polyurethane clear coat is mainly for wood...like minwax stains...
Minwax
most clear coats are the same but if you can afford it there is a nice clear coat you can put on a car and will resist hammer swings...gulfstream puts it on the new g6's here in savannah but it is like $1000/gallon retail!!!
Its got to be good because when planes crash the paint is still nice looking!