Wettability of paraffin surfaces by nonionic surfactants: Evaluation of surface roughness and nonylphenol ethoxylation degree

• We investigate the wetting of three paraffin surfaces by surfactant solutions.
• We evaluated five surfactants with different ethoxylation degree.
• The sessile drop technique was employed.
• The surface morphology was the most important factor governing wetting properties.
• An increase in ethoxylation degree promotes a decline in paraffin wettability.

Wettability is a widely used property in many industrial applications. This study aimed at determining the wettability of long-chain paraffin surfaces by nonionic surfactants, nonylphenol polyethoxylates with different ethoxylation degrees. Interactions between solid and liquid phases were determined by apparent contact angle measurements. The morphology was obtained by atomic force microscopy. The results demonstrated that the molar mass of paraffin has a direct influence on the wettability of the surfaces by surfactant solutions. The rise in paraffin molar mass promoted a reduction of the contact angle between solid–liquid interfaces due to the formation of surfaces with less roughness. An increase in the ethoxylation degree of surfactants reduced the wettability, showing a tendency toward water behavior. It was observed that the melted paraffin crystallized more abruptly due to having a higher melting temperature, which impedes crystal formation and, consequently, decreases its roughness.

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