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D185-07 – Standard Test Method Technical Guide
ASTM D185-07 (Reapproved 2023) provides standardized test methods for determining the amount of coarse particles in dry pigments. These methods are essential for quality control in paint production, focusing on particles larger than 45 µm to ensure film smoothness.
📜 Scope and Significance
These test methods cover the determination of coarse particles in dry pigments. The smoothness of the paint film is of paramount importance, and agglomerates or coarse particles larger than 45 µm are difficult to disperse. These test methods serve as a valuable quality control tool for grading raw materials. The values stated in SI units are regarded as the standard.
🔬 Apparatus and Sieve Specifications
The apparatus consists of a 200 mm (8 in.) 45 µm (No. 325) sieve conforming to ASTM E11. A reference standard sieve should be retained in the laboratory. New sieves must be verified against the reference using a pigment with a significant amount of coarse particles. A reserve stock of such pigment should be kept for this purpose.
| 🟦 Specification | 📏 Detail |
|---|---|
| Diameter | 200 mm (8 in.) |
| Mesh Size | 45 µm (No. 325) |
| Conforming Standard | ASTM E11 |
⚙️ Test Procedure for Dry Pigments
This procedure applies to insoluble dry pigments, except metallic aluminum and bronze powders. Weigh approximately 100 g of the pigment specimen to the nearest 0.1 g. Wet the sieve on both sides with water and transfer the pigment. Hold the sieve under a tap delivering 300 mL to 500 mL of water per minute. Slightly shake the sieve and use a soft camel-hair brush to aid wetting and passage. Continue until no pigment passes through. Tilt the sieve to collect retained particles and rinse into a 100 mL beaker. Allow settling, decant water, and dry at 105°C ± 2°C. Ensure no material is lost by spattering.
| 🎯 Parameter | 📐 Value |
|---|---|
| Sample Mass | 100 g (±0.1 g) |
| Wash Rate | 300-500 mL/min |
| Drying Temperature | 105°C ± 2°C |
Always calibrate new sieves against the reference standard to ensure accuracy in coarse particle detection.
Monitor the water flow rate; exceeding 500 mL/min may cause loss of retained particles.
❓ Frequently Asked Questions
🔍 What is the purpose of ASTM D185-07? It specifies methods to determine coarse particles in dry pigments, crucial for paint film quality and dispersion.
💡 Which pigments are excluded from the procedure? The procedure does not apply to metallic aluminum and bronze powders.
⚡ How is the retained material collected? After washing, tilt the sieve and rinse retained particles into a beaker, then dry at 105°C ± 2°C.
📌 What sieve specification is required? A 200 mm (8 in.) 45 µm (No. 325) sieve conforming to ASTM E11 is required.