Study And Application Of In-situ Modification Precipitated SiO₂ By Hydroxyl Silicone Oil

As the ordinary precipitate silica powder had hydrophilic hydroxyl groups on its surface, it was readily to aggregate during the synthesis. The property of hydrophilic and oleophobic made silica had poor affinity with organic material. In order to solve these problems, in this article the hydroxyl silicone oil (HSO) in-situ modified SiO₂ was prepared with cheap water glass and sulfuric acid as raw material by precipitation method, and the properties of sample were synthesized such as the phase structure, particle size, topography and so on, main content as follows:1. XRD analysis showed that the modified silica by hydroxyl silicone oil was still amorphous silica and don't change the crystal structure of silica. The SEM images indicated that the unmodified silica particals were agglomerated, while the agglomerates phenomenon and the dispersion property were improved by in-situ modification method, particle size distribution was narrower, the particles still were ball particles. The 2970cm-1 spectrum analysis indicated that the smaller molecular HSO was grafted onto the hydroxyl of silica surface by chemical reaction, and the content of hydroxyl and adsorbed water on silica surface were reduced, the hydrophobic property and the content of organic matter were improved, but the oil-absorb ratio of SiO₂ was reduced. The hydrophobic property test shows that when the dosage of the hydroxyl silicone oil 203-B and 203-D reach 17.9%, the hydrophobic degree increased to 24.59% and 22.17% respectively, the smaller molecular of the hydroxyl silicone oil had the higher the hydroxyl content, made the hydrophobic degree increase obviously. All the investigations showed that HSO modified the SiO₂ was a in-situ method.2. The diversity of system determined the complexity of reaction mechanism in silica preparation process. Experiments proved that the particle sizes and morphology of products were different with the addition of HSO under different pH, the particle sizes with the addition of HSO under alkalic condition were smaller than that of under acidic ondition.3. The POM and XRD indicated that Si-CH₃ was grafed onto the SiO₂ surface prevented heterogeneous crystallization of Si-OH and Si-O-Si, eliminatedβcrystallization of PP by SiO₂ induced reaction, leading to the crystal structures of PP/SiO₂/HSO resembled to that of pure PP. Flow tests showed that HSO reduced the viscosity of PP/SiO₂ fluid. The SEM images indicated that in-situ modified method made SiO₂ uniformly dispersed in PP, reduced the interfacial adhesion and improved the compatibilization of the PP/SiO₂ composite.4. That HSO in-situ modification of silica was used in coating as flatting agent, was correspond with industrial production requirement. Resist viscous and dispersion property were better, but the leveling and glossiness were slightly inferior to the industrial production flatting agent。...