Effect of triboelectric charges on friction and wear of polymers at macro scale
Embargo Lift Date: 2020-12-26
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The interest towards the study of underlying mechanism behind tribology has gained enormous attention recently since almost one-fourth of the total produced global energy is consumed by friction and wear. Dry sliding or rubbing two dielectric polymers on each other results in surface charging showing significant effects on friction coefficients and wear. Determination of the correlation between triboelectricity and tribologic events like friction and wear, the control of friction coefficient, and reducing wear by surface charging constitutes the main idea and research topic of this thesis. However, tribological events are very complicated considering the fact that diverse processes encompassing of physical and chemical changes occur at the counterface. Therefore, the fundamentals of friction is still controversial. Owing to tribological actions that occur due to contact between different phases of the matter, interfaces generate tribocharges due to electron, ion, and material transfer mechanisms. Even though the fundamental mechanism is still vague and under debate, it is believed that static electrification due to tribological actions are utterly because of electron transfer. Current studies unveiled that physical based phenomena are not the only source of surface electrification but also chemical changes such as bond rupturing and following surface oxidation that can take place as a result of mechanical actions on an insulating polymer. Consequently, these two groups of surface events; surface electrification and friction are expected to demonstrate a mutual relation, and detailed study concerning this relation needs to be investigated in order to solve e.g. energy loss and wear problems in tribology. To achieve this goal, it is essential to understand the main mechanisms and processes involved, and reveal the connections between tribological events and establish a relationship between all the intrinsic and extrinsic properties of materials from molecular, nano to meso scale. Thus, in this study, we investigated the contribution of triboelectrification to friction by taking into account some factors - surface area, load, atmosphere - between common polymers and pure cellulose under dry friction conditions.