Bonding and sealing have become indispensable techniques for joining and/or sealing two or more substrates with each other, not only in industry but also in everyday life. Bonding allows the production of laminated materials, facilitates mobility and communications, positively influences the handling of foods, supports health and hygiene and improves the quality of our lives. Moreover, many innovative products could not be manufactured without the use of bonding techniques. Sealing allows the infilling of gaps between two or more substrates and is a vital component in building and construction. Today it is an essential part in modern engineering including in the automotive and aerospace industries.
More than 2,300,000 tonnes of adhesives and sealants are produced and used in Europe each year and this volume is on the increase. Adhesive manufacturers offer more than 250,000 different products for the most diverse applications – and these products are customised for virtually every purpose.
Materials and bonding technology
The world around us and hence our lifestyle and the way we work are changing at breakneck pace. Who would have thought 15 years ago that computers and mobile phones would now be a part of everyday life? And who could have dreamed of detachable adhesive strips that do not tear away the wallpaper when a poster is removed? The constantly increasing requirements being put upon new consumer products is the driving force for technological progress: Nowadays, each new product that is developed must – as in the past – not only be better and more favourably priced than its predecessor but must also meet the requirement of sustainability. The consideration of environmental aspects means that the development of new products is becoming ever more demanding and that manufacturers must take into consideration more complex requirements for their new products.
The increasing requirements put upon products has since time immemorial been the key driving force for the development of advanced and new materials.
In addition to the classic metals, these materials include special alloys, plastics and also ceramics and glass. So-called composite materials, produced by combining different materials, have played a major role in this development. Reinforced concrete is a well-known composite material that has been around a long time. Newer composite materials include glass-fibre reinforced plastics and carbon fibre reinforced plastics which are used, for example, for constructing speed boats and yachts and increasingly also for car, rail vehicle and aircraft manufacture.
Another good example of the development and use of new materials is the wheel and tyres. Spoked wheels made of wood met the requirements of the ancient Egyptians. Today, the manufacture of tyres for modern means of transport can no longer be achieved using even natural rubber. The high speeds we now expect of a car can only be achieved using composites of different materials – and a car tyre is nothing more than that.
The development of new materials with diverse applications puts additional challenges upon processing technology. This is particularly so when different materials have to be joined to make components which retain their individual beneficial properties in the composite product. This raises the question: Which joining technique is able to join these different materials in such a way that their specific properties are retained? Traditional joining techniques have well-known disadvantages.
With thermal techniques such as welding, the specific properties of the material alter within the heat-affected zone. Mechanical techniques such as riveting or the use of screws in their turn only allow force transfer at points; In addition, it is necessary to drill holes in the work pieces that are being joined, and this “damages” and hence weakens the materials.
In contrast, bonding technology will assume an ever more important role in industry and the handicraft sector in the future because it permits the joining of disparate materials and does not create stresses and weaknesses in the composite structures. This is critical in many modern products where sustainability, speed of manufacture, recycling and long term performance are the norm.