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Analysis of Core Indicators of Silica
In conclusion, the core rule of silica's core indicators is "Finer particle size leads to lower bulk density; higher oil absorption value/specific surface area leads to lower bulk density". Mastering this rule can accurately match indicators based on application requirements.
Analysis of Core Indicators of Silica: Definitions, Correlation Rules and Typical Data
In the selection and application of silica, bulk density, particle size, specific surface area, and oil absorption value are core indicators. These four indicators have clear internal correlations and directly determine the basic performance of the product. The following is a streamlined professional analysis with unified units of g/cm³ (Note: 1g/ml = 1g/cm³, 1g/l = 0.001g/cm³).
1. Definitions of Core Indicators
1.1 Bulk Density
It refers to the mass of silica particle aggregates per unit volume, reflecting the tightness of particle arrangement. It is affected by the particle's own density, particle size distribution, and pore structure, with the unit of g/cm³.
1.2 Particle Size
It is the size characteristic of particles, commonly expressed by the corresponding relationship between "mesh-micron (μm)": the higher the mesh number, the smaller the particle size (e.g., 200 mesh corresponds to about 75 μm, 1200 mesh corresponds to about 10 μm); characteristic particle size (such as d50) can also be used to reflect the overall center of particle size distribution.
1.3 Specific Surface Area
It refers to the total surface area (including inner pore surface) of silica per unit mass, which is a key indicator for measuring particle activity, with the unit of m²/g. A higher value indicates more active sites on the particle surface.
1.4 Oil Absorption Value
It refers to the volume of oil that can be adsorbed by per unit mass of silica (often expressed by DBP absorption value), reflecting the pore development and looseness of particles, with the unit of ml/100g.
2. Internal Correlation Rules of Core Indicators
2.1 Particle Size and Bulk Density: Finer Particle Size Leads to Lower Bulk Density
Fine particles tend to agglomerate due to high surface energy, and the large proportion of voids inside the agglomerates leads to a decrease in bulk density; coarse particles have a small proportion of voids during arrangement, resulting in higher bulk density.
Data Evidence:
•200 mesh (about 75 μm): Bulk density 0.015-0.018 g/cm³;
•800-1000 mesh (about 13-15 μm): Bulk density 0.009-0.011 g/cm³;
•1200 mesh (about 10 μm): Bulk density 0.08-0.13 g/cm³;
•Nanoscale (5-15 nm): Bulk density 0.2-0.8 g/cm³.
2.2 Oil Absorption Value, Specific Surface Area and Bulk Density: Interactive Control Among the Three
•Positive correlation: The larger the specific surface area, the more developed the particle pores, and the higher the oil absorption value (e.g., when the specific surface area > 300 m²/g, the oil absorption value is often > 280 ml/100g);
•Negative correlation: The higher the oil absorption value/specific surface area, the more voids during particle accumulation, and the lower the bulk density.
Data Evidence:
•High oil absorption value (280 ml/100g): Low bulk density;
•Low oil absorption value (230 ml/100g): High bulk density.
2.3 Pore Volume and Bulk Density: Lower Pore Volume Leads to Higher Bulk Density
Pore volume reflects the total internal pore volume of particles. A smaller pore volume means a denser particle structure, which occupies less space during accumulation, resulting in a higher bulk density; at the same time, products with high bulk density are less likely to generate dust.
3. Reference Data of Typical Categories
| Silica Category | Particle Size Reference | Bulk Density (g/cm³) | Key Features |
| Conventional Grade (200 Mesh) | About 75 μm | 0.015-0.018 | Coarse particles, relatively high bulk density |
| Conventional Grade (800-1000 Mesh) | About 13-15 μm | 0.009-0.011 | Medium-fine particles, medium bulk density |
| Conventional Grade (1200 Mesh) | About 10 μm | 0.08-0.13 | Fine particles, low bulk density |
| Fumed Silica | 7-22 nm | 0.05 (conventional) | Ultra-fine particles, high specific surface area |
| Fumed Silica (Compacted) | 7-22 nm | 0.11 | Increased bulk density after compaction |
4. Core Application Value
2.Dust Control: Products with bulk density ≥ 0.23 g/cm³ have stable particle fluidity, which can reduce dust generation during use;
3.Adsorption/Catalysis: Products with bulk density ≤ 0.05 g/cm³ and specific surface area > 300 m²/g are suitable as adsorption materials or catalyst carriers;
4.System Regulation: Products with bulk density of 0.15-0.2 g/cm³ and high oil absorption value can adjust the viscosity of coating/ink systems and improve coating performance.
In conclusion, the core rule of silica's core indicators is "Finer particle size leads to lower bulk density; higher oil absorption value/specific surface area leads to lower bulk density". Mastering this rule can accurately match indicators based on application requirements.
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