Preparation,Structure And Properties Of Devulcanized Ground Tire Rubber Prepared Via Single-screw Extrusion

With fast development of automobile industry,significantly grown amounts of waste tires are produced worldwide,which causes serious ?black pollution?.An important way for recycling waste tires is to prepare devulcanization ground tire rubber(DGTR).But so far,scientific and pollution-free methods for industrially recycling waste tires to prepare DGTR have not been found yet.An industrial and environmentally-friendly single-screw extruder devulcanization technology has been developed by our group,which can solve the problems of high pollution,high energy consumption,high labor,and so on of traditional devulcanization technologies.In order to explore the devulcanization efficiency and mechanism of the developed devulcanization technology,DGTR samples were produced using an independently developed industrially sized single-screw devulcanization equipment in this dissertation;further,the DGTR samples were revulcanized to produce revulcanized DGTR(RDGTR)samples.The structure and properties of the produced samples were investigated via systematical tests and characterization,such as sol fraction,crosslink density,Fourier transform infrared spectroscopy(FTIR)spectra,X-ray photoelectron spectroscopy(XPS)spectra,Mooney viscosity,curing characteristics,dynamic rheology,tensile properties,thermal stability analysis,and surface morphology.(1)The effects of barrel temperature and screw speed of the devulcanization extruder on the devulcanization efficiency of ground tire rubber(GTR)were investigated.The results demonstrate that the extruder can effectively break up crosslinked structure of the GTR to achieve high devulcanization level(characterized by sol fraction and crosslink density),which is mainly associated with its moderate shear strength.The balance between mechanical properties and processability for the DGTR samples was analyzed.Lower ratios of main-chain to crosslink scission and good processability(mainly characterized by modest Mooney viscosity)for the DGTR samples,and high tensile strengths and elongations at break for the RDGTR samples are obtained via appropriately combining the barrel temperature and screw speed.High quality DGTR sample with tensile strength and elongations at break of up to 11 MPa and 370%,respectively,is prepared under the conditions used.(2)The devulcanization mechanism for the developed extruder was investigated based on analyzing the FTIR,XPS spectra of the GTR powder and DGTR samples and the gases that were generated from the GTR powder during devulcanization.The results demonstrate that physical and chemical changes of the GTR take place and some crosslinking bonds and main chains are broken under the common action of heat,shear stress and ingredient agents.(3)The effects of barrel temperature and screw speed of the post-processing extruder on the devulcanization efficiency of the GTR were investigated.The results demonstrate that the barrel temperature affects the devulcanization efficiency to a certain extent,whereas the screw speed has little influence.(4)The effect of particle diameter of the GTR powder on its devulcanization efficiency was investigated.The results demonstrate that with appropriately increasing the GTR particle diameter,the sol fractions of the DGTR samples are decreased and their crosslink densities and mooney viscosities are increased,and the tensile strengths and elongations at break of the RDGTR samples are increased.Therefore,GTR powder with larger particle diameter is an appropriate choice.(5)The effect of the ingredient contents on the devulcanization efficiency of the GTR and the tensile strengths and elongations at break of the RDGTR samples is generally analyzed The results indicated that appropriate ingredient contents are 10 phr aromatic oil,1.2 phr rosin and 0.3 phr activator.