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Old 07-23-2008, 10:57 AM
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Default Difference between Resins?

What is the difference between epoxy resin, polyester resin, vinylester resin. What is the best use for each? Thanks in advance.
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Old 07-23-2008, 11:57 AM
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Default Re: Difference between Resins?

Just My Opinion.
Epoxy is the best. It bonds better to wood so it is best to use for transom repairs and stringer repairs. It is the best to use for anything structual. It also has the strongest secondary bonding of the three. It is the most expensive though. (If you plan on using fiberglass mat you need to make sure the epoxy you get will work with the mat you get. Not all epoxy will break the bonds in some mat.)

Polyester is the cheapest. It is brittle compared to epoxy. It will work with any mats though. The working times of the resins are almost always shorter then epoxy, and it is hard to predict how much you need. I always would waste some when I started to learn how to fiberglass.

Never used Vinylester but i hear it is in the middle.

What I did on my Boat Project was to use the Epoxy for all structual areas. (transom, stringers and fillets) and polyester for any thing else.
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Old 07-23-2008, 12:06 PM
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Default Re: Difference between Resins?

Are you talking for repair or in construction of a boat? Vinylester is superior in contruction of a hull and is the most expensive.
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Old 07-23-2008, 12:12 PM
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Default Re: Difference between Resins?

Just talking overall. I really am not doing anything that is structural but plan on some fiberglassing because I want to learn how to fiberglass and secondly I want to make some things for my boat that I cannot buy. I was comparing the prices and just don't want to get something that is cheap and will not last.
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Old 07-23-2008, 12:16 PM
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Default Re: Difference between Resins?

I believe gel coat will not adhere to epoxy but I am not a fiberglass guy....
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Old 07-23-2008, 12:42 PM
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Default Re: Difference between Resins?

Actually, gel coat will stick to epoxy just fine. Epoxy is an easier material to work with for patching and minor repairs than dealing with either polyester or vinylester. But epoxy usually has what is known as an aniline blush caused by a very thin layer of wax coming to the surface to seal it from the air, which promotes hardening. That wax film must be removed before applying anything to the epoxy, be it more epoxy, paint or gelcoat. As others have noted, epoxy is not suitable for sun or UV exposure because it turns yellow very quickly. If you don't remove the wax, nothing will bond to it properly.

Vinylester has excellent moisture barrier properties and resists blistering, which is why you'd like to always see at least layer of it under the gelcoat of any boat.
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Old 07-23-2008, 12:43 PM
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Default Re: Difference between Resins?

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Mr. Demeanor - 7/23/2008 12:16 PM I believe gel coat will not adhere to epoxy but I am not a fiberglass guy....
True to most epoxy resin, due to Amine blush.

It isn't impossible to gel coat, but a lot more work. You have to wet sand it with water to get the blush off. A lot harder than it sounds cause there is really no way to know if the blush is gone till you've applied gel coat and it doesn't dry around that area.

Certain epoxy companies make amine blush free epoxy that accepts gel coat with out any extra prep.

Mas brand epoxies are all blush free.



Here's a console rebuild I did for my 23' copntender. I used Mas epoxy for the main part, but used a west system epoxy to "glue" it into place. I had a hell of a time getting gel coat to adhere and dry on those areas around the edges where the WestSystem epoxy squeezed out..



Here's a shot with gel coat on and a layer of mold release...
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Old 07-23-2008, 01:10 PM
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Default Re: Difference between Resins?

Gel coat will not cure when placed over(most) epoxy resins.
Also, polyster resin will not cure over epoxy reins or fillers,however epoxy will cure over polyesters.
There are a couple of epoxy resins that can be supposedly used under a polyester gel coat.System three makes one,but it's best not to try and use a polyester product over an epoxy.

Epoxy resins are very strong,and flexible,and as mentioned will give a better secondary bond to the substrate that you're going over.They are also much more expensive,They have no odor like polyester and vinylester,so you can apply them in closed spaces.They don't wet out mat and it's more work to wet out any cloth. with epoxy.
If you're repairing some crucial high stress area where absolute ultimate strength is required,then epoxy is probably your best bet.

For almost any other repair or build,polyester or vinylester resins are more than adequete.There are virtually no commercial mass produced boat manufacturers building hulls with epoxy.
Look at the damage to any fiberglass boat hull built with polyester or vinylester resin,and you will see that it's never the resin system that failed,but almost always sheer force from impact,or poor quality workmanship.

Another issue,is the quality of the resin that you use,high end high quality polyester resin will give you great results,but cheap boatyard junk resin will not.

