Hi Ted,

As for any filler, 3 things are critical for its use:

- No chemical interaction with the resin: Will insure that either the
filler or the resin are affected by the other materials and chemicals in
play.

- Good wetability: the filler has to mix with the resin. It must be
wetted easily by the resin. An appropriate surface treatment can be done
if the material itself is not wetable enough.

- Good adhesion with the resin: For obvious strength reasons. Goes not
together with the wetability, so you can create a weak bond if the resin
adhesion with the filler is lost during cure.

The best way is to check if cellulose (cotton is about 100% cellulose)
is affected by the vinyl-ester chemicals, then test if the mix is good
and if the cured resistance is Ok... Then you can probably use it.

From a materials science engineer

Luc