Konstruktion & Entwicklung 10/2018
Unfortunately, typical foams cannot be used as a 'material' or pure connecting element for bonding two workpieces. The only exception here are double-sided adhesive tapes with a carrier made of e.g. PE or acrylate foam. Nevertheless, classic foams such as PU, PE and EPDM (apart from the typical construction foam) can also be self-adhesive and therefore interesting for mechanical joining methods.
In contrast to mechanical joining methods, double-sided adhesive tapes do not have a punctiform but an area-wide force transmission by using the entire surface when bonding. No material weakening is caused by drilling or thermal changes in the material, such as welding.
In addition, the adhesive tapes with foam backing form a seal against gases and liquids, dampen vibrations and compensate for different dynamics of the parts to be joined. In addition, they have insulating, thermal properties and are partially UV-resistant. Double-sided adhesive tapes made of acrylate foam are a special feature here.
These have an extremely strong adhesive strength, are extremely resilient, UV-resistant, waterproof and suitable for permanent bonding, as they are resistant to ageing and weathering. They can also be optimally adapted to any application and any substrate as a die-cut part or adhesive tape and are also tension-equalizing as well as cold and heat resistant.
The individual foams and their capabilities
PU foams can be used as rigid or flexible foam depending on the degree of cross-linking. They are usually open-cell and available in a wide hardness and density range. As an open-pore carrier foam, PU has a high elasticity and is ideal for use as rattle protection, soft storage or for heat and cold storage.
PE foams, also known as polyethylene foam or cell ethylene, consist of a closed cell material. They have an enormous type width of cross-linked foams with different densities. PE foams have good weather resistance, good heat insulation, good acid and alkali resistance.
EPDM is a closed-cell, foam-shaped elastomer and has various strengths and densities. It is air- and waterproof, has thermoplastic properties, is deformable depending on temperature and also has good resistance to acids and alkalis.
Foams as a combination with mechanical joining
What if the above mentioned properties of foams could also be used for mechanical joining methods such as screw joints or rivets? In construction, self-adhesive foams are usually used to contain or exclude liquids, sometimes gases, temperatures and noise.
They are, so to speak, the all-rounders for supporting tasks in structural connections. Regardless of whether they are mechanical or adhesive joining methods. Foams specially adapted to the application in form, material and adhesive can be used in connection with almost all joining methods.
If self-adhesive, the foams can be produced as die-cut parts, such as sealing rings or more complex geometries. In this way, screw connections can be protected against corrosion, heat, cold, moisture and much more.