EFFECT OF FORMATION OF SURFACE COMPLEX BE TWEEN HYDROXYPROPYLCELLULOSE AND SODIUM DODECYL-SULFATE ON DISPERSION FLOCCULATION OF O/W-TYPE EMULSION OF SOYBEAN OIL/

An O/W-type emulsion of soybean oil (phi(v)=0.05) was prepared in the presence of various concentrations of hydroxypropylcellulose (HPC) and sodium dodecylsulfate (SDS). The mean diameter (d) of secondary parti cles of the oil droplets decreased with concentrations of SDS and HPC after attaining a maximum at [SDS]=5 mmol/dm(3) and [HPC]=10(-3) g/dl, while the relative viscosity (eta(rel))) of the emulsion increased wi th an SDS concentration after attaining a minimum around 5 mmol/dm(3) when the HPC concentration was kept constant. These facts were explain ed in terms of the formation of a surface complex by hydrophobic inter action between SDS and HPC adsorbed on the surface of the droplets. Wh en the concentration of SDS is low, it bridges between the HPC segment s intra- and intermolecularly on and between the particles, resulting in shrinking of the HPC surface layers as well as in bridging among th e particles. Therefore, the total volume of the secondary particles ef fective on eta(rel) decreases while the d-value increases with the SDS concentration. When the concentration becomes high, the binding ratio of SDS to HPC also increases and the segments are repulsive each othe r owing to the negative charges given by the bound SDS. As a result, t he adsorption layer swells and the secondary particles are redispersed . This fact causes an increase in eta(rel) and a decrease in the d-val ue with a concentration of added SDS.