Aluminium windows and doors and the gluing technique

Unique windows and doors, large glass surfaces and narrow frames would not have become part of our building culture without developments in gluing technology. We talked to Gábor Farkas, head of the industrial glue technology division at Sika Hungária Kft., about the special fixing and sealing processes and innovations that have emerged in this field over the past decade. The cooperation between KAV and Sika goes back many years. In the beginning, they only supplied sealing materials for glass-to-glass connections made on-site, but today they supply KAV’s factory workers and installation team with special materials and tools, and also train our engineers.

– Sika also appears to be a very serious company in the field of innovation and intellectual property protection. Is continuous development and innovation such a defining factor in the field of gluing technology?

– Sika is a Swiss company; its foundation is also linked to innovation. More than 110 years ago, when the Swiss railways wanted to electrify the Gotthard tunnel, they ran into serious difficulties because of water leakage. It was Kaspar Winkler who solved the problem. He developed a concrete admixture, a special sealing material, which stopped water from entering. This is how the company’s history started. Interestingly, Sika materials were still used during the construction of the new 57 km long Gotthard tunnel. The real breakthrough in the history of the Industrial Glue Business Unit came with the development of an innovative material that first broke into the automotive industry. When it was first applied, it turned out to be a lot more than a sealant; it also worked as an adhesive.
Decades ago, when buses were made entirely from steel, the use of plastic started, for various moulding elements. These could no longer be welded or fixed using traditional mechanical fastening methods, but had to be installed by gluing. This is when it turned out that gluing technology could be used in numerous fields: in steel-aluminium, steel-plastic, and then steel-glass connections. For 25 years, the concept of glued buses, i.e. gluing the bodywork to the assembled bus frame, has been a reality in Hungary, and, parallel with this, the use of glue started in the railway vehicle industry. Higher speed trains were increasingly being manufactured, for which rubber-encapsulated glass could no longer be used because of the increased loads.
So with history and technical progress, glue bonding was used in more and more fields, especially in the automotive industry, mainly as flexible bonding. This increased demand could only be met by innovations in bonding technology. And of course we were also looking for new fields of applications.

– Like window manufacturing?

– That‘s right. We started with these questions: how can gluing be introduced into traditional window manufacturing? Most of the glasses used in the automotive industry are already glued, so why not use it for windows in the construction industry? Insulating glass is becoming increasingly bulky, and this requires enormous holding power. If you want to hold a very heavy piece of glass using a frame, we would need a very thick frame. Why not think the other way round? So the glass, which is a rigid structure, should hold the frame. There is no other way to do this except by gluing. What is more, due to thermal expansion, we need a special flexible bonding material for this purpose. This is particularly eye-catching for large-size aluminium windows.
In the increasingly common large floor-to-ceiling structures, there is a thermal expansion difference of several millimetres between glass and aluminium. This is absorbed by the glue.

– Is this how innovation is born?

– Precisely. And, fortunately, we have the appropriate human resources to do it. This is also what we represent towards KAV. If there is a gluing task that seems unworkable, let’s think together! Ideas are important. With the right gluing innovation, the end product is almost certain to be cheaper than if it were fixed using traditional techniques. Continuous development and innovation are a must to stay in the market.

– Might this excellent co-operation with KAV be the result of similar mindsets?

– Of course. You can only achieve a joint product when you have open-minded people working on both sides; who are able to think through an idea, and figure out what can be used in their own field. Innovations may result from these co-operations. This involves long-term thinking. It‘s important to highlight this, since this attitude isn‘t about immediate profit.

– How have gluing techniques changed and developed in the last 15 years in the field of doors and windows?

In this case, the motto is “the glass holds the frame.“ When we started thinking about applying gluing techniques in the construction industry 15 years ago, we talked to several companies in the country. We started with companies using plastic for manufacturing, but back then it was all a matter of price in Hungary. The gluable profiles offered by system suppliers were in a higher price range. At that time, they didn’t commit to launching this. Eventually, we found a company that cooperated in this.

– And did it stop at that point?

– No, as glued systems are also usable by companies manufacturing wooden windows, they reflected more on it. However, they were also in an easier position, because they manufacture the profile that receives the glued parts. These days machines exist where you can produce profiles very freely, even in small quantities. So you’re not locked into a technology that is difficult or has a low return, where you have to stick with the old way. We have achieved results with wooden window manufacturers. This also requires that Hungarian consumers look at wooden doors and windows as being of a higher value. And they are willing to pay more for it. So some contacts have already started in this area

– And where are the aluminium windows?

– When the “Bauhaus” style appeared, the size of windows increased unbelievably. They are from floor to ceiling. These required huge, floor-to-ceiling glass surfaces, for which mainly aluminium frames were necessary. Especially when very heavy triple glazing appeared. And from then on, aluminium system suppliers started looking for the right bonding techniques. This also demonstrates the need for synergy. We, the glue industry, were too small to penetrate the domestic construction industry; we needed aluminium system suppliers who had the emerging need for gluing. Then innovation was added, also due to market competition and the architects, who were less and less keen to see the frame. In fact, as much as possible, we have to make it disappear! This can now only be done using a combination of glass and some kind of glue. These will require newer and newer gluing technology developments. We are constantly working on such solutions with KAV, some of which are now in the patent process. We’re shaping the present and the future together.