Saturday, February 23, 2008
UV resins, pot-life
That's quite an important issue as nobody wants resins to harden in your gear overnight or even worse, while you are printing.
I have found out that on my standard, high reactivity resins (composed of high amounts of any of the new catalyzers, between 4-5 weight% of new catalyzers along with 4-5w% Benzophenone (BP) and 2w% N-Methyldiethanolamine) they have a pot life of a mere 5 days.
This means, to be safe, that you have to clean out your gear with solvents say, every 2 days. Far from ideal.
I know a couple of additives that will lengthen pot-life. One of them is a stabiliser called Hydroquinone. This is a very effective chemical that will stabilize the final resin-mix. I have done a test batch with around 0.05w% of it and these are the results:
The mix containing Benzoinisobutylbether (aka, the expensive mix) has not improved noticeably in pot-life.
The mix containing Benzil (aka, the cheap mix), after 10 days, the resin has remained very fluid, but the reactivity to UV exposure is quite lower.
Conclusions: the expensive mix still has the same problem, and has lowered reactivity. The cheap mix has at least double pot-life, but the reactivity is reduced as well.
Where to go from here: I have to make tests with less concentrations of Hydroquinone (blow 0.01w%). I have to get myself some EDTA, another chemical that will probably longer pot-life without hopefully reducing reactivity.