I would say that almost any repair can be made soundly and incredibly strong with polyester resin,vinylester offers a little better water resistence,and is a bit better in bonding.Why use epoxy,if you don't have too.It would be like building a bird house with 2x4's when 1x2's would work great,and last for years.

In the end,they're all very good resins,and each will excell when used properly,and in the right applications.

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Old 07-23-2008, 01:15 PM
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Default Re: Difference between Resins?

Chances are your boat was not made with epoxy, so dont wast your time with it. It's strong, but more expensive.
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Old 07-23-2008, 01:19 PM
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Default Re: Difference between Resins?

Great info. I too - would eventually like to modify the helm a little bit.
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Old 07-23-2008, 02:58 PM
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Default RE: Difference between Resins?

Thanks for the all the comments. Naturally you would think the more it cost the better it is. I know the epoxies cost more and figured it was better. But it sounds like polyester on vinylester is the way to go for me. Now can any one reccomend what brand is the most affordable (and good quality) in a 5 gallon quantity. I don't want to waste time with cheap stuff that wont work, but since I have no experience I would love a heads up on what to use. Secondly after the fiberglass is laid then tha gel-coat is appied over it? What tools are used to apply gel-coat. And what name brand gel-coat should I be lookg for? Thanks again for the many replies.
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Old 07-23-2008, 04:26 PM
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Default Re: Difference between Resins?

For the most part, when repairing a polyester resin built boat, it should be repaired with "like" materials, in other words, not epoxy. Nothing beats the secondary bonding characteristics of vinylester.
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Old 07-23-2008, 04:35 PM
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Default Re: Difference between Resins?

Epoxy is the stronguest, chemically neutral (non toxic i.e. live well), water proof but UV sensible
Polyester is just at the opposite;
Vinyl ester in the middle, but I do not know re. UV.

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Old 07-23-2008, 06:16 PM
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Default Re: Difference between Resins?

Quote:
big easy - 7/23/2008 11:10 AM

Gel coat will not cure when placed over(most) epoxy resins.
I don't think gel coat cares a lot what it is place over in terms of it curing. If it is properly catalyzed and sealed from the atmosphere, it should harden, no matter what. I've had great luck putting it over epoxy.

As to the question of it not sticking to epoxy, the folks that make the West System epoxy might disagree.

Here's the direct quote form section 2.2 of their manual on fiberglass boat repair and maintenance:
"In answer to questions concerning compatibility and techniques for applying polyester gelcoats over repair made with West System epoxy, we can say epoxy provides and excellent base for polyester gelcoats". They do go on to say "Wash the surface thoroughly to remove any traces of amine blush.

You'll find it on page 7 of the book in Paragraph 2.2.1.
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Old 07-23-2008, 06:48 PM
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Default Re: Difference between Resins?

Quote:
DarthBaiter - 7/23/2008 12:43 PM



Quote:
Mr. Demeanor - 7/23/2008 12:16 PM I believe gel coat will not adhere to epoxy but I am not a fiberglass guy....
True to most epoxy resin, due to Amine blush.

It isn't impossible to gel coat, but a lot more work. You have to wet sand it with water to get the blush off. A lot harder than it sounds cause there is really no way to know if the blush is gone till you've applied gel coat and it doesn't dry around that area.

Certain epoxy companies make amine blush free epoxy that accepts gel coat with out any extra prep.

Mas brand epoxies are all blush free.



Here's a console rebuild I did for my 23' copntender. I used Mas epoxy for the main part, but used a west system epoxy to "glue" it into place. I had a hell of a time getting gel coat to adhere and dry on those areas around the edges where the WestSystem epoxy squeezed out..



Here's a shot with gel coat on and a layer of mold release...
All you need to do is scrub it away with a brush and soap and water.....best not to sand it. Easiest way is to apply nest step before completely cured....then there is no blush
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Old 07-24-2008, 04:59 AM
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Default RE: Difference between Resins?

I know that gel coat will cure over certain epoxies,but as a whole, my experience has been that over regular epoxy resin,gel coat doesn't cure properly.

I just finishied a transom and bile/engine bed replacement on a classic 74 Seacraft,and gelcoated the whole area with a high quality Ferro isothalic gel coat.
In the areas where i used a bit of epoxy,the gel coat did not cure properly.
The epoxy resin used was System Three general purpose epoxy resin

System Three makes a blush free resin(SB-112) that can be used under polyester,or isothalic resins and gel coats.
The same applies to most high quality epoxy manufacturers.

Maybe i should have stated that more clearly.I just feel that for someone without a lot of experience in resins and glasswork,it's very easy to get themselves in a mess. if they use the wrong combinations of materials.

I've done several restorations,and have used several brands of resins like West Systems,-System Three,-Mas epoxy,and lots of polyesters and vinylesters.
All of them worked great for their intended purpose,but i also knew which products worked best with each other.

