Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D3360-96 – Standard Test Method Technical Guide
📐 Scope and Application
This test method covers the determination of the particle-size distribution in the sub-sieve size range of common extender pigments such as aluminum silicate (kaolin clay), magnesium silicate (talc), calcium carbonate (calcite or dolomite or precipitated calcium carbonate), and mica pigments. It may also be extended to denser prime pigments like white titanium pigments (rutile or anatase) and similar mineral pigments when such information is of concern.
Particle-size distribution has significance in evaluating rheological and pigmentary properties of pigments in paint and may also be used to characterize the identity or grade of pigments. Sedimentation methods based on Stokes’ law are used, with results expressed in terms of equivalent spherical diameter (e.s.d.), the diameter of a sphere having the same specific gravity as the particle and settling at the same rate.
This standard does not purport to address all safety concerns. It is the responsibility of the user to establish appropriate safety and health practices and determine regulatory limitations prior to use.
⚙️ Test Method Summary
For the determination of particle-size distribution by the application of Stokes’ law to the sedimentation of particulate material from an initially homogeneous suspension, any systematic set of measurements which permit the determination of the suspension density (percent solids) at some defined distance beneath the surface of the suspension at appropriately selected sedimentation time durations can be converted to a particle-size distribution. In this procedure, the suspension density is estimated at the effective distance beneath the suspension surface of the center of gravity of a floating hydrometer observed at a series of convenient time intervals selected to increase roughly exponentially.
Alternative systems such as the Andreasen Pipet Method, or optical methods based on turbidity, light scattering, or absorption, can also yield a particle-size distribution. The following referenced standards are integral to this test method:
| 🟦 Standard | 📏 Description |
|---|---|
| D 280 | Test Methods for Hygroscopic Moisture (and Other Matter Volatile Under the Test Conditions) in Pigments |
| D 422 | Test Method for Particle-Size Analysis of Soils |
| D 1193 | Specification for Reagent Water |
| E 100 | Specification for ASTM Hydrometers |
| E 300 | Practice for Sampling Industrial Chemicals |
📊 Key Parameters and Limitations
This test method is particularly applicable to pigments if a major fraction of the particles fall in the range from about 15 to 1.5 µm e.s.d., with a total particle-size range of at least two decades. Gravitational sedimentation procedures are relatively inaccurate for particles smaller than about 1 µm e.s.d., and centrifugal procedures may be required for much finer ranges. Data obtained above the 1-µm limitation provide useful information.
Most mineral pigment particles are asymmetrical, but despite differences in the relationship between equivalent spherical diameter and actual dimensions, the results of a sedimentation particle-size analysis can be correlated readily with many pigment properties.
| 🎯 Particle Size Range | 📐 Applicability |
|---|---|
| 15 to 1.5 µm e.s.d. | Major fraction for common extender pigments |
| Below 1 µm e.s.d. | Requires centrifugal procedures for accurate analysis |
| At least two decades | Total particle-size range for effective application |
⚠️ Safety Note: This standard does not address all safety concerns. Users must establish appropriate safety and health practices and comply with regulatory limitations before use.
💡 Alternative Methods: Equivalent measurements can be obtained using the Andreasen Pipet Method or optical methods based on turbidity, light scattering, or absorption, which may offer advantages for specific applications.
❓ Frequently Asked Questions
🔍 What types of pigments are covered by this standard?
This standard covers common white extender pigments such as aluminum silicate (kaolin clay), magnesium silicate (talc), calcium carbonate (calcite, dolomite, or precipitated), and mica pigments. It can also be extended to denser prime pigments like white titanium pigments (rutile or anatase) and similar mineral pigments.
💡 What is the principle behind the test method?
The test method is based on Stokes’ law, which describes the sedimentation of particles in a suspension. By measuring the suspension density at specific depths and times using a hydrometer, the particle-size distribution can be calculated in terms of equivalent spherical diameter (e.s.d.), which represents the diameter of a sphere with the same specific gravity settling at the same rate.
⚡ What is the applicable particle size range for this test method?
This test method is particularly applicable when a major fraction of particles fall between about 15 and 1.5 µm e.s.d., with a total particle-size range of at least two decades. Gravitational sedimentation is less accurate for particles smaller than 1 µm e.s.d., where centrifugal methods may be needed.
📌 What are the limitations of the gravitational sedimentation method?
Gravitational sedimentation methods are relatively inaccurate for particles smaller than about 1 µm e.s.d. Additionally, most mineral pigment particles are asymmetrical, but results can still be correlated with pigment properties despite differences between equivalent spherical diameter and actual dimensions.