Epoxy - Urethane Coating (SP-2888) compatibility with 3LPE substrate 1

[GabrieleB]

I have to verify the feasibility of application of a Epoxy - Urethane Coating (SP-2888) coating on a substrate of 3LPe (3-layer polyethilene. Being the first (SP-2888) a thermosetting resin and the substrate a thermoplastic resin, which kind of reccomendation shall I take into account to garantee a good adhesion. Shall I do some paricular surface preparation to avoid delamination of the 2 different coating?

Thanks for the response

 

[SJones]

The best people to ask are at the manufacturer, SPC. If this is not a field joint coating application with a transitioned edge on the pipe coating, then I wish you all the luck in attempting to get the SP-2888 to stick directly to HDPE. Try a Google search using "coating adhesion to HDPE."

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

 

[epoxybot]

I'm with SJones, the approx surface energy of LDPE at 30 dynes/cm is too low for any durable bond. You would just be molding the material around the LDPE. Polyurethanes may be as low as 38 dynes/cm but epoxies are around 45 dynes/cm. A hybrid would be somewhere in between. DuPont did research on Teflon years ago and determined the surface energy of an adhesive should be 10 dynes/cm "lower" than the substrate surface energy to create a durable bond. This isn't really possible for some materials and research has shown that pressure sensitive adhesives perform better on low surface energy substrates. Their are surface treatment to elevate the surface energy of the substrate. Those should be discussed with the 3LPE supplier.

Depending on what you are trying to do, you might consider using a tape to bond to the 3LPE and then use the medium of the tape as the bonding surface for the hybrid adhesive. 3M and maybe Henkle are good sources. Looking at the SP-2888, I think the dynes/cm will probably be more in line with an epoxy than a polyurethane. If what you are really looking for is a transition between the coating & the 3LPE, then maybe all you really need if a specialty tape.

 

[brimmer]

It is unclear what you are asking. No, epoxy won't "stick" to polyethylene without some sort of surface prep. Or are you are putting the polyethylene over top of the SPC 2888? Or are you just looking at transition areas? There are different solutions depending on what you are doing.