EFFECTS OF HUMECTANTS ON EMULSION OCCLUSIVITY 257 Surfactants: Two couples of non-ionic surfactants were used. One had an ester linkage. It was a sorbitan monooleate ester (Montane 803: HLB 4.3) and a sorbitan monooleate ester with an average of 20 ethylene oxide residues (Montanox 803: HLB 15). The other had an ether linkage. It was an oleyl alcohol derivative with an average of two ethylene oxide residues (Simulsol 923: HLB 4.9) and with an average of 10 ethylene oxide residues (Simulsol 963: HLB 12.4). Humectants: The humectants incorporated into emulsions were: sodium 5-pyrrolidone- 2-carboxylate 4 (NaPCA-50% aqueous solution), sodium lactate 5 (NaL-50% aqueous solution) and urea. 6 They were used at six concentrations, viz: 0, 0.62, 1.25, 2.5, 3.75, and 5%. PREPARATION OF EMULSIONS AND THEIR NON-VOLATILE PARTS On the basis of our previous observations (10) three groups of emulsions were chosen: a) Perhydrosqualene--ester surfactants at HLBs of 8.5 and 11.5, sodium lactate. b) Perhydrosqualene--ester or ether surfactants at an HLB of 9.25--urea. c) Mineral o/l-ester or ether surfactants at an HLB of 9.5, sodium pyrrolidone car- boxylate. The general formula of emulsions (% by weight) used was oil 10, surfactant 10, humectant 0, 0.62, 1.25, 2.5, 3.75, or 5--water q.s. to 100. Emulsions were prepared by phase inversion, emulsifying the oil phase in demineralized water using the couple of surfactants (11). The compositions of the non-volatile parts of emulsions were calculated assuming their evaporative water loss to be more than 90% (8,10) as indicated in Table I. MEASUREMENT OF OCCLUSIVITY The occlusivity was measured by applying emulsions or their non-volatile parts at a dose of 3 mg/cm 2 on the surface of a hydrated gelatin cell (11) which permits water diffusion similar to human skin. Experimental conditions were described in our previous publication (8). The occlusivity (Oc) of products is a measure of resistance to water loss compared to a control measurement and defined by the following equation: Occlusivity (Oc)% = WLB - WLA WLB x lOO WLB: water loss of gelatin cell in mgß cm-2 -2 WLA: water loss of gelatin cell in mgß cm ration. ß rain-• before application. ß rain -• after application of the prepa- Statistical significances were only calculated for emulsions containing 0, 2.5, and 5% humectant using the Mann and Whitney test (12), for which 8 replicates were used. Three replicates were used for other concentrations. 3 SEPPIC, 70 avenue des Champs Elys6es, F. 75008, Paris. 4 U.C.I.B., Ivry la Bataille, France. 5 E. Merk Darmstadt, F.R.G. 6 Rh6ne Poulenc, Paris.

258 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table I Determination of the Composition of Non-volatile Parts of Emulsions Emulsions Non-volatile Parts Composition % Composition Proportion Lipophile phase 10 Lipophile phase 10 (oil) Surfactant 10 Surfactant 10 Humectant 0, 0.62, 1.25, Humectant 0, 0.62, 1.25, 2.5, 3.75 or 5 2.5, 3.75 or 5 Water q.s. to 100 Water 5 More than 90% of the water evaporates from these emulsions in less than 15 min. ISOTROPIC OILY PHASE FORMATION CAPACITY OF EMULSIONS This test indicates the capacity of the residual film, following dehydration of the emulsion on the surface of application to form an isotropic oily phase. Water, 10 or 20% aqueous solution of humectant (NaPCA, NaL or urea) was added to a binary mixture of oil and surfactant (1/1), corresponding to that present in the emulsions until the isotropic oily phase disappeared. The quantity of aqueous phase incorporated into the isotropic oily phase is expressed in terms of a percentage. VISCOSITY MEASUREMENT Viscosity was measured using a rheometer • and expressed in milli Pascal seconds (m. Pa.s). CONDUCTIVITY MEASUREMENT This measurement, expressed in milli Siemens (mS) was done by means of a conduc- timeter CD6NG. 2 MICROSCOPIC OBSERVATIONS In order to elucidate the relationship between the isotropic oily phase formation capacity and the occlusivity of emulsions, we studied the state of the residual "film" formed from emulsions and their non-volatile parts by polarized light microscopy (Leitz type Dialux Pol) and photomicrography (x 100). RESULTS INFLUENCE OF DIFFERENT PARAMETERS ON THE OCCLUSIVITY OF EMULSIONS P.H.S., ESTER SURFACTANT-SODIUM LACTATE. (HLBS 8.5 AND 11.5) Influence of humectant on the occlusivity of emulsions and their non-volatile parts, As shown in Figure 1, the occlusivity of emulsions prepared from P.H.S. with ether surfactant at HLB 8.5 (Oc.% = 51. _+ 2) decreased in the presence of NaL. • Rheomat 30: Viscosimbtre AG., Ets LAMY et Cie S.A., 19 avenue Thimonnier, 69300 Caluire et Cuire. 2 Conductimeter CD6NG: Solea, Lyon, manufactured by Prolabo.