多壁碳纳米管增强炭黑/聚丙烯导电复合材料导电行为

为了充分利用不同导电粒子的导电作用，在炭黑(CB)/聚丙烯(PP)导电复合体系中引入了多壁碳纳米管(CNTs)。研究发现：引入的CNTs分散在CB粒子间起到“桥梁”作用，使体系的导电性能得到明显改善，并且CB∶CNTs为19∶1时其协同导电效果最好，该复合体系出现逾渗现象，对应的导电填料体积分数明显降低。在导电填料总体积分数为4.76%时，少量CNTs的引入就可使复合体系的体积电阻率从109Ω·cm下降到105Ω·cm；同时少量的CNTs能明显抑制炭黑/聚丙烯导电复合材料的正温度效应(PTC)，使PTC强度从6.10降低到1.48，PTC转变峰温度从166℃升高到174℃。少量的 CNTs可以使PP的结晶温度提高12℃，对PP结晶的成核作用比CB更加明显。复合体系力学性能随导电填料体积分数增加而明显降低，但因为体积电阻率一定时CB-CNTs/PP体系所需导电填料体积分数较CB/PP体系明显降低，因此少量CNTs的引入能够使复合体系的力学性能得到更大程度的保持。

Multi-wall carbon nanotubes enhanced conductive behaviors of CB/PP electrical conductive composites

As a kind of fibrillar conductive filler，multi-wall carbon nanotubes (CNTs) are int roduced into carbon black (CB)/polypropylene (PP) composites，so as to combine their different conductive mechanisms. The experimental results reveal that CNTs can form bridges between CB particles and result in a remarkable decrease of volume resistivity of CB/PP composites. CB∶CNTs=19∶1 is the optimum proportion for CB-CNTs/PP composites.The conductive percolation threshold of CB-CNTs (19∶1)/PP composite is much lower than that of CB/PP composite. When the total volume fraction of the conductive filler is 4.76%，due to the addition of CNTs，the volume resistivity of the composites can decrease from 109Ω·cm to 105Ω·cm，the positive temperature coefficient(PTC) intensity of CB/PP composites also decreases from 6.10 to 1.48，and the peak temperature of PTC transition increases from 166℃ to 174℃. The crystallizing point of PP rises by 12℃ even if at a very low CNTs content due to CNTs‘ higher nucleation than CB. The mechanical properties of the composites remarkably decrease with an increase of CB or CB-CNTs filler volume fraction. To reach the same volume resistivity，the conductive filler volume fraction of CB-CNTs/PP composite is much lower than that of CB/PP composite，so the higher mechanical properties of CB-CNTs/PP composite can be maintained by the addition of CNTs.