oilrepellence

Oil repellence, sometimes written as oilrepellence, is the property of a surface to resist wetting by oils and other low-surface-tension liquids. It is the opposite of oleophilicity. In practice, a surface with good oil repellence causes oil droplets to bead up and prevents penetration of oil into porous materials. The concept is important for textiles, coatings, and contamination-prone surfaces.

Mechanisms: Oil wetting depends on interfacial tensions and surface energy. Surfaces with low surface energy, such as fluorinated polymers or silicones, resist oil spreading. Micro- and nano-texturing can enhance repellence by trapping air or creating re-entrant geometries; slippery, infused surfaces can further reduce oil adhesion. Oils, having lower surface tension than water, make achieving high repellence more challenging than for water.

Measurement: Oil repellence is typically assessed by oil contact angle measurements and by resistance to oil penetration under controlled exposure. Standardized tests may involve applying a hydrocarbon oil to a surface and observing spreading, penetration time, or staining after exposure.

Applications: Oil-repellent finishes are used on fabrics to resist stains, on coatings to prevent oil fouling on glass or metal, in food packaging to limit grease penetration, and in medical devices to reduce lipid deposition.

Limitations: Durability and wear resistance of oil-repellent surfaces can limit long-term performance. Environmental concerns about fluorinated chemistries drive research into non-fluorinated alternatives. Trade-offs often exist among repellence, chemical resistance, and cost.