Adhesives for Plastic

JohnAbercrombie

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Dec 7, 2011
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Victoria, BC
I recently had to re-install a skeg control box which had been factory glued in place, into a fiberglass kayak.

I grabbed two similar-looking products from my supply drawer and (luckily) did a quick test on each of them.

The two products:
Devcon Home Plastic Welder

JB Weld Plastic Bonder

The product I needed and used was the Devcon Methacrylate adhesive. Once you use it, you won't forget the characteristic smell. It sets quickly - there's only about 5 minutes working time. It's very aggressive and really inspires a lot of confidence in the bond quality. A friend re-bonded a hatch rim with methacrylate with good success.

The JB Weld Plastic Bonder product seems to be an epoxy, which in my cool shop didn't harden for hours was not fully hard-cured even 18 hours later. (The package advertised 30 minutes till sandable.)

Both products came in double parallel syringe dispensers, and both needed some wasted product before the two nozzles were dispensing equally.

Both have sealer tips for the nozzles; the Devcon is much better designed to prevent putting the sealer 'the wrong way round' and gluing it to the syringe.

You don't get much product for the money - bonding that skeg control box took a full dispenser of Devcon Plastic welder. Still, it's a job I want to last, so I don't mind the expense if it will do the job.
DSCN3949.JPG
 

chodups

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Nov 2, 2005
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John,
Thank you for the report. This question is always coming up here and on other paddling sites and there is a lot of hemming and hawwing. This is to the point. Good documentation.
 

mick_allen

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May 15, 2005
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you didn't quite say, but I presume the skeg control box you reglued in, was made of hard plastic - and that's why the plastic adhesives were tried.
I have no idea, but do you think that g-flex epoxy would be possible for this also?
 

Astoriadave

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JohnAbercrombie

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Dec 7, 2011
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Location
Victoria, BC
you didn't quite say, but I presume the skeg control box you reglued in, was made of hard plastic - and that's why the plastic adhesives were tried.
I have no idea, but do you think that g-flex epoxy would be possible for this also?
It was the skeg control box on a SKUK Romany, which I think was made by KariTek. I didn't try to ID the (black) plastic, but my guess would be ABS.
The reason I used methacrylate adhesive was because I thought that was what had been used originally, and bewcause it would set quickly enough that I could just hold the control box in position without worrying about clamping/movement.

The boat was in a mishap which popped the seam at the skeg control box. The control box was ripped away from the hull/deck - the box was aligned with the seam tape. When I looked at the adhesive, and ground it away from the control box, it didn't seem like epoxy in consistency or smell, and the squeeze-out didn't look like epoxy either - hard to describe. But it may have been epoxy or even a urethane.
Methacrylate would be excellent in a factory situation because it sets so quickly.
Whatever adhesive it was, it had excellent adhesion to the gelcoat, which it tore away from the underlying (mat) laminate.

G-Flex or even regular epoxy would probably have worked well for that job. I was very impressed by the aggressive bond of the methacrylate in the little test I did, so I was happy to use that. It would also be worth considering for inclusion in a (biggish) repair kit on a trip, because it cures so readily.

I have used thickened epoxy to bond ABS hatch rims successfully to epoxy glass, in spite of assurances from KajakSport that it doesn't work. :)
Off topic:The first and only time I tried the recommended procedure from KS (Sika Primer + Sikaflex) the hatch rim popped off after a year or so - luckily at the take-out.
 
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