Barcol hardness of resin

General Discussion
1

I polished a board this weekend that had been finish coated quite recently. I used UV lam resin throughout. I to wondering how long one has to/should wait before polishing. Not just “I usually wait a day” common practice, but I wait a day because of the following FACTS…

Question 1: Has anyone got hard data regarding hardness of cured, catalyzed and/or UV cure resin under some set of standard conditions?

Question 2: can anyone substantiate the correct ratio of MEKP to resin for strongest cure? I thought at one time that poly resin cured best at about 1% MEKP, but that ratio won’t provide sufficient work time for a longboard lam without considerable risk and a lot of waste, which I abhor. Not sufficient time at all for any kind of color work, either. Though I now use UV cure resin, with MEKP I measured to about 0.8%, giving 20 minutes work time.

The time-to-polish issue should be resolved by the response to Q1, eh?

2

In boatbuilding we use a Barcol hardness 0f 25 as standard. This can be achieved without problems using catalyst ratio of between 1 and 2% and correct working temperatures and humidity. Certainly the resins we use say NO MORE than 2% should be used (MEKP). Catalyst is just that, a chemical that speeds-up a reaction. I you leave polyester resin long enough it will go hard without catalyst (the last lot I had left over took 2 years!). You DO NOT get a stronger resin by using more catalyst, merely less working time. In boatbuilding incorrect catalyst ratios have resulted in longterm damage to the laminate (it is one cause of osmosis).

The chemistry of epoxies is completely different and the manufacturer’s ratios should be adhered to (no pun intended) without alteration.

Summer’s here and the surf’s gone on holiday

Rik