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Old Jan 01, 2010, 01:03 AM
Slope Stud
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Polyester glass different from Epoxy glass

I got some free glass and I was told there is a difference between glass made for polyester resin and glass made for epoxy resins...

I didn't know that.

How do you tell the difference???

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Old Jan 01, 2010, 01:51 AM
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Polyester glass has a chemical in it which makes the resin wet the mat out better. I've only struck this with Chopped Strand mat. In my experience any woven cloth should be good with either Poly or Epxoy.
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Old Jan 01, 2010, 07:06 AM
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Actually chopped strand mat is made for polyester resin. The binder used to hold it together will solubilize/wet out with ester resins (polyester or vinyl ester) but not with epoxy. So you need a special mat for epoxy.

But cloths are typically all the same.

BTW the binder used in chopped strand mat is typically starch.
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Old Jan 01, 2010, 07:15 AM
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Interesting!
are we saying chopped strand should not be used with epoxy?
Iain
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Old Jan 01, 2010, 08:08 AM
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Hi
I was always taught to keep chopped strand mat (csm) for use with polyester resins and wovens with epoxy due to the binder in it as stated in the other post.

cheers

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Old Jan 01, 2010, 10:31 AM
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Some mats do work with epoxy and polyester as well as vinylester.

Most chopped strand mats, however, work only with polyester and will not make a good chemical bond with epoxy.

Cloths always have a "finish" or "sizing". The purpose of the finish is to promote the bond between the fibers and the matrix, thus stabilizing the composite.

"Volan", the most common finish in fiberglass cloth, is compatible with epoxy, as well as polyester and vinylester. "Silane" finish is usually found in S-2 glass cloth, and compatible with epoxy. The last finish is F-16 finish.
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Old Jan 01, 2010, 10:37 AM
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That's great..

I got 2 huge rolls of fiberglass and now it looks like I will be able to use them..

Stuff I got for FREE today....

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Old Jan 01, 2010, 10:52 AM
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Hi Oran, have you any idea what the weaves are?

The second looks like a stitched double bias.

If they are 40oz cloths, then they are bound to be stitched with at least two layers

-Alex
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Old Jan 03, 2010, 01:52 PM
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I'll guess at the bottom cloth being a biaxial too but the top one reminds me of a uni-directional roll?
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Old Jan 03, 2010, 03:10 PM
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Be careful, if you need to go around some complex shapes, the epoxy won't disolve the binder in glass that's supposed to be used with poly. So it ends up being a bear to work with. I've used that stuff with epoxy plenty of times to build mold thickness, but best suited for flat projects.
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