Polyester Resin

joe7670 · #1 12-31-2010, 01:27 PM

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?

phatdaddy · #2 12-31-2010, 01:46 PM

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.

tsubaki · #3 12-31-2010, 02:22 PM

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.

dboyd351 · #4 12-31-2010, 06:09 PM

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

bigshrimpin · #5 01-02-2011, 12:52 PM

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.

ssiredfish · #6 01-03-2011, 12:23 PM

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

joe7670 · #7 01-03-2011, 01:52 PM

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.

ssiredfish · #8 01-03-2011, 02:19 PM

Quote:

Originally Posted by joe7670

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.

Is that pre-packaged(what brand) or did someone pour you out a gallon?

joe7670 · #9 01-03-2011, 03:32 PM

Pre-packaged at RiverMarine. I'll have to check the brand, but they sell a lot of stuff and turnover on their resin seems pretty good so it's not old.
A lot of locals shop there.

http://www.rivermarinesupply.com/

Skools Out · #10 01-03-2011, 05:50 PM

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.