Ning Wang;Jiang Guo;Kai Sun;Kai-Xin Yu;J. Zeng;Tingxi Li-Tin
中科院分区：
文献类型：
--
作者：
Kai Zhang;Gen-Hui Li;La-Mei Feng;Ning Wang;Jiang Guo;Kai Sun;Kai-Xin Yu;J. Zeng;Tingxi Li-Tin
通过简单地选择两种不同粘度和堆积度的聚乳酸（PLLA）聚合物，在不牺牲力学性能的前提下，在聚乳酸/多壁碳纳米管（PLLA/MWCNT）纳米复合材料中构建了导电隔离网络。首先，将MWCNT分散在具有低粘度和结晶度的PLLA（L-PLLA）中以获得L-PLANT相。第二，具有高粘度和结晶度的PLLA颗粒（H-PLLA）在低于H-PLLA的熔融温度的140 °C下被L-PLANT相很好地涂覆。最后，将包覆的H-PLLA颗粒在高于H-PLLA的熔融温度下压缩以形成具有分离结构的PLLA/MWCNT纳米复合材料。形态学观察表明，多壁碳纳米管在连续的L-PLLA相的成功的位置，导致在0.019体积%的多壁碳纳米管的超低渗流阈值。具有分离结构的复合材料的电导率和电磁干扰（EMI）屏蔽效能（SE）分别为25 S m-1和30 dB，比具有0.8vol% MWCNT随机分布的样品高出3个数量级和36%。MWCNT负载量。高性能的电磁干扰（EMI）屏蔽也被观察到主要依赖于高效的吸收屏蔽，这可以通过密集连续的MWCNT网络和由隔离结构诱导的丰富界面来实现。此外，具有偏析结构的复合材料不仅表现出更高的杨氏模量和拉伸强度比相应的常规复合材料，但也保持了高的断裂伸长率，这是由于连续和致密的MWCNT网络的偏析结构诱导和高的H-PLLA和L-PLLA之间的界面相互作用。
Electrically conductive segregated networks were built in poly(L-lactide)/multi-walled carbon nanotube (PLLA/MWCNT) nanocomposites without sacrificing their mechanical properties via simply choosing two different PLLA polymers with different viscosities and crystallinities. First, the MWCNTs were dispersed in PLLA with low viscosity and crystallinity (L-PLLA) to obtain the L-PLANT phase. Second, the PLLA particles with high viscosity and crystallinity (H-PLLA) were well coated with the L-PLANT phase at 140 °C which was below the melting temperature of H-PLLA. Finally, the coated H-PLLA particles were compressed above the melting temperature of H-PLLA to form the PLLA/MWCNT nanocomposites with segregated structures. The morphological observation showed the successful location of MWCNTs in the continuous L-PLLA phase, resulting in an ultralow percolation threshold of 0.019 vol% MWCNTs. The electrical conductivity and the electromagnetic interference (EMI) shielding effectiveness (SE) of the composites with the segregated structure are 25 S m−1 and ∼30 dB, showing three orders and 36% higher than that of the samples with a random distribution of MWCNTs with 0.8 vol% of MWCNT loading, respectively. High-performance electromagnetic interference (EMI) shielding was also observed mainly dependent on the highly efficient absorption shielding, which can be achieved by the densely continuous MWCNT networks and the abundant interfaces induced by the segregated structures. Furthermore, the composites with segregated structures not only showed higher Young's modulus and tensile strength than the corresponding conventional composites, but also maintained high elongation at break because of the continuous and dense MWCNT networks induced by the segregated structures and the high interfacial interaction between H-PLLA and L-PLLA.