Bonding processes

New material combinations are of high importance for innovative industrial processes and products. However, the joining technology is often the weak point of these products. In addition to inadequate adhesion of the adhesives on the materials, migration through the adhesive in particular can significantly reduce the long-term durability of the materials.

Low-temperature bonding is an adhesive-free joining technology for joining homogeneous and heterogeneous material composites. At Fraunhofer IST, both inorganic material compounds such as silicone and glass as well as organic materials such as polymers are bonded at low temperatures using atmospheric pressure plasma. The surfaces are equipped with chemically reactive functional groups that react with each other at elevated temperatures and can form permanent bonds in the process.

A new plasma pre-treatment was developed at Fraunhofer IST for bonding silicone. It allows the temperature required for good adhesion to be reduced from 1000 °C to less than 200 °C. Adhesion forces in the range of the silicone breaking strength are achieved in the process. By lowering the temperature, it is also possible to join heterogeneous material pairs with partners that usually have different thermal expansion coefficients.

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