On Mon, 22 Mar 2010 10:28:16 -0400, I am Tosk
wrote:

In article b949f95b-c2cb-481f-a1db-079c341bb469@
15g2000yqi.googlegroups.com, says...


This is what led me to ask if the same was true for UV cured
polyesters.

So, I am now led to ask if he was correct.

And now we have come full circle.

Sorry to have taken your thread off on a tangent Hopefully you can get
your answers now that my curiosity has been satisfied

Scotty

I never worked with the uv part. I also haven't worked with these
resins. I did work with people dealing with them in r&d. Polyester
and vinyl ester resins cure by a completely different mechanism, a
free radical chain polymerization. The reactive diluent is styrene
monomer. The reaction is inhibited by oxygen, hence the wax to exclude
air from the surface, or the use of film for vacuum bagging and resin
infusion molding.

This type of reaction is not nearly as dependent on stoichiometry
(ratio of reactants). The initiator and catalyst are all about
providing free radicals to start the polymerization. UV does the same
thing. The concentration of reactive diluent will affect final
properties. Polystyrene ain't that strong.

To the original two questions:

1. styrene monomer will dissolve polystyrene foam like there's no
tomorrow.

2. Don't know. My guess is the initial free radicals generated will
initiate the reaction, the reaction generates further free radicals,
so the parts should cure eventually. I don't know the effect of a
light blocker like carbon fiber, but the stuff would have no
commercial value if at least some useful depth wouldn't cure.

For my fishing boat, I found one using vinyl ester. It's a hell of a
lot stronger and more chemically resistant than polyester. If I build
a boat (would like to, that's why I read this group), I think it'll be
plywood and epoxy. Also, if you're interested in advanced composites,
make sure the resin you use is recommended for the reinforcement. I
recall a rubber modified vinyl ester as being the very best at wetting
Kevlar.

Good luck.

Pete Keillor