| Natural rubber(NR)is the most widely used matrix material in truck tires treads due to its high tensile strength and tear strength brought by strain-induced crystallization,but it has poor wear resistance.Carbon black can effectively improve the strength and wear resistance of rubber composites.However,the interaction between carbon black and rubber is mainly physical adsorption,which leads to hysteresis loss caused by the sliding of rubber molecular chains on the surface of carbon black and the friction between carbon black particles in the dynamic process,which will increase the tire rolling resistance and heat accumulation,increase energy consumption.Additionally,the abrasion of tires is not only affected by the structure and properties of composites,but also by external factors such as road conditions,load,speed,slip angle and contact area.Therefore,it is necessary to study the impact of these factors on abrasion.Based on carbon black/NR composites,this thesis investigates the effect of interfacial interactions and practical conditions on the wear resistance of composites.It is divided into three parts as follows:(1)5-Amino-1,3,4-thiadiazole-2-thiol(AMT)was grafted onto triethoxysilane-terminated liquid polybutadiene(TTPB)using thiol-ene click reaction in order to adjust carbon black/silica/NR interfacial interactions as a coupling agent,where the amino groups can react with carboxyl/aldol groups on the carbon black surface and the ethoxy groups can react with hydroxyl groups.The effects of in situ and grafting modifications on the filler-rubber interfacial interactions and the properties of composites were studied.The results of infrared spectroscopy showed that AMT was successfully grafted on TTPB.The coupling agent was encapsulated on the filler surface by the abovementioned chemical interaction and physical adsorption,and the interaction between the fillers was reduced.The results of rubber processing analyzer(RPA)and transmission electron microscopy(TEM)showed a significant improvement in the dispersion of the fillers in the composites,and the results of dynamic thermo-mechanical analyzer(DMA)showed a reduction in the loss factor(tanδ)at 60 °C.However,due to the consumption of extra sulfur by the coupling agent,the degree of crosslinking and the mechanical properties of the vulcanizates were decreased,and the heat build-up was increased.Furthermore,the results of solid-state nuclear magnetic resonance showed that as the coupling agent coated on the surface of the filler weakened the interaction between the carbon black and rubber molecular chains,and the strength of the carbon blackrubber interface was reduced,resulting in a decrease in wear resistance.(2)Based on the silane coupling agent bis-[γ-(triethoxysilyl)propyl]tetrasulfide(TESPT)grafted with aliphatic alcohol polyoxyethylene ether(AEO-9),different interfacial interactions were constructed between carbon black and NR depending on the degree of grafting.The effect of carbon blackrubber interfacial interaction on the properties of composites was studied.The results of RPA and TEM showed that the coupling agent could effectively improve the dispersion of carbon black in compounds and vulcanizates.The dynamic hysteresis between carbon black and rubber was reduced,the tanδ at60 ℃ and the compression fatigue temperature rise of the composites were decreased.The RPA analysis showed that the coupling agent with higher grafting degree had the highest obstruction to the flocculation of carbon black during the vulcanization process.With the increase of grafting degree,the stress at 100% and at 300% of vulcanizates decreased,and the elongation at break increased,while the tensile and tear strengths did not change significantly.The reinforcing effect of carbon black originated from its strong interaction with rubber chains,but the coupling agent occupied the active site on the surface of carbon black,weakened the binding of carbon black to rubber chains,and made rubber molecules more prone to detach from the surface of carbon black during wear,which resulting in a decrease in abrasion resistance.(3)The effects of load,speed,slip angle and contact area temperature on the abrasion,surface temperature,side force and abrasion surface morphology of carbon black/NR composites were investigated using the LAT 100 laboratory abrasion tester,and the changes in wear behavior during the abrasion process were described in terms of side force and surface morphology.The results showed that,with the increase of load,speed and slip angle,the abrasion and surface temperature of the rubber composite increased.The slip angle had the greatest effect on the abrasion and surface temperature,while the speed had the least effect on the abrasion,and the load had the lowest effect on the surface temperature.As the temperature of the disc increased,the surface temperature of the composites increased and the abrasion decreased.The effect of side force on wear was much greater than that of friction force,so the wear surface pattern was perpendicular to the side force,and the slip area wears most severely due to the dual effect of side force and load.The change of surface wear pattern was the result of the joint action of side force,temperature and contact area size,and was consistent with the change of abrasion.When the heat loss during the wear process was ignored,the abrasion was exponentially related to the energy loss caused by friction,with an exponent of approximately 2 for the carbon black/NR composites used in this chapter. |
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