Study On Composites Bonding Strength Based On Polymerstainless Steel Direct Injection Molding Process

Direct injection molding technology based on metal surface nanostructures is a new method to achieve combination of metal and polymer.The method joins the metal and polymer together by forming a anchor structure through filling the polymer in a nanopores structure on the metal surface.Compared with other molding methods,this method has the advantages such as high bonding strength,low environmental sensitivity and good surface quality.In this paper,304 stainless steel and polyphenylene sulfide(PPS)were used as research materials to study the bond strength of polymer-metal composites.The main research contents are as follows:Porosity was used to characterize the surface topography,and orthogonal experiments were designed to study the main influencing factors of metal surface treatment.Through orthogonal analysis,it was found that the concentration of nitric acid and the concentration of thiourea have significant effect on the surface morphology.The increasement in the concentration of nitric acid can improve the corrosiveness of the electrolyte and facilitate the formation of nanopores.Thiourea has the effect of inhibiting metal corrosion,and is also beneficial to local corrosion of metal surfaces and formation of nanopores.According to the orthogonal experimental analysis,the optimized combination of surface treatment is obtained.The experiment proves that the optimized combination can increase the porosity of the surface.The main influence factors of nitric acid concentration and thiourea concentration were studied by controlled variable method.It was found that the surface morphology was affected by the combination of nitric acid concentration and thiourea concentration.Under the same conditions,the increasement in the concentration of nitric acid is beneficial to increase the porosity of the metal surface.Under the same conditions,as the concentration of thiourea increases,the surface porosity increases first and then decreases.The optimum concentration of thiourea is related to the concentration of nitric acid.As the concentration of nitric acid increases,the optimum nitric acid concentration for the preparation of nanopores increases accordingly.The relationship between surface morphology and bond strength was investigated by injection molding experiments and tensile tests.Research found that porosity is the main factor affecting bond strength.The higher the porosity of the sample,the higher the bond strength.This is because the increase in porosity means that the number of micromechanical anchor structures formed on the metal surface is increased.The study of the relationship between the injection molding process and the bond strength found that high mold temperature favors the filling of the polymer and was advantageous for obtaining a high bond strength assembly.According to the orthogonal analysis,the optimized combination of the injection molding process was obtained.And it is predicted that the bond strength of the assembly prepared by the optimized injection molding process can reach 24.53 MPa.In addition,through comparison experiments,it was found that the annealing treatment can reduce the residual internal stress and increase the crystallinity,thereby improve the bonding strength of the assembly.The filling effect and fracture mode of the polymer were studied by macroscopic and microscopic analysis of the bonding surface of the assembly after the tensile shear test.The metal and polymer are joined together by inter-phased microscopic contact surfaces that be connected by countless mechanical anchors.When stretched,the fracture occurs at the microscopic contact surface,and a layer of polymer remains on the metal surface after the fracture.In this paper,the bonding strength of stainless steel-polymer composites is improved from two aspects of metal surface treatment and injection molding process optimization.The electrochemical process for preparing high-porosity stainless steel surface and the injection molding process of high-strength assembly were optimized by orthogonal experiments.A theoretical model of micromechanical interlocking of metal and polymer assemblies and its fracture mode are proposed.It has important reference significance for the preparation of nanostructures on stainless steel surface and nano-injection molding.