1. Applications in the Coating Industry
Xanthan gum is a versatile functional additive in coating formulations, primarily acting as a rheology modifier, stabilizer, and anti-settling agent—key to optimizing coating performance during production, application, and storage:
- Controls rheological properties: It imparts shear-thinning behavior to coatings. This means coatings stay thick and non-dripping when stored or applied vertically (e.g., on walls), preventing sagging; but flow smoothly under the shear force of brushes, rollers, or spray guns, ensuring even application and a uniform finish.
- Prevents pigment settling: Coatings contain solid pigments (e.g., titanium dioxide, colorants) and fillers. Xanthan gum forms a viscous network to suspend these solids evenly, avoiding sedimentation at the bottom of containers. This ensures consistent color and texture in every use, eliminating the need for frequent stirring.
- Enhances storage stability: It reduces syneresis (water separation) in water-based coatings and resists viscosity changes caused by temperature fluctuations (e.g., during transportation or warehouse storage). This maintains the coating’s usability and quality over its shelf life.
- Improves film formation: For water-based coatings, it slows down the evaporation rate of water during drying, allowing pigments and binders to arrange uniformly. This results in a smoother, more durable coating film with better adhesion to substrates.
2. Recommended Addition Levels
The addition amount of xanthan gum varies by coating type and formulation requirements, with a focus on balancing functionality and application performance:
| Coating Category | Typical Addition Range (of total formula weight) | Key Reason for Dosage |
|---|---|---|
| Water-based interior/exterior wall paints | 0.1% - 0.3% | Low dosage prevents pigment settling and sagging, while ensuring smooth brushing/spraying without excessive thickness. |
| Architectural latex coatings (high-gloss/matte) | 0.15% - 0.4% | Higher level enhances shear-thinning properties, critical for high-gloss coatings to avoid drips and for matte coatings to maintain uniform texture. |
| Industrial coatings (e.g., metal protective coatings) | 0.2% - 0.5% | Supports suspension of heavy pigments (e.g., anti-rust pigments) and improves coating adhesion to metal substrates, resisting cracking during curing. |
| Artistic/DIY coatings (e.g., textured paints) | 0.3% - 0.8% | Higher dosage creates a thicker, textured consistency, allowing for decorative effects (e.g., stippling, brushing patterns) without sagging. |
Note: All addition levels must comply with industry standards for coatings (e.g., ASTM, ISO). They also need to be adjusted based on the coating’s solids content (high vs. low), pigment type (light vs. heavy), and application method (brush, roller, spray).