I've had very good luck with resin and glass supplies from www.mertons.com
nice guy very knowledgeable,and ships quick,and has tons of stuff.
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Old 07-24-2008, 05:04 AM
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Default RE: Difference between Resins?

Quote:
dolphin233 - 7/23/2008 1:57 PM

What is the difference between epoxy resin, polyester resin, vinylester resin. What is the best use for each? Thanks in advance.
All plastics:
Polyester: +'s: Cheapest; can vary cure time by the amount of catalyst used; most mat and roving designed to be used with polyester
-'s: MEK is smelly/dangerous; not strongest bond on market.

There are two general types of polyester resins: laminating and finishing. Laminating resins do not "fully cure" like finishing which contains a wax that acts as an air-inhibitor which promotes more solid curing. Laminating resin can be user converted to finishing with the addition of the wax.

Vinylester: Polyester-based resin with slightly better bonding and water-proof characteristics of polyester. Jury is still out as to whether the added benefits outweigh the additional costs.

Epoxys: +'s Stronger bond than polyester, more water-proof than polyester
-'s: Cost, must maintain specific ratio of resin to "catalyst" so cannot vary cure time without using a different "catalyst", should use roving/mat designed for epoxy.

All are subject to damage by UV exposure, but epoxy degrades much quicker.

I think on a strength/weight ratio, epoxy is lighter for its strength, therefore its popularity in high end racing boats. Epoxy is more popular in wood boat work because it bonds a little better to wood than do the polyesters.

If using the resin for some type of high wetness/below waterline work, I would go with epoxy. (ie for barrier-coating). If making a deck type fitting (like the helm above) I don't think you would be disappointed with the polyester results.

As far as the bonding characteristics, it is generally accepted that epoxy will bond to polyester, but polyester will not bond well to epoxy. That's not to say that you won't be able to get polyester to stick to epoxy, it just isn't as strong as bonding the other way around without additional preparation to the substrait.

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Old 07-24-2008, 06:11 AM
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Default RE: Difference between Resins?

Chris,

Few corrections on Vinylester.

It is not Polyester based, it is Epoxy based. The epoxy goes through esterification & is dissolved in Styrene.



The jury is not still out on it as it's not a new product it has been around for years and is proven. It is better in many cases for boat construction than epoxy, most epoxies unless post cured at high temps in an oven will not ever reach the barcol hardness and thus it's maximum strength. Epoxy boats that are cooked will not come out of the mold gleaming and beatiful so finish work is needed. Be it fairing & buffing or painting. What I am trying to say is just becuase it is epoxy does not mean it is worth the extra coin, read up on the product before using it.

Vinylester weighs approx 30% less varying blend to blend thany Polyester when used in layup. It is not just the material weight but it has better wet out properties (penetrates the glass better). Vinylester is much stonger in every aspect than Polester the amount again varies here but is quite considerable. Vinlyester can take much more stress before stressing or breaking again this all varies blend to blend.

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Old 07-24-2008, 06:51 AM
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Default RE: Difference between Resins?

Quote:
big easy - 7/24/2008 7:59 AM

I know that gel coat will cure over certain epoxies,but as a whole, my experience has been that over regular epoxy resin,gel coat doesn't cure properly.

I just finishied a transom and bile/engine bed replacement on a classic 74 Seacraft,and gelcoated the whole area with a high quality Ferro isothalic gel coat.
In the areas where i used a bit of epoxy,the gel coat did not cure properly.
The epoxy resin used was System Three general purpose epoxy resin

System Three makes a blush free resin(SB-112) that can be used under polyester,or isothalic resins and gel coats.
The same applies to most high quality epoxy manufacturers.

Maybe i should have stated that more clearly.I just feel that for someone without a lot of experience in resins and glasswork,it's very easy to get themselves in a mess. if they use the wrong combinations of materials.

I've done several restorations,and have used several brands of resins like West Systems,-System Three,-Mas epoxy,and lots of polyesters and vinylesters.
All of them worked great for their intended purpose,but i also knew which products worked best with each other.

I've had very good luck with resin and glass supplies from www.mertons.com
nice guy very knowledgeable,and ships quick,and has tons of stuff.
Thanks for the link. That is actually the site I was looking at with the different resins. I had never heard of them and was unsure about buying from them. This clears up some hesitation. Thanks.
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Old 07-24-2008, 06:57 AM
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Default Re: Difference between Resins?

Thanks for the clarification Nomad. I have to admit, I have not used Vinylester, and have gotten conflicting information regarding its base; I went with similar based to polyester since they are both referred to as "esters".

Can you vary vinylester's cure time by varying catalyst?
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