ABOUT AUTO PAINT - HARDENER IN ENAMEL
DO I HAVE TO USE A CATALYST OR HARDENER IN ACRYLIC ENAMEL?

You should, to speed up the curing time of the paint. However, acrylic enamel will cure over time by absorbing oxygen from the atmosphere to complete the molecular cross linking needed to create the polymer. The addition of a catalyst accelerates this process greatly (a few days versus a few months without a catalyst agent). Most catalysts contain isocyanates which can be a health hazard if inhaled. A fresh air supply is strongly recommended. And warning labels are often not as adequate as they should be. Methylenedianiline is used primarily as a chemical intermediate in the closed system production of isocyanates and polyisocyanates and is also a curing agent for epoxy resins and urethane elastomers, a dye intermediate, and a corrosion inhibitor.