Encapsulated Connection Microcapsules Optimize Reliable Bonding at the Push of a Button

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FAULHABER Drive Systems

Microcapsules with reactive 2-component adhesive can simplify bonding processes in industry and assembly while improving work safety. How this works is well known at the IAP in Potsdam (Germany)...

Bonding is known to join components, often over large surfaces, and can also combine different materials. It enables relatively lightweight constructions. However, in industrial practice, adhesive application is often an additional process step, which is not always advantageous. Adhesives must also be dosed, applied, and cured. The direct handling of reactive adhesive components can present additional requirements in terms of occupational safety, process management, and training efforts, as explained by researchers at the Fraunhofer Institute for Applied Polymer Research (IAP). Depending on the material system, temperature, substrate, and load, the adhesive effect of conventional adhesive tapes can also vary. A novel approach based on microcapsules aims to solve some of these issues. The researchers are using isocyanate-free adhesives based on acrylates or epoxies for this purpose.

Differently Filled Capsules Enable Bonding Only Under Pressure

At the institute, as part of the Fraunhofer Cluster Programmable Materials (CPM), microscopic capsules are being developed that each enclose a single substance of a two-component adhesive. These microcapsules can be imagined as tiny reservoirs for adhesive. Each capsule contains one of the two components. As long as the capsules remain intact, the system stays inactive. However, when pressure is applied, causing the capsules to burst, the two components mix and undergo a cross-linking reaction. This creates a strong bond precisely at the contact surface. A major advantage is that this cross-linking occurs at room temperature, eliminating the need for additional heating processes or curing steps. The technical challenge lies in the encapsulation process itself. Two-component adhesives are reactive materials and could potentially react with the chemicals used to create the capsule shell. However, the researchers emphasize that they can adjust the capsule chemistry with extreme precision. This ensures that the adhesive components remain active, are reliably encapsulated, and can be safely stored and processed, only to open specifically during pressing. These are critical criteria required by the industry.

Adhesive Textiles are Intended to Enable Surface Bonding

The microcapsules are now being applied to sheet-like carrier materials that can be processed like an intermediate layer material. Suitable options include textile carriers, fiber fabrics, or other planar materials. This makes the adhesive a manageable material, as it can be positioned within the component and only activates its function during the joining process. Potential applications include processes where components need to be bonded over a large area, in a controlled manner, and without an open adhesive application. In the automotive industry, this could be used for battery stacks. Other application areas include mechanical engineering, electronics manufacturing, or microstructured components with fine channels, where traditional dispensing and application methods are technically complex, hard to access, or economically less viable. For the development of these adhesive textiles, the IAP combines its expertise in microencapsulation with application-oriented testing. The strength of the resulting bonds is then analyzed together with the Fraunhofer Institute for Machine Tools and Forming Technology (IWU), forming the basis for systematically evaluating suitable application fields with partners.