Capturing properties What is adhesive technology?
Bonding technology is one of the oldest joining methods. Even the Neanderthals utilised the properties of birch pitch to join different materials together for their tools, making bonding a historically proven yet highly modern process that has become an integral part of industrial production today.
Bonding technology is a joining process in which two or more materials are permanently joined together using adhesive. In contrast to mechanical joining methods such as screwing, riveting or welding, bonding enables a material-to-material connection over the entire contact surface. Bonding technology is one of the modern joining techniques and is becoming increasingly important in numerous industries - especially when processing different materials.
Adhesion and cohesion - the physical principles of bonding technology
In bonding technology, it is important to understand the physical principles of bonding. The terms adhesion and cohesion form the physical basis of bonding. Adhesion (adhesive forces) describes the molecular adhesion between different materials. This effect is also known as surface adhesion and is responsible for the bond between the adhesive and the surface of the material to be joined. Cohesion (adhesive layer strength), on the other hand, describes the adhesion between similar particles within a material - i.e. the internal strength of the adhesive itself.
Based on these two adhesion mechanisms, a distinction can also be made between the fracture types of adhesive bonds. In the case of an adhesion fracture, the bond separates directly at the interface between the adhesive and the material - an indication that the adhesion was insufficient. Cohesive failure, on the other hand, occurs within the adhesive. In this case, the adhesive itself fails because its internal strength (cohesion) is insufficient.
Applications of adhesive technology
Bonding technology is used in many areas, including the automotive industry:
- Automotive industry: joining of bodywork and interior elements, bonding of glass, sealants and lightweight materials.
- Aerospace: structural bonding of aircraft parts, weight reduction through bonding instead of screws/rivets.
- Electrical engineering & electronics: fixing of components, heat dissipation through thermally conductive adhesives.
- Construction industry: Bonding of insulating materials, floor coverings, façade and window constructions.
- Medical technology: Skin-friendly adhesives in plasters, prostheses, disposable products.
- Packaging industry: box bonding, labelling, seals
- Furniture and wood industry: assembly of wooden panels, veneers, coatings.
- Sports and leisure equipment: bonding of materials such as carbon, plastic or metal in bicycles, surfboards, skis and much more
The role of the surface in bonding technology
The quality of the surface plays a central role in the quality of a bonded joint. The following terms are used in adhesive bonding technology
Surface energy
- It describes the amount of energy required to overcome the intermolecular bonds on the surface of a material. Materials with a low surface energy are difficult to wet - this means that adhesives adhere less well to them.
Surface tension
- This physical property describes the endeavour of liquids to minimise their surface area in order to achieve an energetically stable state. For this reason, liquids such as water typically form a drop shape.
Wetting
- This refers to the behaviour of a liquid when it comes into contact with a solid material. With good wetting, the liquid spreads evenly over the surface without forming droplets - an important prerequisite for a stable adhesive bond.
Surface roughness and its significance for bonding technology
The condition of the surface of the bonded part is of central importance for an optimum bonded joint.
Looking at the surface of a material under a microscope shows that it is never completely smooth. Rather, it resembles a hilly landscape - a so-called microscopic roughness. These irregularities reduce the actual contact area between the adhesive and the material, which in turn has a negative effect on the adhesive forces and therefore the bond strength. The unevenness can also mean that the materials do not make ideal contact, which further weakens the bond.
In order to achieve a reliable and stable bond, it is often necessary to pre-treat the surfaces. Depending on the material, different processes are used for this - for example
- Sandblasting for mechanical cleaning and roughening
- Acid treatment to remove oxide layers
- Mechanical grinding to increase the surface roughness
- Degreasing to remove oily or greasy residues
These measures improve the wettability of the surface by the adhesive and thus significantly increase the adhesive strength of the bond.
Systems for automated bonding Bonding technology from FFT
Whether you want to optimise your production, improve your products or create innovations in new fields of application - we will find the right solution for your application and use our expertise in the field of adhesive technology to meet your requirements.
Technological advantages of adhesive technology in modern applications
Gluing systems
Bonding is a manufacturing process from the main joining group. Adhesive bonding is used to join parts by means of an adhesive. The adhesive adheres to the surface of the part to be joined through physical (rarely also chemical) interactions. From a technical point of view, almost all materials can be joined together and with each other. The bonding technique is particularly gentle as it does not require high heat, which can result in distortion, cooling stresses or structural changes to the parts to be joined. No weakening holes in the parts to be joined are required for bonding. The force is transferred from one joining part to the other over the entire surface.
The design of the bond and the choice of adhesive is made by the customer and is provided in the form of a process specification for the project.
In order to achieve the best possible adhesive bond between the components, the surface is pre-treated with an adhesion promoter such as a primer or activator or a cleaner.
Areas of application for our gluing systems
- Windscreens, rear windows and side windows
- Roof (aluminium roof, skyroof or glass roof, convertible roof, aerial, panels)
- System carrier, boot recess
- Sensor or camera holder on the windscreen
- White goods, such as: Oven glass door, ceramic hob bonding
Use of modern adhesive technology for the application of door seals
The continuous door seal is supplied on a roll as a coil and is fitted with a double-sided adhesive tape. During application, the liner is removed from the adhesive tape and the door seal is applied all round the door under pressure. As this is an unstable product, compression and stretching of the door seal during application is not permitted, as the door seal will come loose and lead to leaks in the vehicle.
The design of a system is primarily determined by the processing specifications of the seal manufacturer. Environmental conditions and customer requirements are also decisive factors.
The following concepts are possible as examples:
- Application is stationary and the door is removed from the hanger with the robot
- Application is robot-guided and the door remains in the hanger
- Stand-alone solution with one turntable input to several interlinked stations
- Manual to fully automatic pre-treatment of the gluing surface
The future of adhesive technology
With the increasing use of lightweight construction and multi-material systems, particularly in the context of e-mobility and ecological construction, the need for adhesive technology continues to grow. Bio-based adhesives, recyclable adhesive bonds and intelligent adhesives with sensor functions are also seen as future drivers of innovation.
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