Waste plastics,such as waste polyethylene terephthalate(PET)beverage bottles and waste rubber tyres are major municipal solid wastes,which may lead to various environmental problems if they are not appropriately recyc...Waste plastics,such as waste polyethylene terephthalate(PET)beverage bottles and waste rubber tyres are major municipal solid wastes,which may lead to various environmental problems if they are not appropriately recycled.In this study,the feasibility of collectively recycling the two types of waste into performance-increasing modifiers for asphalt pavements was analyzed.This study aimed to investigate the recycling mechanisms of waste PET-derived additives under the treatment of two amines,triethylenetetramine(TETA)and ethanolamine(EA),and characterize the performances of these additives in modifying rubberized bitumen,a bitumen modified by waste tyre rubber.To this end,infrared spectroscopy and thermal analyses were carried out on the two PET-derived additives(PET–TETA and PET–EA).In addition,infrared spectroscopy,viscosity,dynamic shear rheology,and multiple stress creep recovery tests were performed on the rubberized bitumen samples modified by the two PET-derived additives.We concluded that waste PET can be chemically upcycled into functional additives,which can increase the overall performance of the rubberized bitumen.The recycling method developed in this study not only helps alleviate the landfilling problems of both waste PET plastic and scrap tyres,but also turns these wastes into value-added new materials for building durable pavements.展开更多
Increasing production and use of various novel plastics products,a low recycling rate,and lack of effective recycling/disposal methods have resulted in an exponential growth in plastic waste accumulation in landfills ...Increasing production and use of various novel plastics products,a low recycling rate,and lack of effective recycling/disposal methods have resulted in an exponential growth in plastic waste accumulation in landfills and in the environment.To better understand the effects of plastic waste,Life Cycle Analysis(LCA)was done to compare the effects of various production and disposal methods.LCA shows the specific effects of the cradle-to-grave or cradle-to-cradle scenarios for landfill,incineration,and mechanical recycling.The analysis clearly indicates that increasing recycling of plastics can significantly save energy and eliminate harmful emissions of various carcinogens and GHGs into the environment.As recycling increases,the need for virgin-plastic production can be greatly reduced.Furthermore,the results of this study may help improve current mechanical recycling processes as well as potential future recycling methods,such as chemical recycling.Concerns about the current recycling/disposal methods for plastics have brought increasing attention to the waste accumulation problem.However,with the current COVID-19 pandemic,plastic accumulation is expected to increase significantly in the near future.A better understanding of the quantitative effects of the various disposal methods can help guide policies and future research toward effective solutions of the plastic waste problem.展开更多
The aim of this study is to enhance the recycled PVC (polyvinyl chloride) related material property by formulation technology and develop the recycling product processing technology furthermore develop the chemical ...The aim of this study is to enhance the recycled PVC (polyvinyl chloride) related material property by formulation technology and develop the recycling product processing technology furthermore develop the chemical recycling technology for last stage of PVC wastes. The formulation technology is composed of pre-treatment (crushing, separation etc.) and post-treatment (material ratio, additives, stabilizer etc.) to enhance the recyclate property. The formulation for recycled PVC by application basis and processing technology is applied to produce the structural product for civil and construction application such as pipe fittings and water drainage cap for environmental waterway. Also chemical recycling technology for end life PVC scrap which causes environmental pollution by incineration or landfill is studied for producing hydrocarbon and hydrogen chloride for VCM.展开更多
