Effect of dispersion method on tribological properties of carbon nanotube reinforced epoxy resin composites

Epoxy/CNT nanocomposites were synthesized in various ways to examine the effects of dispersion methods on its tribological properties. The carbon nanotubes (CNTs) were pre-treated in three different ways: no pre-treatment, activation in HNO3, and activation in HNO3 plus application of a coupling agent. The dispersion and mixing methods used were: dual asymmetric centrifuge, sonication, hand mixing. The CNTs were mixed either into the hardener or the resin. The curing behaviour was studied via DSC, and the thermomecanical properties were determined using a DMA. The tribological properties were investigated in a ball-on-prism test rig under unidirectional continuous sliding against austenitic stainless steel. For the untreated CNTs, it seems that the wear resistance improves with increasing effort put into dispersion: sonication has a positive effect, sonication plus dual asymmetric centrifuge proves even better. A pre-treatment with HNO3 or a silane-coupling agent can improve the wear resistance of the composite. However, the pre-treated CNTs should be dispersed without the use of ultrasound, which seems to damage the pre-treated CNTs. The results showed that the wear resistance in general increases with improved dispersion and integrity of the CNTs. (C) 2006 Elsevier Ltd. All rights reserved.