tartansailor wrote:
BTW I prefer Imron, because it can be buffed.
Not so with Awlgrip.
Dick
I believe what you mean to say is that you prefer Acrylic Urethanes over Polyester Urethanes. The Awlgrip company also makes an Acrylic Urethane that they call Awlcraft.
The difference between the two, without getting long and boring boils down to this:
Polyester Urethane molecules are much smaller than Acrylic molecules. So when they cure the Polyester Urethane forms a tighter matrix which gives a harder, more abrasion resistant film, with better chemical resistance than the Acrylic.
Acrylics are more forgiving in application, trap less dust and are buffable. When an acrylic urethane is buffed, due to the lower cross-link density the melting point of the resin is much lower i.e. it is softer. When buffing is carried out the resin rich layer "melts" and reflows into the scratch. It is possible to retain an in-tact resin-rich layer at the surface protecting the pigments and not losing significant thickness. The edges of touch ups can be blended carefully in the same way. Long term performance is not affected as much of the resin layer remains.
With the Polyester Urethane, the paint is a very hard rigid film, and to get rid of a scratch you need to cut deeply into the paint, leading to the exposure of the pigments. This looks shiny to begin with but the long term performance of the finish is now compromised.
I am currently following the build of a 95 footer in Viareggio, Italy. We are using Awlcraft (Snow white), and almost finished painting her. I am happy to use the Acrylic because we have found fairing issues on the hull, even with the white paint, and with the Acrylic we can re-fair this 6 square foot area, reshoot the area and blend in. We don't have to repaint the entire 95 foot hullside as we would with the Polyester!
Ok... so maybe I got long and boring.