1 -10 BASIC KNOWLEDGE ABOUT PAINTS AND PAINTING (2) DUAL-COMPONENT POLYMERIZATION (DUAL-COMPONENT PAINTS) This type of paints is commonly known as dual-component paints because an additive called har- dener (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 develops faster under a higher temperature. Normally, hot air of 40 to 80°C is used to accelerate the drying process for the sake of work efficiency. Most of the paints used in repainting stations fall in this type.
They vary greatly in their net size and density, resulting in a wide range of coat performance from one far higher than paints for new vehicles to paints that are close to the solvent evaporation (air-drying) type paints. The table below lists dual-component paints that are used with automobiles. The following table illustrates "molecular images" of resins before and after drying:
- 12- Paint name Main use Acrylic urethane (urethane) Undercoat and top coat in repainting Quick-drying acrylic urethane (quick-drying urethane) Undercoat and top coat in repainting Acrylic urethane lacquer (urethane lacquer) Undercoat and top coat in repainting Epoxy Undercoat in repainting Drying type Solvent evaporation Paint name When wet When dry - ~ ~~- ...., ..-.- NC acrylic lacquer ~ .,;; .....- zu:1 CAB acrylic lacquer Dual-component polymerization Acrylic urethane lacquer Quick-drying acrylic urethane Acrylic urethane Heat polymerization Thermosetting amino alkyd