Why Pigment Brown 24 is the Most Popular Infrared Reflective Pigment

Introduction

Pigment Brown 24 (CAS No.: 68186-90-3; C.I. No.: 77310), commonly known as titanium chromium brown, is a leading inorganic composite infrared reflective (IR) pigment widely adopted across coatings, plastics, construction, and automotive industries. As a rutile-type mixed metal oxide pigment with a chemical composition of chromium-antimony-titanium oxide [(Ti, Cr, Sb)O₂], it stands out among IR brown pigments due to its unique combination of superior infrared reflectance, exceptional durability, broad compatibility, and environmental safety. Its popularity stems from addressing the critical industry need for dark brown pigments that avoid heat accumulation— a limitation of conventional brown pigments (e.g., iron oxide brown). This document systematically explains the reasons for Pigment Brown 24’s dominance in the IR pigment market and details its core properties, supported by technical data and industry applications.

Core Reasons for Pigment Brown 24's Popularity

Balanced Infrared Reflectance and Aesthetic Appeal

• Pigment Brown 24 resolves the long-standing trade-off between dark color and thermal performance:
• Infrared Reflectance Performance: It exhibits a Near-Infrared (NIR) reflectance of 45-50% (700-2500 nm) and Solar Total Reflectance (TSR) of 40-43%, significantly higher than conventional brown pigments (e.g., iron oxide brown with TSR 5%). This enables it to reduce surface temperature by 10-15℃ under direct sunlight compared to non-IR brown pigments.
• Color Versatility: It presents a natural yellowish-brown to reddish-brown shade (CIE L*=45-55, a*=8-12, b*=15-20) that blends seamlessly with outdoor environments (e.g., building exteriors, natural landscapes). Unlike other IR brown pigments (e.g., Pigment Brown 29 with a greenish-brown tint), Pigment Brown 24 offers a warmer, more aesthetically pleasing hue that meets consumer preferences for brown-toned products.

Exceptional Durability for Long-Term Applications

• Its high-temperature calcination manufacturing process (≥1000℃) endows it with industry-leading durability:
• Light Fastness: Grade 8 (on the 1-8 blue wool scale), indicating no significant fading even after 10+ years of outdoor exposure. This outperforms Pigment Brown 29 (light fastness 6-7) and organic brown pigments (light fastness 4-5).
• Heat Stability: Withstands temperatures up to 800℃ (10-minute stoving), making it compatible with high-temperature processes such as plastic extrusion (160-250℃), powder coating curing (180-220℃), and ceramic glazing (600-700℃).
• Chemical Resistance: Rated Grade 5 (highest) for acid and alkali resistance (per EN ISO 787-24), resisting degradation from rain, acid rain, and industrial chemicals. It also shows no solvent bleeding (Grade 5) in ketones, esters, and aromatic solvents, ensuring stability in solvent-based formulations

Broad Compatibility and Processing Ease

• Pigment Brown 24’s physical and chemical properties make it adaptable to diverse manufacturing systems:
• Medium Compatibility: Suitable for water-based, solvent-based, and powder coating systems, as well as thermoplastic and thermosetting resins. It disperses easily in acrylic, polyester, polyurethane, and epoxy resins without requiring specialized dispersants.
• Plastic Compatibility: Compatible with all major polymers, including PE, PP, PVC, ABS, PC, PET, and EVA  . Its low oil absorption (15-25 g/100g) and primary particle size (D₅₀=~1.5 μm) ensure uniform dispersion during extrusion and injection molding, avoiding "color spots" or processing defects.
• Processing Flexibility: Requires minimal modification to existing production lines. Typical dosage ranges from 0.5-2.0% (by weight of substrate), reducing material costs while maintaining performance.

Environmental Safety and Regulatory Compliance

• In an era of strict environmental regulations, Pigment Brown 24’s non-toxic profile is a key advantage:
• Toxicity: Free of heavy metals (lead, cadmium, mercury) and harmful impurities, with water-soluble matter ≤0.5%. It is classified as non-toxic and environmentally friendly, meeting global safety standards.
• Regulatory Compliance: Complies with EU REACH, RoHS, and FDA 21 CFR Part 73 (for food contact plastics). For textiles, it meets Oeko-Tex Standard 100 (Class I for infants), expanding its application scope to sensitive products.

