Polyester resin is a solution of polyester polymers dissolved in styrene.
Polymer molecules are long strings of atoms. When a small amount of a
catalyst like Methyl Ethyl ketone peroxide is added the
it starts a reaction that makes the styrene molecules attach to the sides of
the polyester molecules linking them together in a 3 dimensional matrix.

for example uncured polyester molecules look like this:

A---B---A---B---A---B---A---B

It reacts with the styrene like this:

A---B---A---B---A---B---A---B A---B---A---B---A---B---A---B
| | | |
| | |
S S S S S
S S
| | | |
| | |
A---B---A---B---A---B---A---B A---B---A---B---A---B---A---B

I am no chemist but as I understand it oxygen molecules will loosely bind
with one side of the styrene molecules preventing the double bond. The
styrene molecule prefers the polyester molecule and eventually cast off the
oxygen in favor of the polyester but the process is slowed.

You want those cross linked molecules between coats so that you get a solid
matrix. If the surface is fully cured because a wax film prevents oxygen
getting to it there will be no free styrene molecules for the next layer to
link up to. The new coat will only be mechanically bonded by hooking into
the nooks and crannies on the surface of the cured coat.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

wrote in message
ups.com...
ah ha. Completey different explanation from the first posters.
What does the styrene do? Is it just a functional group of the
polyester? You seem to have taken ochem, perhaps if you care to you
could email me the mechanics and all. I suppose I could look it up but
that would be bothersome.