Pigments play a vital role in coatings, affecting color, opacity, gloss, and performance. However, understanding key terms like oil absorption, pigment volume concentration, and pigment-to-binder ratio can be challenging. This article breaks down these essential concepts and calculations into five friendly, practical chapters.

Oil Absorption & Surface Area

Oil absorption measures how much oil (e.g., linseed oil) is required to wet pigment particles until they pack densely—a lab test based on ASTM standards .

• Importance: Helps formulators determine compatibility and maximum pigment loading.
• Modern alternative: Surface area (m²/g), measured by nitrogen absorption, offers more precise data—especially for water-based coatings.

Pigment Volume Concentration (PVC)

As PVC increases toward the critical PVC (CPVC), more pigment but less resin causes gloss, flexibility, and durability to decline. CPVC varies per system and must be determined experimentally. For most architectural paints, staying below CPVC is standard.

PVC is calculated as:

PVC = (volume of pigment ÷ total volume of pigment + resin) × 100%

Pigment-to-Binder Ratio (P:B)

The P:B ratio measures the weight of primary pigment relative to binder at a determined dry film thickness (commonly 25 µm). It’s a universal reference across pigment and resin types . This calculation guides hiding power and opacity in industrial and decorative coatings.

Key Formulation Considerations (List)

When selecting and formulating pigments, keep these five factors in mind:

• Particle morphology: Shape and size affect packing and film smoothness.
• Surface charge or pre-treatment: Influences dispersion and stability.
• Oil absorption/surface area: Dictates binder compatibility.
• Tinting strength: Determines how much pigment needed to achieve desired shade.
• Color index and lightfastness: Ensures consistency and resistance to fading.

Applying These Concepts

• Start with supplier data: Use provided oil absorption, surface area, and pigment density values.
• Prototype in lab: Determine PVC/CPVC and P:B experimentally for each formulation.
• Balance trade‑offs: Higher PVC = better hiding but lower gloss; P:B impacts opacity.
• Adjust for resin types: Water-based systems may require lower PVC or surface treatments to maintain performance.
• Verify performance: Test film flexibility, gloss, stain resistance, and opacity after full cure.

SEO‑Optimized Conclusion

Understanding oil absorption, PVC, and P:B—along with practical formulating tips—empowers formulators to create coatings with optimal balance of hiding, durability, gloss, and stability. Armed with lab data and an awareness of these key terms, you can design reliable, high‑performance pigment systems tailored to your application.

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