STABILIZATION OF NONIONIC AEROSOL EMULSIONS Table V Relationship between Aerosol Emulsion and Foam Properties 587 POE Fatty Ether Emulsion Stability" Alcohols in Alcohols Aqueous in Phase Propellant Foam Stability • Alcohols - in Alcohols Aqueous in Phase Propellant POE (2) cetyl ether Lauryl alcohol 30-60 rain Lauryl/myristyl (1/9) 4 days Lauryl / cetyl (6 / 4) 4 days Lauryl/stearyl (8/2) 4 days POE (10) cetyl ether Lauw1 alcohol 1 •nin Laurylhnyristyl (1/9) 1-5 min Lauryl/cetyl (6/4) l_ min Lauryl/stearyl (8/2) 1 min POE (10) stearyl ether Lamyl alcohol 1-5 min Lauryl/myristyl (1/9) 1-5 rain Lauryl/cetyl (6/4) 1-5 min Lauryl / stearyl (8/2) 1-5 min "Tim• •o first observable phase separation. •Per cent decrease in height in 60 min. 16 hrs 0 0 4 days 0 0 4 days 0 0 4 days 0 0 1--5 min 29 33 24 hrs 22 21 24 hrs 24 39 24 hrs 25 39 1--5 min 13 24 24 hrs 23 25 24 hrs 31 25 24 hrs 31 31 Table VI Effect upon Aerosol Foam Density of Adding Fatty Alcohols in the Prope]lant Density (g/cc) Fatty Alcohol or Alcohol Blend Lauryl/ Lauryl/ Lauryl Myristyl (1/9) Cetyl (6/4) Polyoxyethylene Fatty Ether Aq? Prop) Aq. Prop.-' Aq. Prop. Lauryl / Stearyl (8/2) Aq. Prop. POE (4) ]auryl 0.094 0.100 0.076 0.086 0.081 0.077 0.070 0.135 POE (23) lauryl 0.063 0.062 0.070 0.135 0.062 0.072 0.058 0.064 POE (2) cetyl 0.086 0.108 0.125 0.24 0.14 0.18 0.090 0.14 POE (10) cetyl 0.067 0.063 0.067 0.089 0.070 0.086 0.066 0.072 POE (20) cetyl 0.077 0.068 0.100 0.125 0.068 0.098 0.065 0.071 POE (10) stearyl 0.072 0.069 0.076 0.102 0.071 0.106 0.069 0.098 POE (20) stearyl 0.071 0.065 0.095 0.135 0.078 0.115 0.066 0.085 'Alcohols initially in aqueous phase. •Alcohols initially in propellant. it was concluded that any variations were the result of experimental error. It is possible that increasing the number of measurements might detect an effect not readily noticeable with duplicate determinations only. Typical foam stability, drainage, and stiffness data obtained when the alco- hols were placed initially in the aqueous phase are given in Table VII. These

588 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table VII Aerosol Foam Properties (Alcohols in Aqueous Phase) Foam Property Polyoxyethylene Fatty Ether POE POE POE POE POE POE POE (4) (23) (2) (10) ('20) (10) ('20) Lauryl Lauryl Cetyl Cetyl Cetyl Stearyl Stearyl Stability (% decrease in 60 min) Lauryl alcohol 67 39 0 29 33 13 27 Lauryl/myristyl (1/9) 40 7 0 12 19 13 19 Lauryl/cetyl (6/4) 43 18 0 24 11 31 28 Lauryl/stearyl (8/2) 67 28 0 25 24 31 38 Drainage (% in 60 min) Lauryl alcohol 79 34 0 33 2 51 38 Lauryl / myristyl (1 / 9) 18 0 0 0 i 0 0 Lauryl / cetyl (6/4) 51 i 0 0 3 0 2 Lauryl/stearyl (8/2) 74 29 0 17 13 0 25 Stiffness (g) Lauryl alcohol 7 54 12 30 38 21 40 Lauryl/myristyl (1 / 9) 26 79 58 65 60 49 53 Lauryl/cetyl (6/4) 18 49 52 47 53 55 46 Lauryl/stearyl (8/2) 12 38 30 41 51 41 39 data are presented to illustrate the general magnitude of the values. The re- sults obtained when the alcohols were added with the propellant were similar. The lauryl/myristyl (1/9) blend gave foams with the best stability, the least drainage, and the highest stiffness in the majority of eases. This blend provides the highest concentration of fatty alcohol other than lauryl. Previous work on the effect of molecular complexes upon aerosol foam properties had shown that lauryl alcohol was the least effective of the four fatty alcohols in improving foam properties (6, 9). DISCUSSION Previous work had shown that when certain polyoxyethylene fatty ether- fatty alcohol complexes were preformed in the aqueous phase, they stabilized aerosol foams but not the initial emulsions. Data illustrating this, summarized from Reference 9, are given in Table VIII. The surfactants that failed to stabi- lize the aerosol emulsions in combination with fatty alcohols were POE (23) lauryl ether, POE (10) cetyl ether, POE (20) cetyl ether, and POE (20) stearyl ether. POE (10) stearyl ether should probably be included in this group be- cause the increase in emulsion stability was marginal compared to the foam stability. In the present investigation, increased emulsion stability was obtained with POE (2) cetyl ether when lauryl alcohol was added with the propellant. Since POE (2) cetyl ether by itself gives fairly stable emulsions, it is not surprising that lauryl alcohol, normally rather ineffective, would show an effect with