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D4764-01 – Standard Test Method Technical Guide
This article outlines the key principles and procedures of ASTM D4764 −01 (Reapproved 2023), the standard test method for determining titanium dioxide (TiO₂) content in liquid paints using X-ray fluorescence (XRF) spectroscopy. This method provides a rapid, accurate, and reliable alternative to traditional wet chemical analysis, serving as an essential tool for quality control and formulation verification in the coatings industry.
📘 Scope and Significance of D4764
ASTM D4764 covers the determination of titanium dioxide content in both water-reducible and solvent-reducible liquid paints. Titanium dioxide pigments are critical components in coatings due to their high refractive index, significantly influencing the opacity, whiteness, and durability of the final film.
Compared to traditional wet chemical analysis (Test Methods D1394), this XRF method is notably quicker and easier to perform. It is ideally suited for routine analysis of single samples as well as high-throughput testing of large batches. A significant practical advantage is the indefinite stability and reusability of prepared drawdown standards.
| 📊 Feature | ⚡ XRF Method (D4764) | 🧪 Wet Chemistry (D1394) |
|---|---|---|
| Speed of Analysis | Rapid | Slow, laborious |
| Sample Throughput | High | Low |
| Standard Stability | High (indefinite storage) | Moderate (frequent prep required) |
| Operator Complexity | Straightforward | Careful technique required |
⚙️ Test Procedure and Internal Standard Technique
The method relies on an internal standard to compensate for variations in film thickness and matrix effects, ensuring consistent quantitative results. The core procedure is as follows:
- Preparation: A paint sample with a known TiO₂ content serves as the reference standard. A solution of tetraethylammonium bromide in 2-ethoxyethanol is added as an internal standard to both the reference and the unknown test paints.
- Drawdown: Uniform drawdown films of the prepared standard and test paints are cast onto thin plastic sheets.
- Measurement: The baseline-corrected intensities of the Ti Kα and Br Kα X-ray fluorescence peaks are measured from the prepared films.
- Calculation: The TiO₂ content is determined by comparing the intensity ratio (Ti Kα / Br Kα) of the test