The Cooperation Of Nanokaolin,Carbon Black And Silica And Their Applications In Tire

For different tire products,a series of rubber composites filled with naokaolin,silica,carbon black were prepared in this paper by methods which are most popular in industry.Based on multi-filler-net consisting of NK,carbon black and silica,the affection of cooperation of different fillers on processing properties,mechanical properties,durability properties,gas barrier properties of mineral tire,radial tire gas barrier innerliner,side wall,tread,were investigated.Relevant models of filler-net were built,and the mechanisms were studied.The results are shown as follows:(1)The modified kaolin used in this research is very pure,the kaolinite has very low crystalline and vey high activity surface,which endow it a very good nano two dimension filler.The carbon black,silica,NK are dispersed in nanoscale in rubber matrix.A series of rubber nanocomposites are obtained.Different filler-nets appear when the ratio of these three fillers is different.(2)In sidewall rubber composites,when the fraction of carbon black and silica is low(<45phr),the entrapment of filler-net on rubber molecule chains is weak.When a few(5phr)NK are added,the platy NK particle insert into the gap of basic enforcement units.The movement of rubber molecule in this area are limited,in a transition state between elastomeric state and glass state because the rubber molecules are not completely trapped yet.The multi-fillers-net are continually broken and rebuilt in cyclic strain,consuming more energy.Therefore the Tan? and loss module increase.The diffusion path of gas molecules don't change because of the low fraction of NK,therefore the diffusion coefficient don't change much.The rubber chain used to be free state are trapped by fillers-net,resulting in the increasing of storage module of composites.But the rubber chains are not in glass state yet,so the solubility coefficient doesn't change much.(3)In mineral tires,gas barrier innerliner and tread,when the fraction of carbon black is high(>50 phr),a full-order filler-net are built by carbon black and revealing a good trappment.After adding a few(5phr)NK,the aggregation of carbon black are broken by kaolinite,the trappment of carbon black on rubber molecule are weaken,resulting the occluded rubber are released and translating from glass state into elastomeric state.The solubility coefficient of rubber composites increases with the increasing of rubber fraction in elastomeric state.But the original carbon black filler-net still maintain good,and the NK extend the gas molecule diffusion path,therefore the diffusion coefficient of rubber composite decreased.The fraction of rubber chains in glass state decreases,resulting in the decreasing of storage modules of composites.Compared with only carbon black filler-net,multi-filler-net consumes more energy in broken-rebuilt circulation,therefore the loss modules of composites increase.(4)In mineral tire and tread rubber,when the fraction of NK increase,the contacting of platy kaolinite particles appears in partial area,forming new kaolinite filler-net.Therefore the fraction of occluded rubber increases.The surface-edge contacting of kaolinite particles in partial area accelerate the diffusion of gas molecules.At this time,the original carbon black filler-net are broken,and the new kaolinite filler net are not built up completely,therefore the mechanical properties,durability properties,gas barrier properties and dynamic mechanical properties are not promote much.(5)when the fraction of NK increase,the number of kaolinite particles increase.The platy kaolinite filler-net become more and more complete.Meantime,carbon black particles insert into kaolinite filler-net,extended the diffusion path of gas molecules again,resulting the decreasing of diffusion coefficient of nanocomposites.The rest properties of tire rubber are promoted as well.In gas barrier inner liner and tread,the total fraction of NK and carbon black is more than 80 phr,carbon black particles are inserted into the gap between kaolinite particles,trapping the rubber chains well in this area.Kaolinite and carbon black cooperates well with each other,resulting the fraction of occluded rubber and bonded rubber increase rapidly,enhance the properties of rubber nanocomposites.(6)In mineral tire and tread rubber,NK are introduced into rubber with silica.Platy kaolinite particles not only destroy the trapment resulted from silica filler-net,but also adsorb silica particles by weak physical force forming “core-shell structure”,where the flaw is easily to extend.The tear strength decrease hence.The broken silica filler-net release occluded rubber,decreasing the solubility coefficient and storage modules.But it also lower the energy consumed in filler-net broken-rebuilt circulation,therefore the loss storage decrease.This phenomenon is improved better when rubber filled with carbon black,white carbon black and kaolinite.(7)When filled with NK,the processing properties of rubber compound are apparently optimized.Carbon black aggregations and silica aggregations particles are divided by platy kaolinite particles,reducing the collision of aggregation.At mean time,the kaolinite particles on carbon black and silica filler-net nodes,destroy the stress transferring of filler-net,loosen the structure of filler-net.These two factors decrease the compound Mooney viscosity,making the mold filling in calendar easier.The platy kaolinite particles prevent heat flow into matrix slowing down the curing speed at the early stage of vulcanization,increasing the safety of operation.Vulcanization is a exothermic reaction.The platy kaolinite particles prevent heat flow out of matrix accelerating the curing speed at the lately stage of vulcanization,increasing production efficiency.(8)The analysis of SEM indicated that,when kaolinite particles are wrapped well by rubber matrix when its fraction is low,and the surfaces of composites are smooth.The rubber between adjoining particles plays buffering function,avoiding the collision of particles.Therefore the wear properties of composites are good.When the kaolin fraction increase,nanocomposits reveals stepladder morphology,large number of kaolinite particles expose from rubber matrix,adding the holes formed by kaolinite particles,the wear properties of rubber composites are remarkable reduced.(9)In rubber aging,flexible long rubber chains transited into rigid short rubber chain and recombined together.After aging,stress at definite elongation increase,the tensile and tear strength decrease.The analysis of IR reveal that,aparting from nature rubber,NK can absorb rubber chain,limiting the movement of unsaturated bond.At mean time,platy kaolinite particles prevent the oxygen from flowing into the inner matrix.Because of these two factor,the activity of reaction between rubber chain and oxygen are reduced,the oxygen concentration reduces.Therefore,the anti-aging properties of composites are enhanced,tensile and tear strength increase.For nature rubber,dosage of antioxidant should be properly increased.(10)Nanokaolin used in this study,possess a good application prospect in mineral tire,gas barrier innerliner.At proper filling fraction,nanokaolin can improve processing properties,durability properties,wet-skid resistance properties and gas barrier properties,decrease dynamic heat build-up of tire.But in mineral tire and tread rubber filled with NK and silica,the tear strength of composites deteriorated seriously.