Bonding polymer plain bearings – How it works

Lars Butenschön | 28. May 2020

Plain bearings are usually pressed or clamped into the housing hole. They hold securely in the hole and do not rotate unintentionally. But what if this is not possible due to manufacturing tolerances? Another case: the plain bearing should even rotate. Even if it is not part of the standard repertoire of many plain bearings – polymer bearings can also slide on the outer diameter. Many a machine manufacturer therefore falls back on plain bearings made of plastic. The bearing is placed on a bolt and should then – together with the bolt – turn in or roll on something. Then the question also quickly arises: “How do I get this to hold?”. In these cases, the machine builder often ends up with bonding as the most suitable solution. But there are probably as many adhesives as bearing materials. Which is the right one? And what do you need to consider when bonding plastics? Here are a few tips:

Bonding plastic plain bearings – with the right adhesive

There are many adhesives for bonding plastics. The problem: plain bearings are often not made of “simple” plastics, but of plastic compounds or plastic blends. These are mixtures of plastic-polymers and additives and fillers that complement their properties. Materials that improve the sliding properties, such as silicones, MOS2 or PTFE, can be particularly problematic here. In these cases you should seek advice directly from the plain bearing manufacturer.

In reality, however, these ingredients have different effects. In most cases, even with these ingredients you can handle them quite well with special adhesives. We at igus® have had good experiences especially with two-component adhesives, e.g. the combination of Loctite 406 and Loctite 770 Primer. For plain bearings made of plastics with lower proportions of substances to improve the sliding properties, Loctite 401 without primer also offers good results. Of course, comparable adhesives from other manufacturers can also provide potentially good results.

Important: ensure that the surfaces to be bonded are well prepared.

As in many life situations, the same applies to the bonding of plastic plain bearings: preparation is everything. To make sure that in the end everything holds well, you should consider the following:

• Clean the surfaces to be bonded to remove dirt, rust and other foreign matter.
• Roughen the surfaces slightly by sanding.
• Degrease the adhesive surfaces thoroughly, e.g. with alcohol, nitro thinner or acetone.
• Let the glued areas dry well afterwards.

We would be happy to advise you!

Bonding of plain bearings is often not the ideal form of plain bearing assembly. Especially with moderate quantities, the additional assembly work represents a substantial cost factor. Often even small changes to component tolerances or component geometry can make bonding superfluous.

But even if there is no way around gluing – we not only advise you on possible alternatives to gluing, but also on the best design and execution of glued joints for plain bearings if the situation warrants it.