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D5137-07 – Standard Test Method Technical Guide
📊 Properties and Specification Requirements
Hexyl acetate conforming to ASTM D5137-07 (2021) must meet specific compositional and physical limits to ensure its efficacy as a high-boiling active solvent in industrial coatings. The standard details strict requirements for purity, distillation behavior, and physical properties. Below is a summary of the mandatory specification limits and the associated ASTM test methods for certification.
| 🧪 Property | 📏 Specification Limit | 🔬 Test Method |
|---|---|---|
| Acidity (free acid as acetic acid), wt% | 0.02 max | D1613 |
| Apparent Specific Gravity (20/20 °C) | 0.872 – 0.876 | D4052 |
| Apparent Specific Gravity (25/25 °C) | 0.868 – 0.872 | D4052 |
| Color, Pt-Co units | 15 max | D1209 / D5386 |
| Distillation Range, Initial Boiling Point | 162 °C min | D1078 |
| Distillation Range, 95% Point | 176 °C max | D1078 |
| Electrical Resistivity (Ransburg) | 20 MΩ·cm min | — |
| Ester Value, wt% | 99.0 min | D1617 |
| Water Content, wt% | 0.05 max | D1364 |
⚡ Conformance Rounding: Per Section 1.3 of the standard, conformance must be determined by rounding off observed or calculated values “to the nearest unit” of the specification limit, strictly following the methods outlined in ASTM Practice E29.
🔬 Sampling Protocols and Testing Guidance
The standard references several critical ASTM methods for evaluating hexyl acetate. Sampling must be conducted in accordance with Practice E300. Specific properties are assessed using standardized methodologies: Test Method D1078 defines the distillation range procedure, color can be assessed visually by D1209 or instrumentally by D5386, and water content is determined via Karl Fischer titration under D1364. The ester value, a direct measure of compound purity, is determined by D1617, while density is measured using a digital density meter per D4052.
💡 Color Testing Note: While Test Method D1209 is the long-standing visual standard for Pt-Co color, Test Method D5386 (Tristimulus Colorimetry) yields statistically equivalent results. However, Note 1 in the specification advises that it is unknown if hexyl acetate was specifically part of the interlaboratory study dataset for D5386.
⚠️ Referenced Document Status: Users should be aware that several key documents referenced in D5137, including Guide D268 and Test Methods D1364, D1476, and D1617, have been officially withdrawn with the latest edition of D5137. It is the user’s responsibility to identify suitable alternative standards or historical versions for full compliance.
📦 Applications and Key Quality Metrics
Hexyl acetate classified under D5137 is specifically intended for use as an active tail solvent with a high boiling range, optimizing the evaporation profile of lacquers and automotive coatings. A critical quality parameter for electrostatic spray applications is the minimum electrical resistivity of 20 megohms. Additionally, the stringent limit on water content (0.05 wt% max) prevents adverse reactions in moisture-sensitive coating systems. The standard permits flexibility in specific gravity reporting, offering limits at both 20/20 °C and 25/25 °C, and the selected temperature must be stated in the test report.
❓ Frequently Asked Questions
🔍 What is the primary application of hexyl acetate under this specification?
Hexyl acetate is predominantly utilized as an active tail high boiling solvent in lacquers, automotive coatings, maintenance paints, and other related coatings.
💡 What is the minimum ester value required for compliance with D5137?
The ester value, which indicates the purity of the hexyl acetate, must be a minimum of 99.0 weight percent as determined by Test Method D1617.
⚡ What are the distillation range requirements for hexyl acetate?
The standard requires an initial boiling point (IBP) of no less than 162 °C and a 95% distillation point of no more than 176 °C, as determined by Test Method D1078.
📌 How is the water content of hexyl acetate specified in this standard?
The water content of hexyl acetate must not exceed 0.05 weight percent, tested according to the Karl Fischer Reagent Titration Method (ASTM D1364).