Load and temperature dependence of frictional force and frictional electrification in friction between polymer films obtained by simultaneous measurements

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Abstract
Simultaneous measurements of frictional force (F) and frictional electrification charge density (σ) were carried out for PS/Ny, PC/PET, and PS/PC polymer film sample systems in the temperature range of 10° to 100°C under various loads (W). Load dependence of F and σ were expressed by F = αWn and σ = βWm. Values of n and m changed with the number of rubbings and temperature. Rate of decrease in n became larger at about 90°C for all sample system. For PS/Ny systems, the values of m and n changed in a similar manner. This behavior was explained in terms of variations in true contact area. Values of F and σ were at maxima and/or began to increase at the temperatures corresponding to the glass transition temperature of the α‐peak temperature in viscoelastic polymers. The maxima of F and σ may appear when the frequency of thermal motion of molecules taking part in the adhesion and separation process coincides with the frequency of mechanical motion of adhesion and separation (friction) between two surfaces, namely, when the true contact area becomes maximum.