Epoxy and Mat

[jameskb2]

Re: Epoxy and Mat

It's not the type of mat, the weave as you understand it. It's the process of how it's made. Since mat is composed of compounds to hold it's shape, a glue if you will, some of it is not compatible with either poly or poxy.

However, most is compatible with both.

Just be sure when you order the type you desire, whether mat, roving, cloth or biax, that it's compatible with the resin type you are using. It has nothing to do with strand orientation, again, it's the glue used when creating the fabric.

 

[ondarvr]

Re: Epoxy and Mat

I don't think anybody said epoxy takes the place of mat in a laminate schedule, they said you don't need to use mat with epoxy, you can use it, but it's not needed.

Other types of glass add more strength for less weight, so mat doesn't get used that often with epoxy.

 

[BillP]

Re: Epoxy and Mat

I don't think anybody said epoxy takes the place of mat in a laminate schedule, they said you don't need to use mat with epoxy, you can use it, but it's not needed.

Other types of glass add more strength for less weight, so mat doesn't get used that often with epoxy.

Can you be more specific and give some examples of professionals who do boat stringer re-work and don't use mat with epoxy? The vacuum bag, high tech, carbon fiber, composite sandwich crowd certainly isn't a good example for what is needed in backyard boat projects.

bp

 

[i386]

Re: Epoxy and Mat

I knew that mat was held together with an adhesive (called a binder) that dissolved when the resin came in contact with it. What I didn't know was that polyester contains the chemical (styrene) that breaks down the binder. This chemical is not present in epoxy. So based on that I will have to assume that epoxy will wet out mat, it just won't behave the same way as when wetted out with polyester resin. Therefore it may not easily form itself to shapes like it does when used with polyester and should be treated more like using cloth (Meaning make fillets if you're doing a lamination at a 90 degree angle for example).

Also since epoxy resin has "gap filling" properties (whereas polyester resin does not behave this way) it is not necessary to lay down a layer of mat between layers of cloth or roving.

Have I got it now?

 

[ondarvr]

Re: Epoxy and Mat

i386

I think you just nailed it.

 

[erikgreen]

Re: Epoxy and Mat

Well... "it depends".

Even though mat isn't needed with epoxy for adhesion, some people do use it as a cheap way to build up thickness of glass. Like if you have a large area to build up and strength isn't the primary need. Like playground equipment, or cosmetic parts of a boat, or a car.

So there are mats that are made with a binder that will dissolve in epoxy. I think actually the bondo mat sold in most home stores will work that way. I know when I used it with my US Composites epoxy it practically flew apart. I pretty much used it because I had it, and figured it wouldn't hurt

Erik

 

[ondarvr]

Re: Epoxy and Mat

Mat can vary a great deal, even the same type and even from the same roll.
Depending on the type of binder and how evenly it gets dispersed, you can get a very fuzzy roll that almost falls apart, or a very stiff material that resin has a difficult time wetting out, but they're both designed for polyester. I doubt the product you bought was an epoxy compaitable product, just one with less binder, and regular mat can be used at times with few issues with epoxy, it just depends on what that roll happens to be like. Some fiberglass is made in the US, but the majority of it now comes from China, the Chinese product is getting better, but there were many issue for quite a few years.

One thing to remember, is that what you buy retail from a company may change at any time without notice, they (company name on the container) don't make the resin, gel coat, glass, catalyst, or other items they may market. They buy it, then repakage it in to smaller quantities to sell to DIY'rs, their buying decision is frequently base on price, so it can change at any time.

 

[erikgreen]

Re: Epoxy and Mat

Oy... so, basically then, try to see the actual product outside the package before I buy, and don't trust it until I've tried it out?

And here I thought I was getting sorta good at this fiberglass stuff

 

[BillP]

Re: Epoxy and Mat

Thinking mat can be left out of a lamination schedule with epoxy because it "gap fills" and prevents laminate peel or "print though" is only a small piece of the engineering equation. The structural component of mat shouldn't be played down like it has nothing to offer but "cheap fill" material...that's a flawed perception. Thinking it's "not necessary" to use mat if you don't need stiffness is more accurate.

Non structural Fabmat type materials are used when "cheap fill" is needed and many high end and custom built boats use it. If only standard woven cloth (no high tech carbon veil stuff,etc) is used with epoxy the lamination will be thicker and heavier to get the same stiffness as a combination using mat. The all woven lamination will be stronger and heavier (and flex more before ultimately breaking) than needed just to get the required stiffness. Epoxy resin is also more flexible than polyester resin and compounds flex issues in comparison. This is another reason why biaxial has mat. Even the most expensive high tech (composite sandwich with epoxy) boats use mat or $high tech graphite/carbons$ as a structural component. Nobody in the boat building industry glasses stringers, transoms, builkheads, etc without mat...it just doesn't happen because it produces heavy tubs. The bottom line is use mat in the lamination if you want the best (engineering wise) layup for strength and stiffness with less weight.

bp