Preparation Of Zinc Stannate Based Flame Retardant By Mechanochemistry And Its Application In PVC

Rrecently zinc stannate?ZnSnO₃?has been widely used as a flame retardant in plastics which showed excellent smoke suppression and flame retardancy.The traditional preparation methods of ZnSnO₃ have great negative impact on the environment due to generation of the waste residue and waste water during the process of production.In this paper,ZnSnO₃ and clay loaded ZnSnO₃ based flame retardants?ZnSnO₃@clay?were prepared by mechanochemistry.The prepared ZnSnO₃@clay was applied into PVC and the effects of flame retardants on PVC materials and the mechanism of flame retardancy were investigated.The aging properties of the flame retardant PVC samples were also discussed.The first part:Taken Zinc Oxide?ZnO?and two tin oxide?SnO₂?as raw materials,ZnSnO₃ was prepared by mechanochemical method.The influence of speed,ratio and milling time on the generation of ZnSnO₃ were discussed and ZnSnO₃ were characterized by XRD,particle size analysis,SEM,TEM and TGA.The experimental results showed that when the molar ratio of two kinds of oxides was 1:1,speed was 2500 rpm and grinding time was 12 h,XRD characteristic diffraction peaks the product was according with ZnSnO₃?SEM and TEM confirmed that the morphology of the obtained Zn SnO₃ was cubic crystal,but there are minor defects on the surface.Particle size analysis showed particle size decreased first and then increased during the process of mechanochemical preparation ZnSnO₃.The second part:ZnSnO₃@clay with different loading ratios was prepared by mechanochemistry or ball milling dry method and the ZnSnO₃@clay was applied to the flame retardancy of PVC.The experimental datas show that the LOI of PVC samples increased with the increase of ZnSnO₃ loading ratio in the ZnSnO₃@clay but the mechanical properties of the PVC samples increased first and then decreased.When 10phr ZnSnO₃@clay was added to PVC and the load rate of ZnSnO₃ was 10%,the performance of PVC was better,the LOI reached 33.4%,and the elongation at break reached 339.4%.After adding ZnSnO₃@clay-10,the initial decomposition temperature of PVC sample reduced to 208.1?from 237.1?and the residual char increased significantly.CONE data showed the total heat release,heat release rate,total smoke release and smoke release rate were significantly decreased.XPS analysis indicated that the new bond?Sn-O-Si?appeared in PVC char after adding ZnSnO₃@clay-10.All the data showed that there was synergistic effect between ZnSnO₃ and clay when ZnSnO₃@clay was used as flame retardant to promote the carbon formation of PVC.The third part:The effect of ZnSnO₃@clay on the aging properties of PVC samples was analyzed by Taken Sb₂O₃ as reference.The experimental data showed that:for the UL-60cable aging standard,after aging the elongation at break of PVC-6?PVC with ZnSnO₃@clay-10?reached 368.1%,which was higher than that of PVC-2?PVC with Sb₂O₃?and the thermal weight loss of PVC-6 only was 0.53mg cm^-2,which was far lower than 1.08mg cm^-2 of PVC-2.The above data showed that the anti-aging performance of ZnSnO₃@clay-10 was better than Sb₂O₃ for the UL-60 cable aging standard.However,under the UL-75 cable aging standard,the anti-aging performance of PVC-6 is inferior to PVC-2.In the FTIR spectrum of PVC-6 the new-C-O-C-vibration peak at 1066 cm^-11 could be observed,which confirmed that Zn SnO₃@clay promoted the crosslinking reaction of PVC.Under the aging standard of UL-60 cable,the LOI of PVC samples decreased after aging which was consist with the change of CONE data.While the LOI increased of PVC samples significantly after aging under the aging standard of UL-75 cable due to the crosslinking reaction in higher temperature.