Hydrophobic fumed silica (Fusil615) was used in polyurethane adhesives for power batteries to investigate its effects on the viscosity, thixotropy, mechanical properties, bonding strength, anti settling, and thermal stability of the polyurethane adhesive. The application performance was compared with competitors A and B of fumed silica sold in the market under different components. The results showed that with the addition of hydrophobic or treated fumed silica, the viscosity and thixotropy of polyurethane adhesive were significantly improved and improved, and the control effect during the construction process was better.

The structural adhesive for power batteries mainly meets the mechanical performance requirements of power batteries, achieving safe and reliable lightweight design. It is applied in the bonding of load-bearing structural components and can withstand large dynamic and static loads, and can be used for a long time. It mainly includes polyurethane structural adhesive, acrylic structural adhesive, silicone adhesive, epoxy structural adhesive, UV adhesive, and high-temperature hot melt adhesive. It is applied in different scenarios according to different characteristics, Their roles and functions mainly focus on strength, adaptability of bonding materials, elasticity (flexibility), aging resistance, flame retardancy, insulation, and thermal conductivity.

1、 Effect of Fusil615 and its competitors on thickening and thixotropy of polyurethane adhesive

The main role of fumed silica Fusil615 in the power battery adhesive industry is as a thickening and thixotropic additive. Adhesives require the system to maintain low viscosity during the high shear rate application process, and under static conditions or low shear rate conditions after application, the system should have high viscosity to achieve good anti sagging performance. From the data in Table 1, it can be seen that adding fumed silica can improve the viscosity and thixotropy value of the two-component power battery adhesive. Combining the data of components A and B, Fusil615 has higher thixotropy compared to competitors, moderate thickening performance, and better workability.

Vapor phase silica Fusil615 is obtained by treating hydrophilic vapor phase silica with a specific surface area of 200 m2/g with a modifier polydimethylsiloxane (PDMS, silicone oil). It has good thickening, thixotropy, anti sagging, and stability. High filling content can provide excellent reinforcement performance for silicone rubber without structural effects, making it very suitable for transparent systems and does not affect the transparency of the product itself, Simultaneously providing high hydrophobicity. Therefore, its excellent reinforcement, thickening, and thixotropic properties can prevent sedimentation during storage and sagging during curing of power battery adhesives, improving their tear strength and adhesive strength.