Comprehensive Analysis of Defoamers for Oil-Based Coatings: Characteristics, Selection, and Application

1. Definition and Core Advantages of Defoamers for Oil-Based Coatings

Oil-based coatings (also known as oil-based paints) primarily use drying oils as their film-forming agents and include categories such as clear oils, thick paints, and oil-based mixed paints. During production, the addition of chemical additives often leads to the formation of large amounts of foam, resulting in defects such as pinholes and shrinkage in the coating. As a result, oil-based paint defoamers have become a critical solution.

Core Advantages:

High-Efficiency Foam Suppression: Formulated by blending dimethyl silicone oil with foam-suppressing active agents, it demonstrates significantly superior foam suppression and prevention performance compared to single-component silicone oils.

Excellent Compatibility: Highly compatible with oil-based systems (such as hydrocarbons), it does not affect paint transparency and maintains leveling properties after addition.

Wide Application Range: Controls foam throughout the entire process of paint production, packaging, and application. Resistant to acids and alkalis (effective over a wide pH range) and provides long-lasting stability.

II. Negative Impacts of Foam on Oil-Based Paints

Production Efficiency: Foam accumulation reduces equipment operational efficiency and leads to raw material waste (e.g., volume expansion during mixing).

Surface Defects: Residual bubbles form defects such as pinholes, fish eyes, and orange peel on the surface.

Performance degradation: Foam weakens paint film adhesion, gloss, and water resistance; severe cases may cause peeling or cracking.

Application challenges: Foam rupture during spraying or rolling causes “volcano” phenomena, affecting coating uniformity.

III. Selection criteria and practical recommendations for defoamers in oil-based coatings

1. Stability first: Ensure compatibility with the system and no side effects

Physical stability: Observe whether the defoamer separates or precipitates during storage. High-quality products should remain uniformly emulsified or transparent.

Chemical stability: Does not react with paint components (e.g., resins, solvents, additives). This can be tested by mixing the defoamer with the paint and observing for flocculation or color changes after 24 hours of static mixing.

2. Small-scale testing: Accurately verify defoaming performance

Foam elimination speed: Add the defoamer to the foaming solution dropwise and time the duration until all foam is completely eliminated (faster is better).

Foam suppression duration: Simulate production conditions with continuous stirring and record the interval time until foam reappears (longer is better).

Leveling: Apply the sample by brushing or spraying and inspect the surface for smoothness and absence of pinholes.

Transparency: After adding the defoamer, let the coating stand for 2 hours and observe for cloudiness or separation.

3. Dosage control: Balancing economy and effectiveness

Standard dosage: 0.1%–0.3% of the total paint volume. Start with a 0.2% ratio for initial testing, then adjust slightly based on foam severity.

Special cases: For high-viscosity systems or processes prone to foaming (e.g., high-speed stirring), the dosage may be increased to 0.5%, but avoid excessive amounts to prevent pinholes.