Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D6093-97 – Standard Test Method Technical Guide
This article provides an overview of ASTM D6093-97, a standard test method for determining the percent volume nonvolatile matter in clear or pigmented coatings using a helium gas pycnometer. This method offers improved accuracy over traditional liquid displacement techniques, particularly for coatings with pores or defects, by leveraging helium gas to penetrate small surface irregularities.
📐 Scope and Key Constraints
The test method covers the determination of percent volume nonvolatile matter for various clear and pigmented coatings. It is faster and more accurate than Test Method D2697, especially for coatings that are difficult to wet or contain voids. The use of helium gas under pressure allows penetration of very small pores and surface irregularities in dried films, providing a more accurate void volume determination.
Valid results require the following constraints:
| 🟦 Constraint | 📏 Requirement |
|---|---|
| Helium Gas Pycnometer Stability | > 0.005 cm³ |
| Test Specimen Weight | > 1 g |
⚙️ Test Procedure and Summary
This procedure measures the volume of nonvolatile material in a dried or baked coating film. A helium gas pycnometer determines the volume occupied by the film by measuring the reduction of gas capacity in the sample chamber due to the specimen. A pressure transducer measures the difference in pressure between empty and loaded compartments, and the volume is calculated using the Ideal Gas Law. The specimen weight is also measured to calculate dry film density.
💡 This method provides superior accuracy compared to liquid displacement techniques because helium gas can penetrate pores and voids that liquids cannot, giving a true volume measurement of the solid film.
The percent volume nonvolatile content is then calculated using the dry film density, liquid coating density, and weight percent nonvolatile content of the coating.
📊 Calculations and Referenced Standards
The dry film density is derived from the weight and volume measurements. The percent volume nonvolatile matter is calculated based on this density, the density of the liquid coating, and the weight percent nonvolatile matter. The method references several ASTM standards for related measurements:
| 🟦 Standard | 📐 Description |
|---|---|
| D1475 | Test Method for Density of Liquid Coatings |
| D2369 | Test Method for Volatile Content of Coatings |
| D2697 | Test Method for Volume Nonvolatile Matter |
| D3960 | Practice for Determining VOC Content |
| D4708 | Practice for Preparation of Uniform Free Films |
⚠️ Ensure the helium gas pycnometer is properly calibrated and maintained to meet the stability requirement of >0.005 cm³ for accurate results. Specimen weights should exceed 1 gram.
❓ Frequently Asked Questions
🔍 How does this method improve accuracy over D2697?
Helium gas under pressure can penetrate very small pores and surface irregularities in dried films that liquids cannot, providing a more accurate determination of void volumes and true film density.
💡 What types of coatings are suitable for this test?
The method covers a variety of clear and pigmented coatings, particularly those difficult to wet or containing voids, cracks, or other defects.
⚡ What are the key constraints for valid results?
The helium gas pycnometer must have stability greater than 0.005 cm³, and test specimen weights must exceed 1 gram.
📌 How is percent volume nonvolatile matter calculated?
It is calculated using the dry film density (from weight and volume measurements), liquid coating density, and weight percent nonvolatile content, as outlined in the standard.