Gluing POM: why it's difficult
Polyoxymethylene (POM, acetal) is strong, has good lubrication, and is chemically resistant – which is precisely what makes it one of the most difficult plastics to bond. Virtually no adhesive will hold without pretreatment. This article shows realistic ways to reliably join POM nonetheless.
To the point
POM has a low surface energy and a smooth, non-polar surface. Standard adhesives will not adhere without pretreatment (roughening, flame/plasma treatment) or a special primer . Bonding is possible with a primer and cyanoacrylate, a two-component structural adhesive, or surface activation – albeit with limited strength.
Why POM sticks so poorly
The low surface energy of POM means that adhesives wet poorly and bond very weakly. Additionally, POM is semi-crystalline and chemically very resistant, so most adhesives fail to form a chemical bond. The result: seemingly strong bonds that detach again under slight loads.
The realistic ways
- Surface pretreatment: Roughening plus flame treatment or plasma significantly increases the surface energy (see surface preparation).
- Cyanoacrylate with special primer: A primer for low-energy plastics such as the LOCTITE Primer SF 7701 in combination with a cyanoacrylate such as LOCTITE 406 improves adhesion.
- 2K structural adhesive: For large, stressed connections, 2K acrylate or epoxy systems (e.g. Araldite 2012) are an option – with pretreatment.
Realistic expectations
Even with a primer, POM remains a borderline case: For highly stressed connections, form-fitting or mechanical solutions are often more reliable than adhesive bonding. Where bonding is necessary, pretreatment and primer determine success or failure. For adhesive selection for each type of plastic, see Bonding Plastics; for cyanoacrylate limitations, Cyanoacrylate; and for the classification of adhesive classes, see Industrial Adhesives in Comparison.
Frequently Asked Questions
Which adhesive will bond to POM? None reliably without pretreatment. It becomes possible with a primer plus cyanoacrylate or a two-component structural adhesive after roughening/flame treatment.
Why is my POM adhesive coming loose? Because of the low surface energy without pretreatment – the adhesive doesn't wet and bond properly.
Is there an alternative to gluing? For high loads, yes: welding, snap-fit or screw connections are often the safer choice for POM.
Consultation and samples
Tell us about the component, partner material, and load – we'll recommend pretreatment and adhesive and provide a sample. Contact us or write to info@silitech.ch.
