Study On Performances Of Polyaspartic Ester Polyurea Used For Battery Box Protections Of New Energy Vehicles

The battery box is the bearing part of new energy vehicles’power battery.Structure damage on the box directly affects the power battery’s safety.Meanwhile,the battery box faces the same long-term problems as a traditional fuel car’s chassis does.The main problems are metal corrosion and stone impact,which shall be more severe on the battery box due to its lower ground clearance.Aimed at the protection issues of the battery box on new energy vehicles,this thesis systematically discusses the feasibility of polyaspartic ester（PAE）polyurea coating as protective material applied on battery box surface.Based on deep analysis of composition,structural properties and related applications of PAE polyurea coating,the two-component PAE polyurea coating,with excellent surface protection performances,is developed to adapt vehicle production processes.Wear and impact resistance,comprehensive aging and corrosion resistance of the two-component PAE polyurea coating is tested under simulated road condition and atmospheric environment.The results show that the two-component PAE polyurea is a long-term effective protective coating for battery boxes,which has excellent performances on corrosion and stone impact resistance.The main research contents are as follows:（1）The preparation of two-component PAE polyurea coating started from defining its main components,dosage range and synthesis process in terms of gel time,mechanical properties and adhesion.Then,orthogonal experiments of composition content were designed to determine the best formulation with the goal of excellent tensile strength,tear strength,elongation at break and adhesion to the battery box.Two different PAE polyurea coatings were prepared by adding appropriate amounts of Si O₂,Ti O₂ and single-layer graphene on the formulation basis to meet different needs of the battery box protections on new energy vehicles.Their SEM,FT-IR and main mechanical properties were analyzed.The results showed that PAE polyurea coating had excellent performance on compactness and mechanical properties.With the addition of single-layer graphene,the mechanical properties of PAE polyurea coating were significantly improved.（2）UV-condensation test as well as alternating high and low temperature aging test were performed to simulate the atmospheric environment under the battery box of new energy vehicles.The comprehensive aging performance of PAE polyurea coating was evaluated by SEM,EIS,water absorption,adhesion between the coating and the battery box after aging.And the performances of the coating were compared with those of commercial PVC coating.The results showed that PAE polyurea coating had excellent weatherability,and could be applied to the aging environment under the battery box of new energy vehicles for a long time.With the addition of SiO₂,TiO₂ and single-layer graphene,the comprehensive aging performance of PAE polyurea coating was significantly improved.（3）Considering the coating on the bottom of the battery box was required to have excellent corrosion and stone impact resistance,neutral salt spray test and water immersion test were performed to simulate the corrosion environment under the vehicle.And the corrosion resistance of PAE polyurea coating was tested.The stone impact resistance of the coating was tested by the self-made stone impacting test platform.The results showed that PAE polyurea coating had excellent corrosion resistance and stone impact resistance,and could be applied to the battery box protections of new energy vehicles for a long time.