Green Modification Of Natural Rubber And Preparation Of High-performance Natural Rubber Composites

Natural rubber has some excellent properties that synthetic rubber can't compare with,such as high elasticity,good mechanical properties and wear resistance.The rubber products made of natural rubber are widely used in people's life and national construction.In this study,environmental friendly and low-cost modifier was used to modify natural rubber to prepare high-performance natural rubber.It was also used in the preparation of NR/filler composites to explore its application prospect in industrial products.During the long-term storage of natural rubber,due to the aldol condensation reaction on its macromolecular chain,Mooney viscosity gradually increases,resulting in"storage hardening",which seriously affects the processability of rubber and the performance consistency of rubber products.In this study,a new type of constant viscosity agent alkyl hydrazine compound(OP)and traditional constant viscosity agent hydroxylamine hydrochloride(HH)were used to modify natural rubber latex,and the optimum dosage,process conditions,modification mechanism and comprehensive properties of the prepared constant viscosity rubber(CV-NR)were explored.The results show thatOP and HH can react with aldehydes on natural rubber macromolecular chain to shield aldehydes and reduce the crosslinking of molecular chain,so that Mooney viscosity is decreased obviously,and the initial value of plasticity(P0)is decreased but higher than 30,and the plastic retention index(PRI)is higher than 60,which fully meets the standard of constant viscosity rubber CV60.Moreover,CV-NR molecular chain is flexible,Tg is lower and crystallinity is better.The dosage ofOP is not more than 0.2phr,which is the best dosage.The constant viscosity rubber has lower molecular weight,less gel content,better processability and good physical and mechanical properties and aging resistance.In order to explore the application of constant viscosity natural rubber in industrial production,constant viscosity natural rubber/silica composites(CV-NR/SiO₂)were prepared to explore the effects of constant viscosity natural rubber on the physical and mechanical properties,micro morphology and dynamic mechanical properties of CV-NR/SiO₂ composites.The experimental results show that when the dosage ofOP is 0.1phr,the wet skid resistance of the composite is improved,the rolling resistance is reduced,the Payne effect is reduced and the processability is improved.And it has good physical and mechanical properties and aging resistance.The distribution of silica in constant viscosity rubber matrix is more uniform,and the compatibility and adhesion are improved.Cashew fruit phenol is a kind of phenol compound,which contains benzene ring,phenol hydroxyl group and fatty family leader side chain,so it has special chemical properties.In this study,it was used to modify natural rubber latex,and the optimum dosage,modification process and comprehensive properties of high strength natural rubber(HSNR)were studied.The results showed that the gel content of modified HSNR increased significantly,the crosslinking density of molecular chain increased,Tg increased,and crystallinity decreased.When the dosage of cardanol was 1.0phr,the elastic modulus G'of the HSNR was the largest,the tensile strength increased by 7.8%,and the tear strength increased by 5.3%.At the same time,it has excellent aging resistance,and the aging coefficient is increased from 0.31 to 0.50.As domestic aviation tire is listed as the key research field in the future,people pay more and more attention to aviation tire.Most of the aircraft tires are made of ribbed smoked sheet(RSS),but the production of RSS has been banned in China.Therefore,it is urgent to seek new production technology to fill the demand of RSS in China.In this experiment,cardanol modified high-strength natural rubber was used as raw material,and compared with 1#RSS,to explore its application value in the tread compound of aviation tire.The results show that the tensile strength of the high-strength natural rubber/carbon black(HSNR/CB)composites increases to 30.4MPa,the tear strength reaches74.7k N·m^-1,and the anti-aging property is outstanding.At the same time,it has excellent wear resistance,bending crack resistance,compression temperature rise resistance,good wet sliding resistance and low rolling resistance.