Research On Direct Reaction Molding Of Rubber Powder And Its Application In Styrene Butadiene Rubber

With the rapid development of automobile industry,the problems of environmental pollution and waste of resources caused by waste tires need to be solved urgently.Recycling waste tires in an environmentally friendly and efficient way has become a research focus.Production of rubber powder does not produce secondary pollution with the recycling rate of waste tires close to 100%,which has become the dominant direction of waste tire recycling.However,the application of rubber powder is limited due to its dense three-dimensional network and inert surface.Nitroxide radical can be used to modify rubber powder which can produce reproducible elastomer by direct reaction molding or fill in styrene butadiene rubber with a large amount.This efficient recycling process of rubber powder is conducive to solve the problem of shortage of rubber resources in China,which has practical and economic value.In this paper,reproducible elastomer material was prepared by direct reaction molding between rubber powder and DTEMPO containing bifunctional nitroxide radical.The mechanism of direct reaction molding was analyzed by crosslinking density and sol fraction measurement,FTIR,XPS,EPR,etc.Finally,the microstructure of the material was observed by SEM,and mechanical properties of the material were measured.The results showed that nitroxide radical on DTEMPO can capture sulfur free radicals generated in the process of mechanical shearing,while part of nitroxide radical attached to surface of rubber powder can react with rubber chain during compression molding,then reversible alkoxy amine structure was formed at the interface of rubber powder.Full rubber powder elastomer with excellent properties was obtained.When the dosage of DTEMPO is 3 phr,the material has the best mechanical properties,whose tensile strength is 12 MPa and elongation at break is 290%,and recovery efficiency of tensile strength after reprocessing for two times is higher than 80%.What's more,the rubber powder elastomer can be broken into modified rubber powder under the action of high temperature and weak shear force,and the modified rubber powder filled in styrene butadiene rubber will have a positive effect on the structure and properties of the composite.Particle size analysis,SEM,XPS,EPR and other tests were used to characterize the modified rubber powder.Further,the influence of modified rubber powder on curing characteristics was analyzed by rotor-free vulcanization meter.The interaction between modified rubber powder and SBR matrix was investigated by Payne effect,Mullins effect and Mooney-Rivlin model.The results show that the surface of modified powder is rougher and contains active groups such as nitroxide radical.The interaction between modified powder and SBR matrix is significantly enhanced.Compared with the unmodified rubber powder,the dispersion of the modified powder in SBR matrix is better,and the Payne and Mullins effects are improved.The tensile strength and elongation at break of SBR composites filled with 80 phr modified rubber powder are still up to 19 MPa and 460%,respectively.The mechanical properties of SBR composites filled with 80 phr modified rubber powder are superior to the composites containing 30 phr unmodified rubber powder.