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I'm an electrical engineer trying to understand a failure in a plastic part that I'm working with.

I am using a plastic called polysulfone- and the data sheet has a lot of words ending in "amine" that are listed as not-being compatible with said plastic.

I want to bond this plastic with an epoxy, but the very-vague datasheet states that the hardener contains 80% "Modified Cycloalipathic Amines".

With this admittedly limited information, should I look for a different adhesive?

The process temp is $5$ to $85~^\circ\mathrm{F}$ ($-15$ to $29~^\circ\mathrm{C}$).

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  • $\begingroup$ I have a bachelor's in chemistry, but I am not an expert in materials science. All I can tell you is that looking at the structure of a polysulfone polymer, going by textbook logic I would not expect much reactivity with typical amine compounds. Perhaps the amines listed in your MSDS have functional groups, other than the amino group, that would react with your polysulfone. From a glance at structures found by googling "modified cycloaliphatic amine", it looks like such compounds (representing the epoxy) will likely behave like typical amines (which may or may not react with your polysulfone). $\endgroup$ – electronpusher Mar 29 '17 at 16:50
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I suggest taking the experimental route and exposing another test piece of the plastic you are working with to the hardener. Keep an eye out for any softening, swelling, change of color and any other indicators of a reaction occuring.

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Short answer: yes.

Every manufacturer of two-part, room temperature cure epoxies has their own formula. There is no way to know without either knowing the formula or testing your specific application whether the one you are talking about is or isn't compatible.

First thing you want to find out is the composition of the other 20% of the hardener. It could easily be a tertiary amino phenol (or just phenol itself), which might be a problem since it would tend to be "fugitive". I can think of at least a couple of dozen questions that might need answering (by empirical test). How is dielectric surface break-down affected by the epoxy, for instance. No way you're going to find that data - someone will have to generate it for you (I'm assuming this isn't a one time thing. If it's a one time thing, I'd advise against an amine cured epoxy if you're concerned with anything except bond strength (and even that would have to be tested).There are a number of mercaptan cure epoxies that would be my first picks - but I've no direct experience with this adhesive/substrate combination.

To keep it simple, I'd suggest you try a 2 part acrylic adhesive (they are expensive). Also, the stoichiometry (ratio of epoxy to hardener) could be important. More epoxy reduces the amount of low molecular weight amine (meaning less will diffuse out of bond and into Polysulfone). But higher epoxy means a more brittle bond, generally. So, this isn't something that can be answered without testing.

If you're a "big customer" perhaps the adhesive or polysulfone part or resin manufacture can help. I used to be an adhesive formulator, so perhaps I'm overly complicating this, but I wouldn't be confident in making a recommendation about type of adhesive without knowing a whole lot more. You've not mentioned even one requirement of this "bond", bond strength of 1 nanogram/m² or 1 Gigaton/cm² for instance, and as I said, there are several dozen more characteristics that are probably required.

Incidentally, marine supply stores may have two-part acrylics, if you're at the retail level. FWIW, talking about epoxy adhesives as if they are all one thing is like talking about the 0-to-60 acceleration of "cars". There may actually be more epoxy formulations available than car models. My experience is that the more vague the data sheet the more it is targeted for the retail market (that is, clueless consumers). This type of epoxy might work just fine, or might cause a failure. No way for us to tell you that. Heck, you didn't even tell us what the application or maximum use temperature was.

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