Re: Working with Epoxy (Peanut Butter)
Polyesters typically make better, more workable putties than epoxies and VE's do, they just aren't very strong. Cutting up mat works OK, but buying milled fibers works better. Since with polyester the resin needs to break down the binders in mat, and epoxy won't break the binders down much, if at all, there may be some stiff fibers in mat that won't easily conform to the shape needed. Milled fibers can be purchased in many different lengths for the specific need and have no binder. In the work place I normally buy milled fibers, on home projects I?ll frequently use cut up, or pulled apart mat just because I have it handy.
The binders have nothing to do with holding the resin (of either type) in the glass, it only holds the mat together until the styrene in polyester resin breaks it down and lets the fibers easily conform to the surface profile.
Epoxy compatible mat is stitched (no binders) to hold it in place, just like on products like 1708. While some types of normal mat will sort of work with epoxy and it will get used in some situations, its not designed for that purpose.
Resin draining out can be due to many things. Polyester is the most forgiving and can be formulated for virtually no draining, VE and epoxies aren?t as forgiving and tend to drain out of the glass easier, with slow cure formulas this can be can be even more of a problem. Roving, cloth and biax have a much tougher time holding resin than mat does, so the mat on 1708 makes it much easier to use and not experience drain out.
I know , when I get started I tend to over explain things.
