Relationship between the dynamic softening transition and wet sliding friction of elastomer compounds

For properly chosen elastomer compounds, thermorheological characterization is combined with an examination of the variation of the wet sliding friction with temperature. A conceptual argument leads to the assumption that the wet sliding friction should maximize at the energy dissipation peak associated with the dynamic softening transition at a characteristic frequency determined by the sliding speed and the effective smallest surface asperity scale. The dynamic softening transition is characterized with the peak in tan delta/G'(n) where tan 5 is the loss tangent, G' is the elastic modulus, and n is a constant between 0 and 1. The William-Landel-Ferry transform is uncritically applied for extrapolating the position of the peak in tan delta/G'(n) at high frequencies. Even based on the criterion of tan 5, the results obtained on a concrete surface indicate that the effective smallest asperity scale is of order of 100 mum. (C) 2004 Wiley Periodicals, Inc.