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Why epoxy over polyester resins? - 12/14/2002 7:24:47 PM   
imp pwr online


 

Posts: 19
Joined: 12/4/2002
From: Baltimore MD
Status: offline 		I have used polyester a few times...Man does that stuff stink up the whole house...For hours.....

What are all the positives and negatives of Polyester?

What are all the positives and negatives of Epoxy?


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Why epoxy over polyester resins? - 12/14/2002 8:06:19 PM   
jettstarblue



Posts: 3199
Joined: 10/5/2002
From: Ashtabula county, OH, USA
Status: offline 		Polyester melts foam, smells real bad, but is cheap, and faster curing. You can also adjust the ratio of resin to hardener somewhat. Buy it at the K-mart.
Epoxy is foam safe, and much more user friendly-still use ventilation whenever possible. There are cure times of 1 min. to 2 Hrs., so "open time" is more adjustable.
You CAN get relatively inexpensive epoxy-Evercoat Everfix epoxy, No. 100643 available at Lowe's or Home Depot . 32 oz. total for about 15.00 bucks, and works great!!!!!

Jetts

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Evercoat epoxy - 12/15/2002 4:13:07 PM   
djmrozinski


 

Posts: 7
Joined: 10/23/2002
From: Essexville, MI,
Status: offline 		I have seen the evercoat epoxy at Home Depot. Sounds like you have had good experience with the product. It sure is a lot cheaper than West System, etc. Are there other inexpensive epoxy products out there with a proven track record. Can you give some more detail on the Evercoat product. Viscosity, etc.

Thanks
Dave Mrozinski

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       Post #: 3

Why epoxy over polyester resins? - 12/15/2002 7:06:46 PM   
Ed Smith


 

Posts: 2834
Joined: 12/29/2001
From: Brantford, ON, CANADA
Status: offline 		There are not many positives with Polyester. I can think of only a couple. Cheap, If you are in a hurry you add more hardener for a faster cure, it can be purchased almost anywhere.

Negatives.
The hardener should not be allowed in the house. One small amount in your eyes and you will lose eyesight. It cannot be washed out quickly enough, it is over!

The smell will last for weeks not hours.

It attacks a lot of materials other than foam, some paints especially.

You can never determine exactly what you are buying or who makes it. The product sold in a lot of the hardware and automotive stores has a preserver in it to extend the shelf life. Have you ever purchased a can and it has all of that gunk around the neck? Have you noticed it seems to come in a variety of colours? What is this stuff?

It will not cure over some materials, or glues.

when making molds or molded parts it will shrink and warp.

I stopped using it years ago and I will never use it again. It is smelly, inconsistent, inconvenient and dangerous.

-----------------------------------
Epoxy positives:-
Does not smell.

does not attack materials foam or paint.

Stronger for molded parts, does not shrink like polyester.
When mixed properly it will always cure.

It is far more consistent. Fewer "house" brands. more product information available from the manufacturer

Is multi purpose. I use it for mold and part making, glue for wing skins, filler with microballons and as a finishing resin. I use the same brand for all.

Negatives:-

about twice the price of polyester.

Not as readily available as polyester. However there are good sources of supply around.

More sensitive to mixing. Cure rate cannot be changed by adding more or less hardener. Different hardeners are required for different cure rates.
________________________

There are several good quality epoxies available for our use. They may have slightly different characteristics but they are all good.

Since I started using a good quality brand all of my resin problems stopped.

Ed S

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       Post #: 4

Epoxy - 12/16/2002 1:52:06 AM   
jettstarblue



Posts: 3199
Joined: 10/5/2002
From: Ashtabula county, OH, USA
Status: offline 		Dave,
The Evercoat epoxy is a medium viscosity, clear, two part (50/50) epoxy. It is slightly thinner than general purpose hobby epoxy, though not so thin as to be problematic. If I need it to be thicker, I add flox, or micro. T-88 is another good alternative, available from Spruce Specialties, Wicks, and other aircraft supply houses. It's around 22.00 bucks for a quart kit, is amber in color, and is fairly thick when mixed, it will barely run down a vertical surface. It is THE BEST as far as I've found, and is a "structural epoxy", used in homebuilts for wood, foam, ect.
I have used the Evercoat thinned as well, with no problems, good for all around hobby applications.
I will also add, that the Evercoat "sets up" to a gel in about 15 minutes, but can be worked for about 10 to 15 more before it takes a permanent set. Very handy as it give a little "warning".

Jetts

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       Post #: 5

Why epoxy over polyester resins? - 12/16/2002 4:41:37 AM   
Ollie


 

Posts: 958
Joined: 12/8/2001
From: Punta Gorda, FL
Status: offline 		Polyester resin is not as good a strain match for glass fiber as epoxy. As a glass-polyester composite is put under load the glass will only have reached about half its ultimate strain when the polyester begins to fail. Epoxy allows the glass fibers to realize there full structural potential without the epoxy failing. Vinylester resins, whose chemistry is similar to polyester, is structurally efficient like epoxy.

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Regards, Ollie

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       Post #: 6

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