The Study Of Preparation And Application Of Woliastonite Coated With Nano Sb-SnO₂Composite Powder

Wollastonite has been widely used in many industries such as plastic andpapermaking, because of the special fibrous crystal formation and highwhiteness as a new kind of industrial mineral materials. The insulatingproperties of the wollastonite have restricted its application in polymers and it isprone to produce and accumulate electric charge in the polymer composites.In this work,we will prepare a new kind of light color conductivewollastonite based composite with chemical coprecipitation method by coatingSb-SnO2(ATO) particles. Choosing wollastonite as reactants, the tin chloridepentahydrate (SnCl4·5H2O) and antimony chloride(SbCl3) as coating modifiersbased on the excellent conductive property of ATO, higher whiteness of mineralfibers and their wide application in plastics, painting and paper field.ATO/wollastonite composite was acquired by this method. The mechanisms ofmodification and coating were detailed introduced and the antistatic mechanismwas preliminary discussed.The volume resistivity of conductive wollastonitecomposite powder would be dramatically reduced by modulating and optimizingthe parameters of preparation process of the conductive composite powder. Thecomposite was characterized and measured by EST121powder volumeresistance tester, TEM, X ray diffracmeter, EDX, SEM, infraredspectrometer,whiteness apparatus,surface area analyser to its resistivity,phase,structure,composition and chemical methods.etc. The results showed the best conditions are: covering amount:2.5%; calcining temperature:700℃;roasting time:2h; reaction temperature:60℃; dropping speed:1mol/L; n(SbCl3)and n(SnCl45H2O) molar ratio:1:8~1:10;action time:30min;pH:7~11. Byorthogonal experiments, we draw a conclusion that calcination temperature andcoating amount had a significant effect on the volume resistivity of compositepowders and pH had a significant effect on the whiteness. The best conditionsare: covering amount:3.0%; calcining temperature:600℃; roasting time:3h;n(SbCl3) and n(SnCl45H2O) molar ratio:1:8;pH:7. By analyzing the infraredspectrum of wollastonite coating before and after coated,we knew that ATO wasnot combined by electrostatic force, but the bond strength; SnO2and Sb2O3released some free electrons by the solid phase doping reaction on the suface ofwollastonite in the process of the crystal growth,so that the volume resistivity ofwollastonite composite powders was decreased by the movement of freeelectron. This was the coating mechanism and antistatic mechanism ofwollastonite composite powders.The conclusions demonstrated that a layer of Sb-SnO2was coated on the thesuperficies of wollastonite evenly, the whiteness has been reduced from91.7to90.5, the particle size increased from10.81μm to11.46μm, the specific surfacearea increased from1.4068m2g-1to3.6532m2g-1, and the resistivity declinedfrom3.36×1010Ω cm to0.75×105Ω cm. We cut the PVC-EVA/carbon blackcopolymer into pieces and plastify the modified wollastonite and the cutedPVC-EVA/carbon black copolymer.Its volume resistance was reduced from1.60×109Ω·cm to2.58×107Ω·cm and reached the operating requirements ofpolymers in mining industry and other industries.