Wettability of natural microcrystalline graphite filler with pitch in isotropic graphite preparation

Natural microcrystalline graphite (MG), which shows highly graphitized structure and near-isotropic material properties, can be used as filler material in isotropic graphite preparation. The final properties of graphite artifacts are largely determined by the interaction between pitch and filler particles during kneading. To achieve a better understanding of the wetting mechanism of MG filler, wetting behavior of pitch on substrates with different crystal structures was studied by measuring their contact angles. The results showed that both crystalline orientation and degree of graphitization of substrates could significantly influence the pitch wettability. Edge planes of graphite surface showed better wetting capacity than basal planes. And cokes obtained at very high temperature with highly graphitized structure tended to prevent pitch from wetting. Further wetting test showed that MG substrate was totally wetted by pitch drop, and its wetting time was shorter than coke. The wetting behavior of MG was related to its unique crystalline structure and surface morphology, and beneficial to the mechanical strength of MG-based isotropic graphite.