Adhesive for bonding liquid/cast cured polyurethane to neoprene 1

[PU2RUBBER]

Can anyone suggest adhesives for bonding/casting a liquid polyurethane (2 part thermoset MDI based) to neoprene?

I am also trying to cast the same polyurethane to a rigid thermoset polyurethane substrate using the same process.

Background:

Surfaces of both substrates have been touch ground and then cleaned with MEK. I have tried several Chemlok products without much success as well as a 3M product. I can preapply the adhesives, use heat but would like to stay within the confines of a 1 component system.

For the neoprene application I have tried 3M 1300L diluted with MEK and Toluene. That yields a modest bond but will not produce a cohesive failure of the polyurethane...which is what I am looking for.

For the thermoset PU substrate I have tried Chemlock 219. It also produces a modest bond with the same failure mode mentioned above.

Can anyone help with process and or adhesive suggetions. Thank you very much!

 

[MintJulep]

Where are your current bonds failing?

Are you confident that the MEK will really remove all traces of whatever mold release agent is used in the urethane casting process?

I'm too lazy to look up the adhesives you mentioned. Are any of them polyurethane based? If not, try a PU based adhesive.

Have the Chemlok and 3M products you have tried been at the recommendation of those companies? If not, call their tech support lines.

 

[PU2RUBBER]

Thank you MintJulep,

Sorry, this is my first posting and I should have given a bit more detail.

Both fail adhesively away from the polyurethane. The PU peels away from the substrate and leaves the adhesive behind with little to no trace on the cast PU surface...an adhesive failure of the PU away from the adhesive tie layer on the substrate. It suggests that the bond to the substrate is OK, but the bond to the PU needs improvement.

Our PU is applied in liquid form right onto the substrate. It is spun cast as a liquid right onto the neoprene or PU substrate. Each have been touch ground and then cleaned with MEK to remove any surface contaminants. It might be possible that one of the components in the liquid PU is traveling to the bond interface and acting to weaken the bond or even have some mold release characteristics.

I believe the 219 is urethane based and the 3M 1300L is neoprene based.

I have made multiple calls to these companies regarding my bonding application. These are the products that come highly recommended. I have also tried numerous other products with no luck at all.

Thanks again. I will try to search for more urethane based adhesives and go from there.

 

[MintJulep]

Ok, then I am confused. If you are attempting to cast the PU directly onto the neoprene substrate, where does the adhesive go?

 

[PU2RUBBER]

The adhesives are being applied directly to the neoprene and thermoset PU substrates. I know that I am being vague about this process but I can't give all the specifics as we are working on a proprietary project.

The adhesive acts as a tie layer between the substrate and the cast PU. Without an adhesive or some type of tie layer, the PU when cured, will easily peel away from the substrate with very little applied force.

 

[MintJulep]

So you apply the adhesive to the substrate, let it cure, then cast the PU on top?

The adhesiver really isn't working as an adhesive then is it? Have you disclosed this to 3m or Chemlok when soliciting their recommendation?

 

[PU2RUBBER]

Yes, that is correct. It is acting as an adhesive tie layer between the cast PU and the substrate. I did let 3M and Chemlok know specifically what I was trying to accompolish and even sent samples of my substrates and liquid PU to one for their own tests prior to receiving a recommendation.

Do you think that I should try to add some kind of adhesion promoter to the liquid PU formulation?

 

[MintJulep]

Maybe look at plasma etching of the substrate.