Study On Performance Optimization Of Waste Polyolefin Modified Asphalt

In this paper,the structure and properties of modified asphalt based on waste polyolefin were studied.Firstly,three kinds of recycled polyethylene resin particles which are used as milk box,fishing net and daily film are selected,which are referred to as rPE1,rPE2 and rPE3 respectively,and the corresponding modified asphalt is referred to as B/rPE.And three kinds of recycled polypropylene resin particles used as lunch boxes,woven bags and ton bags,respectively referred to as rPP1,rPP2 and rPP3,and the corresponding modified asphalt is referred to as B/rPP.Then the asphalt was modified by the mixture of high density polyethylene and different content of carbon black,and the effect of different content of carbon black on the structure and properties of polyethylene modified asphalt was studied.The best carbon black content was selected and fixed,and the asphalt was modified by the combination of carbon black and different types of waste polypropylene,and the structure and properties of different types of waste polypropylene and carbon black composite modified asphalt were compared.Finally,the office waste paper fiber recycled from daily life was selected and compounded with rPE2,and the effect of different content of waste paper fiber on the structure and performance of rPE2 modified asphalt was studied.The melting crystallization behavior of polymer in modified asphalt was studied by differential scanning calorimeter(DSC).The glass transition temperature and tensile toughness of modified asphalt at low temperature were studied by double cantilever mode and tensile mode of dynamic thermomechanical analysis(DMA).The high temperature rutting resistance and fatigue performance of modified asphalt were studied by dynamic rotary rheometer.The micro-phase structure of polymer and the micro-aggregation structure of nanoparticles in modified asphalt were observed by optical microscope and atomic force microscope.(1)Performance comparison of waste polyolefin modified asphalt.The addition amount of waste polyolefin is kept at 6wt.% of the base asphalt(Bitumen),with the new material PE(v PE)and the new material PP(vPP)as the control.The results of DSC show that the highest crystallinity of PE in recycled polyethylene modified asphalt is B/rPE2,and the lowest crystallinity of PP in recycled polypropylene modified asphalt is B/vPP and the lowest is B/rPP2.Because B/rPE2 and B/rPP3 have the highest crystallinity,they have the highest anti-rutting ability and the best temperature stability in rheological tests.In terms of microstructure,their continuous structure is also one of the reasons for their better anti-rutting performance.DMA test showed that the glass transition temperature of B/rPE was higher than that of B/vPE,and B/rPE2 has the best low temperature performance.B/rPP was lower than that of B/vPP,and B/rPP1 has the best low temperature performance(2)the effect of carbon black on high density polyethylene modified asphalt and the high and low temperature performance of waste polypropylene modified asphalt.Polyethylene was premixed with carbon black,and polyethylene was fixed as 10wt% of matrix asphalt in the modified asphalt.on the basis of forming a network structure,the effects of different contents(0,0.5,1,2,3wt.%)of carbon black on the structure and high and low temperature properties of polyethylene modified asphalt(PMB-X%)were investigated.The rheological results show that the rutting resistance of modified asphalt decreases at first and then increases sharply with the increase of carbon black content,and the rutting resistance of PMB-3% is the best.DSC test shows that the law of crystallinity is consistent with the law of rutting resistance.The change process of carbon black content from 0 to 3 wt.% was observed in the microstructure,the phase structure of polyethylene experienced the transition from network to island-network,and the double percolation network of polyethylene/carbon black appeared in PMB-3%,and the network structure had good stability at high temperature.DMA results show that PMB-3% has the best anti-cracking performance at low temperature.For polypropylene/carbon black modified asphalt,the optimal carbon black content(3wt.%)and waste polypropylene modified asphalt were selected,and vPP and rPP bulk modified asphalt were used as control to explore the effect of carbon black on the structure and high and low temperature performance of waste polypropylene modified asphalt.The results of DSC and rheology show that the crystallinity and rutting resistance of modified asphalt added with carbon black in B/rPP system are lower than that of B/rPP,and the anti-rutting performance of B/vPP/CB system is the best,but the DMA results show that the low temperature cracking resistance of modified asphalt is improved.Through the microscope,it is observed that the microstructure of all the samples shows the droplet-matrix structure.(3)the effect of waste paper fiber on the high and low temperature performance of rPE2 modified asphalt.Keep the content of rPE2 as 6wt.% of the base asphalt,modify the asphalt with different content(0,0.5,1,2,4wt.%)of waste paper fiber and rPE2,study the effect of different content of waste paper fiber on the high and low temperature performance of rPE2 modified asphalt,and use 6wt.% waste paper fiber modified asphalt as control.DSC test showed that the highest crystallinity of polymer was rPE2 modified asphalt with 0wt.% waste paper fiber.The crystallinity of rPE2 in all modified asphalt with waste paper fiber decreased,but the crystallinity increased with the increase of waste paper fiber content.The rheological results show that the rPE2 modified asphalt with 4wt.% waste paper fiber has the best rutting resistance at 60 ℃,and the pure waste paper fiber modified asphalt is the worst.The DMA results show that the rPE2 modified asphalt with 0.5 wt.% waste paper fiber has the best low-temperature toughness.When the content of waste paper fiber is less(0.5-1wt.%),the modified asphalt mainly shows low-temperature toughness enhancement,while when the waste paper fiber content is more(2%-4wt.%),it mainly shows low-temperature rigidity enhancement.The microstructure shows that the rPE2 modified asphalt with 0wt.% waste paper fiber shows a partially continuous structure,while the other samples are droplet-matrix structure.Waste paper fiber/rPE2 composite modified asphalt has a slight mass loss after water absorption,so it is necessary to improve the water absorption of modified asphalt in the future research process.