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D2636-07 – Standard Test Method Technical Guide
🧪 Specification Scope and Referenced Documents
This specification, designated ASTM D2636 −07 (Reapproved 2012), is issued under the jurisdiction of ASTM Committee D01 on Paint and Related Coatings, Materials, and Applications. It covers the requirements for hexylene glycol (2-methyl pentanediol-2,4) intended for use in paints, varnishes, lacquers, and related coating products. The standard explicitly states that for determining conformance, observed or calculated values shall be rounded off “to the nearest unit” in the last right-hand digit used in expressing the specification limit, in accordance with Practice E29.
The standard references several key ASTM methods, including D268 (Guide for Sampling and Testing Volatile Solvents), D1078 (Distillation Range), D1209 (Color), D1364 (Water by Karl Fischer), D1613 (Acidity), D1722 (Water Miscibility), D4052 (Digital Density), D5386 (Instrumental Color), and Practice E300 (Sampling Industrial Chemicals). Packaging must comply with U.S. Federal Specification PPP-C-2020.
📊 Physical and Chemical Property Requirements
Hexylene glycol must conform to strict property limits to ensure suitability for high-performance coatings. The table below outlines the mandatory requirements as detailed in Section 3 of the standard.
| 📏 Property | 🎯 Specification Limit | ⚡ Test Method |
|---|---|---|
| Apparent Specific Gravity (20/20°C) | 0.921 to 0.925 | D268 / D4052 |
| Apparent Specific Gravity (25/25°C) | 0.918 to 0.922 | D268 / D4052 |
| Color, Pt-Co units, max | 15 | D1209 (Note 1) |
| Distillation Range | 3.0°C to include 197.1°C | D1078 |
| Acidity (as acetic acid), wt %, max | 0.005 | D1613 |
| Water, wt %, max | 0.1 | D1364 |
| Water Miscibility | Passes Test | D1722 |
⚠️ Note on Color Testing: Instrumental Pt-Co color determined by Test Method D5386 has been shown to have no statistically significant difference from Pt-Co color determined by Test Method D1209. However, it is not known if hexylene glycol was part of the sample set included in the interlaboratory study (Refer to Note 1 in the standard).
⚙️ Test Methods and Sampling Procedures
The properties enumerated in this specification must be determined in accordance with the referenced ASTM methods. The apparent specific gravity must be determined by any method accurate to the third decimal place, with the temperature of both the specimen and water controlled at exactly 20°C or 25°C (see Guide D268 and Test Method D4052). Color is determined via Test Method D1209, and distillation behavior is evaluated per Test Method D1078, verifying the boiling range includes 197.1°C within a 3.0°C window.
Water content is strictly controlled using the Karl Fischer Reagent Titration Method (D1364), and acidity must be monitored to a maximum of 0.005% as acetic acid (D1613). Sampling of the material must be conducted in accordance with Practice E300, which covers the sampling of industrial chemicals.
✅ SI Units and Rounding: The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. Always round off test results “to the nearest unit” of the last right-hand digit in the specification limit per Practice E29 when determining conformance.
❓ Frequently Asked Questions
🔍 What is the primary application for hexylene glycol under this standard?
ASTM D2636 specifically covers hexylene glycol intended for use as a solvent or chemical intermediate in the formulation of paints, varnishes, lacquers, and related coating products.
💡 How is the purity assessed regarding water content?
The standard mandates a maximum water content of 0.1% by weight. This is rigorously determined using the Karl Fischer Reagent Titration Method as described in ASTM D1364.
⚡ What are the specific gravity requirements?
At a temperature ratio of 20/20°C, the apparent specific gravity must be between 0.921 and 0.925. At 25/25°C, it must be between 0.918 and 0.922. Measurement must be accurate to the third decimal place, typically using a digital density meter per D4052 or a hydrometer per Guide D268.
📌 What is the maximum allowable acidity level?
The acidity, expressed as free acid equivalent to acetic acid, must not exceed 0.005% by weight. This is determined following the procedure outlined in Test Method D1613.