Last updated: 2026-01
Material Identity
- Chemical name: Cobalt aluminate
- Color Index designation: Pigment Blue 28 (PB28)
- Representative formula: CoAl2O4
- CAS number: 1345-16-0
- Physical form: inorganic pigment powder
- What it is not: not an organic pigment, not a dye, not a carbon-based blue
Activation & Trigger Conditions
- Trigger: interaction with visible light
- Energy domain: electronic transitions within the cobalt–aluminate spinel lattice
- Absent trigger: no color expression without light interaction
- Insufficient condition: poor dispersion reduces color strength and uniformity
- Excess condition: excessive mechanical processing can alter surface condition and appearance
Functional Role
- Provides stable blue coloration
- Maintains color at elevated processing temperatures
- Resists chemical and environmental degradation
- Supports long-term color durability in inorganic systems
Application Windows
- Compatible systems: engineering plastics, industrial coatings, ceramic bodies and glazes, glass coloration
- Loading range: formulation-dependent; no universal loading applies
- Processing notes: dispersion quality and particle distribution influence shade strength and surface finish
Limitations & Failure Modes
- Poor dispersion → pigment agglomeration → uneven color or streaking
- Incompatible binder or resin → flocculation → gloss loss or color shift
- Over-milling or excessive shear → surface damage → reduced color consistency
Alternatives & Trade-offs
- Organic blue pigments: higher tinting strength but lower heat resistance
- Ultramarine blue: different hue and lower chemical resistance
- Phthalocyanine blue: strong color but limited high-temperature stability
When to Use
- When blue coloration must withstand high processing temperatures
- When inorganic pigment durability is required
- When long-term color stability is critical
- When organic blues are unsuitable due to heat or chemical exposure
FAQ
Is PB28 the same as organic blue pigments?
No. PB28 is an inorganic spinel pigment with much higher thermal and chemical stability.
Can PB28 be used in high-temperature plastics?
Yes. As an inorganic pigment, it is commonly used in plastics processed at elevated temperatures.
Why does shade vary between formulations?
Variation is typically caused by dispersion quality, pigment concentration, and interaction with the matrix.
Data
No numerical values are listed. Color strength, heat resistance, and chemical stability are grade- and formulation-specific and should be verified via COA and application testing.
Sources
Supplier technical documentation and general literature on cobalt aluminate spinel pigments.