Abstract
Structural dependency of surface activity was investigated with various sucrose esters of fatty acid which were different in substitution degree and fatty acid constituent.
Sucrose esters were prepared from the respective methyl ester of caprylic, lauric, myristic, palmitic, stearic, behenic, oleic and linoleic acid, and hydrogenated tallow. Surface activities of these esters were compared with each others in terms of turbidity, surface tension, wetting power and foaming power at 0.1 or 0.3% level in water, and of HLB value.
Hydrophilic capacity of the sucrose esters was dependent on mono-ester content; sucrose esters containing 74, 62, 50, 41 and 32% mono-esters on weight basis, which were prepared from hydrogenated tallow, showed HLB values of 15, 13, 11, 8 and 6, respectively. Hydrophilic capacity was also variable with molecular species of fatty acid used; the longer-chain or the more saturated fatty acids showed the lower hydrophilic capacity. Solution containing sucrose esters of the shorter-chain fatty acids or of the lower degree of substitution exhibited the lower surface tension, but the higher foaming power. The longer-chain or the more saturated fatty acids showed the poorer wetting power. Dissolving power for n-hexane became higher with the increase in the substitution degree of the esters.
