Effects of oil type on the stability and rheological properties of W/O Pickering emulsions
Using dimethylsilylated silica as emulsifier,W/O Pickering emulsions were prepared by homogeneous emulsification.The kinds of oils,rheological modifiers and their effects on the stability and rheological properties of the W/O Pickering emulsions were studied.The results showed that,compared with the nonpolar oil,the W/O Pickering emulsion prepared with polar oil had smaller droplets and better stability,e.g.,the emulsion prepared with jojoba oil had narrow particle size distribution,uniform shape and good stability.With the addition of rheological modifier,the particle size of the emulsion decreased to a certain extent,and the stability at room temperature and at low temperature was both slightly increased.For different oils,the rheological modifier which was similar to the oil in molecular structure had better effects in the reduction of particle size and the improvement of stability.All these W/O Pickering emulsions prepared with different oils were non-Newtonian fluids.With the increase of shear rate,the viscosity of the emulsions decreased,and the elastic modulus(G')of all emulsions was higher than viscous modulus(G").All the emulsions were gel emulsions,and the linear viscoelastic region was 0.001%-0.100%.With the addition of rheological modifier,the viscosity of the emulsion increased and the shear thinning phenomenon was basically unchanged,but the linear viscoelastic region was enlarged,which might be related to the change of emulsion particle size and oil-water interfacial energy.
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