Study On Performance Of Nitrile Rubber Composite Reinforced By Aramid Fiber

As a kind of high-performance synthetic fiber,aramid fiber has excellent physical and mechanical properties.It can be used as a framework material to reinforce rubber matrix.Nitrile rubber is an amorphous synthetic rubber with good oil resistance,wear resistance and corrosion resistance.Blending aramid fiber with nitrile rubber can greatly improve the mechanical properties of rubber composites.However,the aramid fiber has large aspect ratio,smooth surface and chemical inertness,resulting in poor dispersion and interface adhesion in rubber matrix.In view of this,this paper is based on the wet mixing technology to prepare aramid fiber reinforced nitrile rubber composite materials,and systematically investigated the factors such as fiber content,fiber surface modification and fiber size on the performance of the composite material.In order to improve the dispersion of aramid fiber in rubber matrix,two thickeners,sodium polyacrylate and polyethylene oxide,were added to thicken the nitrile rubber latex,and then premixed with aramid fiber to prepare masterbatch,and the effect of thickener types on the mechanical properties of the composite was studied.The research results show that the tensile mechanical properties of the composites prepared by sodium polyacrylate thickened latex are superior to polyethylene oxide,and the tensile strength of the composites prepared by the concentration of 0.75% sodium polyacrylate thickened latex reaches the maximum.At the same time,in order to improve the interfacial adhesion between aramid fiber and nitrile rubber,the surface of aramid fiber was modified by dopamine oxidation polymerization.The experimental results show that after the aramid fiber was immersed in the dopamine buffer solution added with sodium persulfate for 24 h,the prepared fiber-reinforced nitrile rubber composite has the best performance;and under the same modification conditions,the surface modification of the aramid nanofiber is higher than that of aramid microfiber.On the basis of the above research,the effects of fiber content and surface modification on the microstructure,processing and mechanical properties of aramid fiber reinforced nitrile rubber composites were studied in detail through characterization methods such as rubber processing analyzer,tensile testing machine and scanning electron microscope.The results showed that when the amount of aramid fiber is increased and the surface of the fiber is modified,the minimum torque,maximum torque and torque difference of fiber and nitrile rubber compound increased,the Payne effect enhanced,and the vulcanization time of the modified aramid nanofiber and nitrile rubber compound was prolonged;there should be an optimal amount of aramid fiber to enhance the mechanical properties of nitrile rubber,below the optimal amount of fiber,with the increase of fiber content,the filler network structure is improved and the tensile properties of composites are enhanced.When the amount of fiber added exceeds a certain value,the dispersion of fiber in the rubber matrix becomes worse,so the mechanical properties of the composite also decline;due to the diameter of the aramid nanofiber is smaller,and the dispersion in the rubber matrix is better than the aramid microfiber,so the optimal addition amount is increased;after surface modification,the mechanical properties of aramid nanofiber are higher than the aramid microfiber.The optimal addition amount of the two fibers is affected by the surface modification differently,the optimal addition amount of modified aramid microfiber is reduced,while that of modified aramid nanofiber is increased.In order to further improve the mechanical properties of unmodified aramid nanofiber reinforced nitrile rubber composites,a series of fiber-reinforced rubber composites were prepared by using cellulose nanocrystals instead of sodium polyacrylate to thicken nitrile latex.Preliminary research results showed that cellulose nanocrystals not only improve the dispersion of fibers in the wet predispersion process of fibers,but also act as a reinforcing agent,and there is a synergistic effect on the tensile mechanical properties of nitrile rubber composite reinforced by cellulose nanocrystals and aramid nanofibers.