High-solids paints

Dr. Dmitri Kopeliovich

High-solids paints are the paints containing at least 65% of solid components (binders, pigments and additives) mixed with a solvent serving as a vehicle.

Due to low content of solvent the viscosity of high-solids paints is 3-4 times higher than in conventional Solvent-borne paints and may reach 10000 cP (centipoise).

The viscosity of high-solids paints may be reduced chemical modification or heating the paint before application to 104-150°F (40-66°C).

High-solids paints are formulated as either a single-component or two-component systems:

• Two-component high-solids paints start chemical curing (cross-linking) just after the components (resin and cross-linking agent) have been mixed together. The paints have very short pot life when mixed.
  
• Single-component high-solids paints cure by heating (baking) to about 300-400°F (150-200°C).
  
• Air dry single-component high-solids paints cure as a result of chemical reaction with Oxygen or moisture of the surrounding air at normal or slightly elevated temperature.

Polymer resins used as the binders in high-solids paints:

• Epoxies
• Urethanes
• Alkyds
• Vinyls
• Acrylics

High-solids paints are applied by spray guns.
High pressure pumps are used in the spray equipment for application of high viscosity high-solids paints.
The paint viscosity may be reduced by a heater mounted between the pump and the spray gun. Two-head spray guns may be used for application of two-component high-solids paints. Two-head spray equipment provides mixing the components in atomized state. The resin and the hardener (cross-linking agent) are supplied from different containers by individual pumps preventing clogging the system due to possible early thickening of the paint.

Advantages of high-solids paints as compared to conventional solvent-borne paints:

• Low toxicity due to low content of VOC (volatile organic compounds).
• Low fire hazard.
• Low amount of paint is stored, shipped and sprayed for obtaining a coating of a given thickness and area.
• Simpler and less expensive exhausting equipment is required.
• Wide range of the coating thickness may be obtained.
• Fewer spraying operations is required for building a coating of a given thickness.
• Help self-orientation and alignment of metal flakes in automotive metallic paints.

Disadvantages of high-solids paints as compared to conventional solvent-borne paints:

• High viscosity causing difficulties in pumping and atomizing.
• Limited application methods may be used.
• Better Surface preparation is required due to insufficient cleaning effect of low solvent.
• Short pot life.
• Modification of spraying equipment (heater, high pressure pumps, two-head gun) is required.

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• Composition of paints
• Classification of paints
• Solvent-borne paints
• Water-borne paints
• Powder coatings
• Application of paints
• Radiation curable coatings
• Enhancement of adhesion
• Hydrocarbon solvents

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