聚丙烯/碳纳米管复合材料的结构与导电性能:注塑工艺与膨胀石墨的影响

获得高性能碳纳米管（MWCNT）增强聚合物复合材料的关键在于控制碳纳米管在聚合物基体中的分布与取向。传统的注塑成型工艺下，碳纳米管容易发生取向，其表面电阻率远远大于模压成型时的电阻率。本文通过调整注塑工艺改变剪切场实现对碳纳米管在基体中分布与取向的控制。结果表明：在低熔体温度和高注射速度下，碳纳米管局部取向，导电性能下降；而在高熔体温度和低注射速度下，碳纳米管分散良好，导电网络优良，聚丙烯/碳纳米管（PP/MWCNT）注塑制品的导电性能得到有效提升，其表面电阻率下降了约5个数量级。加入膨胀石墨（EG）有增强导电网络的作用，使PP/MWCNT/EG复合材料的导电网络更为完善，其导电性能进一步提高，尤其在低熔体温度和高注射速度下最为明显；随着EG含量的增加，PP/MWCNT/EG的表面电阻率下降了3个数量级。

Structure and Electric Conductivity of Polypropylene/Carbon Nanotubes Composites:Effect of Injection Process and Expanded Graphite

Distribution and orientation of carbon nanotubes are key parameters to achieve high performance of MWCNT reinforced polymer composites.Under the traditional injection process,surface resistivity of injection molding samples is far higher than that prepared by compression molding,because MWCNT is prone to orient along the direction of flow.In this paper,by adjusting the injection molding process to change the shear field,the distribution and orientation of MWCNT in the matrix were controlled.At a low melt temperature and high injection velocity,carbon nanotubes were locally oriented in the flow direction,which reduced the conductivity.However,at higher melt temperature and lower injection speed,fine conductive network was formed with well dispersion of MWCNT,which effectively improved the conductivity of PP/MWCNT injection samples to reduce the surface resistivity by 5 orders of magnitude.Addition of the expanded graphite,led to enhance and improve the conductive network and thus to increase the electrical conductivity of PP/MWCNT/EG composites,especially at low melt temperature and high injection velocity.With the increase of expanded graphite content,surface resistivity of the composite decreased by 3 orders of magnitude.