Saltwater — wettability on polymer surfaces and determination of surface tension

Static contact angle measurement was performed using saltwater for unsaturated polyester plates and high-density polyethylene sheets. The dependency of the saltwater concentration on wettability and an estimation of surface tension for the saltwater are presented. It is indicated that as the salt concentration increases, the contact angles on polyester tend to increase, while polyethylene generally shows poor wetting of the saltwater. The results are further discussed by deducing the polar and dispersive components of surface tension of the saltwater at different concentrations. The polar component tends to increase as the salt concentration increases, while the dispersive component scatters. The different performance of the wettability at different salt concentrations can be attributed to the difference of the polar components of surface tension of these polymers. This technique can be also used for deducing the polar and dispersive components of surface tension of general liquids in a simple manner.