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Friction and wear of tips sliding on polymeric surfaces is relevant to nanoscale probe-based storage, metrology and manufacturing. At the same time, trobological studies of polymeric materials are directly linked to molecular mobility and dissipation modes.
Here, data of sliding friction between a silicon tip and a highly cross-linked polyaryletherketone film using friction force microscopy are presented. Energy dissipation into molecular relaxations (alpha and beta relaxations) is identified as distinctive maxima of the friction force as a function of temperature between 150 and 500 K. A strong shift of such peak temperatures as a function of applied load is observed. This effect is modeled with an Arrhenius activation by incorporating the applied shear stress in the effective activation energy of the two relaxations. The effect of the stress-shifted relaxation on friction-versus-load experiments is discussed. The results are discussed in the context of tip wear of a silicon tip sliding on polymer surfaces. |
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