Analysis And Research On Plastic Paint Removal Of Retired Passenger Cars Based On Mixed Jet Technology

Compared with ordinary plastics,automotive plastics have better performance.When automobiles are scrapped,scientific and reasonable recycling and recycling of automotive plastics at the same level are important for environmental protection and sustainable development of the industry,Among them,polypropylene(PP)bumper with large volume and single composition has always been the primary target of automotive plastic recycling.However,as exterior plastic,the surface of such parts will be painted.However,the painted plastic is not treated and can only be used to produce low-end products after recycling.Therefore,removing the paint layer on the surface of such plastic parts is particularly important in the recycling process.At present,the domestic methods for removing the paint layer on the surface of plastic parts include solvent method,hydrolysis method and mechanical method,in which the solvent method and hydrolysis method will produce chemical waste liquid or the removal is not in place;Mechanical methods include lapping method,water jet,shot peening method,dry ice jet and mixed jet.The mixed jet method requires moderate pressure,can be used repeatedly with abrasive materials,is efficient and environmentally friendly,has strong adaptability to materials,and has a simple process flow that is not easy to raise dust.In the actual use of mixed jet paint removal,abrasive particles in the jet play an important role in material removal,which requires time to evaluate the particle process parameters to prevent too large or too small impact velocity,resulting in cost increase,matrix damage,paint layer residue and other problems.In order to select process parameters suitable for actual working conditions,finite element numerical simulation method was adopted in this paper to study particle size,impact velocity,impact Angle and particle distribution involved in the mixed jet paint removal operation.The main work is as follows:(1)The motion mechanism of abrasive particles and the basic law of fluid motion in the process of jet formation are discussed.Based on elastoplastic mechanics theory,the wear removal model of abrasive particle impingement material in jet is described.The effects of particle size,impact Angle,target distance,velocity and other factors on the mixed jet are discussed.(2)On the basis of ABAQUS software,Cohesive element cohesive force model was used to simulate the paint-matrix interface.The effects of particle size,impact velocity,interfacial energy accumulation,and impact angle were analyzed.The results show that the damage process starts from the middle layer with weak mechanical properties.When abrasive particles are impacted vertically,the removal amount of paint layer is the highest.The larger the particle size and velocity,the more obvious the paint removal effect(3)The DPM Discrete Phase Method particle model,multiphase flow model and Realizable k-ε turbulence model were used to numerically simulate the internal and external field characteristics of the fan-jet mixed jet by FLUENT software.The influence of the change of inlet water pressure,impact distance and impact Angle on the cleaning effect was discussed,and the appropriate process parameters were selected for the actual working condition.The results show that the fluid accelerates obviously at the exit of the fan-shaped nozzle,and a narrow strip with uniform velocity distribution is formed in the outflow field plane perpendicular to the X-axis.At the same time,there are high-speed moving particles on both sides of the long axis of the elliptic outlet of the nozzle,but the particle velocity decreases rapidly in the short axis direction,forming a slow velocity zone.When the impact Angle is reduced,the distribution of particles diffused outward is elliptical,and the distribution of particles in the center area of the jet is gradually loose.The mechanism of mixed jet is studied to remove the paint layer on the surface of plastic parts of retired vehicles,which is helpful to improve the actual operation efficiency and achieve a wide range of applications.