| Carbon nanotubes are an emerging carbon family material with unique structure,excellent mechanical properties and high thermal conductivity.It has become a research hotspot since its inception.However,carbon nanotubes also have some shortcomings in processing applications.In this paper,the surface modification of carbon nanotubes is carried out for the disadvantage that carbon nanotubes are not easily dispersed and the binding ability to the substrate is poor,and The pre-dispersion is obtained for the disadvantages of easy flying and difficult transportation during processing.Then,the composite thermal conductive filler is prepared by further introducing fly ash to further improve the thermal conductivity of the carbon nanotubes.Finally,the prepared modified carbon nanotubes are applied to the nitrile rubber,and the advantages of high thermal conductivity,high heat dissipation and improvement of high temperature mechanical properties and aging retention of the rubber are used to prolong the service life of the rubber compound and to carry out the thermodynamic properties of the rubber compound.Test characterization to achieve improved vulcanization efficiency,reduced energy consumption,reduced heat generated during use,and extended rubber life.The results showed that,when carbon nanotubes are added,the torque of the nitrile rubber increases and the vulcanization time decreases.In order to improve the dispersibility of the carbon nanotubes and the binding force to the rubber matrix,the carbon nanotubes were subjected to surface modification by two methods.The acrylic acid modified carbon nanotubes have better reinforcing effect on the nitrile rubber,and the tensile strength,tear strength and tensile stress are higher than those of the couplingagent modified carbon nanotubes,and the optimum dosage is 2 phr.At high temperature,carbon nanotubes can effectively improve the high temperature mechanical properties of nitrile rubber.Among them,acrylic acid modified carbon nanotubes have better improvement of high temperature mechanical properties of nitrile rubber.Compared with the acrylic carbon nanotubes which have not been treated by a high-speed mixer,the treated modified carbon nanotubes are superior in all aspects,indicating that the carbon nanotubes are modified by a high-speed mixer and acrylic acid in-situ polymerization.A viable option.The nitrile rubber added with the acrylic acid modified carbon nanotube has the advantages of good processing property,high degree of dispersion of the filler and good reinforcing effect.In order to solve the disadvantages of difficult processing and transportation of carbon nanotubes,a carbon nanotube predispersion is prepared.At the same time,because the rubber matrix is not resistant to high temperature,the viscosity is inconvenient to realize the operation in the process of extrusion preparation,and the thermoplastic elastomer SBS which is easy to process and has good compatibility is selected as a carrier.The optimal preparation process of SBS-based carbon nanotube pre-dispersion is as follows: component ratio SBS: CNTs: operating white oil = 2.5:1:1.5;mixer temperature 190?,stirring at 2800r/min for 5min,Then,the mixture was stirred at a speed of 1400 r/min for 5 minutes,and finally stirred at a speed of 2800 r/min for 5minutes,and discharged at a temperature of 200? and a rotation speed of 150 r/min.The carbon nanotube predispersion has a great improvement in the electrical conductivity of SBS,and the addition amount is preferably 12.5 phr.Compared with the direct addition of the same components,the SBS-based carbon nanotube predispersion has little effect on the mechanical properties of the nitrile rubber,but solves the problem of the addition and transportation of the carbon nanotubes,and has certain practicability.Since the long diameter ratio of carbon nanotubes is high,the heat conduction effect is good in the axial direction,but the heat conduction effect is deteriorated in the radial direction,so a spherical filler(fly ash)is introduced to improve the radial direction.The thermal conductivity of the composite thermally conductive filler is prepared.The thermal conductivity of the composite thermally conductive filler is better than that of alumina,and can improve the physical and mechanical properties of the rubber to a certain extent.After replacing the carbon black N550 with the same amount of composite filler,the mechanical properties of the NBR vulcanizate increased first and then decreased with the increase of the number of replacement parts.The thermal conductivity of NBRincreased with the increase of the number of replacement parts,NBR glue The high temperature mechanical property retention rate of the material has increased,and the optimum replacement number of the composite thermal conductive filler is 10-20 parts.At this time,the processing property of the rubber compound is good,the Payne effect is low,and the dispersibility is good.When the amount of the replacement carbon black N550 is excessive,the rubber substrate is liable to be defective when subjected to a force.The acrylic modified carbon nanotubes can be added as a compatibilizer to the NBR/EPDM blend,which can effectively improve the properties of the blend.In the aging process,as the aging time prolongs,the hardness of the nitrile rubber will gradually increase,the elongation at break will gradually decrease and the tensile strength will increase first and then decrease,and within a certain temperature range,with the aging temperature increased rate of increase in tensile strength and hardness,in the experiment,the mechanical properties of the blended rubber using the surface-modified carbon nanotubes as the compatibilizer were better than that of the non-blended NBR.Through experiment,fitting curve equation and reaction activation energy calculation,it is concluded that the service life of NBR/EPDM blend rubber is longer than that of unblended NBR.The experimental results and actual use analysis are feasible. |
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