PIGMENT BLUE 28/ Cobalt Aluminate Blue 91477
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Technical Information
What Is PB28 / Cobalt Aluminate Blue 91477
CAS 1345-16-0, CI 77346, PB28 / Cobalt Aluminate Blue 91477 is a cobalt aluminate (CoAl2O4) pigment with a spinel crystal structure. It delivers a distinctive reddish-blue shade and withstands temperatures exceeding 1000°C, surviving conditions that destroy any organic pigment. This inorganic pigment offers excellent lightfastness, chemical resistance, and complete inertness, making it non-migrating and durable in demanding environments. Its spinel crystal structure provides unmatched chemical and thermal stability.
Why Choose Cobalt Aluminate Blue 91477
This specific grade, Cobalt Aluminate Blue 91477, is engineered for plastics applications where extreme thermal and chemical stability are critical. Its spinel structure ensures it remains intact during high-temperature processing, such as injection molding or extrusion, without fading or degrading. While its tinting strength is lower than organic blues like phthalo blue, its unmatched durability justifies its higher cost over ultramarine or phthalo alternatives. For plastics requiring prolonged exposure to UV light, harsh chemicals, or elevated service temperatures, this grade outperforms any organic alternative. No sibling grades exist for this product, so this is the sole option for achieving cobalt aluminate blue performance in plastics, offering reliability where other pigments fail.
Key Features
- Heat resistance above 1000°C enables use in high-temperature plastics processing and applications.
- Reddish-blue shade provides a distinct color profile with excellent lightfastness and chemical resistance.
- Non-migrating and completely inert, preventing bleeding or reactivity in plastic matrices.
- Lower tinting strength than organic blues but delivers unmatched long-term durability.
- Specifically formulated for plastics, offering superior performance in engineering plastics and architectural coatings.
C.I.NO.: PB28
Advantage:
Main Application Recommended: Plastics
>Product Description – PB28
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Cobalt Aluminate Blue 91477 (PIGMENT BLUE 28) consists of minute,very thin, more or less hexagonal flakes. A high-temperature calcined blue pigment with excellent chemical resistance, outdoor durability, light fastness, thermal stability, no bleeding and no migration. Widely used in fields with high requirements for heat resistance, weather resistance and light resistance; compatible with most resins or polymers. Reddish hue, small particle size, easy to disperse; strong tinting power, good hiding power, etc.
>Recommended Application
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Coatings: solvent based paints, water based paints, auto paints, industrial coatings, powder coatings, wood coatings, coil coatings
Plastics: PE, PP, PBT, PVC, PET, EVA, ABS
>Technical Data
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| Product Information | ||||
| Chemical Type | Co-Al-O | CAS NO. | 1345-16-0 | |
| C. I. Name | Pigment Blue 28 | EINECS / ELINCS NO. | 310-193-6 | |
| C. I. Constitution No. | 77346 | Chemical Formula | ||
| Technical Performance | ||||
| Full Shade | Tint | |||
| Weather Resistance | 5 | 5 | Heat Stability °C | 800°C |
| Light Fastness | 8 | 8 | ||
| Physical Properties | ||||
| Physical Form | Powder | Sieve Residure On 45 microns % | 0.5% max | |
| Specific Density (g/cm3): | 4.2 | Primary Particle size D 50 um | ~1.2 | |
| Oil Absorption | 16-26 | Resistance to Acid | 5 | |
| Water Solube Matter % | < 1.0 | Resistance to Alkali | 5 | |
| Volatile Matter | 1.0% max | |||
| PH | 7.5~9.5 | |||
| Packaging | ||||
| 25kgs/bag 1000kgs/Pallet | ||||
| Storage | Shelf Life | 5 years | ||
| Should be stored in cool, dry and ventilate place. | ||||
| TRANSPORTATION | ||||
| Avoid inversion, sunlight, moisture and crash. Avoid damage the package. | ||||
- Light fastness: Light fastness rating is assessed on 1 to 8 Blue Wool scale where 1 = ‘Poor’ and 8 = ‘Excellent’.
- Heat Stability : Heat stability values given indicate the maximum temperature at which the pigment can be stoved for 10 min. on the full shade and in reductions without undergoing any significant change in shade.
- Oil absorption: The oil absorption is determined on the basis of EN ISO 787-5 and given in g linseed oil per 100 gm. pigment.
