The Research On Modification On Oxides Nano-particles And Its Applications

The performance of conventional composites have been proved to be improved greatlyafter addition of nano-materials into their formulations, while the tendency of aggregation ofoxide nanoparticles due to large surface energy and poor interface compatibility between thehydrophilic filler surface and hydrophobic polymer matrix confine the industrial applicationof oxide nanoparticles. The effective solution is deployment of surface modification on oxidenanoparticles. This approach normally involves two aspects. One is procedure regulation ofnanoparticles during their synthesis process; the other is conduction of surface modificationon the existing oxide naoparticles. For the former approach, there are many technical processconcerns and complex factors, and it is difficult to prevent the re-aggregation. For the later,the modification is carried out in case oxide particles are applied, which favors highlighting ofthe advantages of nanoparticles. In this work, wet modification is adopted for altering surfacefeature of oxide nanoparticles. Adsorption behaviors of various surfactants on oxide surfacewere investigated in details, and the mechanism on stabilization of aqueous dispersions wasalso discussed. Moreover, PP matrix composites were prepared by addition of modified oxidenanoparticles. Systematic experimental study was carried out to reveal the influences ofmodified nanoparticles on the mechanical performance of the composites.Belows are the main work scopes and the relevant results in the dissertation.（1） Individual and simultaneous adsorption behaviors of various surfactants （TPB, CTAB,SDS and PEO） on surface of oxide nanoparticles were studied. FTIR results indicated that theadsorption of ionic surfactants CTAB, TPB and SDS on oxide surface originated from theelectrostatic interaction, while adsorption of non-ionic polymer PEO depends on hydrogeninteraction. Simultaneous adsorption occurred on the oxide surface in the binary mixturessystem （CTAB/PEO and SDS/PEO）, and the competitive behavior was also observed.Experimental study on adsorption isotherm demonstrated that the absorbed amount of ionicsurfactants greatly depends on the concentration, pH value, electrolyte ionic concentration andit’s type. While the absorption amount of non-ionic polymer is closely related to the molecularweight and their configuration on oxide surface.（2） Charge density, zeta potential and double layer structure of oxide particles showeddifferent properties after surface modification. The pHiepof oxide particles moved towards tolower or higher pH value after adsorption of ionic or cationic surfactants, respectively. The shift extent depends on the surfactant concentration and the polymer molecular weight. Theabsolute value of the zeta potential of oxide particles would reduce after the adsorption ofnon-ionic polymer, while, the pHiepremains constant.The repulsion interaction of oxide particles modified by ionic surfactant comes from theimprovement of static interaction in aqueous solution. Non-ionic polymer offers stericrepulsion for dispersion of oxide nanoparticels. The electrostatic repulsion can be realized inbinary mixtures solution of ionic surfactant and non-ionic polymer to provide improvement ofdispersion of oxide nanoparticles.（3） Surface of ZrO₂particles was modified by silane coupling agent （A151） inalcohol-water solvent and used as filler in PP/ZrO₂nanocomposites. Chemical reaction wasfound between A151and ZrO₂from the FTIR analysis results. The wettability of ZrO₂nanoparticles has been promoted effectively upon the modification of A151. Surface of theoxide was changed to hydrophobic from hydrophilic, which enhances the interfacecompatibility with polymer matrix. Experimental results on mechanical performanceindicated that the addition of the modified nano-ZrO₂particles improves the tensile strengthand the elongation performance, as well as the impact strength and module of the composites.It should be noted that the improvement of mechanical performance was confined by thedispersion of nano-ZrO₂.（4） Intercalation modification of montmorillonite by OTAC was studied to improvePP/OMMT composites performance. XRD and FTIR results presented that the lamellarstructure of the layered OMMT was intercalated by OTAC. The layer spacing was extendedfrom1.51nm in Na-MMT to3.80nm by intercalation with alkyl chains. The SEM analysisrevealed that the morphologies change from sopherical-like particles to high-aspect ratioflakes after modification. The hydrophilic surface of Na-MMT was tranfered to hydrophobicafter modification, which greatly benefits the interface compatibility between the filler and PP.In case of addition of OMMT with3⁴wt%, the tensile and impact performance wereimproved obviously. Besides, the thermal degradation temperature of the nanocompositeslowers25oC in the DSC curve, revealing the improvement of the thermal stability of thePP/OMMT composites.