Cost-Effectiveness and Market Availability

• Pigment Brown 24 offers superior total cost of ownership compared to alternatives:
• Dosage Efficiency: Its high color strength and hiding power (≥95% coverage at 100 μm film thickness) allow lower dosages than organic brown pigments (30-50% dosage reduction).
• Long Service Life: Reduces maintenance and replacement costs for end products (e.g., building coatings, automotive parts) by extending their service life by 5-10 years.
• Market Accessibility: Produced by major global pigment manufacturers (e.g., Honor Pigments, Hunmem, Baoxu) with consistent supply and technical support, ensuring reliability for large-scale production.

Core Properties of Pigment Brown 24

Physical and Chemical Properties

Functional Performance Properties

• Infrared Reflectance: 45-50% (700-2500 nm); TSR=40-43%  .
• Light Fastness: Grade 8 (ISO 105-B02)  .
• Weather Fastness: Grade 5 (2000h UV aging, ΔE*   .
• Heat Stability: ≤800℃ (no significant shade change)  .
• Chemical Resistance: Acid resistance (Grade 5), alkali resistance (Grade 5), solvent resistance (Grade 5)  .
• Migration Resistance: No color migration in plastics or coatings  

Key Application Fields

Pigment Brown 24's versatility drives its adoption across multiple industries:

Coatings Industry

• Applications: Solvent-based/oil-based paints, water-based architectural coatings, automotive coatings, industrial maintenance coatings, powder coatings, and coil coatings  .
• Benefits: Reduces coating temperature buildup, enhances weather resistance, and maintains color stability. A case study in Florida, USA, showed that building exteriors coated with Pigment Brown 24 saved 20-25% in annual cooling costs compared to conventional brown coatings.

Plastics Industry

• Applications: General-purpose plastics (PE, PP, PVC), engineering plastics (ABS, PC, PET), plastic films, and wood-plastic composites.
• Processing Parameters: Compatible with extrusion (160-250℃) and injection molding (180-280℃) processes. Recommended dosage: 0.8-1.5% for general plastics, 1.2-2.0% for engineering plastics.
• Benefits: Prevents plastic degradation from heat accumulation, extending product service life in hot climates (e.g., Middle East, Southeast Asia) .

Construction Industry

• Applications: Roof tiles, exterior wall cladding, concrete pavements, and decorative ceramics.
• Compliance: Meets green building standards such as LEED v4 (TSR ≥30%) and China GB/T 25261-2018 (reflective insulating coatings).
• Benefits: Reduces urban heat island effect by reflecting solar radiation, while its natural brown shade integrates with architectural designs.

Automotive and Transportation Industry

• Applications: Automotive exterior coatings (SUVs, off-road vehicles), truck bed liners, and marine coatings.
• Performance Requirements: Withstands salt spray (≥1000h), scratch resistance (≥4H pencil hardness), and temperature fluctuations (-40℃ to 80℃).
• Benefits: Lowers vehicle body temperature by 8-10℃ under sunlight, improving cabin comfort and reducing air conditioning energy consumption.

Comparison with Alternative IR Brown Pigments

To highlight Pigment Brown 24's advantages, below is a comparison with two common alternatives:

Application Guidelines

Dosage Optimization

• Conduct gradient tests (0.5-2.0% by weight) to determine the minimum effective dosage. Excessive dosage may reduce NIR reflectance due to particle aggregation.
• For coatings, blend with white IR pigments (e.g., rutile TiO₂) to adjust shade without compromising thermal performance.

Dispersion Recommendations

• Use high-shear mixing or media milling for aqueous systems to achieve uniform particle distribution (target particle size: 1-5 μm) .
• For plastics, pre-disperse into masterbatches (10-20% pigment concentration) to ensure consistency during processing.

Storage and Handling

• Store in a cool, dry, and well-ventilated warehouse (relative humidity ≤60%) to avoid moisture absorption.
• Shelf life: 5 years from production date when stored properly.

References

• Chemical Abstracts Service (CAS). (n.d.). Pigment Brown 24 (CAS 68186-90-3). Retrieved from https://www.cas.org/support/documentation/chemical-substances
• International Organization for Standardization (ISO). (2023). ISO 105-B02: Textiles - Tests for Color Fastness - Part B02: Color Fastness to Artificial Light.
• European Committee for Standardization (CEN). (2022). EN ISO 787-24: General Methods of Test for Pigments and Extenders - Part 24: Determination of Resistance to Acids and Alkalis.
• Ministry of Industry and Information Technology of the People’s Republic of China. (2018). GB/T 25261-2018: Reflective Insulating Coatings for Buildings.
• American Society for Testing and Materials (ASTM). (2023). ASTM E903-19: Standard Test Method for Solar Absorptance, Reflectance, and Transmittance of Materials Using Integrating Spheres.

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