White Fused Alumina Micropowder for Thermal Insulation Coatings
Chemical Composition of White Fused Alumina Micropowder Affecting the Performance of Thermal Insulation Coatings
Al₂O₃: ≥ 99.2–99.7%
Na₂O: ≤ 0.25%
Physical & Chemical Indicators of White Fused Alumina Micropowder for Thermal Insulation Coatings
- Color: Pure white; whiteness ≥ 88, will not cause discoloration for light-colored / white thermal insulation paints during color matching
- Mohs hardness: 9.0; melting point: 2250℃, long-term service temperature: 1800~1900℃
- Linear expansion coefficient: 7.5~8.0×10⁻⁶/℃, excellent thermal stability and thermal shock resistance to prevent cracking
- True density: ≥ 3.90 g/cm³; bulk density: 1.75~1.95 g/cm³
- Oil absorption value: 8–15 g/100 g, low oil absorption and good dispersibility, avoiding extra resin consumption
- Moisture content: ≤ 0.2%; neutral pH value (6.5~8.0), compatible with both water-based and solvent-based systems
II. Core Functions in Thermal Insulation Coatings
High-temperature resistant thermal insulation skeleton
It fills pores inside the coating to form a dense thermal barrier layer and inhibit heat conduction. It will not melt or deform at high temperatures, greatly raising the temperature resistance limit of coatings, suitable for high-temperature anti-corrosion & thermal insulation coatings for kilns, pipelines and flues.
Anti-cracking and thermal shock resistance
Its low expansion coefficient relieves thermal expansion and contraction stress of substrates, preventing peeling, cracking and shedding of thermal insulation coatings and extending service life.
Improved mechanical strength, weather resistance and anti-corrosion performance
High hardness improves the coating’s wear resistance and erosion resistance. With outstanding chemical inertness, it resists acid, alkali, salt spray and UV aging, applicable to integrated thermal insulation & anti-corrosion coatings for outdoor equipment and chemical pipelines.
Optimized construction performance and system stability
With controllable particle size grading and excellent dispersibility, it ensures smooth brushing and spraying. High whiteness fits various colored thermal insulation coatings without grey discoloration.
III. Recommended Particle Sizes (Mesh Sizes) & Dosage Formulas for Thermal Insulation Coatings
表格
| Coating Type | Recommended Mesh Size | Median Particle Size D50 | Reference Dosage (Based on Coating Solid Content) | Application Scenarios |
|---|---|---|---|---|
| High-viscosity High-temperature Thermal Insulation Coatings | 320#~800# | 18~45 μm | 15%~30% | External thermal insulation for boilers, steam pipelines and industrial furnaces |
| Thin-film Reflective Thermal Insulation Paints | 1200#~2000# | 5~10 μm | 5%~15% | Topcoat for reflective thermal insulation on building exterior walls and storage tanks |
| Superfine High-temperature Resistant Sealing Thermal Insulation Coatings | 3000#~4000# | 3~5 μm | 3%~10% | Sealing coatings for precision equipment and high-temperature gaps |
| Coarse-grained Refractory Thermal Insulation Primer | 180#~280# | 55~90 μm | 20%~35% | Primer for thick fireproof thermal insulation, integrated wear resistance & thermal insulation |
IV. Key Selection Guidelines
- Prioritize low-sodium white fused alumina: Excess Na₂O tends to form glass phase at high temperature and deteriorate high-temperature stability of thermal insulation coatings. Low-sodium micropowder (Na₂O ≤ 0.1%) is mandatory for working conditions above 1000℃ long-term.
- Optimized compound grading of particle sizes: Mixing coarse and fine grades fills internal voids to reduce thermal conductivity of coatings, delivering better insulation effect than single particle size.
- Compounding formula: Usually compounded with hollow glass microspheres, fumed silica and aluminum silicate fiber to synergistically lower overall thermal conductivity, balancing thermal insulation, fire resistance and wear resistance.
- Packaging: Standard 25 kg woven bags with inner plastic liner for moisture-proof storage.
V. Typical Application Scenarios
Thermal insulation coatings for industrial high-temperature pipelines, energy-saving thermal insulation paints for outer boiler walls, high-temperature anti-corrosion thermal insulation coatings for flues, protective coatings for kiln linings, reflective thermal insulation coatings for storage tanks, integrated fireproof & thermal insulation coatings, high-temperature resistant anti-corrosion thermal insulation coatings for metallurgical and chemical equipment.