On Thursday, February 18, 2016 at 9:48:19 AM UTC-5, wrote:
My paint supplier told me there were much cheaper urethane paints available, so I sent a note to PPG. Told them we loved Concept, but it was getting hard to get (in my county) and very expensive. Asked if other urethane paints would be a suitable substitute for Concept? Got a nice reply that stater poly-urethane paints would become brittle with age. Concept is acrylic-urethane (not poly-urethane) and remains slightly flexible throughout its life span.
JJ

There are modifiers available to make the polyurethane paint flexible. These modifiers are used when painting plastic parts on cars to allow paint to flex with plastic. AU is however the best paint all around for application and sanding/polishing