Fiberglass mat with Epoxy resin?

[KenB]

I agree with shrimp but I think there is some 1708 that is more malleable, which might work with epoxy.

My plan is to coat the back of whatever poly I plan to cover with epoxy first before laying down mat and resin... I think epoxy with less that a few days of cure will bond to fresh resin. (old poly bonds to epoxy, which bonds to new resin... old epoxy will not bond to new resin...right?)

Dumb idea? Only one way to find out!

[McReef]

I realize this is a few months after the question was posed, but I figured I'd report back with what I have learned along the way in case someone else goes searching for answers and finds this thread.

I'd also like to thank those who chimed in earlier for their help.

From what I have seen, both 1708 and 1808 biaxial fabrics from the same manufacturer are both equally compatible with epoxy resins. I would be inclined to think (you should verify this before buying materials for a given job) that most any biaxial, triaxial, or quadraxial stitched fabric would likely share this trait and be compatible with epoxy resin systems (with exceptions)

The key to making sure you get what you want/need in a particular material is to due your homework and know what you are buying. While there are plenty of vendors out there who sell fabric as (for example) "1708 Biaxial Fabric", it should be noted that there are multiple manufacturers of this type of fabric, and it would behoove you to ascertain who it is that supplies your vendor with fabric so that you may investigate their product's suitability for a given purpose.

When it comes to mat, the vast majority of what you encounter for retail sale is indeed likely to contain binders. Those binders, as mentioned by others, render this type of material unsuitable for use with epoxy resins. However, there are mat materials available that do not have this problem, you just need to do your research.

Here are a couple links to manufacturers of fiberglass reinforcement fabrics, you should be able to find just about anything you need there. They also have listings on their sites of where their products may be purchased.

Fiberglass Industries - Biaxial Page

Vectorply - Fabrics Information Page

[shine]

Biaxial glass (with matt) will vary in the amount of binder used depending on the manufacturer. Just be sure the biaxial cloth you buy (if it includes matt) will wet out with epoxy. We use/sell epoxy exclusively and the 1708 we sell will wet out almost transparent, its held together with stitching, no (almost no) binder.

With epoxy laminates, the only reason to use matt tis to build thickness quickly. Matt is not needed for inter-laminate bonding as it is with polyester. Unless I trying to build thickness, i use combination of biax without mat for all my bonding. For instance, 2 layers 12 oz biax is much stronger than 1 layer of 1708, but it uses less epoxy (less overall weight)

I have two different biax for the rebuild of my 23SC transom. you can see the difference in the two. Here are two layers of the good (more stitching, less binder) 1708 overlapping a PVC pipe along the keel.



and here is a layer of 1810 with a lot of binder in it. it is a pain to wet out and I would only use it on simple surfaces and curves, but it does build thickness quickly