I am a quality engineer looking for some chemistry expertise that can hopefully assist in solving a problem we are having at our company. We are a water filtration company and our location produce the filters used for our machines which are in restaurants and stores around the world. For simplicity, the filter is comprised of an aluminum can that we extrude, wash, add a polyethelyene coating (liner), then add the filter material and a cap with an O-ring. We often get reports from the field of filters that are leaking during use. Upon return, we open the filter up and see that the polyethelyene liner is not adhering to the inside of the aluminum can and has started to tear, creating a leak path past the O-ring. Our current focus is on the cleanliness of the inside of the aluminum can. Much like anything else, the more dirt on the surface, the less likely anything will adhere to it. We are trying to improve cleanliness to increase adhesion. Another thought I had was when we heat the cans to around 500F during the polyethelyene coating process, the contraction of the can after the thermal expansion when we quench is causing the liner to detach. What I am asking from a chemist is, what can improve the adhesion of the polyethelyene to the inside of the aluminum can? Are we chasing the wrong thing with cleanliness? Is my thermal expansion theory completely off?
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$\begingroup$ Maybe you should try to avoid quenching and to cool the pieces of aluminum coated with polyethylene as slowly as possible. $\endgroup$– MauriceCommented Nov 9, 2022 at 21:56
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$\begingroup$ If you want to fix this completely, then you'd need different polymer altogether, I'm afraid. PE isn't something that's gonna stick to Al. It difficult to even dye, much less bind to stuff. On the other hand, if you used epoxy... $\endgroup$– MithoronCommented Nov 9, 2022 at 23:26
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$\begingroup$ Have you tried anodizing the aluminum? You'd need to test, but the increased surface porosity and roughness should give the plastic a larger surface to which it could adhere. $\endgroup$– DrMoishe PippikCommented Nov 10, 2022 at 3:11
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