Polyester Resin

J

joe7670

Junior Member
OK, so i'm tired of paying a premium for epoxy resin. Now that I think I can work the glass a bit and the epoxy I decided to buy polyester resin.

Any tips on mixing resin and hardener proportions or steps to get right proportion? Is the working time similar to the epoxy?
 
not an expert, by any means, but poly has a lot more variables than epoxy. temp & humidity are big factors, as well as shelf life.
 
The only thing about any stuff needing a catalyst I can tell you is to mix up a small test batch almost immediately prior to doing the actual work.
Around here the temperatures and humidity spike back and forth so quickly it's hard to get any of it just right reading off the directions.
 
I've always heard Vinyl Ester resin is superior to Poly Ester resin for boat building. You might want to consider that because from the prices I'm seeing West System Epoxy is around $300 for 5 gallons, poly ester resin is about $150 and vinyl ester resin is about $170. Big difference between epoxy and the others, not so much between poly and vinyl esters.

(http://www.uscomposites.com/polyesters.html.)

Hope I'm not breaking any rules by posting a link. Vinyl Ester
 
Poly is fantastic and wets out fabric much better than epoxy. With Poly you can also use mat (the glue binder in Fibeglass mat generally doesn't break down when using epoxy). Epoxy bonds better . . . and is less brittle. Both have their strengths . . . if you are wetting out large areas or doing transom job Poly is fine. If you are making parts in a mold . . . Poly is the ONLY way to go. patching holes under the waterline . . . I'd chose epoxy.

The only other time I'd use epoxy is when smell factor is an issue (working inside or in residential neighborhood with folks close by)

ISO poly was $125/pail when I bought it last year at composites one. Sometimes boat builders will sell you a few pails for $100'ish It's much cheaper when they buy 55gallon drums. Save epoxy for special occasions.
 
I use Poly resin frequently and here are my preferances:
-6 drops of Cat to every OZ of resin
-Hardens best, I think, around 85 deg

You should be able to pick up smaller amounts for much less also. The one I buy is 32oz for around $30
 
Thanks for the input guys. We'll see how it goes. Got 1 gallon for $16 locally. Cuddy should be repaired in a few weeks.
 
make sure what you are working on is at or above 70* hull must be that warm too for a good bond and needs that min temp for couple days afterwards.
 
Hold on given that bit of info, it's in the 70's here but at night 60's. Should I be waiting until later in the season?
 
joe7670 said:
Hold on given that bit of info, it's in the 70's here but at night 60's. Should I be waiting until later in the season?
Click to expand...

Depends on how thick you pour it. At about an inch thick it takes about 3 hours to harden but "overnight" to cure. I have worked on material after 4 hours before with no problems.

I'd be willing to bet if your surface was warm enough in the a.m. and you did your work then, you would be fine by 6pm. If you are worried about it just point a halogen at it. That will produce enough heat to keep it stable and keep it from cracking, clouding or becoming brittle. I use an infrared laser temp. gun to check mine periodically through the curing process.

BUT, doing this in the high 70's to mid-80's produces a much stronger pour, mold, etc.........I always use a lamp when temps are lower than what I want.
 
What resin did you buy?

Joe,
What resin did you get from River Marine for $16/gallon? The only thing I see on there is MAS epoxy resin for $19.95 a QUART and MAS Hardener for $16.95 a PINT. I can't find anything else on their website.:head:
David Boyd
 
They don't sell the poly stuff online. Slight correction it was 16.95 and container says Fiberglass Coatings Inc.
 
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