Paint Drying and Curing - Reactive Type
1. Reactive Type
In this type of paint, the solvent and thinner in the paint evaporate and, in addition, resins are hardened and dried by a chemical reaction (called polymerization):
While heat is not required to dry and from a film, applying heat will accelerate the chemical reaction. The paint’s structure also changes from a paint molecule to polymer coating. It then becomes a high performance, weatherproof, and solvent resistant paint film.
Resin molecule forms high-molecular-weight compound through chemical reactions and binding of low-molecular-weight compound.
1.
Coating condition immediately after painting.
2.
Resin molecules in the paint start to react along with the evaporation of paint reducer/thinner and solvent during drying process.
3.
The coat is completely free of solvents or thinners. The chemical reaction of the resin molecules is completed and they form a net-like coat (3D paint structure).

Heat Polymerization:
This type of paint is called baked finish paint. These paints start a chemical reaction when heated (typically over 248 °F (120 °C) for 20 to 30 minutes) after application. This forms a net-like structure as the paint hardens, ensuring outstanding coating performance and are high solvent resistance once completely dried.
Most of the paint used for automobile production is the heat polymerization type, including thermoset aluminum alkyd (baking melamine) and thermoset acrylic.
This paint type is rarely used for repairs because plastic parts and electric components would need to be removed from the affected area in the car, or otherwise protected from heat.

Dual-Component Polymerization (Dual-Component Paints):
This type of paint is commonly known as dual-component paint because an additive called hardener (kept in a separate container) is added to the paint to start a reaction and form a hard netted coat. This reaction takes places at a normal temperature, although it can be accelerated at higher temperatures 104?140 °F (40?80 °C).