Notes on Adhesion Improvement between PE and PA in Multilayer Rotational Molding

Before sharing this study on improving adhesion in our member newsletters, we asked Technical Director Nick Henwood to let us know whether the paper would be valuable to rotomolders. He offered some notes for context:

I think this is work is useful, especially in relation to rotomolded gas tanks.

Gasoline permeates PE too easily to pass current conformance tests (EPA and CARB requirements).

PA-Polyamide (aka “nylon”) has much better permeability characteristics, but is also much more expensive than PE.

Therefore it makes sense in principle to make a two-layer moulding using PE with an internal “lining” of PA.

Problem is that inner layer of PA will not adhere to PE and delamination occurs to a considerable extent. Often the delamination is complete.

Anything that improves the adhesion of the two layers would be very helpful.

The first option put forward, plasma treatment of PE powder, is known already, primarily as a way of improving adhesion of PE with polyurethane (PU) foam. Interesting to see it being used for PA.

The second option mentioned, creating polymer “entanglements” has been put forward in principle previously, but actual performance data takes this option forward considerably.