Can anyone explain Urethane Enamel paint?

Answer 1

If I am not mistaken, urethane enamel is an automotive product and would not be used in doing artwork, except maybe in certain instances.
Perhaps if you want to know more about this product you can go into an auto body forum on the internet.

Answer 2

The term urethane and polyurethane apply to certain types of binders used for paints and clear coatings. (The binder is the ingredient that holds the pigment together in a tough, continuous film, and provides film integrity and adhesion.) Urethane binders are made be reacting a compound with an isocyanate group with another group, often a hydroxyl group: R1-N=C=O + R2-OH --> R1-NH-COO-R2. The urethane polymer is also called a polyurethane. Aliphatic solvents and polymers are preferred over aromatic types in that they provide greater flexibility and exterior durability, although they are more costly.

There are different types of urethane systems:

TYPE I: one-component, alkyd reacted with a polyisocyanate; this is the usual "polyurethane" varnish used in residential and commercial applications on bare or stained wood (floors, furniture, doors, etc.); offers greater toughness and abrasion resistance than do unmodified alkyds;

TYPE II: one-component, has a polymer with unreacted isocyanate in the backbone; reacts and crosslinks upon application and exposure to moisture from the air; known as "moisture cure urethane";

TYPE III: one-component, heat-cured; the polymer contains isocyanate that is chemically blocked from reacting with hydrogen donors in the product, until the heating drives off the blocking agent; used in factory application;

TYPE IV: two-component, a polymer containing free isocyanate groups is mixed at time of use with a catalyst of monomeric polyol or polyamine; has short pot life; TYPE V: two-component, a poly-isocyanate polymer is mixed at time of use with a resin containing active hydrogen groups; limited pot life;

TYPE VI: one-component, unreactive urethane polymer in solvent solution; forms the film upon solvent evaporation, but otherwise does not change (crosslink); PUD: "polyurethane dispersion"; dispersion of unreactive urethane polymer in water; used to modify latex coatings, particularly clear coatings, to boost mar resistance.