Application Of Plasma Modified Silica In Green Tire Tread Compounds

Since the mid-20th century,green tires have been widely studied and utilized because of their unique advantages of low-energy and environmental protection.Silica,as the main component of green tires,has draw more and more attention in rubber tires.The addation of silica in tire recipes can significantly improve the wet skid resistance and abrasion resistance while reducing rolling resistance.However,a large number of hydroxyl groups on the surface of silica,resulting in severe agglomeration in the rubber matrix.Therefore,the application of silica is often accompanied by surface modification.The silica surface was modified by means of plasma with different powers,and the rubber composites filled with silica was prepared in this work.The relationship between modified silica surface structures and properties of its filled SSBR composites was investigated with the help of FTIR,TGA,TEM and static/dynamic properties.The results showed that the silicon hydroxyl content on the surface of plasma modified silica was reduced,and its reduction is proportional to the modified power.The cross-linking density and static/dynamic mechanical properties were improved to some degree for in the modified silica filled SSBR system.In which,the dispersion of the silica modified with 200 w improved obviously,and it increased the cross-linking density and dynamical properties of the filled SSBR.However,the Si-O-Si structure existed for the silica modified with 800 w.The dispersion state in rubber matrix and the enhancement degree for the cross-linking density as well as static/dynamic properties of the vulcanizates were less than those of silica modified with 200 w.Afterwards,the effect of the content of silica modified with the two different powers on the curing characteristics and combination mechanical properties of the filled SSBR was compared.In addition,the filler network threshold was calculated for the three different kinds of silica filled system.The results showed that the scorch time was prolonged for the modified silica filled system,and it had the best processing security.The filler network threshold was calculated by percolation theory based on mechanical properties parameters.It was found that the modified silica network threshold was increased obviously comparing with that of unmodified silica network threshold.The 200 w modified silica network threshold was the highest.It indicated that the rubber content could be reduced efficiently with the help of plasma modification.Finally,the effect of silane coupling agent content on mechanical properties of both the unmodified and 200 w modified silica filled SSBR systems was studied.The results showed that the optimal silane coupling agent content was dependent on the kinds of mechanical properties.In which,the optimal silane coupling agent content was 6% of the plasma modified silica in the filled system.There are much less silane coupling agent in the plasma modified silica filled system,comparing with that in the unmodified silica filled system,when the corresponding properties was almost the same.That is,the silane coupling agent content could be reduced to some degree when the plasma modified silica was used,instead of the unmodified silica.Above all,the NH₃ plasma modification method has a remarkable effect on the surface treatment of silica.Due to the etching effect of plasma modification,the hydroxyl groups content on the silica surface decreased obviously.The surface activity of silica is reduced,thereby weakening the aggregation behavior of silica in the SSBR matrix.As the same time,the increase of the critical filler volume fraction enables the application of high content of silica in rubber composites.Furthermore,the plasma modified silica becomes less dependent on Si69,thus reducing the use cost of rubber composites.