Young's equilibrium contact angle on rough solid surfaces. Part I. An empirical determination

—The influence of the roughness of solid surfaces on the contact angle hysteresis, Δ, was studied for low-energy solids (paraffin, PTFE, PMMA) using pure liquids. Taking Δ as dependent on the roughness, the contact angle data can be linearly approximated. The value of Δ = 0 is considered as the equilibrium contact angle e known from thermodynamic considerations. The slopes of these straight lines form another linear function of the corresponding e. Hence e can be calculated from a single measurement of a,e and r,e for the systems under consideration.