Bonded transparent room systems

New business worlds, increasingly fast-changing working, office and organizational structures as well as the flexibility required in modern companies prompted König+Neurath AG to search for a novel philosophy for solutions to transparent room systems and constructional elements, in close and creative cooperation with the University of Stuttgart, Germany, and DELO Industrial Adhesives, Germany.

Glass is an excellent material to build the transparent boundaries for these areas – provided that the corresponding joining technology is available: bonding. No other connection offers the elasticity, which is required by, e. g., a glass/metal connection, in order to absorb the different linear expansions of these two materials.

Besides innovative design, new glass adhesives, modern production technologies, and the necessary quality assurance, the flexibility of the new room system was high on the agenda right from the start. Many approaches have already been put into practice and the further development steps might be able to provide a “plug and play” module in the future, which would offer the solution for the flexibility required in our business world.

The construction
In most cases, today’s standard room systems separate the functions – in a manner similar to façade technology – into constructional elements and fillings, which are mainly linear components made of steel, aluminum, etc., and two-dimensional components such as glass plates. This type of construction “wastes” the constructional potential offered by the filling elements. The approach of the transparent room system aims at a method known from modern vehicle construction. Nowadays it is common for the large-area and partly double-curved glazings of cars and, more importantly, of tourist busses to make a considerable contribution towards stiffening and, thus, to the total stability of the car or vehicle body. Bondings of different materials lend themselves to this constructional approach as ideal joining technology requiring a two-dimensional and force-fitted composite. Thanks to the new, highly transparent acrylates, the glass plates seem to hover in front of the constructional profiles. These actually form a constructional unit, that is to say literally the transparent room system. This system significantly increases the elements’ static efficiency. Although, the adhesive joint is a layer constructionally connecting as well as construction-physically separating within the overall system.

The new adhesive generation
For a long time mainly silicones, polyurethanes, and transparent adhesive tapes have been bonding glass partition wall systems. For years silicones have proven to be successful for this type of use, are nearly aging-resistant, and their elasticity offers the required equalization of tensions. But they have the disadvantage of very long curing times of up to 24 h and temporary storage must be organized. Additionally, the silicone must be adjusted in color to the respective subsoil in order to reach invisibility. Polyurethanes have a high strength and elasticity but they are not UV-stable. Up to now adhesive tapes have met the requirements on a transparent bonding best. However, when processing them, air bubbles are regularly encased when joining the glass panel to the adhesive tape rolled out on the frame. These bubbles tarnish the general impression of an optically transparent bonding. Here, bubble-free bondings are only achieved with liquid adhesives.

Liquid acrylates, DELO-PHOTOBOND, offer a completely new approach. They combine a band of properties which are essential for this kind of bonding. Up to now UV-curing acrylates have been used for glass/glass and glass/metal bondings in the field of furniture and design. The products used do distinguish themselves by high strengths and absolute transparency, but they are brittle and little tension-equalizing at the same time – thus, not suitable for large areas with high forces. Therefore, the challenge for the adhesive developers was to combine good adhesion with high flexibility in order to be able to play the clear advantages of the acrylates also on large-area glass/metal connections. The high transparency of these adhesives is a clear advantage.

The requirements on the DELO-adhesive:

• Light-fast and UV-resistant
• Long-term bearing of loads
• Tension-equalizing and flexible for the connection between glass and aluminum
• Fast curing
• Process-reliable processing in automated production lines