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D2372-85 – Standard Test Method Technical Guide
ASTM D2372-85 (Reapproved 2022) provides a standardized practice for separating the liquid vehicle from the pigment in solvent-reducible paints. This procedure is a critical preliminary step for analysts needing to isolate the binder for compositional analysis via chemical, spectroscopic, or chromatographic methods, as the vehicle formulation fundamentally dictates the performance characteristics of the final coating.
🔬 Scope and Significance
The practice specifically covers the separation of the vehicle from the pigment phase. It was validated using a range of white paints, including soya and fish oil isophthalic alkyd semi-gloss enamels, linseed oil paints, and o-phthalic alkyd enamels. It is generally considered applicable to similar solvent-reducible systems. All values in the standard are regarded as standard in SI units, and users are responsible for establishing appropriate safety protocols (Section 1.4).
⚙️ Apparatus and Procedure
The central piece of apparatus required is a high-speed centrifuge. The centrifuge must be capable of achieving a relative centrifugal force (RCF) well in excess of 10,000 g to ensure effective sedimentation of the fine pigment particles.
| 🟦 Apparatus Parameter | 📐 Required Specification |
|---|---|
| Centrifuge Type | High-Speed Centrifuge |
| Minimum G-Force | In excess of 10,000 g |
| G-Force Formula (Note 1) | g = 1.118 × 10⁻⁶ × r × n² (r = radius in mm, n = speed in r/min) |
| Specimen Volume | ~20 mL of whole paint |
| Optional Solvent Volume | 10 mL of a suitable solvent |
The following procedural