Study On The Modification Of Polyolefin Plastics With Waste Printed Circuit Boards Powders

With the rapid development of electronic information industry,the continuous introduction of new electronic products leaded to a large number of electronic products being abandoned which generated amounts of electronic wastes.Waste printed circuit boards?WPCB?were important byproduct in the dispose process of electronic wastes which caused serious secondary pollution.WPCB were always treated by combustion and landfill directly without any further disposal due to their special physico-chemical characteristic.However,the heavy metals and halogen contents of WPCB caused the contamination of soil and groundwater during the landfill treatment,and the combustion disposal of WPCB produced large amounts of carcinogens.The severe conditions of environmental pollution and ecosystem destruction caused by WPCB seriously influenced the sustainable social and economic development.The scientific and reasonable treatment of WPCB had become a globle issue,especially the sustainable utilization of waste printed circuit boards powders?WPCBP?.Therefore,in order to combine with the control of environmental pollution and resource utilization on WPCBP,physico-chemical evaluating of WPCBP,decopperring,surface modification,in-situ hybridization and its utilization in multiple polyolefin composites were evaluated,and the detailed preparation,properties and structure ralationship of poleolefin/WPCBP composites were studied in this thesis.Moreover,a series of high performance,environment protecting and high value-added polyolefin composites were achieved.Through these key scientific studies and combining pilot-plant test research,summarizing regularity to offer reliable foundation and guideline for the high-value added utilization of WPCBP,which offered a great technical potential to apply WPCBP efficiency and bring forward a new way to reuse WPCBP for a sustainable world.Firstly,the physical-chemical properties of WPCBP were evaluated,and then it was selected as a reinforcing filler in HDPE composites,and the detailed properties and atructure of HDPE composites filled with different particle size and contents were also evaluated.Incorporation different mesh of WPCBP into HDPE composites substantially decreasedits properties,and 60 mesh of WPCBP modified HDPEcomposites showed balanced mechanical properties and viusl appearences.With increasing the loading of WPCBP,the mechanical properties and melt index of HDPE composites were decreased,while the thermal and combustion properties were impoved.Adding aluminium hypophosphite?AHP?into HDPE/WPCBP composites colud efficiently improve its combustion behavior,with the consumption of WPCBP and AHP fixed at 20 wt.%and 10 wt.%,the oxgen index of HDPE composite was 28.4 and the UL-94 rating reached V-0 level.On this basis,we explored the potential use of WPCBP as a reinforcement to replace wood flour?WF?for engineering value added HDPE-wood composites.It turned out that HDPE-wood composites achieves balanced properties when the consumption of WPCBP and WF was fixed at 20 wt.%and 10 wt.%,respectively.To give HDPE/WPCBP-wood composites better use,the micromolecule silane coupling agent KH550 and macromoleculer graft PE-g-MAH were selected to improve the interfacial adhesion between the fillers and HDPE matrix,and the results turned out that the synergistic effects led to a remarkable increase in mechanical properties of HDPE composites,which produced high value added wood composites with better mechanical properties,lower production cost and less pollution,provide a new way for sustainable utilization of WPCBP.We continued to study the possibility of recycling WPCBP in PP composites.OIT value and mechanical properties after thermal oxidative ageing revealed that the weathering properties of PPcomposites were decreased dramatically with increasing the loading of WPCBP,which extremely restricted its potential application in PP composites,which was caused by the transition metals that WPCBP contained could accelerate the degradation of PP molecule chains,and then decreased the weathering properites of PP composites.Then,we investigate the possibility of pre-processing WPCBP with different concentrations of nitric acid which acted as copper remover and then improved anti-ageing properties of PP/WPCBP composite.When increasing the concentration of nitric acid,the OIT value of the ensuing PP/WPCBP composites improved,but the mechanical properties of the composite decreased dramatically,which might be due to the glass fibers in WPCBP were fretted by high concentrations of nitric acid,and then deteriorated its capacity of stress-transfer in PP composites.Nitric acid treated WPCBP reinforced PP composite showed better thermal ageing resistance and mechanical performances compared to virgin PP and PP/WPCBP composites.It turned out that nitric acid pretreatment could efficiently improve the thermal oxidative ageing properties of PP/WPCBP composite,extending the potential application of the composite.Acid/alkali pre-treatment could efficiently remove the residue transition metals contained by WPCBP,but it caused serious secondary pollution.On this basis,we used spent lye to synthesis Nano-magnesium hydroxide which can be used as a fire retardant for polymersand eliminate the effluent secondary pollution,furthermore,in-situ method was selected to prepare WPCBP/Mg?OH?₂ hybrid filler?MW?,and the combustion behavior?thermal and mechanical properties of PPcomposites filled with MW was evaluated.The combustion behavior of PP/MW composite increased with increasing the hydrid ratio of Mg?OH?₂,and MW hybrid filler reinforced PP composite showed better thermal and mechanical properites compared to PP/WPCBP composite.Furthermore,the dynamic mechanical properties of PP/MWcompostes were aldo increased which were due to the improved interfacial adhesion between the MW fillers and PP matrix.Sol-gel method was performed to prepare a series of WPCBP/SiO₂ hybrid filler?TSW?under different pH value synthetic reaction.The physical-chemical analysis of TSW reaveld that SiO₂ was decorated onto the surface of WPCBP,and with increasing the pH value,the particle size of SiO₂ were increased while its content were decreased,and it is interesting that the content of Cu in TSW was also decreaed.Compared to PP/WPCBP composite,incoperating TSW into PP composites could efficiently inprove its mechchanical properties?OIT value and thermal properties,it was due to the serrated interface formed between the filler and matrix which could enhance the interfacial interaction between the hybrid filler and PP matrix.