Abstract:

Hybrid filler with proper filler ratio can better improve the thermal conductivity of polymer composites than the single filler. However, there is a lack of an effective thermal conductive equation of the hybrid filled composites. In this paper, a two-step analytical model was developed for calculating the effective thermal conductivity of composites containing hybrid single-walled carbon nanotubes (SWCNTs) and graphite nanoplatelets (GNPs) filler. Based on the experimental observation in the literature, a unit cell containing a "bridging connection" structure was abstracted, and thermal resistance method and Maxwell-Garnett effective medium approach were used to derive the model with the assumption that the unit cell is an equivalent uniform matrix and the non-bridging SWCNTs is the filler. By order of magnitude analysis, the thermal conductive equation was simplified. The modeling results were highly consistent with the experiment results in the literature. When the total mass fraction of hybrid fillers is constant, the effective thermal conductivity of composites firstly climbs up and then declines with the increase of GNPs, showing a clear synergistic effect. At a certain mass fraction ratio of hybrid filler, the effective thermal conductivity of composites rises with the increase of mass fraction of hybrid fillers.

Key words: composites, thermal conductivity, model, predict, carbon nanotubes, graphite nanoplatelets

摘要：

混合填充复合材料的导热特性好于单一填充。根据碳纳米管与纳米片状石墨在高分子基材中的分布形态, 将碳纳米管与纳米片状石墨的"桥状搭接"结构作为等效基材, 未搭接的"游离态"碳纳米管作为填料, 利用串并联热阻模型和Maxwell-Garnett等效介质法建立了混合填充复合材料的导热模型, 并通过数量级分析对热导率方程进行了简化。结果表明, 在混合填料质量分数不变的情况下, 等效热导率随纳米片状石墨的增多呈现先增加后减少的趋势, 表现出明显的协同效应;在质量分数配比不变的情况下, 等效热导率随混合填料的质量分数增大而增大。

关键词: 复合材料, 热导率, 模型, 预测, 碳纳米管, 纳米片状石墨