| The flexible packaging material for lithium ion batteries is provided with the characteristics of light weight,thinness and high shape freedom.Compared with traditional metal shell materials,the flexible packaging material has certain advantages in achieving high safety and energy density,therefore it has broad application prospects and market demands in the field of electronic products and new energy vehicles.One of the technical difficulties in the current production of the flexible packaging material is that the bonding between aluminum foil and the outer nylon film.The main problems of aluminum and nylon bonding are:(1)environmental protection issues:at present,the chromium-containing surface treatment formulas of aluminum foil are widely used domestically,which contain substances that seriously endanger the environment and human health;(2)low adhesive strength:the adhesive strength of aluminum and nylon(Al/PA)composite bonded by commercially available polyurethane adhesive is mostly below 7 N/15mm,making it easily delaminated during processing.In view of the above problems,this paper uses a chromium-free process to treat the surface of aluminum foil.The treatment solution A of the amino-silane coupling agent KH550,the mixed solution AE of KH550 and KH103 were used to treat the aluminum,using the "molecular bridge" of silane film to promote the bonding force between aluminum foil and adhesive,thereby improving the bonding strength between aluminum foil and nylon.The hydrolysis kinetics of the silane treatment was studied by the infrared spectrum and conductivity test,and the shortest time required for the hydrolysis stability was obtained,as a reference for the hydrolysis reaction conditions.5%NaOH and 30%HNO3 were used to pre-treat the aluminum foil,and the conditions of the silanization process were optimized.The following conclusions were drawn:the aluminum foil was immersed in the treatment solution of 1%A for 30 s,and cured for 3 hours at 95?,the adhesive strength of AlA/PA composite film was the highest,the T-peel strength was 11.15 N/15mm and it was reduced to 5.67 N/15mm after curing at room temperature.Electron microscopy observed that there was adhesion failure on the surface of the aluminum foil after peeling.After being soaked in the treatment liquid AE for 30 s,the T-peel strength of the AlAE/PA composite film was 10.95 N/15mm,and the bonding strength was basically unchanged after curing at room temperature.It can be seen that the long-term storage at room temperature has little effect on the surface properties of AlAE,which meant that the silane film was more stable.The surface of nylon was treated with plasma and primer,respectively.The results showed that the surface tension of the treated nylon was increased,and polar functional groups such as carbonyl and hydroxyl groups which could easily interact with the binder were formed,and the adhesion performance of AlA/PA composite film has been improved to a certain extent.The strength after plasma treatment was higher,and the T-peel strength was 12.03 N/15mm.Waterborne epoxy resin and acrylic resin were used to modify the AlAE film.Studies have shown that resin particles were filled in the silane film to increase the surface roughness of the aluminum foil,and the contact area between the aluminum foil and the binder was also increased.In addition,the functional groups such as carboxyl and hydroxyl groups on the surface of the particles further improved the adhesion strength of the aluminum foil to nylon.After waterborne epoxy resin treatment,the T-type peeling strength of AlAED/PA composite film reached 12.35 N/15mm. |
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