Accession Number : AD0692383

Title :   EFFECT OF ADSORBED MONOMOLECULAR FILMS ON THE EVAPORATION OF VOLATILE ORGANIC LIQUIDS.

Descriptive Note : Interim rept.,

Corporate Author : NAVAL RESEARCH LAB WASHINGTON D C

Personal Author(s) : Nernett,Marianne K. ; Halper,Laura A. ; Jarvis,N. L. ; Thomas,T. M.

Report Date : 09 JUL 1969

Pagination or Media Count : 19

Abstract : An investigation was made of the effect of adsorbed surface-active films on the rate of evaporation of volatile organic liquids. A series of partially fluorinated compounds were studied either as monolayers adsorbed from solution or as insoluble films spread at the liquid/vapor interface. In no instance was the rate of evaporation significantly reduced by the presence of a monomolecular film. Insoluble multimolecular films of polydimethylsiloxanes, however, were found to reduce effectively the rate of evaporation, provided the film thickness was sufficient to decrease the rate of diffusion of the solvent molecules through the film to a value below their rate of diffusion through the saturated, nonturbulent vapor layer overlying the surface. In addition to polydimethylsiloxane polymolecular layers, thin layers of water, containing suitable fluorocarbon spreading agents, were also found to reduce the rate of evaporation of certain volatile organic liquids. These aqueous films are similar to the thin layers of interlamellar water present in aqueous foams used to extinguish gasoline fires, such as the fluorocarbon-containing Light Water foams. (Author)

Descriptors :   (*EVAPORATION, *MONOMOLECULAR FILMS), (*SURFACE ACTIVE SUBSTANCES, MONOMOLECULAR FILMS), (*ORGANIC SOLVENTS, *FIRE EXTINGUISHERS), (*SILOXANES, MONOMOLECULAR FILMS), FLUORINE COMPOUNDS, HALOGENATED HYDROCARBONS, WATER, FOAM, TOLUENES, AMMONIUM COMPOUNDS

Subject Categories : Physical Chemistry
      Safety Engineering

Distribution Statement : APPROVED FOR PUBLIC RELEASE