Effect of Polar-Nonpolar Additives on Oil-Spreading on Solids, with Applications to Nonspreading Oils

摘要

The work of Zisman and associates has established that most nonspreading oils do not spread be¬cause they deposit monolayers which modify the surface so that the critical surface tension for spread¬ing is less than the surface tension of the oil. Nonspreading oils can be prepared from aliphatic and aromatic hydrocarbons and from many synthetic oils by the proper choice of an absorbable additive, but an additive which makes one oil nonspreading may cause violent spreading of another oil of much higher surface tension. This anomalous spreading is produced by surface tension gradients that result from decreases in the concentration of additive at the oil/air interface as adsorption on the solid pro¬ceeds.nOily contamination of a surface may cause spreading of an otherwise nonspreading oil because the contamination raises the critical surface tension of the surface above the surface tension of the oil. Such contamination rarely produces a critical surface tension above 30 dynes/cm. Consequently practical nonspreading oil should have a surface tension above 32 dynes/cm so that oily contamination of the surface near the oil will not induce spreading.nEffective additives for producing nonspreading include the silicones, various fluoroesters, and salts of organic amines with organic acids, high molecular weight organic acids, alcohols or amines, and some oil soluble soaps. A predeposited film of a dimethyl or methylphenyl polysiloxane is found to prevent the spreading of diester or hydrocarbon oils on stainless steel surfaces for as long as nine months. Such a treatment provides an alternative approach to the control of spreading.