EFFECTS OF HUMECTANTS ON EMULSION OCCLUSIVITY 263 • 30 20 ESTER o EMULSIONS SURFACTANT: © NON VOLATILE PARTS [] EMULSIONS ETHER ß NON VOLATILE PARTS o 3.% Figure 3. Influence of NaPCA on the occ]usivity of emulsions prepared from mineral oil with ester- or ether-type surfactants of HLB 9.5. Significance of the difference between emulsions with and without humectant: •p 0.01 (Mann-Whitney). % humectant values shown for non-volatile parts are concen- trations of humectants in emulsions before volatiles are removed. Table IV Isotropic Oily Phase Formation Capacity of the Binary Mixture Mineral Oil Surfactant: Viscosity and Conductivity of Emulsions and Their Non-volatile Parts [Mineral oil-ester or ether surfactant (HLB 9.5)-NaPCA] Parameters Type of Surfactant % of NaPCA in Emulsions Water 10% aqu. 20% aqu. sol. sol. of NaPCA of NaPCA % of water or aqueous solution of NaPCA incorporated into Mineral oil-surfactant Ester 1.8--6.9 1.6--6.9 1.6--7.1 mixture 1:1 Ether 11.5 9.5 9. Viscosity of non-volatile parts of emulsions Ester 545 586 637 (mPa.s.) Ether 812 380 262 Conductivity of emulsions and their [ Emulsions 3.5 X 10 -2 2.5 4.5 non-volatile parts Ester Non-volatile parts 0 6 X 10 -5 l. 1 X 10 -4 (m.S.) Ether Non-volatile parts 6.1 Emulsions X 10 -2 3.1 3.6 1 X 10 -5 4 X 10 -5 4.6 X 10 -4 --': same as Table III.

264 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS with ether surfactant. Conductivity rose in all cases in the presence of NaPCA. It is higher in emulsions than in their non-volatile parts. RELATIONSHIP BETWEEN ISOTROPIC OILY PHASE AND OCCLUSIV1TY OF EMULSIONS Occlusivities of the three groups of emulsions studied in the presence of humectants seemed related to the capacities of the corresponding oil-surfactant mixtures to produce isotropic oily phases upon addition of water or aqueous solutions of humectants. On the contrary, variations of occlusivity were independent of viscosity and conductivity of non-volatile parts of emulsions. In order to clarify the role of the isotropic oily phase in occlusivity, we prepared a number of ternary mixtures comprised of oil and surfactant (10 g + 10 g) in the same ratio as in emulsions and 0.5 g of water or 0.5 g of a 10% aqueous solution of sodium lactate. Their occlusivities were then measured. For each mixture, the quantity of water or 10% aqueous sodium lactate incorporated without destroying isotropy was deter- mined and expressed in terms of a pecentage. As shown in Table V, for P.H.S., the mixture with HLB 9.25 surfactant having the largest isotropic oily phase formation capacity showed the greatest occlusivity. With the HLB 11.5 surfactant the mixture was not able to form an isotropic oily phase and its occlusivity was negligible. For HLB 8.5 and 10.5 intermediate values of occlusivity and isotropic oily phase formation capacity were obtained. The same phenomena hap- pened when 10% sodium lactate was present. With mineral oil, the mixture with HLB 9.5 surfactant formed an isotropic oily phase most easily and its occlusivity was the strongest (Table VI). With the HLB 11.5 surfactant the mixture was unable to form an isotropic oily phase and manifested a negligible occlusivity. Comparable phenomena were observed when 10% sodium lactate was present. MICROSCOPIC STUDY OF RESIDUAL "FILMS" This study was carried out to better understand the role of the isotropic oily phase in the occlusivity of emulsions. A selected member of microphotos have been presented here. Table V Occlusivity of Ternary Mixtures Prepared From Perhydrosqualene and Ester Surfactant Parameters HLB 8.5 9.25 10.5 11.5 Water Nature I.O. I.O. N.I.O. N.I.O. Occlusivity(%) 52 -+ 4 78 + 1 41 -+ 4 2 + 2 I.O. (%) 5.5 1.8---10.1 3--4.8 0 Nature I.O. I.O. N.I.O. N.I.O. NaL Occlusivity(%) 35 + 4 78 -+ 1 45 ñ 1 4 _+ 3 (10%) I.O. (%) 4.8 1.7--8.3 3--5.2 0 I.O.: Isotropic oily. N. I. O.: Nonisotropic oily. The sign "--•" indicates the interval of percentages of aqueous phase which are solubilized in the isotropic oily phase (I.O. %).