Study On The Green Nano-reclaimation Of Tire Rubber And Its Fundamental Applications

With rapid development of automobile industry,the accumulation of a large amount of waste tire has caused serious environmental pollution problem.In addition,rubber as strategic material,the production capacity of rubber in our country is limited and it is difficult to meet the demand for rubber resources.Therefore,it is imperative to recycle waste tire with an effective,green and value-added way.High energy consumption and serriouly secondary pollution problem are existing in current industry of reclaimed rubber.This paper proposes a method for preparing reclaimed rubber at low temperature in an environmental-friendly way.Through accelerating the thermal oxidative aging of tire rubber and swelling effect of vegetable oil,an efficient reclaimation effect was realized,and the main research work as following:Firstly,with swelling effect of vegetable oil,green nano-reclaimation of grond tire rubber?GTR?is achieved at low temperature.Based on the reclimed method of supercritical carbon dioxide and the mechanism of thermal oxidative aging,soybean oil is choosed as a green softener to fully swell crosslinked network of GTR,and then reclaimed rubber is prepared at 150°C for 4 h.The mechanism of degradation was studied by extraction experiments,Horikx theory and Fourier transform infrared spectroscopy?FTIR?analysis.Gel permeation chromatography?GPC?,thermogravimet--ric analyzer?TGA?and scanning electron microscopy?SEM-EDS?were used to analyze the component of reclaimed rubber,and the microstructure of carbon black?CB?was observed by transmission electron microscope?TEM?.Finally,the effect of reclaimed rubber on mechanical properties of solution-polymerized styrene butadiene rubber?SSBR?was studied.The results show that high degradation of GTR is achieved due to the occurance of thermal oxidative scission reaction in molecular chains of GTR.As increase of soybean oil content,sol fraction gradually increases?about77%?and the number average molecular weight?M_n?of sol part gradually decreases,and the Mn of styrene-butadiene rubber?SBR?in sol part is significantly higher than that of natural rubber?NR?.In gel part,it is mainly composed of carbon black with core-shell structure and bound rubber adsorpted on its surface.In addition,reclaimed rubber can disperse uniformly with nanometer-scale when blended with SSBR,and it has excellent reinforcing effect and plasticizing effect to SSBR.Due to complex components in GTR,it is difficult to explore reinforcement mechanism in depth,and a relatively single system is necessary to do a furthur research.Secondly,in view of efficient degradation of cured rubber,it is helpful to deeply analyze micro-morphology and chemical composition of bound rubber layer on surface of carbon black in vulcanizate.The vulcanizate is prepared by NR and commercial carbon black?N330?.It is completely degraded by same degradation method and stepwise exfoliation of bound rubber from carbon black is realized.Through the test of sol fraction,residual rubber fraction,TGA,TEM,AFM,XRD,XPS and dispersibility experiment,the difference of bound rubber between vulcanizate and rubber compound,loosely and tightly bound rubber in vulcanizate were compared.The results show that a small amount of loosely bound rubber and tightly bound rubber?its thickness is about 1-2 nm?exist on surface of carbon black in vulcanizate,and some O,S,N and Zn elements in bound rubber are detected.The crosslinking bonds formed in bound rubber are mainly composed of disulfide bond?S-S?and polysulfide bond?-S_x-?,and the content of monosulfide bond?C-S?is lower than that of them.In addition,loosely bound rubber disperses uniformly on the surface of CB in rubber compound.For core-shell structured carbon black with chemical activity on its surface,whether it has a reinforcing effect similar to that of commercial carbon black which requires further analysis.Finally,on the basis of clarifying the structure and composition of reclaimed rubber?RGTR?,the influence of its addition on performance of NR was explored.With addition of RGTR into NR,the vulcanization and rheological properties were investigated by rubber processing analyzer?RPA?,and the uniformity and dispersion of reclaimed rubber in NR matrix were analyzed by SEM and Payne effect.Finally,the thermal stability and mechanical properties of NR/RGTR were studied.The results show that the addition of reclaimed rubber significantly reduces the scorch time of rubber compound and enhances the minimum torque?M_L?and the maximum torque?M_H?,and strengthens the nonlinear viscoelasticity of NR.In addition,gel fraction of NR/RGTR increases due to the presence of core-shell structured carbon black with chemical activity on its surface in reclaimed rubber.As the degree of degradation increases,the reclaimed rubber can disperse uniformly with nanoscale.Besides,the initial thermal decomposition temperature?T₅?of vulcanizate is improved,and RGTR has both reinforcing and plasticizing effect to NR.In summary,the green nano-reclaimation of GTR was realized at low temperature by accelerating thermal oxidative degradation with swelling effect of soybean oil.The relationship between structure and performance was established based on research work of degradation mechanism and exfoliation of carbon black with core-shell structure.This efficient and green recycling method is significant for environmental-friendly development of reclaimed rubber industry.