So, a couple PhDs and half a chem lab later, are the essential oils properly labeled yet?
Question is more than fair. Not yet. Holiday distractions have displaced chem lab activities. I want to re-find the article that lists hot melt glue resins, and use all those names to search for a vendor who sells end user quantities of several of them (so far the only vendors who do list the base polymer are listing ethylene-vinyl acetate (EVA). It’s easy to find that – I could probably have gotten some at the grocery store yesterday! I want to try several on my test caps and test bits of aluminum. I might also use a few of the suggestions like TriPolar’s above.
I overheard some reindeer whispering together, from which I gleaned that the collection is going to grow slightly tomorrow. So it’s still absolutely a priority – but so is the gift wrapping.
Let us know what your testing reveals!
Another test video. Haven’t watched it yet. Polyethylene/propylene are regarded as very difficult materials to glue, and aluminum is not that easy either. One to the other is a special problem.
This is the 'Dope after all. It does take the full panoply of human knowledge to resolve even the simplest of problems. Fortunately, we have that full panoply well-covered. And this is not one of the simpler problems. 
A strong join of polyethylene to aluminum is a special problem. A join that’s just strong enough to hold on a label is much easier.
Which doesn’t stop Dopers from trying to solve the hard problem anyway, because that’s just how we are.