Mike:
Just a few thoughts to start the discussion, since I might be off base, and the more I'm wrong, the more we will both learn. I don't work with UV every day. We are a conventional oil based operation with three ink sets, coated, uncoated, and plastic. I am a chemist, and figure that the inks we use for plastic are high solids drying oils, like linseed oil or tung oil.
What I THINK I know about UV inks, well, yeah, they are 100% solids since it all becomes part of the final film after cure. Therefore, no VOC's. The thinning solvents, like acrylates and styrene and a host of other monomers and oligomers, are petroleum by-products, made from that barrel of oil and follows the trend of the gas pumps, and can even get scarce when the world economy is running at a 2006 pace. They cost the printer about 30% more per pound than oil based ink. The initial press installation costs multiple units of 5 zeroes to be UV capable. The electric meters fly at a dizzying pace, when the lamps are on, altho this could be WIND POWER and therefore more expensive. The inks have a shorter shelf life, since the free radical curing reaction can just start all of a sudden. This may be an issue of the past. The inks are harder to handle by the press operators, and the photoinitiators can be pretty toxic. This may be a thing of the past, I hope.
Just my humble thoughts about the subject. Can't be beat for printing on plastic, but then again, we print on plastic all the time without UV. I think you don't need to worry as much about primers and top coats with UV plastic printing.
John Lind
Cranberry Township, PA
724-776-4718