- Solvent bleeding: The bleeding in solvents is tested using the powder grades and the visual rating given on 1 to 5 Grey scale
where 1 = ‘Heavy bleeding’ and 5 = ‘No bleeding”
Technical Note — The data and recommendations provided are based on HONOR Pigment’s internal testing and manufacturing experience. They are offered in good faith to assist customers in evaluating product suitability for their specific applications. As processing conditions, formulations, and end-use requirements vary widely, customers should conduct their own validation under actual use conditions. HONOR Pigment makes no warranties, express or implied, regarding the accuracy of this information or its fitness for any particular purpose. Nothing herein shall be construed as a license or recommendation to infringe any patent. HONOR Pigment’s standard terms and conditions of sale apply.oduct contains particles < 0.1 μm. Any user of this product is responsible for determining the suitability of Honor Pigments’s products for its particular application & to ensure that any proprietary rights & existing laws & legislation are observed.
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Frequently Asked Questions About PB28
Which plastic applications are best suited for Cobalt Aluminate Blue 91477 (PB28)?
PB28, or Cobalt Aluminate Blue 91477, is primarily designed for high-performance engineering plastics and rigid PVC. It excels in applications requiring long-term outdoor durability, such as automotive parts, architectural panels, and garden furniture. This pigment offers exceptional heat stability, performing reliably in polymers processed at temperatures exceeding 280°C, like polycarbonate (PC) and polyamide (PA). It is also ideal for masterbatch systems, providing consistent color dispersion. Due to its high opacity and chemical resistance, it is a top choice for colored pipes, industrial containers, and injection-molded components that must resist ultraviolet (UV) radiation and chemical degradation without fading or chalking.
What are the performance limits of PB28, especially regarding weatherability and chemical resistance?
While Cobalt Aluminate Blue 91477 is one of the most robust blue pigments available, it has specific limitations. Its primary strength is excellent lightfastness (ISO 105 B01 rating of 7-8) and outstanding weatherability in exterior applications, outlasting most organic blues. However, it may exhibit slight color shift in extremely acidic environments (pH below 3) or when used in direct contact with strong alkalis over extended periods. Transparency is limited; it is a high-opacity pigment, so it is not suitable for high-gloss, translucent finishes unless heavily over-pigmented. Additionally, very high doses (above 5%) can affect the mechanical impact strength of certain engineering plastics due to particle agglomeration.
How does Cobalt Aluminate Blue 91477 compare to other blue pigments, such as Ultramarine Blue (PB29) or Pithalo Blue (PB15)?
PB28 outperforms PB29 (Ultramarine) and PB15 (Phthalocyanine) in heat stability and acid resistance. While PB15 offers higher tinting strength and a sharper, greener shade, it degrades rapidly above 200°C and under UV exposure. PB29 is very heat-sensitive above 250°C and reacts poorly with acidic polymers like PVC. In contrast, PB28 withstands 300°C+ processing and resists acid attack. However, PB28 is much darker and duller (earthy red-blue) than the vibrant, high-strength PB15, which makes it unsuitable for high-gloss packaging. PB28 also has lower tinting strength per gram than PB15, requiring higher loadings for deep colors. Its production cost is also significantly higher.
What special processing considerations are needed for extruding or injection molding with PB28?
PB28 requires careful dispersion to avoid streaking or “fisheyes” in finished parts. Pre-dispersion in a carrier wax or using a high-shear mixer during masterbatch production is recommended. Due to its high density (4.5 g/cm³), it can settle in hoppers if the polymer melt flow is too low; use a tailored screw design for uniform feeding. Ensure processing temperatures stay between 260°C and 300°C; while PB28 is stable, extended dwell at 320°C may cause minor shade dulling. For polyolefins, use a white base (TiO2) to enhance color brightness. Avoid using with strong oxidizing agents like certain peroxide-based stabilizers, as this can catalyze a reaction that reduces color strength.
How should Cobalt Aluminate Blue PB28 be stored, and are there viable substitutes if it becomes unavailable?
Store PB28 in dry, cool conditions below 40°C, in sealed containers away from moisture. Unlike some organic pigments, it is non-hygroscopic and does not require special explosion-proof handling (non-combustible). It has a shelf life of at least 5 years under proper storage. If PB28 is unavailable for high-heat applications, the most direct substitute is Cobalt Chromite Blue (PB36) or a mixed-metal oxide blend like Titanium Cobalt Blue (PBr29). However, these will shift the shade greener or browner. For low-heat applications (under 200°C), a combination of Ultramarine Blue (PB29) with a UV stabilizer can mimic its appearance, but outdoor durability will significantly decrease.
Cobalt Aluminate Blue 91477 takeaway: This pigment is the gold standard for demanding plastic systems, offering unmatched heat stability, acid resistance, and UV permanence. While its earthy red-blue shade and higher cost limit it to industrial and engineering applications, PB28 remains the most reliable choice when long-term color integrity in harsh processing or exterior environments is non-negotiable.
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