Polyester vs. Epoxy resin

Ok, this one is for your fiberglass guys. I by all mean am no expert at fiberglass like I am with metal, so I need some help. Talking to my uncle who is like a fiberglass guru he told me not to get Polyester Resin, and get epoxy resin.

Its for a school project...Im not spending a ton of cash on Epoxy Resin for school, nor can I get it anywhere around here and dont have time to order it. I just wanted to use some of the Bondo Fiberglass/Polyester Resin.

So whats the difference besides price/availability? Could I use it for a school project and it come out ok?

Look here...
http://www.shopmaninc.com/resins.html
I would imagine the hardware store resin will work fine for your project. I use it for a lot of automotive applications will no problems...
Mark

Polyester resin is the cheepest, most redaly available resin you can get, It works great with all types of fiberlass. If your planning on using fiberglass matt you have to use polyester resin because it uses a polyester soluable binder and wont work with epoxy. Epoxy resins are essentually stronger but are more expensive, harder to find, and have a more limited shelf life. For most everything I do (including cosmetic carbon work) I use polyester resin. That Bondo brand is accually very decent for the price and availability, hell its what I learned with. I would use it and not bother with the epoxy resin.

^^ amen.... Epoxy is stronger and after it cures it is slightly lighter...but it cost more... the only thing i dont like about polyester resin is that it eats away at a lot of things that you can use to make forms, styrene foams, plastics, etc... where as, for the most part, epoxy doesnt. The bondo stuff you get at home depot is good, it is what i started out with and, unless i am doing a project that needs extra strength, it is what i use most of the time.
Epoxy should be avalable from home deopt and lowes in smalle quantities, but it is bonding epoxy, and it can be used for glassing, but it isnt the best thing and you would be better of just using polyester....

Got to jump in here...newbie to your forum so bear with me. I feel that I need to start with a basic concept here. Epoxy resin is an adhesive...glue if you will. It will saturate most all glass materials (mat and woven cloth) and provides great strength to weight ratio. I prefer West System epoxy, the only drawback to MOST epoxies, NO UV PROTECTION (sunlight will kill it back down to the upper level of glass strands.) Polyester resin was formulated for strength when applied with a glass strand substrate. And, the thicker you can make it the stronger it is. West system cleans up with regular ol' white vinegar...beats the thunder out of acetone or lacquer thinner. Cost is a little high, about 100$ for a gallon and a quart. Use the polyester resin for all the rough work for all the parts you want to make??? then attach them to the metal parts with the epoxy, if you have ever tried to fiberglass something to sheetmetal, the more it flexes...well there ya have it. I have been using both for a bunch of years, no real expert, but have a good deal of field experience. let me know if this helps???
gonzo

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