epoxy vs polyester

[Manureva]

I would like to know why everybody that talks about repairing their fiberglass boat talks about using epoxy? i know it is good stuff but isn't it harder then polyester resin, arn't most boat made of polyester resin from the factory, i know mine is a tin coat of gel coat, then fiberglass mat and polyester resin.

 

[Ross]

Epoxy sticks to old work better than polyester but if you do a good preparation then polyester will do a good job. It is not as forgiving as epoxy.

 

[Manureva]

so it is more sticky for people with less experience? what about the fact that it dry harder then polyester resin, wouldn't that make the repaired area more prone to cracks?

 

[Shoaldrafter]

polyester vs epoxy

so it is more sticky for people with less experience? what about the fact that it dry harder then polyester resin, wouldn't that make the repaired area more prone to cracks?

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Polyester resin is much cheaper than epoxies.

As to flexibility, I have asked same question and not given scientific answer that I can give to you. However, some very high end boats are completely made of epoxy. Some formulations are more flexible than others. See West Flexible formula.

For boats in general it it much more water resistent therefore there are less moisture intrusion issues.

Another medium is vinyl ester which is also water resistent but more toxic requiring strict OSHA and personnel saftey requirements.


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Ed K

 

[monkeybars]

the short answer is whatever repair or mod you are planning you can easily double if not triple the cost by using epoxy.is it better, yes but so is a gold rolex but i dont have one of those either.

 

[Ross]

Actually a gold Rolex doesn't keep time better than a Timex quartz.

 

[Merlin Clark]

25yearslater posted a very good explanation as to why epoxy bonds better on the thread "Painting a blasted hull" in Ask all sailors.
For me, if I were building, I'd worry about cost and go with poly. A gallon kit of epoxy cost a good bit but last me a few years 'cause I don't use much at a time.
Just my 2c.

 

[Barnacle Bill]

Most boats are built with polyester because epoxy is too damned expensive. It depends on the repair you wish to do. For most repairs polyester is just fine and as explained above, it is cheaper. Polyester is safer to use too. Epoxy, if you don't protect yourself can make you sensitized to it after prolonged exposure so that you cannot be in the same room with it. Epoxy has to be very accurately mixed with the catalyst, while polyester isn't so fussy.
If you are doing underwater repairs (parts of boats that are exposed to water and not repairing while swimming) then epoxy is definitely more waterproof. Working with wood or metal? Epoxy has better adhesion. Epoxy is incompatible with gelcoat. If you repair your boat with the idea of gelcoating the repair, it won't take. Polyester is not incompatible with gelcoat (it is also polyester). Epoxy is wonderful stuff, but many people think it is the best thing to use for all repairs. Not necessarily so.

 

[AtlanticAl]

Actually a gold Rolex doesn't keep time better than a Timex quartz.

It does if you get a fake gold rolex, with a quartz movement.

 

[thinwater]

... Polyester is safer to use too.

When polyester resin kicks there can be quite a styrene release. Three guys died in the next plant over because of poor ventilation. Not sensitized, dead. I've not heard of that with epoxy, but it has happend a number of times with polyester resins. Styrene is also a likely carcenogen:http://www.osha.gov/SLTC/styrene/index.html. You can work safely with it, but good precausions are needed.

Also, epoxy boats are virtually imune to blisters, in my expereince. We use epoxy undercoats, right?

I've used both. I like the long-tern epoxy results better.

 

[Chuckbear]

I have been in the marine industry for over 35 years. In all of my years I have never encountered any deaths or ill affects attributed to using any types of resins. I personally have used both epoxy and polyester resins in outdoor and indoor applications for years and on an almost daily bases for years, and as of now at least, I am in excellent health. My exposure is probably a thousand times more than the average boat owner making repairs. Yes proper ventilation is important, as it is with ANY chemical process we use on a boat including but not limited to cleaners, solvents, paints, etc. So whether or not to use epoxy or polyester shouldn't have any bearing on whether or not it will kill you, extremely low odds. The underlying resins and the results of the repair should dictate that. As with any product we use, know the limitation, follow the manufactures recommendations and use common sense. Not all boats are built with polyester resins so If you do not know with absolute confidence then use epoxy. It will adhere to any other resins where some fiberglass resins are not compatible. Chuck