A mechanical separation process was developed for recovering metals from printed circuit board(PCB) scrap;it included three steps:impact crushing,sieving and fluidization separation.The mechanism of the technique was ...A mechanical separation process was developed for recovering metals from printed circuit board(PCB) scrap;it included three steps:impact crushing,sieving and fluidization separation.The mechanism of the technique was based on the difference in the crushabilities of metallic and nonmetallic materials in the PCBs that led to the concentrated distribution of metals in particles of larger sizes and nonmetals mostly in particles of smaller sizes.It was found that crushed PCB particles from 0.125 mm to 1.000 mm contained about 80% of metals in the PCBs.Metals acquired satisfactory liberation in particles smaller than 0.800 mm.The crushed PCB particles were sieved into fractions of different size ranges.Each fraction separately went through a gas-solid fluidized bed operating at a selected optimal gas velocity for the specific size range.Approximately 95% of metals in printed circuit board particles from 0.125 mm to 0.800 mm was recovered by the gas-fluidized bed separator at the selected optimal gas velocity.However,separation of metals from particles smaller than 0.125 mm was not satisfactory.Further study is needed on metal recovery from fine particles.展开更多
In order to extend the application of epoxy vitrimer, 1,4-cyclohexanedicarboxylic acid(CHDA) was used as a co-curing agent and structure modifier for sebacic acid(SA) cured diglycidyl ether of bisphenol A(DGEBA)...In order to extend the application of epoxy vitrimer, 1,4-cyclohexanedicarboxylic acid(CHDA) was used as a co-curing agent and structure modifier for sebacic acid(SA) cured diglycidyl ether of bisphenol A(DGEBA) epoxy vitrimer to tailor the mechanical properties of epoxy vitrimers with 1,5,7-triazabicylo[4.4.0]dec-5-ene(TBD) as a transesterification catalyst. The glass transition temperature(Tg) of vitrimer increased gradually with the increase in CHDA content. Vitrimers behaved from elastomer to tough and hard plastics were successfully achieved by varying the feed ratio of CHDA to SA. Both the Young's modulus and storage modulus increased apparently with the increase in CHDA content. Stress relaxation measurement indicated that more prominent stress relaxation occurred at elevated temperatures and the stress relaxation decreased with the increase of CHDA content due to the reduced mobility of the vitrimer backbone. The vitrimers showed excellent recyclability as evidenced by the unchanged gel fraction and mechanical properties after compression molded for several times. With tunable mechanical properties, the epoxy vitrimers may find extensive potential applications.展开更多
基金support from the Hong Kong Environment and Conservation Fund through ECF Project(84/2017)Science and Technology Project of Henan Provincial Department of Transportation(2020J6).
文摘Waste plastics,such as waste polyethylene terephthalate(PET)beverage bottles and waste rubber tyres are major municipal solid wastes,which may lead to various environmental problems if they are not appropriately recycled.In this study,the feasibility of collectively recycling the two types of waste into performance-increasing modifiers for asphalt pavements was analyzed.This study aimed to investigate the recycling mechanisms of waste PET-derived additives under the treatment of two amines,triethylenetetramine(TETA)and ethanolamine(EA),and characterize the performances of these additives in modifying rubberized bitumen,a bitumen modified by waste tyre rubber.To this end,infrared spectroscopy and thermal analyses were carried out on the two PET-derived additives(PET–TETA and PET–EA).In addition,infrared spectroscopy,viscosity,dynamic shear rheology,and multiple stress creep recovery tests were performed on the rubberized bitumen samples modified by the two PET-derived additives.We concluded that waste PET can be chemically upcycled into functional additives,which can increase the overall performance of the rubberized bitumen.The recycling method developed in this study not only helps alleviate the landfilling problems of both waste PET plastic and scrap tyres,but also turns these wastes into value-added new materials for building durable pavements.
