Pigment Blue 28 (PB28) Cobalt Aluminate Blue for High-Temp Ceramics & Plastics | HONOR Pigment
Pigment Blue 28 (CI 77346, CAS 1345-16-0) maintains ΔE ≤ 0.3 after 500 hours of QUV accelerated weathering and shows no color shift after 24 hours at 1300°C. This cobalt aluminate blue spinel (CoAl₂O₄) is engineered for applications requiring extreme thermal and chemical stability. HONOR Pigment’s PB28 grade delivers consistent hue (L*=40.2, a*=-12.8, b*=-38.5 under D65/10°) and a narrow particle size distribution (D50 = 1.8 μm, D90 ≤ 5.5 μm), making it suitable for powder coatings, engineering plastics (PA6, PBT, PPS), and ceramic glazes.
Key identifiers: CI 77346 · CAS 1345-16-0 · Chemical formula: CoAl₂O₄ · Spinel crystal structure · Density: 4.2 g/cm³ · Bulk density: 0.85–1.05 g/cm³ · pH (aqueous slurry): 7.0–8.5
Pricing range: USD $18–$35 per kg (FOB, depending on quantity and packaging). Minimum order: 25 kg.
Product Overview
PB28 (Cobalt Aluminate Blue) is a high-performance inorganic pigment with a spinel lattice that provides outstanding heat resistance, lightfastness (ISO 105-B02 rating: 8/8), and chemical resistance. Unlike organic blue pigments (e.g., PB15, phthalocyanine) that degrade above 250°C, PB28 withstands prolonged exposure to 1300°C and brief peak temperatures of 1400°C. It is insoluble in water, organic solvents, and most acids/bases (except concentrated H₂SO₄ at elevated temperature).
HONOR Pigment’s manufacturing process produces a phase-pure CoAl₂O₄ structure verified by XRD, with CoO content between 28–32% by weight. Typical lot-to-lot ΔE is below 0.5 (CIE76), ensuring batch consistency for critical color formulations. Estimated annual global demand for PB28 in high-temperature applications is 8,000–10,000 metric tons (2024), with strongest growth in automotive ceramic coatings and halogen-free flame-retardant plastics.
Technical Specifications
| Parameter | Value | Test Method |
|---|---|---|
| CI Number | 77346 | Colour Index International |
| CAS Number | 1345-16-0 | Chemical Abstracts Service |
| Particle Size (D50) | 1.8 ± 0.3 µm | Laser diffraction (ISO 13320) |
| Particle Size (D90) | ≤ 5.5 µm | Laser diffraction (ISO 13320) |
| Specific Surface Area (BET) | 8.2 m²/g | ISO 9277 |
| Oil Absorption | 22 g/100g | ISO 787/5 |
| Tinting Strength (relative to standard) | 100 ± 5% | ISO 787/16 |
| Density | 4.2 g/cm³ | ISO 787/10 |
| Bulk Density | 0.85–1.05 g/cm³ | ISO 787/11 |
| Thermal Stability (24h) | 1300°C (1400°C peak 1h) | Internal (isothermal furnace) |
| Lightfastness (ISO 105-B02, Xenon) | 8/8 | ISO 105-B02 (blue wool scale) |
| Weather Resistance (500h QUV-A) | ΔE ≤ 0.3 | ASTM G154 |
| Color Coordinates (D65/10°) | L*=40.2, a*=-12.8, b*=-38.5 | Spectrophotometer (d/8, SCI) |
| pH (aqueous slurry) | 7.0–8.5 | ISO 787/9 |
| Moisture Content | ≤ 0.3% | ISO 787/2 (105°C, 2h) |
*Typical values. Tolerances per HONOR Quality Standard QS-PB28-2024. Certificates of analysis available per lot.
Application Scenarios
High-Temperature Ceramics
PB28 is the standard blue pigment for ceramic glazes fired at cone 6–10 (~1200–1300°C). At 4–8% addition in transparent or opacified glazes, it produces a clean, intense blue with minimal color drift from Ca, Zn, or Ba fluxes. The spinel structure prevents dissolution in molten frits; typical firing cycles of 8–12 hours at peak temperature show ΔE < 0.5 compared to unfired blend. Used in sanitaryware, tableware, and architectural tiles (e.g., full-body porcelain with 6% PB28 yields consistent CIELAB L* 38.5, a* -10.2, b* -35.1).
Engineering Plastics (PA6, PBT, PPS)
PB28 withstands processing temperatures of 280–330°C in polyamide 6 (PA6) and polyphenylene sulfide (PPS). In 30% glass-filled PBT at 300°C (5 min residence time), color shift ΔE is less than 1.0. Typical loading: 0.5–2.0% for opaque shades, 2.5–4.0% for deep tone. The pigment does not catalyze polymer degradation; tensile strength retention in PPS with 2% PB28 was 97% vs. unfilled resin (ISO 527). For food-contact plastics seeking compliance with EU 10/2011 or US FDA 21 CFR 178.3297, PB28 has no migration issues — verify with your converter as application-specific approvals vary.
Powder Coatings & Industrial Coatings
When dispersed in epoxy-polyester hybrid systems, PB28 provides a deep blue with gloss retention >85% after 2000 hours QUV (ASTM G154 cycle 1). Recommended dispersion: high-speed dissolver (20 min, 3000 rpm) followed by bead mill (0.6–0.8 mm zirconia beads, 45 min). Particle size after milling: D50 = 1.6 μm, fineness of grind < 10 μm (Hegman gauge ≥ 7). For coil coatings, PB28 combined with CI 77891 (TiO₂) yields heat-reflective blues (TSR > 70% at 50% tint) suitable for cool-roof applications.
Processing note: For plastic applications, predispersion in a carrier resin (e.g., PE wax masterbatch at 40% pigment loading) improves color development and reduces dust. We offer PB28 as microgranules (100–500 µm) for low-dust handling — add $1.50/kg to base price.
Frequently Asked Questions
Why Choose HONOR Pigment
- ✓ 25+ years specializing in high-temperature cobalt pigments — PB28 produced since 1999 with continually improved purity.
- ✓ Every batch XRD validated for phase purity (no CoO, Co₃O₄, or spinel impurity). Typical XRD pattern matches ICDD card 01-075-2284 (CoAl₂O₄).
- ✓ Global logistics — stock in Shanghai (China), Rotterdam (EU), Houston (USA). Lead times: 7–15 days for standard grades.
- ✓ Technical support — free color matching (ΔE ≤ 0.5) and formulation recommendations by experienced colorists.
- ✓ Flexible packaging: 25 kg paper bags (with PE liner), 500 kg super sacks, or 1000 kg jumbo bags. Custom labeling available.
Request a Quote
Fill out the form below or contact our sales team directly. We provide free samples (250g) for qualified trials.
Email: sales@honorpigment.com (include product code: PB28-HN-001) | Phone: +86 21 6039 8600 | Web: honorpigment.com
For immediate assistance, please provide: your company name, application, required quantity (kg/month), and target price FOB/UOM. We typically respond within 2 business hours.
Related products:
PB29 Ultramarine Blue ·
PG50 Cobalt Green ·
PBr33 Zinc Iron Chromite
Internal resources:
PB28 Technical Data Sheet (PDF) ·
Safety Data Sheet (SDS) ·
Certificate of Analysis (Sample)
HONOR Pigment — Global Supplier of High-Performance Inorganic Pigments
CI 77346 · CAS 1345-16-0 | Over 12,000 tons supplied in 2024 | Serving 60+ countries
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