The effect of type of mechanical processing on electrical conductivity and piezoresistive response of CNT and graphite composites

Nanocomposite materials are attracting significant interest as matrices for conventional composite materials, where their increased electrical conductivity present the possibility of multi-functional properties, such as embedded heating and electromagnetic shielding. One problem facing the increased use of the nanocomposites is their rapid and efficient production. Three different mixing methods: 3-roll mill, shear mixing and hand mixing were tested to mix carbon nanotubes (CNTs) and graphite into epoxy resin. The electrical conductivity and piezoresistive response of the resulting nanocomposites were measured and compared to the relative rate of nanocomposite could be produced. Maximisation of the functional properties is important, but speed of throughput is also essential, thus enabling larger and production ready components to take advantage of the additional functionality. Because of health and safety concerns during material handling of nanoparticles, this study employed a premixed CNT masterbatch (Arkema) and graphite powders (Superior Graphite), as these do not require specialised health and safety equipment to process, making industrial application more viable. It was found that the 3-roll provided the largest increase in conductivity out of the three mixing methods, and hand mixing and shear mixing performed similarly. Piezoresistivity was seen in all modified samples, however gauge factors were difficult to determine due to underdeveloped sample contact and preparation methods.