油相组成对W/O型Pickering乳液稳定性和流变性能的影响

Effects of oil type on the stability and rheological properties of W/O Pickering emulsions

以二甲基甲硅烷基化硅石为乳化剂,采用均质乳化法制备W/O型Pickering乳液,通过偏光显微镜、表面张力仪、接触角测量仪和流变仪研究了油脂的极性、流变改性剂对W/O型Pickering乳液稳定性及流变性能的影响。结果表明,相比于非极性油脂,极性油脂制备出来的W/O型Pickering乳液液滴更小,稳定性能更优,其中霍霍巴油制备的Pickering乳液粒径分布较窄,形状均一,稳定性好;添加流变改性剂后,Pickering乳液的粒径有一定的下降,常温稳定性和低温稳定性均有小幅度提升,对于不同的油脂,与之结构上存在相似性的流变改性剂对粒径的降低及稳定性的提高效果较好。不同油脂制备的W/O型Pickering乳液均为非牛顿流体,随着剪切速率的增大,Pickering乳液的黏度降低,并且所有Pickering乳液的弹性模量(G')高于黏性模量(G''),均为凝胶乳液,线性黏弹区为0.001%~0.100%,添加流变改性剂后,Pickering乳液的黏度上升,剪切稀化现象基本不变,但线性黏弹区增大,可能与Pickering乳液的粒径和油水界面能的变化有关。

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.