| With the rapid development of the automotive industry,the production and holding quantity of automotives in China are increasing linearly,and the number of end-of-life vehicles is increasing which will increase the enviormental protection risk if they are disposed inappropriately.Hence the recycling of end-of-life vehicle resources gradually aroused the concern of the community.Automotive polypropylene contains a high recovery and utilization value.Therefor,how to achieve high efficiency reuse of waste polypropylene and reduce the waste of resources is a difficult problem to pay more attention.In this thesis,firstly,the automotive polypropylene material was aginged with the artificial accelerated aging method to reveal the aging properties of the automotive polypropylene material with modern analysis methods.Uniform design test method was adopted to conduct uniform mixing test design,and the effects of the material components on the modified properties of the recycled material were analyzed.Combined BP neural network with genetic algorithm,the modified formula of the mixed recycled material was optimized,and the high efficiency regenerating method of the waste polypropylene was put forward.Finally,the process route of the modified regeneration was laid out rationally according to the characteristics of the automotive waste plastic parts,and the feasibility of the high efficiency regenerating method was verified.The main research results of this paper are as follows:(1)Under xenon lamp aging conditions,the melt flowability of automotive polypropylene composites showed a downward trend followed by a rising trend.At680 hours,the MFR decreased to 19.5 g/10min.As the aging progresses,the impact toughness continued to decrease.After aging for 1400 hours,the notched Izod impact strength dropped to 6.63kJ/m~2,a drop of 71.56%.Tensile strength and flexural strength increased first and then decreased with aging.(2)The content of VPP had little effect on the change of tensile strength and flexural strength of regenerated materials,but it could improve the notched Izod impact strength of regenerated materials.The elastomer POE had a good toughening effect.The higher the proportion of POE,the impact strength of regenerated materials increased significantly,but also reduced the tensile strength and flexural strength.(3)A BP neural network prediction model of modified performance for recycled material was accurate.The maximum relative errors of the predicted and actual values of tensile strength,flexural strength,and impact strength were 4.92%,3.20%,and 4.98%.The average relative errors were 2.41%,1.60%,and 2.91%.Therefore,the prediction model could be used in the optimization of modified formula for recycled materials.(4)When RPP/VPP/POE=57.53/32.31/10.17,the material properties meet the requirements of the performance indicators of automotive parts materials and the cost of modified regeneration is the lowest.The tensile strength of the material decreased from 31.2 MPa to 25.72 MPa,decreased by 17.56%.The flexural strength decreased from 35.13 MPa to 29.98 MPa,decreased by 14.66%.The notched impact strength increased from 6.15kJ/m~2 to 12.10kJ/m~2,an increase of 96.75%.(5)A high-efficiency regeneration method for recycled polypropylene was proposed and the accuracy of the prediction model was high.The relative errors of RPP content,VPP content and POE content were 7.63%,14.39%and 9.8%,respectively.The research of this paper provids a theoretical basis and a more convenient,efficient,effective way for the recovery of waste polypropylene.It is of great significance to solve the efficient recycling technology problems of automotive lightweight plastics,to achieve the efficient regeneration with equivalent performance of end-of-life vehicles plastics,and to improve the recycling rate of automotives,so as to save energy and protect environmental,and to promote the sustainable development of the automotive industry. |
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