| Natural rubber（NR）has excellent mechanical properties,tear resistance,elasticity,etc.,and is widely used in various fields.Tires are one of the main application fields of NR,and the preparation of tires with low rolling resistance,high wear resistance and wet skid resistance has always been the pursuit of researchers.However,rubber tires serving under dynamic conditions often face the problem of hysteresis loss due to their viscoelasticity.Macroscopically,the rubber tire has obvious internal heat generation and high energy consumption.However,the thermal conductivity of NR itself is low,and the heat caused by hysteresis cannot be efficiently transferred to the outside,resulting in a large amount of heat accumulation inside the rubber,accelerating the aging rate of rubber,which seriously shortens the service life of the product.Therefore,controlling the temperature rise of rubber materials under dynamic conditions is crucial for the preparation of high-performance rubber products.The continuous development of high thermal conductivity polymers provides a new method to control the dynamic temperature rise of rubber.The thermal conductivity of rubber materials can be improved by adding thermally conductive fillers to the rubber matrix,constructing thermally conductive pathways,and reducing interfacial thermal resistance.New functional nanomaterials such as graphene oxide（GO）,carbon nanotubes（CNTs）,and silicon carbide（Si C）are used to replace or partially replace traditional reinforcing fillers to prepare high-performance rubber composites.It can not only play a reinforcing role of traditional fillers,but also endow rubber with multiple functions（thermal conductivity,electrical conductivity,etc.）.However,the high content of fillers also brings many problems,such as higher heat build-up,decreased processing performance,and poor mechanical properties.At present,the research on reducing the hysteresis heat build-up of rubber mainly starts from improving the dispersion of fillers and enhancing the interface between fillers and rubber.However,the requirement of filler dispersion is contradictory to the construction of thermal conduction network in rubber.Therefore,it is necessary to ensure the dispersion of the filler while reducing the phonon scattering and phonon transmission distance,so as to improve the thermal conductivity of the rubber composites,reduce the heat build-up,and achieve the purpose of controlling the rubber temperature rise under dynamic conditions.This paper discusses how to balance the thermal conductivity,heat buld-up and mechanical properties of natural rubber for tires with low filler content.And researches were carried out with Si C and GO as the main fillers,to improve the filler-matrix interfacial interaction and filler dispersion as the main approach,and to control the dynamic temperature rise of the rubber material for treads as the main goal.The main research contents are as follows.（1）Firstly,the effect of silicon carbide nanowires（Si Cnw）with high thermal conductivity and large aspect ratio as filler on the thermal conductivity and mechanical properties of NR was investigated.Then,the thiol functionalized Si Cnw（Si Cnw SH）filler was prepared by modifying and functionalizing Si Cnw with silane coupling agent（KH590）containing thiol functional groups.The thiol functional groups grafted on the surface of Si Cnw by chemical bonds could increase the interaction between the Si C filler and the NR matrix through a thiolene click reaction.The thermal conductivity of NR composites was improved by adjusting the arrangement direction of fillers with the ice template process.When the content of Si Cnw-SH was 25 wt.%,the thermal conductivity of the NR/Si Cnw-SH composite could reach 0.856 Wm-1K-1,which was 4.3 times that of pure NR.And the tensile strength was 14.8 MPa.In order to balance the thermal conductivity and mechanical properties of rubber composites,NR composite was prepared by rubber mixing process with thiol functionalized silicon carbide nanoparticles（Si Cnp-SH）as reinforcing filler.Compared with the composites prepared with the same content of Si Cnw-SH,the tensile strength of NR/Si Cnp-SH composites reached 20.6 MPa,an increase of 39%,while maintaining a high thermal conductivity(0.570 Wm-1K-1).（2）The principle of stable dispersion of graphene/latex mixed system,the mechanism of synergistic flocculation of graphene and NR,and the interaction between GO and latex during the preparation of graphene master rubber by aqueous phase synergistic precipitation process were discussed.The results showed that the small molecules in the natural rubber latex had an obvious intercalation effect on graphene oxide.In addition,GO was covalently coated on the surface of Si C particles to form point-surface structure Si C/GO（SG）composite particles,which could not only promote the dispersion of Si C thermal conductive particles,but also improve the interaction between filler and matrix.When the ratio of Si C to GO was 4:1,and the filler content was 4 phr,the tensile strength of NR/SG composite was 25.9 MPa,and the thermal conductivity was 0.343 Wm-1K-1,and the compression fatigue temperature rise was5.3℃,showing good comprehensive performance.（3）On the basis of SG composite particles,in order to further improve the interface interaction between filler and matrix,SG particles were modified by in-situ chemical deposition of sulfur to prepare SG-S particles with both vulcanization and reinforcement functions,and then NR/SG-S composites was prepared by aqueous phase synergistic coagulation process.On the one hand,sulfur was adsorbed on the surface of SG fillers in the form of nanoparticles,which effectively realized the uniform dispersion of sulfur in the matrix.On the other hand,sulfur loaded on the surface of SG filler can be used as a sulfurizing agent to cross link with NR molecular chain,thus forming strong interface interaction between SG particles and NR molecular chain.When the filler content was 4 phr,the tensile strength of SG-S reinforced NR composites was 27.3 MPa,elongation at break was583.8%,compressive fatigue heat generation was 4.4°C,and thermal conductivity was 0.377Wm-1K-1.Compared with the NR/SG composites without strong interfacial interaction,the thermal conductivity and low heat build-up value were improved by 9.9%and 17.0%,respectively,achieving simultaneous improvement in mechanical properties and dynamic temperature rise control capability.（4）In order to investigate the actual control effect of the prepared natural rubber composites on the tire temperature field when it was used in tires.Took the solid tire as the object,the temperature field under different driving conditions were simulated and predicted by ANSYS software,and quantitatively analyzed the influence of rolling speed,tire load and external temperature on the internal temperature field of the solid tire.The results showed that with the increase of rolling speed,the radial temperature difference of tire basically presented a linear increase trend.The radial temperature difference increased linearly with the increase of tire rolling speed.The ambient temperature had little effect on the radial temperature difference of the rim.With the increased of radial load,the radial temperature difference increased gradually as an upward quadratic function of the opening.In addition,the temperature life relationship of rubber materials during thermal aging was established.The results showed that the life of NR tire decreased exponentially with the increase of tire temperature.The results effectively revealed the rule of the influence of tire service temperature on its service life,which was of great significance for the design,development and application of long-life rubber tires. |
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