Urethane to Steel Epoxy Suggestions

[lucky-guesser]

Hello all, we are currently using J-B Weld # 8280 (aka 8281) two component epoxy to bond small pieces of urethane to zinc plated mild steel. These urethane pieces are not critical in any way to the function of the assembly, more of just a minor convenience so if they fall out off in the field, obviously we don’t want that but it’s not the end of the world. Issue is, we are getting complaints that the urethane pieces are falling off on the way to the customer, not even getting out to the field before having issues.

We have a reference model on hand from 2017 and when I compare it to current production models I can see a substantial difference in quality over how the epoxy was applied. In this particular case there was much more epoxy than what was needed, but with the labor situation we all deal with today, the next batch could just as easily not have enough epoxy.

All that to say, this is likely operator error, however I still want to cover all my bases. After doing a quick look on the J-B Weld website, it looks like their 8265S may be better for our needs. Looking for thoughts on if you all would agree with that, as well as any products from other companies that may be better than that. I’m sure the purchasing dept would like it if we stayed with a J-B W product but they will change if we need them to.

Completed assemblies will likely be outside 24/7 in assorted weather, but no unnatural hot/cold situations. Will be subject to repeated light impacts but for relatively short periods of time.

 

[blakmax]

This is a surface preparation issue. To achieve an adhesive bond the surface:
1. must be clean (we all know that).
2. must be chemically active. (not so well known).

Unless the adhesive reacts strongly with the ahderends, you must undertake measures to get the surface chemically active. Abrasion or a light grit blast would help significantly. But do not solvent clean after abrasion or you will leave a layer of contamination. Just blow the dust off with clean, oil free dry air.

Keep the components in a dry atmosphere before bonding as well.

Regards

Blakmax

 

[Martin238]

It could also be that the adhesive is not suitable for bonding plastic. Urethane (plastic) has a very low surface energy. As Blakmax already mentioned, it may be necessary to activate the surface. There are different primers that establish a bond between the adhesive and the surface.

If you're not too reliant on the adhesive, you could also consider a different chemical base, such as acrylate/urethane adhesives.

 

[drwebb]

Which side is debonding- the zinc-plated steel side or the PU side?

I don't really see any formulation difference between those product SKUs- looks like just different tube sizes.

 

[lucky-guesser]

Which side is debonding- the zinc-plated steel side or the PU side?

I took a good one that seemed to have a good bond and snapped the plastic off with a pair of pliers. Half of the JB weld stayed stuck to the metal and half stayed stuck to the plastic. So not exactly conclusive.

I don't really see any formulation difference between those product SKUs- looks like just different tube sizes.

"J-B Weld # 8280 (aka 8281)"
"aka" being also known as. They have two SKUs that are in fact the same formula and just differ by packaging. I threw both #s out just so if someone had dealt with 8280 they wouldn't see 8281 and think I must be referring to something they had no experience with, or vice versa.