基金The authors would like to thank the University of Massachusetts Lowell for providing start-up funds.N.F.andW.-T.C.would like to thank the financial support by the U.S.Department of Energy’s Office of Energy Efficiency and Renewable Energy(EERE)under the Advanced Manufacturing Office Award No.DE-EE0007897。
文摘Increasing production and use of various novel plastics products,a low recycling rate,and lack of effective recycling/disposal methods have resulted in an exponential growth in plastic waste accumulation in landfills and in the environment.To better understand the effects of plastic waste,Life Cycle Analysis(LCA)was done to compare the effects of various production and disposal methods.LCA shows the specific effects of the cradle-to-grave or cradle-to-cradle scenarios for landfill,incineration,and mechanical recycling.The analysis clearly indicates that increasing recycling of plastics can significantly save energy and eliminate harmful emissions of various carcinogens and GHGs into the environment.As recycling increases,the need for virgin-plastic production can be greatly reduced.Furthermore,the results of this study may help improve current mechanical recycling processes as well as potential future recycling methods,such as chemical recycling.Concerns about the current recycling/disposal methods for plastics have brought increasing attention to the waste accumulation problem.However,with the current COVID-19 pandemic,plastic accumulation is expected to increase significantly in the near future.A better understanding of the quantitative effects of the various disposal methods can help guide policies and future research toward effective solutions of the plastic waste problem.
文摘The aim of this study is to enhance the recycled PVC (polyvinyl chloride) related material property by formulation technology and develop the recycling product processing technology furthermore develop the chemical recycling technology for last stage of PVC wastes. The formulation technology is composed of pre-treatment (crushing, separation etc.) and post-treatment (material ratio, additives, stabilizer etc.) to enhance the recyclate property. The formulation for recycled PVC by application basis and processing technology is applied to produce the structural product for civil and construction application such as pipe fittings and water drainage cap for environmental waterway. Also chemical recycling technology for end life PVC scrap which causes environmental pollution by incineration or landfill is studied for producing hydrocarbon and hydrogen chloride for VCM.
基金the Shanghai EXPO Special Project from the Ministry of Science and Technology of China under the Grant No. 2004BA908B02
文摘A mechanical separation process was developed for recovering metals from printed circuit board(PCB) scrap;it included three steps:impact crushing,sieving and fluidization separation.The mechanism of the technique was based on the difference in the crushabilities of metallic and nonmetallic materials in the PCBs that led to the concentrated distribution of metals in particles of larger sizes and nonmetals mostly in particles of smaller sizes.It was found that crushed PCB particles from 0.125 mm to 1.000 mm contained about 80% of metals in the PCBs.Metals acquired satisfactory liberation in particles smaller than 0.800 mm.The crushed PCB particles were sieved into fractions of different size ranges.Each fraction separately went through a gas-solid fluidized bed operating at a selected optimal gas velocity for the specific size range.Approximately 95% of metals in printed circuit board particles from 0.125 mm to 0.800 mm was recovered by the gas-fluidized bed separator at the selected optimal gas velocity.However,separation of metals from particles smaller than 0.125 mm was not satisfactory.Further study is needed on metal recovery from fine particles.
基金financially supported by the National Natural Science Foundation of China (No.51703188)Fundamental Research Funds for the Central Universities (Nos.XDJK2017A016 and XDJK2017C022)
文摘In order to extend the application of epoxy vitrimer, 1,4-cyclohexanedicarboxylic acid(CHDA) was used as a co-curing agent and structure modifier for sebacic acid(SA) cured diglycidyl ether of bisphenol A(DGEBA) epoxy vitrimer to tailor the mechanical properties of epoxy vitrimers with 1,5,7-triazabicylo[4.4.0]dec-5-ene(TBD) as a transesterification catalyst. The glass transition temperature(Tg) of vitrimer increased gradually with the increase in CHDA content. Vitrimers behaved from elastomer to tough and hard plastics were successfully achieved by varying the feed ratio of CHDA to SA. Both the Young's modulus and storage modulus increased apparently with the increase in CHDA content. Stress relaxation measurement indicated that more prominent stress relaxation occurred at elevated temperatures and the stress relaxation decreased with the increase of CHDA content due to the reduced mobility of the vitrimer backbone. The vitrimers showed excellent recyclability as evidenced by the unchanged gel fraction and mechanical properties after compression molded for several times. With tunable mechanical properties, the epoxy vitrimers may find extensive potential applications.