| China is one of the biggest countries that consume rubber products,and more than 70%of the rubber was applied as tires.With the development of automobile industry,increasing requirements on wear resistance,wet-skid resistance and safety performance of tires have drawn many research attentions.However,traditional tires rubber can't meet these requirements,and thus it is very necessary to find new rubber materials with higher properties.At present,eucommia ulmoides gum has made great progress in replacing some tire rubber materials,but it also faces many challenges.In this paper,natural eucommia ulmoides gum(EUG)was firstly extracted from the eucommia ulmoides leaves and waste materials of eucommia ulmoides powder,and then blended with nitrile butadiene rubber(NBR),natural rubber(NR)and butadiene rubber(BR)to fabricate blend systems.Subsequently,molecular chain models of EUG with NBR,NR and BR individually were built by Materials Studio software,and the compatible mechanism was further discussed based on the results of molecular dynamics,mesoscopic dynamics,radial distribution function and interaction parameters.Then this compatible mechanism from simulations was checked by scanning electron microscopy(SEM),differential scanning calorimetry(DSC),Dynamic thermomechanical analysis(DMA)and fourier transform infrared spectroscopy(FTIR).Furthermore,the effects of EUG on the tensile strength,aging behavior and friction as well as wear of blends were investigated systematically.Main conclusions of this paper are as follows.1.Simulation results suggest that EUG has different compatible performance with different comer rubbers.EUG can be compatible with NBR only when the blending temperature is higher than 100?,but can compatible with NR even at room temperature,BR can be compatible with EUG at room temperature when its content in BR/EUG system is lower than 50%,but can not be compatible when its content is higher than 50%.2.Blending experiments were carried out on EUG/NRB,EUG/NR and EUG/BR systems,and the results agree well with that of compatible simulations.Blending parameters for these systems are as follows:the best blending temperatures are 90,70 and 60 ?,while blending time are 30,30 and 40min for EUG/NBR,EUG/NR and EUG/BR systems,respectively.Before blending,the EUG must be treated at 80? for 20min.3.With the decrease of the temperature,long molecular chain of EUG would precipitate as micro-crystals from the vulcanized blends,and present to be small particles in the molecular chain of common rubber.Such particles will limit the movement of molecular chain of common rubber,and thus result in the improvement of strength.When the amount of these small particles exceeds a certain content,the blends can get a good mechanical performance.4.Compatible mechanisms of EUG blending with NBR,NR and BR are investigated by molecular simulation.For EUG/NBR blends,-CH=CH-chain units of EUG have good compatibility with-CH2-CH=CH-CH2-and-CH2-CH-CN chain units of NBR,and-CH2-CH-CN chain units benefit more to the compatible.For EUG/NR blends,the good compatibility comes from the cis-trans molecular structure,which has the same molecular geometries but non-symmetrical structure.For BR/EUG blends,although both of them have-CH=CH-chain units,there are more than two saturated carbon atoms spaced apart in the-CH=CH-chain units of BR,and the structure around carbon-carbon double bond is symmetrical,leading to a poor compatibility.5.When adding graphene into the binary blending system,it was found that graphene has poor compatibility with EUG/NBR but good compatibility with EUG/NR matrix.With the increase of graphene content,both friction coefficient and wear rate of EUG/NBR/GO ternary blend increases,but the friction coefficient decrease and wear rate decrease followed by increase for EUG/NR/GO.Wear mechanism of the former is mainly abrasive wear accompanied by slight adhesive wear,while the latter one is mainly adhesive wear accompanied by a small amount of oxidation. |
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