Cruz Heidy, Son Younggon
Division of Advanced Materials Science and Engineering, Kongju National University, Cheonan, Chungnam 331717, S. Korea.
J Nanosci Nanotechnol. 2018 Feb 1;18(2):943-950. doi: 10.1166/jnn.2018.13950.
Since the discovery of carbon nanotubes (CNT), significant research works have focused on the application of CNT as conductive filler to polymer nanocomposites which can be used in several fields such as electrostatic dissipation (ESD), electrostatic painting and electromagnetic interference shielding (EMI-shielding). However, the main challenge in the large-scale manufacturing of this technology is the poor electrical conductivity of polymer nanocomposites produced by injection molding process. This study aims to investigate the effect of CNT aspect ratio in improving the electrical conductivity of injection molded nanocomposites. In this work, three types of multiwall carbon nanotubes with different lengths were melt-mixed with polycarbonate in a twin screw extruder followed by injection and compression molding. Results show that nanocomposites with higher CNT aspect ratio exhibit higher electrical conductivity. Longer nanotubes form a stronger conductive network during secondary agglomeration which can withstand the high shear forces during injection molding. Higher melt viscosity and storage modulus were observed in nanocomposites with higher CNT aspect ratio which is attributed to the effective constriction of polymer chains by longer nanotubes. It was also found that Tg of the composites increased with nanotube aspect ratio and the addition of CNT causes degradation which leads to the general Tg depression of polycarbonate.
自从发现碳纳米管（CNT）以来，大量的研究工作都集中在将碳纳米管作为导电填料应用于聚合物纳米复合材料，这些复合材料可用于静电耗散（ESD）、静电喷涂和电磁干扰屏蔽（EMI屏蔽）等多个领域。然而，这项技术大规模制造的主要挑战在于注塑工艺生产的聚合物纳米复合材料的导电性较差。本研究旨在探讨碳纳米管长径比在提高注塑纳米复合材料导电性方面的作用。在这项工作中，将三种不同长度的多壁碳纳米管与聚碳酸酯在双螺杆挤出机中熔融混合，然后进行注塑和压缩成型。结果表明，具有较高碳纳米管长径比的纳米复合材料表现出更高的导电性。较长的纳米管在二次团聚过程中形成更强的导电网络，能够承受注塑过程中的高剪切力。在具有较高碳纳米管长径比的纳米复合材料中观察到更高的熔体粘度和储能模量，这归因于较长的纳米管对聚合物链的有效约束。还发现复合材料的玻璃化转变温度（Tg）随纳米管长径比的增加而升高，并且碳纳米管的添加会导致降解，从而导致聚碳酸酯的总体Tg降低。
