epoxy on poly

I’ve been making a couple bows of late, and the epoxy that is used for the laminations is called “smooth-on”. It’s good stuff although it takes 24 hrs to harden unless you hot box it at 180F…then it’s less than 4 hrs. Anyhow, I had a bit of extra mixed up and figured I’d experiment a little by applying dabs to my Prijon Kodiak. I put one dab on with no surface prep, one where I scuffed the surface with 80 grit sandpaper, and one where I heated the surface with a torch for a couple seconds.

Results: Both the unsanded and sanded dabs where difficult to remove. I basically had to chip them away; they didn’t come off in one piece. Much better than I thought they’d do, though I wouldn’t trust it for mounting anything essential. The dab that went on after heating formed a very strong bond and I actually had to sand it away. Obviously, this wasn’t long term and I’m not sure how it would hold up with freezing/thawing or impact/flexibility. However, given the epoxy’s primary purpose of making bows it would probably be fine.

If you’re interested in experimenting yourself, it’s $20 and change for a pint, and $35 for a quart from BinghamProjects.com.

More real good stuff…
…believe it or not Devcon plastic weld.

I think your results are due to the HTP
that Prijon uses for blow molding. Try it on a linear poly boat and your results may be less impressive.

Anyway, the cheapest approach to a trial is to buy the 4 oz tubes of West G-flex. It will outperform any other epoxy I have seen.

flame treatment
"I then flame treated the polyethylene surface after sanding. To flame treat a plastic surface, hold a propane torch flame about 4" to 6" from the plastic (with the tip of the flame just above the surface) and move it across the surface at a rate of 2 or 3 inches per second overlapping the previous pass slightly. Keep the torch moving and only allow the exhaust gases to hit the surface. If done correctly, the surface will not discolor or burn in any obvious way. This technique oxidizes the surface and improves adhesion. For best adhesion, bond to the surface within 30 minutes of treatment."


Interesting - I used West Systems G-Flex epoxy to fill holes in a P&H plastic kayak. I roughed up the holes with a small round file. The stuff has held perfectly.

I’ve not tried it on the surface of the plastic.


another option …
there was or still is … a company called NorthSea Resin. that made epoxy repair kits for poly boats. seen a demo @ a kayak show.