Abstract:
Adsorption and wetting on different hydrophobic surfaces with aqueous binary mixed solutions of cationic surfactant – cetylpyridinium bromide (CPB), and nonionic surfactant – polyoxyethylene octyl phenyl ether (OP(EO)₁₀) were investigated at molar fractions of the nonionic surfactant of 0.25, 0.50 and 0.75. The six plastics used for this study were high density polyethylene (HDPE), polycarbonate (PC), polyvinylchloride (PVC), acrylonitrile butadiene styrene (ABS), polymethyl methacrylate (PMMA), and polyhexamethylene adipamide (Nylon66). The mixed surfactant systems showed a positive effect in adsorption with increasing molar fraction of nonionic surfactant, leading to wetting improvement. The addition of the nonionic surfactant into the CPB solution increased the CPB adsorption onto the studied plastic surfaces because of the reduction of electrostatic repulsion among cationic head groups and it also increased the surface excess concentration at the solid/liquid interface. Surfactant molecules likely adsorb at the liquid/vapor interface more than at the solid/liquid interface when the polarity of surfaces increased. Interestingly, the masking of negative change plastic surfaces by the CPB monomeric adsorption obstructed the OP(EO)₁₀ adsorption. In addition, wetting of the studied plastic surfaces was found to increase with increasing polarity of surfaces.
