The viscosity selection of hydroxyl silicone oil for electrophoretic paint mainly depends on its functions in the formula, such as working as a leveling agent or modifier, and its compatibility with the system. The mainstream recommended viscosity range is 350~1000 cSt (mPa·s at 25°C). For special applications, the viscosity can be adjusted to 100~350 cSt or 1000~5000 cSt.
Core Criteria for Viscosity Selection
| Viscosity Range (cSt) | Characteristics | Application Scenarios in Electrophoretic Paint |
|---|---|---|
| 100~350 | Low viscosity, excellent fluidity, easy to disperse and high reactivity | For systems requiring rapid substrate wetting and improved permeability; also used as reactive diluent for viscosity adjustment |
| 350~1000 | Medium-low viscosity with good fluidity, balancing dispersibility and film-forming property | Universal leveling agent for electrophoretic paint, providing good leveling, surface slip and crater resistance |
| 1000~5000 | Medium viscosity, good film-forming performance and high crosslinking density | For high-grade electrophoretic paint that needs higher film hardness, scratch resistance and anti-graffiti performance |
| Above 5000 | High viscosity and strong crosslinking capacity | Mainly applied to supporting products such as post-electrophoresis sealants, not suitable for direct use as leveling agent in electrophoretic paint |
Functions and Application Notes
Main Functions
- Reduce surface tension, improve substrate wettability and prevent craters and pinholes.
- Optimize film leveling and gloss, and deliver good surface slip.
- Enhance scratch resistance, anti-blocking performance and anti-graffiti property.
- Hydroxyl groups can take part in film crosslinking reactions to improve coating adhesion and durability.
Selection Guidelines
- Water-based system adaptation: Most electrophoretic paints are water-based. Hydroxyl silicone oil with hydroxyl content of 0.5%~3% is recommended to balance hydrophilicity and reaction activity.
- Compatibility test: Verify the compatibility between hydroxyl silicone oil and electrophoretic resins like epoxy resin and polyurethane resin to avoid coating defects.
- Dosage control: The typical addition amount is 0.1%~1.0% of the total formula. Excessive dosage will cause gloss loss and weakened adhesion.
Typical Application References
- Automotive cathodic electrophoretic paint: Hydroxyl silicone oil of 500~800 cSt is recommended to balance leveling performance and corrosion resistance.
- Anodic electrophoretic paint for home appliance shells: 350~500 cSt is preferred to improve surface gloss and processability.
- Special functional electrophoretic paint for high temperature resistance and anti-graffiti: 1000~2000 cSt is adopted to enhance relevant functional properties.
Summary
350~1000 cSt is the general applicable viscosity range of hydroxyl silicone oil for electrophoretic paint. The final viscosity should be adjusted according to paint type, performance requirements and construction process. It is suggested to carry out laboratory tests first to check the effects of products with different viscosity on film appearance, performance and system stability before mass production.
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