Surface Modification Of Sericite And Its Evaluation

Sericite is a new kind of non-metallic mineral filler, widely used in the fields ofhigh molecular materials and compound materials industry, such as coatings, plastics,rubbers, glutinous and paper-making agents. To cover the metal surface with epoxycoatings is the most commonly used method to anti-corrosive of metal surface.Sericite have unique flaky structure and physical and chemical properties.Whensericite is added to epoxy coatings, it not only can partially replace zinc powder andtitanium dioxide and so on to reduce productive costs, but also increase the acid andalkali resistance, abrasion resistance and heat resistance properties of coatings.Sericite is a hydrophilic non-metallic mineral filler. The interfacial propertiesbetween sericite and organic polymers is different. Sericite is difficult to be dispersedin the polymer and compatibility is also poor. Therefore, it is required to modify thesurface of sericite to improve physical、chemical and the dispersion properties,improve mechanic intensity and synthetic capability.The present thesis use sericite from Sichuan Leshan as test specimen. The mainchemical composition and mineral composition is analyzed by XRF and XRDpatterns. The result showed that the main component of the mineral is sericite, withless mount of quartz. Dry process is used to make sericite powder products, andanalyze all kinds of its index. Sericite powder products can be in line with qualitystandards of MCA-1grade in industrial standard of YS/T467-2004.In this paper, silane(KH-560) and silane(KH-570) are chosen to modify thesurface of sericite. The research content includes the amount of silane, the amount ofadditives, the temperature of modification and the time of modification. Accordingto determination pre-evaluation index of sedimentation volume, the value of oilabsorption and activation index, the optional modification process conditions aredetermined. When silane coupling agent KH-560is modifier, the optionalmodification conditions are the amount of silane1.2%, the amount of additives1.0%, modified temperature100℃and modified time60min. When modifier is KH-570,the optional conditions are amount of modifier1.0%, the amount of additives0.8%,modified temperature100℃and modified time80min.Studied show that sericite powder after modified by KH-560, the value of oilabsorption reduce from30.10%to25.73%, the activation index rise to74.05%from47.79%. When it,s modified by KH-560, the value of oil absorption reduce from30.10%to18.56%, the activation index rise to80.67%from47.79%. The resultsillustrate that the surface of sericite is organic. Hydrophilic fillers become tohydrophobic packing. Sericite before and after modified are characterized byscanning electron microscopy(SEM), fourier transform infrared spectroscopy(FT-IR)and thermal gravimetric analysis. Results showed that the silane coupling agents areabsorbed by chemical bonds on the surface of sercite powder. The dispersion ofsericite powder has been improved.The dispersion and compatibility of sericite powder before and aftermodification added into epoxy coatings is observed by scanning electron microscopy.The result showed that the agglomeration of modified sericite in epoxy coatings isreduced and the compatibility with epoxy coatings improved to some extent. Theeffect of modified sericite on anti-corrosion properties of coatings are studied byelectrochemical impedance spectrum(EIS). Studies show that: under the sameconditions, the value of resistance with added modified sericite by KH-560andKH-570to epoxy coatings are9.75×106Ω(1d) and9.91×107Ω(1d). But the value ofresistance with added unmodified sericite is only4.02×106Ω(1d).