Organic Modification Of Hectorite And Mechanism Analysis

Hectorite, one of important smectites, has a 2:1 layered crystal structure, and possesses excellent properties of hydrophilic swelling and suspension thixotropy, and can disperse in water very well; however, it can not be dissolved in organic solvents, thus inhibited its applications. In this study, the techniques for improving the lipophilicity of hectorite via modifying the microstructure of hectorite with organic agent was experimentally investigated, and the modification mechanism was discussed.The synthetic hectorite was used as the raw materials in this study, and was initially and secondly modified with three organic modifiers, cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS) and silane coupling agent KH570, thus obtained a series of modified organic hectorites.Wettability of the organic hectorite samples and the viscosity of organic gel made with the organic hectorite samples were measured. The results show that the wettability of the organic hectorite modified with KH570 in heat transfer oil was better than other samples; and the improvement of secondly modification was higher than initially modification. Meanwhile, the viscosity of organic gel made with the organic hectorite through secondly modification was higher than that through initially modification.The microstructures of the organic hectorite samples were analyzed by X-ray diffraction (XRD), infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results show that all of modifiers SDS, CTAB and KH570 inserted into the interlayer of hectorite, and enlarged the layer spacing of organic hectorite from 1.14nm to 1.63nm (CTAB) and 1.65nm (KH570). Second modification did not further increase layer spacing, and maintained the coral-like structure. The microstructures suggested the modification mechanism of organic hectorite would be as follows:for initially modification, the adsorption form of CTAB was exchange adsorption, SDS physical adsorption, KH570 chemical adsorption through covalent bond; the three kinds of organic modifiers inserted into interlayer of hectorite in single-layer flat horizontal model, but in different orientation; for secondly modification, KH570 overlayed the crystal layer, and partly inserted into the interlay taking place CTAB; however, SDS did not insert into the interlayer to replace CTAB, and did not overlay the surface of organic hectorite.