polyester or epoxy

[Eric]

What is the best way to repair te polyester parts?
Polyester or epoxy resin?

eric hendriks

[akarmy]

What is the best way to repair te polyester parts?
Polyester or epoxy resin?

eric hendriks

I always heard that Polyester sticks to Polyester, Epoxy sticks to either.

[FoxDB]

Definitely Polyester for Polyester.

[szicree]

There is no problem at all with using epoxy over prepped polyester. It's done all the time in boat repair. The only good thing about polyester resin is that it's cheap. Epoxy is more flexible, more dimensionally stable, stronger bond, etc.

[HighWing]

I have always used epoxy. I just checked the place I get my resins for some data and this is their heading over their epoxy page.

"Epoxy Resins

Our epoxy resin is a better adhesive and forms a superior bond to polyester and many other fiberglass materials. TAP epoxy resins has no significant shrinkage during cure."

My reasons for using epoxy: It will cure with a hard sandable surface because there is no oxygen inhibited uncured surface layer as with polyester. You won't need two types of resin - the lay-up resin which will not surface cure; then the surfacing resin that has the wax that rises to the surface to protect the surface layer from air for a hard surface cure. The wax layer also has to be sanded away before painting and before modifying the part. I use a flap disk that fits in a 4-1/2 inch angle grinder. With epoxy, it is also easy to make a "micro" batch as a light weight bondo like filler which sands very easily. Just add approximately 1/5 by weight microballoons.

It cures more slowly which in some instances is a good thing - the "micro", but in the winter, it can take two days for a good cure in my hangar. I made a curing oven made with one inch foam construction insulation and clear strapping tape that is heated by a single low voltage desk lamp incandescent bulb. This bulb keeps the oven at 106°. This makes for a good 3-4 hour cure and because of the low temps, I don't worry about keeping it powered up overnight to cure a late evening layup
Lowell.

[flybymike]

Definitely polyester to polyester, although vinyl ester is far superior to polyester. So, I would use the vinyl ester to repair polyester.
Epoxy uses a physical bond so it only sticks as well as your sanding or surface preperation.
Poly / vinyl esters have a chemical bond which means the new resin being applied actually eats into the previous application.

[jrevens]

I believe that is incorrect. Once the polyester resin is fully cured, additional application is strictly a mechanical bond, for all practical purposes. It will be inferior to epoxy in every way but cost of material. Please check out the following articles - just 2 of many available on the subject.:

http://www.boatus.com/boattech/TipResins.htm

http://www.westsystem.com/ss/west-system-epoxy-for-fiberglass-repair/

I would definitely use epoxy for repair whenever possible.


Definitely polyester to polyester, although vinyl ester is far superior to polyester. So, I would use the vinyl ester to repair polyester.
Epoxy uses a physical bond so it only sticks as well as your sanding or surface preperation.
Poly / vinyl esters have a chemical bond which means the new resin being applied actually eats into the previous application.