> On Tue, Feb 11, 2020 at 10:30 AM Gene Heskett <[email protected]> > wrote: > >> Cleaned up with acetone of course.
Cleaning with acetone will result in a good epoxy bond. Cleaning with isopropyl alcohol will result in an excellent epoxy bond. Commercial acetone, at least in the US, is recovered from industrial processes. It's distilled, but a trace amount of the waste oil remains in the acetone after the distillation process and will leave a slight oily film on your parts after the acetone evaporates. It's not enough to feel or see, but it's enough to prevent the best possible epoxy bond. Maybe remove most of the oily gunk with acetone, scrub with 60-100 grit sandpaper to create a rough surface for the epoxy to grab, then flood with isopropyl alcohol to thoroughly degrease the part prior to applying epoxy. I'll sometimes use a clean blue paper shop towel or toothbrush with the alcohol at first if some physical scrubbing is still needed. I'll finish the job with a spray bottle with isopropyl alcohol to blast off the last traces of oil, allowing the alcohol and suspended oil to drip off the part, and then I don't touch the part with my bare hands. You've made your own printed circuit boards and the process is similar to the final step of cleaning the bare copper board before the etch resist process. When the board is clean of oxides and oil free, the solvent will uniformly wet the board, drip off the bottom edge, and the board will dry from the top down leaving a matte finish. Pro Tip: for the very best bond when using a filled epoxy, first paint the bare surface with a thin layer of raw epoxy (resin and hardener) before applying the filled epoxy (such as JB Weld). The unfilled epoxy can more easily penetrate the fine scratches on the substrate, and the filled epoxy then binds to the unfilled epoxy. That's a tip from people who build composite fiberglass airplanes. _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
