A life-long bond – what does it take?

Bonding is rewriting the rules of joining two materials, and is opening up completely new possibilities. Especially when it comes to connecting both small and large components cost-effectively and without any mechanical impairment. But what exactly do we have to bear in mind if we want the bond to be permanent?

Adhesive bonding does not affect or damage the materials and is lightweight, which is an important factor in the automotive industry, for example. Vehicles need to become lighter so they consume less fuel and less electrical power. Bonding is a major factor here because between 15 and 18 kilos of adhesive is used in the average vehicle, among other things for potting and bonding chips and sensors, for stiffening the chassis and for fixing the interior linings.

Adhesive bonding: Dispensing system applying adhesives
Adhesive Bonding
Sebastian Schmitt
Sales expert

With 14 years of experience in dispensing technology and an in-depth knowledge of the industrial electronics market, Sebastian Schmitt is our expert for reliable adhesive bonds.

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How does adhesive bonding work?

Bonding is a technique for joining two or more parts using an adhesive substance. Hybrid processes, in which bonding is supplemented by a further operation such as sealing or heat dissipation, are becoming increasingly important in addition to standard bonding applications. They offer many advantages including simpler component handling and weight savings, as mentioned above, which is why they are supplementing or replacing more and more classic joining techniques such as welding and bolting in the industrial sector.

In industrial applications, the dots or lines of adhesive often have to be applied at precisely defined locations on or in the components to be joined. For this reason, highly viscous 1K or 2K adhesives based on polyurethane, silicone or epoxides are usually used as they will not run. Depending on the application and the bonding properties to be achieved, low-viscosity adhesives may also be the materials of choice.

The sequence is always the same: apply evenly – match – bond. The adhesive should be applied as evenly as possible, and the bead diameter and length should be matched to the adhesive joint. The parts that are to be bonded with adhesives and cross-linked under the influence of moisture must be combined before the adhesive has formed a skin. What’s more, the pressure must be as uniform as possible.

The adhesive and the parts to be bonded can be affected by a wide variety of factors during use, all of which also interact with one other, so it is crucially important to conduct an in-depth analysis in advance. This graphic shows what needs to be done to ensure a durable bond.

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Factor chart adhesive bonding
Good planning is key – and starts with the design

The quality of the surfaces to be bonded has a major influence on the bonding function in addition to the factors we mentioned above and the materials involved. Is the material strong enough? Should the surfaces be precleaned and are the materials even suitable? The keyword here is adhesion. Surface tension is also important. For example, polyamides, glass-fiber-reinforced plastic and polycarbonates have much better adhesion than rubber, polyethylene or polyoxymethylene.

The geometric shape of the surfaces is very important for the success of the bond. Surface tension needs to be as evenly distributed as possible. The graphic shows unfavorable shapes and suggests ways in which the design can be optimized.

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Systems for reliable connections

If the geometry of the materials to be joined is correct, all that remains is to select the appropriate system technology. Suitable material preparation, feed and dispensing systems are required to ensure that the bonds are durable, especially in safety-relevant applications. The plant must be adapted to suit the properties of the adhesive, such as its reactivity, and appropriate health & safety measures must be taken. At the same time, the requirements of the components in terms of their variants and geometries must be taken into consideration. It is also important to take into account factors from the production environment, such as the cycle time and the location of the plant. Well planned adhesive processes can be reliably integrated in series production.

If you’re looking for the perfect solution for your specific problem simply ask our experts. Tip: Laboratory tests during the tendering phase ensure that the solution is ideally adapted to the customer’s specific requirements. To sum up, bonding is one of the most efficient and productive joining techniques.

FUN FACTS: How long have people been using adhesives?

Gluing has a tradition that goes back a long way.

Asphalt/pine resin mixtures, an early form of today’s hot-melt type adhesive were in use as early as the building of the Tower of Babel. Bonding of materials such as wood, stone and ceramics with the aid of adhesives, glues or putties is something which goes back to prehistoric times. Fragments of an alabaster statuette crafted between 3000 and 3300 BC were found in Uruk (modern-day Iraq). The eyeballs were fashioned from mussels into which pupils of lapis lazuli were stuck using an adhesive based on fish skin and bone glue.

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