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D2320-98 – Standard Test Method Technical Guide
📐 Scope and Essential Apparatus
This test method, designated D2320-98 (Reapproved 2022), specifies the procedure for determining the density and relative density of solid pitch using a pycnometer. It is intended for pitch that can be handled in fragments. The standard strictly utilizes SI units for all measurements.
| 🟦 Apparatus | 📏 Specification / Detail |
|---|---|
| Glass Pycnometer | Capacity of approximately 25 mL, fitted with a glass stopper having a capillary tube 1.0 mm to 2.0 mm in diameter. |
| Water Bath | Maintained at 25.0 °C ± 0.1 °C with mechanical stirring. |
| Vacuum System | Vacuum pump or aspirator capable of achieving 2.7 kPa (20 torr), monitored by a manometer, used within a vacuum desiccator with guard. |
| Sieves | U.S. Standard 2.36 mm (No. 8) and 600 µm (No. 30) sieves conforming to Specification E11. |
⚙️ Test Procedure and Critical Parameters
The sample is weighed, and its volume is determined by the mass of water it displaces in the pycnometer. Bulk samples are obtained according to Practice D4296 and must be free of foreign substances. A representative portion is thoroughly mixed and sieved to the required particle size.
⚠ Critical Vacuum Step: A vacuum of 2.7 kPa (20 torr) must be applied and held until all entrapped air is removed from the pitch sample. This ensures the water completely fills all voids, allowing for an accurate volume measurement. A wetting agent (0.1 g/mL Aerosol OT or BRU 35) is used to facilitate water penetration and displacement.
The test is conducted at a tightly controlled temperature of 25.0 °C ± 0.1 °C to minimize thermal expansion errors.
📊 Key Measured Properties and Calculations
The standard defines and determines two closely related values essential for material characterization and commercial transactions.
| 🎯 Property | ⚡ Definition (per Standard) |
|---|---|
| Density | The mass per unit of volume at the standard test temperature of 25.0 °C. |
| Relative Density | The ratio of the mass of a given volume of the material at the standard test temperature to that of an equal volume of water at the same temperature. |
📌 Key Application: These values are fundamental for converting volumes of solid pitch to units of mass. This conversion is critical for compliance with other ASTM standards and for the execution of sales transactions.
❓ Frequently Asked Questions
🔍 What is the fundamental principle behind this density test?
The method is based on weighing the sample and determining its volume by measuring the mass of water displaced when the pitch is submerged in a pycnometer.
💡 Why is a wetting agent specified in the procedure?
A wetting agent (0.1 g/mL Aerosol OT or BRU 35) is required to break the surface tension and ensure complete water penetration into the pores and surface irregularities of the pitch fragments, which is essential for accurate displacement.
⚡ What is the required vacuum level and why is it important?
The apparatus must be capable of producing a vacuum of 2.7 kPa (20 torr). This vacuum is applied to remove entrapped air from the sample and the water, ensuring the measured volume corresponds strictly to the solid material.
📌 What sample preparation is required regarding particle size?
The sample must be prepared to pass through a 2.36 mm (No. 8) sieve but be retained on a 600 µm (No. 30) sieve, per Specification E11. This ensures uniform fragment size for consistent density measurement.