EFFECTS OF HUMECTANTS ON EMULSION OCCLUSIVITY 259 60 50 40 30 H.L.B. 8.5 H.L.B. 11.5 0 EMULSIONS ß NON VOLATILE PARTS [] EMULSIONS ß NON VOLATILE PARTS 20 lO , , , , '( ) 0 0.62 1.25 2.5 3.75 Na-LACTATE % Figure 1. Influence of sodium lactate on the occlusJvJty of emulsions prepared from perhydrosqualene and ester surfactants of HLB 8.5. and 11.5. Significance of the difference between emulsions with and without humectant: **p 0.01 (Mann-Whitney). % humectant values shown for non-volatile parts are concentrations of humectants in emulsions before volatiles are removed. The emulsion made with the HLB 11.5 surfactant was poorly occlusive (16 q- 3%). Occlusivity was not altered by the presence of NaL. The occlusivities of non-volatile parts were comparable to those of their respective emulsions. It is surprising to note that the non-volatile parts made with HLB 11.5 surfactant were less occlusive than their corresponding emulsions. Isotropic oily phase formation capacity of P. H.S.-ester surfactant mixture. The mixture P. H. S.: HLB 8.5 ester surfactant is able to incorporate about 5.5 % of water to form an isotropic oily phase (Table II). This capacity, as well as occlusivities of emulsions, decreased in the presence of NaL in the aqueous phase. P.H.S.: HLB 11.5 ester surfactant was not able to form an isotropic oily phase with water or an NaL aqueous solution. Viscosity of non-volatile parts of emulsions. Without humectant (Table II), the viscosity of the non-volatile part made with HLB 8.5 surfactant (180 mPa.s) was much lower than

260 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table II Isotropic Oily Phase Formation Capacity of the Binary Mixture P.H.S.-Surfactant: Viscosity and Conductivity of Emulsions and Their Non-volatile Parts [Perhydrosqualene-ester surfactant (HLB 8.5 and 11.5)-sodium lactate (NaL)] % of Sodium Lactate in Emulsions Parameters HLB 0 2.5 5 Water % of water or aqueous solution of NaL incorporated into P. H.S.-surfactant 8.5 5.5 1: l mixture 11.5 0 10% aqu. 20% aqu. sol sol. of NaL of NaL 4.8 4.3 0 0 Viscosity of non-volatile parts of emulsions 8.5 180 447 298 (mPa.s.) 11.5 699 40l 195 Conductivity of emulsions and their 8.5 ( Emulsions 5.4 X 10 -3 3. l 4 non-volatile parts Non-volatile parts 0 8 X 10 -5 7 X 10 ¸ (mS) Emulsions 11. X 10 -2 9.6 16.6 11.5 Non-volatile parts 3.2 X 10 -3 6 X 10 -2 4.6 X 10 -3 that made with HLB 11.5 surfactant (699 mPa. s). Addition of NaL increased viscosity in the HLB 8.5 surfactant emulsion and decreased it in the HLB 11.5 emulsion. Conductivities of emulsions and their non-volatile parts. The conductivities of emulsions made with HLB 8.5 surfactant were less than those made with 11.5 surfactant (Table II). Conductivity rose in all cases in the presence of NaL. The conductivities of non-volatile parts were always much lower than those of corre- sponding emulsions. P.H.S.-ESTER OR ETHER SURFACTANT-UREA (H.L.B. 9.25) Influence of humectant on the occlusivities of emulsions and their non-volatile parts. Figure 2 indicates that the occlusivities of emulsions prepared from P.H.S. with either ester or ether surfactants having an HLB of 9.25 did not noticeably change in the presence of urea. The emulsions prepared with ester were more occlusive (about 52%) than those prepared with ether type (about 21%). The non-volatile parts manifest the same oc- clusive characters as did their corresponding emulsions. Isotropic oily phase formation capacities of PHS surfactant mixtures. Isotropic oily phase formation capacities of mixtures prepared from P.H.S. with ester or ether surfactants having an HLB of 9.25 were similar and did not seem to noticeably change in the presence of urea (Table III). Viscosities of non-volatile parts of emulsions. The viscosity of the non-volatile part of the emulsion prepared with ester surfactant (205 mPa. s) was lower than that (334 mPa.s) of the non-volatile part prepared with ether surfactant (Table III). introduction of urea increased viscosity in both cases.