On Sun, 21 Mar 2010 12:10:58 -0400,
wrote:

In article , keillorp135
says...

On Tue, 16 Mar 2010 13:42:41 -0400, Paul Oman
wrote:

wrote:
On Mar 14, 12:31 pm, Paul Oman wrote:

wrote:

Two questions for people with knowledge or experience with the UV
curing polyester resins:

1) Are they (any of them) compatible with polystyrene foam?

2) Once the UV light has initiated the polymerization, will it spread
through the layup even into places where the light did not
penetrate? I'm thinking, for instance about the underside
of carbon fiber cloth.

Thanks.

--

FF

it makes more sense to use thermo set epoxies. Stronger, better bond,
probably cheaper.
epoxies will not dissolve foam


Thermo set meaning that they don't begin to cure until they are
heated?
I ask because I am looking for a very long working time.

If so, do you have a recommendation?

Otherwise, can you answer the first question? I was quite aware of
the
other issues.

----------------------
thermo set means a chemical reaction between parts a and b and these
reactions produce heat. This is how epoxies work. You can get slow
epoxy curing agents and you can also slow down the reaction by working
in cooler temps.

paul oman - progressive epoxy polymers inc

More importantly, it means crosslinks between molecules, as when parts
a and b or their reaction intermediates have more than two reaction

That's a bit beyond my area of expertise, but are you saying Epoxy that
is mixed more perfectly, has more heat resistance? At least that is what
I am getting from your post.

Scotty

I was just saying that "thermoset" refers to a crosslinked resin,
which epoxy may or may not result in, depending on the hardener.
Actually, epoxy is a reactant, there ain't any left in the finished
product. Most epoxies are dgeba (diglycidyl ether of bisphenol A)
with various oligomer mixes left in. Commonly reacted with various
high functional amines to make thermosets. I also reacted epoxies
with difunctional amines and various difunctional organic acids to
make a bunch of different thermoplastics.

Heat resistance is partially related to crosslink density (affects Tg)
but more related to the backbone molecule. Bisphenol A based resins
generally had a Tg around 100 C. Novolac and resorcinol based resins,
etc. could be higher. All of it gives up under enough heat to destroy
the chemical bonds in the backbone. That's why I used fluidized bed
burnouts to clean dies and stuff. Nothing I made would stand 900 C.

None of this is important to boat building. The very high temp resins
are way too expensive, and were developed primarily for use in
aerospace. Garden variety epoxy has plenty of temperature capability
for boats.

Getting the mix right does directly affect crosslink density, and is
important in developing the correct properties of the resulting resin
matrix.