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D476-15 – Standard Test Method Technical Guide
📜 Scope and Significance of the Classification
ASTM D476-15 (Reapproved 2021) provides a standard classification for eight types of dry pigmentary titanium dioxide products. These types are grouped by their composition, typical end-use applications, and fundamental performance properties. The standard is strictly limited to dry, hiding pigments and explicitly excludes pigment dispersions and non-hiding specialty titanium dioxide products, as defined in Section 3.1.
The classification is intended as an aid in determining the fitness for use of a titanium dioxide pigment for a coating application. Per the standard, the values stated in SI units are to be regarded as the standard unit of measurement. The document outlines general differences between pigment types to guide selection while allowing maximum flexibility.
💡 Key Clarification: While this standard classifies pigment types by minimum composition, desired performance properties beyond the scope of Table 1 must be based on a mutually agreed match between the submitted pigment sample and a previously agreed-upon reference sample between the purchaser and the seller (Section 5.2).
📐 Composition Requirements and Pigment Types
Per Section 5.1, all classified titanium dioxide pigments must be chemically prepared with either an Anatase or Rutile crystalline structure. They may include modifications with water-insoluble oxides of aluminum, silicon, or zinc specifically to improve performance properties. Crucially, the pigments must be free of extenders such as barium sulfate, clay, magnesium silicate, and whiting. The standard classifies these dry hiding pigments into eight distinct types as detailed in Table 1 below.
| 🟦 Type | 📏 Crystal Form | 📐 Min. TiO₂ (wt%) | 🎯 Typical End Use |
|---|---|---|---|
| I | Anatase | ≥ 94 | General purpose, high pigmentation |
| II | Anatase | ≥ 92 | Medium durability coatings |
| III | Rutile | ≥ 90 | General purpose interior/exterior |
| IV | Rutile | ≥ 87 | High gloss enamels |
| V | Rutile | ≥ 93 | High durability exterior (high PVC) |
| VI | Rutile | ≥ 90 | High durability exterior (medium PVC) |
| VII | Rutile | ≥ 80 | Multifunctional, high hiding power |
| VIII | Rutile | ≥ 80 | High gloss, high durability |
⚙️ Standard Test Methods for Evaluation
Section 6 of the standard specifies that all testing must be conducted according to specific ASTM test