超细TiO₂颗粒因无毒、稳定性高,成为一种化妆品中的重要无机紫外线防护材料。将TiO₂粉体分散在液体介质中形成紫外防护能力强、稳定性好的分散液受到了学术界的关注。为了控制分散液的分散稳定性,使用3种带有不同支链结构的硅氧烷作为分散剂。结果表明:当使用聚甘油和烷基支链的硅氧烷作分散剂时,随着剪切速率的增大,黏度基本不变,表现为牛顿流体,无明显的絮凝沉降结构,而选用聚醚和烷基支链的硅氧烷作分散剂时,分散液表现出剪切稀化现象,有明显的絮凝结构。同时考察了3种分散液的储能模量。随着剪切应力的增加,聚甘油和烷基支链改性的硅氧烷分散剂制备的分散液的储能模量基本不变,结构没有破坏,而聚醚和烷基支链改性的分散剂制得的分散液在30Pa时,储能模量明显下降,表明体系内有粒子絮凝且结构被破坏。光学测量结果证实紫外保护性能随着絮凝程度的增加而降低。因此,聚甘油和烷基支链改性的分散剂能够很好地分散TiO₂,所得分散液无明显的絮凝结构,紫外保护能力强、储存稳定性好。通过流变学参数为桥梁,建立了分散液的絮凝结构与紫外保护性能的反比关系。

Due to non toxicity and high stability,ultrafine titanium dioxide (TiO₂) particles are used as important inorganic UV protective materials in cosmetics.Dispersing TiO₂ powder in liquid medium to form a strong UV protection and stable dispersion has received great attention in academy.In order to control the dispersion stability,three kinds of siloxanes with different branched structures were applied as a dispersing agent.The results shown that when polyglycerol and alkyl branched siloxanes were used as dispersing agents,the viscosity was basically unchanged with the increase of shear rate,which was expressed as newtonian fluid without obvious flocculation and sedimentation structure.When the ether and the alkyl branched siloxane were used as dispersing agents,the dispersion exhibited shear thinning and had a remarkable flocculation structure.The storage modulus of the three dispersions was also investigated.With the increase of shear stress,the storage modulus of the dispersion prepared by polyglycerol and alkyl branched modified siloxane dispersant was basically unchanged,indicative of a stable structure.In comparison,when the dispersant prepared by the polyether and alkyl branch modification at 30Pa,the storage modulus decreased significantly,indicating that the particles in the system were flocculated and the structure was destroyed.Optical measurements confirmed that the UV protection performance decreased as the degree of flocculation increased.Therefore,the polyglycerol and alkyl branch-modified dispersant can highly disperse TiO₂,and the obtained dispersion had no obvious flocculation structure,and had strong ultraviolet protection ability and good storage stability.Through the rheological parameters of the bridge,the inverse relationship between the flocculation structure of the dispersion and the UV protection performance was established.