Adhering to Metals
Question:
Dear Professor Polymer, Is there any way to get polypropylene or a similar polymer to adhere to metals? - MZ
Answer:
Dear MZ, Olefins, such as polypropylene and polyethylene, do not adhere to metals very well. This is due to the non-polar nature of the base molecules.
Large improvements in bonding can be made with the addition of polar copolymers. This can be done either in the reactor, or by compounding with polymers with polar side-groups. Examples of such polymers are acid copolymers such as EVA, EMA, and EMAA.
Polypropylene is available in maleated acid copolymer, which has up to several percent maleic anhydride bonded onto the polymer chain. High temperatures and fast injection help greatly to enhance the bond. For other processes such as coextrusion/lamination, the use of film-grade polar copolymers is well-established; these are often used to integrate a metallic component, such as aluminum foil barrier layers, into a multi-layer film structure.
If you are looking to bond the already formed PP to metal, that's a tougher proposition. I believe that hot adhesives would have the best chance, again likely an acid copolymer derivative.
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