I just got into messing around with UV catalyst in Polyester resins. I had a few questions though. Where have you purchased UV Bulbs and/or ballasts. Any help on a setup would be very much apreciated. As well is the a UV Catalyst for Epoxy resins because other then price cure times seem to be terrible with epoxy. We were using an Epoxy 195 and it was curing in about 6hrs which is way too long but on the other hand the faster curing epoxies are almost twice the price. So as of now I have been using Polyester instead but would rather use epoxy any help with that would also be much apreciated.
the sun is your best source for UV light or you can get the stuff you need from surfsource.net
I don't think they have UV catalyst for epoxy or at least they haven't perfected it yet.
yeah i have done epoxy boards before they just take too long to cure what is the fastest curing epoxy suitable for surfboards available i mean a 6hr cure is just way too long.
It doesn’t exists for epoxy, because epoxy is not a catalyst reaction but a polyaddition.
A catalyst is a product that accelerates the reaction, but comes back out afterwards. (a UV catalyst get’s activated by UV-rays)
With epoxy you have A and B comp wich bind to A+B (that’s also why mixing epoxy correctly is a must, preferably by weight)
This is maybe too much info, but now you have it anyway 
The only way to speed up epoxy curing is by adding heat.
It is wise to only apply moderate heat (up to around 40 degC is safe, but not much higher) until peak exotherm is passed, then you can ramp the heat up more.
Peak exotherm happens around when the resin is seen to “gel”, at the end of the pot life. At low temperatures you don’t get a pronounced “gel” like with poly resin, it just thickens more gradually.
Larger thicknesses of resin gel a lot more abruptly as the heat builds in the large mass more than it does in a thin film.
If you chose the fastest harder available for your resin system, and cured it at a high temp, you could easily get a 3 hour turn-around.
The problems are that the other parts of the surfboard might not be able to handle the high temp, and you get outgassing or even melting.
There’s nothing that matches the speed of UV poly unfortunately.
And the sun is the most powerful source of UV, it takes a suprising about of UV lights to equal its power.
Gotta add that the more heat you put into the system, the more problems you uncover. But if you experiment, there is probably an optimal temp you can find that gives you the shortest turn-around time with manageable side effects.
Keith and I have seen ResinX's Urethane Epoxy harden up in 1/2 hr to an hour over at BammBamm's
If you put it underpressure like in a vac bag or spritz water vapor in the air it'll kick and harden even faster
Doesn't get to hot either
But its kind of spooky stuff if you don't know what you're doing though..
Matt and Mark are good references on the stuff.
Great, clear explaination. I teach it this way:
compostion reaction (polyaddition): A and B are the reactants, and AB is the desired product.
A + B = AB
catalytic reaction: A and B are the reactants, C is the catalyst. AB is the desired product.
A + B + C = (A and B don’t like each other…)
AC + B = (but A likes C, so they hook up.)
ACB = (B doesn’t like A, but digs threesomes, so he gets in the action)
AB + C (C says, “hell no!” and leaves.)
High school teenagers tend to remember that little story.
Greg makes an Accelerator (X55) that works well. In a warm place, with fast hardener, I can flip in a couple of hours. Done it many times. Still a little tacky, but the lam is tight to the foam and it’s flip-able.
I wonder if his accelerator will work in other epoxy systems…
Nice explanation for catalytic reactions! But I thougt it was different:
A is a girl, C is a boy
A and C form a couple -> AC
C want’s to try a threesome -> ACA
The girls A like eachother more then they like the boy C and become lesbian -> AA + C
important note: The more boys there are, the faster the girls get lesbian!
That’s why adding more catalist fastens the reaction, but that’s not true for epoxy!
(I always thougt that there was no B in the poly reaction but I can be wrong!)
You can use user friendly epoxies that give you the option of work and cure time thru choice of the hardeners. Both Fiberglass Hawaii and Resin Research (and others) offer this optio.
However, nothing is faster than good poly UV resin. You can get Silmar 249A premixed UV resin in straight Orthothalic or an Isothalic/Ortho blend at Fiberglass Hawaii. Just stick them in your browser for locations. The sun is the best cost effective method for curing surfboards using UV resin. Some manufacturers have elaborate black light set ups (tunnels, light boxes) depending upon individual factory locations, climate, or permit requirements. You can also use premixed UV polyester resin with regular MEK catalyst for applications such as setting leashcups or fin boxes. Some laminators use a small percentage of MEK in their laminates when applying densely colored or black logos under the fiberglass where they are concerned that UV light will not penetrate underneath the logo.
The advatnages of using UV poly is quick turn around (I can build a board in one day or produce multiples through glassing stages on any given day) combined by the fact that the finished board is FULLY cured versus using MEK (catalyst). It is believed that the hot coats of MEK catalyzed surfboards release hamrful chemicals when sanded whereas UV hot coats do not.
You can purchase UV powder separately and mix it into your own polyester resin, but care has to be taken when doing so and you should follow manufacturers directions in doing so. I have used both the powder and the premixed resins with great success, and use as little MEk catalyst as possible. The rapid curing of UV resin reduces the overall fumes emitted during the production process, and allows me greater freedom in the overall production process. Proper mixing or use of the premixed UV based resins does not present a problem with all but the most heat sensitive polyurethane blanks currently on the market whether they are TDI (Toulene Di Isocynate) or MDI (Methyl Phenol Di Isocynate) based.