Study On Al-TPU Integrated Injection Molding Technology And Interface Bonding Properties

Lightweight and high strength damping hybrid plays an important role in weight reduction,vibration and noise reduction of transportation locomotives and mechanical equipment.The damping hybrid is usually made of constraining layer(e.g.,steel,aluminum alloy,fiber reinforced polymer)and damping layer(e.g.,polyurethane,rubber)The damping layer is pre-formed by molding or casting,and then bonded to the constraining layer through vulcanization process or adhesives.These methods are inefficient and difficult to form complex structures.Therefore,it is urgent to seek an effective method for combination of damping layer and constraining layers.In this paper,the surface-treated aluminum alloy was combined with thermoplastic polyurethane(TPU)by injection molding,and the preparation process of efficient preparation of high-strength Al-TPU hybrids was discussed.The main research contents are shown as follows:1.After anodizing and pore enlarging treatment,the aluminum alloy was combined with TPU by injection molding direct joining technology.The effects of pore size,porosity and oxide layer thickness formed on the metal surface on bonding strength of the hybrids were discussed.The metal surface with high porosity oxide layer can effectively improve the bonding strength of the hybrid.When the porosity of the oxide layer is 61%,the bonding interface of the composite structure can’t fail under tensile shear test even the TPU itself is destroyed with a tensile strength of 17.6MPa.Cyclic stress and service environment with high temperature and humidity are damage to the Al surface,causing the oxide layer easily falling off and reducing the bonding strength.Reducing the porosity to 53% can improve the above situation.After dynamic loading test in the ambient temperature of-10 ℃ and 25 ℃,the bonding strength of the hybrids decreases by no more than 1.2%,however,the hygrothermal aging test induced the maximum bonding strength decreased by 11.1%.2.The anodized aluminum alloy was modified by 6-(3-triethoxysilylpropyl)amino-1,3,5-triazine-2,4-dithiol monosodium salt,and the influence of surface composition of aluminum alloy on the bonding strength and corrosion resistance of hybrids was investigated.The resultant strength of the hybrids considerably increased without interface fracture even the TPU itself was torn at 17 MPa when tensile shear tests were performed.Furthermore,the hybrids exhibit excellent corrosion resistance when subjected to Na Cl solution.The mechanical properties of Al-TPU hybrids decreases by only 8% after the corrosion test,which is much lower than that of the common hybrids fabricated without the silane agent(36% down).Lastly,the interface bonding mechanism for the hybrids was revealed.The mechanical interlocking effect caused by microstructures as well as the silane layer formed on the metal surface contributes significantly to the bonding strength of the hybrids.3.The surface of aluminum alloy was treated by coblast treatment and an orthogonal experiment was designed to analyze the effect of brown corundum particle size,doping amount of epoxy resin and injection mold temperature on Al-TPU hybrids.The orthogonal experiment shows that when the doping amount of epoxy resin is 5 wt%,the particle size of brown corundum is 120#,and the mold temperature is 150 ℃,the bonding strength reaches 14.2MPa and the failure form is interface failure.Among the above factors,mold temperature has the greatest influence on the bonding strength of hybrids,followed by the particle size of brown corundum,and finally the doping amount of epoxy resin.High mold temperature is conducive to filling the surface microstructure of aluminum alloy with polymer melt,so as to enhance the mechanical interlocking effect and improve the bonding strength,but too high mold temperature will lead to defects such as flying edge.The particle size of brown corundum mainly affects the surface morphology of aluminum alloy.With the increase of the mesh number of brown corundum,the surface roughness of aluminum alloy gradually decreases.Appropriate surface roughness is conducive to the improvement of the bonding strength of Al-TPU hybrids.The doping amount of epoxy resin of epoxy resin mainly affects the surface composition of aluminum alloy.Compared with the aluminum alloy surface only treated with blasting,the content of carbon on the aluminum alloy surface after coblast treatment is significantly increased,and is positively correlated with the doping amount of epoxy resin.The epoxy resin layer deposited on the surface of aluminum alloy by coblast treatment can effectively improve the compatibility between Al and TPU,so as to improve the bonding strength of Al-TPU hybrids.