Sieve Residue Analyzer and Sieve Analysis for Determining Pigment Particle Size Distribution

Principle

The sieve residue analyzer is an instrument based on the principle of mechanical screening to determine the particle content in a specific particle size range in powder materials such as pigments. Its core components include a standard screen, vibration device and weighing system. When working, the sample of known quality is placed on the top screen and the particles are passed through the screen of different pore sizes step by step through mechanical vibration, so as to achieve particle size classification. Particles that fail to pass through the designated screen are defined as sieve residue, and the percentage of their mass to the total mass of the sample is the sieve residue content. The process strictly adheres to domestic and international standards such as GB/T 1715 and ISO 787-7, ensuring the repeatability and comparability of the measurement results.

The relationship between screen size and pigment particle size distribution

The pore size specification of the screen directly determines the grading point of the particle size distribution. Standard screen series are usually expressed in microns or mesh, such as 45μm, 63μm, 125μm, etc. The particle size distribution of pigments is usually not singular, but presents a range. By using a series of screens with different pore sizes for graded screening, the mass distribution data of pigment samples over different particle size ranges can be accumulated. For example, particle size distribution information in the 63-125 μm range can be obtained by measuring the particle mass that passes through a 125 μm screen but remains on a 63 μm screen. This relationship is the basis for constructing a complete granularity distribution curve.

Assay method

Standard assay methods require stable environmental conditions and use analytical balances with an accuracy of 0.1mg. The specific steps include: sample drying, weighing the appropriate amount of specimen (usually 10g to 100g), assembling the screen stack, setting the vibration time and intensity, and accurately weighing the material on each screen layer and chassis after screening. At the heart of data analysis is the calculation of the mass fraction of each particle size. Let the total mass of the sample be M, and the mass of the particles remaining on the ith layer screen is m_i, then the mass fraction of the particle size (between the pore diameter of the upper and lower screens) is X_iIt can be calculated according to the following formula:

X_i = (m_i / M) × 100%

The cumulative distribution D under the screen can be expressed as: D = Σ (the mass fraction of each particle size passing through the screen). By drawing the cumulative distribution curve under the screen, the overall fineness and uniformity of the pigment can be visually assessed.

Influencing factors

To ensure accurate measurements, several key factors need to be controlled. The first is the representativeness of the sample, which needs to be fully mixed through techniques such as the four-part method. The second is the screening parameters, insufficient vibration time may lead to incomplete screening, and too long may cause particle fragmentation or electrostatic agglomeration. Improper control of ambient humidity can lead to fine powder adhesion, affecting results. In addition, the calibration and maintenance of the screen itself is crucial, and the screen should be regularly checked for damage or blockage and calibrated according to the standard. For samples prone to static electricity, consider using antistatic agents or operating at appropriate humidity.

Scope of application:

The screening method is suitable for the determination of pigments and similar powders with particle sizes ranging from approximately 20 microns to several millimeters. It is widely used in raw material quality control and product research and development in coatings, inks, ceramics, building materials and other industries. However, the method has low efficiency for the determination of ultrafine powders with a particle size of less than 20 microns, and it is difficult to distinguish the morphological differences of particles. For precise distribution analysis of sub-micron particles, techniques such as laser diffraction or sedimentation are often required. The value of screening methods lies in their intuitive principle, ease of operation, low cost, and ability to provide particle size data with good process guidance.

Parameter reference table

References

GB/T 1715-1979 Determination of pigment sieve residues

ISO 787-7:1981 Test methods for pigments and constitution pigments - Part 7: Determination of sieve residues - Water method

ASTM D185-07 Standard Test Method for Coarse Particles in Pigments, Paste Oils, and Paints