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Covering power is one of the core indicators for measuring the performance of water-based paint, which refers to the ability of the paint film to cover the underlying substrate or the original color, directly affecting the coating effect, construction cost, and product competitiveness. Improving the coverage of water-based paint requires comprehensive optimization from multiple dimensions such as pigment system, formula design, and construction technology. The following is a specific strategy analysis:

1、 Optimizing pigment system: the core foundation of hiding power

Pigments are the key factors determining coverage, and their type, particle size, and dispersibility directly affect the efficiency of light scattering.

1. Selection of pigment types

-Titanium dioxide: As the main covering pigment for white water-based paint, rutile titanium dioxide (refractive index 2.76) has a covering power 20% -30% higher than anatase titanium dioxide (2.55) due to its more stable crystal structure and stronger scattering ability for visible light.

-Inorganic pigments, such as iron oxide red and carbon black, have better coverage than organic pigments (such as phthalocyanine blue), but organic pigments have brighter colors and can balance coverage and color expression through the combination of “inorganic+organic”.

2. Particle size and distribution of pigments

The particle size of the pigment needs to match the visible light wavelength (0.4-0.7 μ m): a particle size of 0.2-0.3 μ m (about half of the wavelength) results in strong scattering effect. If the particle size is too small, it is easy to transmit light, while if it is too large, the scattering efficiency decreases and it is prone to settling. It is necessary to control the uniform particle size distribution through grinding process to avoid agglomeration.

3. Dispersion of pigments

Agglomerated pigment particles will reduce the effective scattering area and lower the coverage power. Using anionic or non-ionic dispersants, pigment particles are uniformly dispersed in aqueous systems through electrostatic repulsion or steric hindrance, improving coverage efficiency. For example, adding 0.5% -2% dispersant can improve the dispersibility of titanium dioxide.

2、 Adjusting formula composition: balancing performance and coverage

Formula design should take into account pigment concentration, resin film-forming properties, and synergistic effects of additives.

1. Selection of base resin

The resin shall have good film-forming property and pigment compatibility: such as acrylic lotion, polyurethane dispersion, etc., which can wrap pigment particles and form a continuous and dense paint film to reduce light penetration. The greater the difference in refractive index between resin and pigment, the stronger the covering power (the difference in refractive index between titanium dioxide and resin is about 1.2, with scattering effect).

2. Control of pigment volume concentration (PVC)

The critical point of PVC is when the pigment particles in the paint film just fill the resin voids (usually 25% -35% for water-based paints). Below the critical PVC, the pigment content is insufficient; Above the critical PVC, pores appear in the paint film and transparency increases. PVC needs to be controlled near the critical value to balance coverage and film density.

3. Reasonable application of additives

-Thickener: controls the viscosity of the system, prevents pigment settling, and ensures even distribution of pigments during construction.

-Leveling agent: reduces defects such as pinholes and shrinkage in the paint film, improves surface smoothness, and indirectly enhances coverage.

-Anti settling agent: such as fumed silica, which prevents pigments from aggregating and settling during storage, maintaining covering stability.

3、 Standardize construction technology: unleash product potential

The construction process directly affects the actual covering effect of the paint film.

1. Control the thickness of the paint film

Insufficient dry film thickness can lead to incomplete coverage: white water-based paint needs to reach 30-50 μ m, and dark paint needs to be higher (such as 50-70 μ m). During construction, multiple coatings (2-3 times) can be applied to avoid sagging caused by one-time thick coating.

2. Choose a suitable construction method

-Spray coating: The uniformity is better than brush coating/roll coating, and the cross spraying method (one horizontal and one vertical) is used. The spray gun is 30-50cm away from the substrate, and the pressure is 0.2-0.3MPa to ensure consistent film thickness.

-Brush/roll coating: Pay attention to consistent direction to avoid missed brushing, and strengthen coverage at edges and corners.

3. Optimize the construction environment

Temperature of 20-25 ℃ and humidity of 50% -70%: Excessive temperature can cause rapid evaporation of moisture and cracking of the paint film; If the humidity is too high, it will dry slowly and be prone to sagging. Good ventilation can accelerate film formation and reduce defects.

4. Bottom level processing

The surface of the substrate needs to be cleaned (to remove oil and dust), polished (with 240-320 grit sandpaper), and if necessary, a primer should be used: the primer can seal the pores of the substrate to prevent the penetration of the topcoat, while providing a basic cover (such as gray primer and dark substrate, reducing the amount of topcoat used).

4、 Auxiliary strategy: Enhance details to improve coverage effect

1. Pigment combination optimization: Add a small amount of titanium dioxide (5% -10%) to the colored paint to enhance scattering and improve coverage by utilizing its high refractive index.

2. Resin crosslinking degree adjustment: By adding crosslinking agents (such as isocyanates) to enhance the resin crosslinking degree, the paint film becomes denser, reducing light transmission, and preventing pigment migration, maintaining long-term coverage stability.

In summary, improving the coverage of water-based paint requires a full chain control from pigment selection, formula optimization to construction standards. By scientifically adjusting the parameters of each link, a balance between coverage and cost can be achieved on the premise of environmental friendliness.