Estimating strongly wetting to non‐wetting contact angles for pure and mixed liquids on solids by considering film pressure

Abstract

In solid–liquid–vapour systems, the effect of film pressure () by vapour adsorbate molecules becomes significant when the solid surface energy is similar to or larger than that of the liquid. We extend Young equation applicability to estimate contact angles of pure and mixed liquids on smooth solids by including , obtained from a novel dimensionless surface energy parameter. We use the Owens–Wendt–Kaelble interfacial tension model and perturbed‐chain polar statistical associating fluid theory (PCP‐SAFT) to calculate dispersion and non‐dispersion surface energy contributions. The model is developed using diverse solid–liquid systems with 39 liquids and 30 solids. For binary liquid mixtures, conventional PCP‐SAFT and molar‐average mixing rules are used to obtain surface energies. We correlate to dispersion and non‐dispersion contributions to the liquid and solid surface energies and use to improve estimation accuracy. Using a comprehensive dataset, comprising of 107 experimental datapoints, the average absolute deviation (AAD) decreases from 6.5° to 3.6° by including . Using the correlation developed for pure systems, we accurately predict contact angles of binary liquid mixtures. Interestingly, the molar‐average mixing rule gives more accurate contact angle results despite its simplicity where PCP‐SAFT is only executed for the pure components comprising the liquid mixture. Overall, for binary mixtures, the AAD decreases from 9.2° to 4.5° using 105 datapoints and by including . Our proposed framework significantly improves the contact angle estimations and enables the estimation of the contact angle of liquid mixtures for diverse systems.