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D1823-24 – Standard Test Method Technical Guide
📐 Scope and Terminological Framework
Standard D1823 − 24, under the jurisdiction of ASTM Subcommittee D20.15 on Thermoplastic Materials, defines a definitive test method for determining the apparent viscosity of plastisols and organosols under high shear rate conditions using an extrusion viscometer. It serves as a companion to Test Method D1824, which covers low shear rate measurements, providing a comprehensive understanding of a material’s flow characteristics. The standard emphasizes that SI units are the official standard, with inch-pound values provided purely for reference as stated in Section 1.3.
The terminology section establishes critical definitions. For instance, a plastisol is strictly defined as a liquid suspension of finely divided PVC polymer or copolymer in a plasticizer, while an organosol introduces a volatile organic liquid into this suspension. Understanding these precise definitions is fundamental to the correct application of the test method. The standard also provides a technical discussion on viscosity, clarifying that the “apparent viscosity” derived from this test acknowledges the non-Newtonian behavior of these materials, where the ratio of shearing stress to rate of shear is not constant.
| 🟦 Clause / Term | 📐 Key Definition / Requirement |
|---|---|
| 📏 Plastisol (3.3.3) | A liquid suspension of a finely divided PVC polymer or copolymer in a plasticizer. |
| ⚡ Organosol (3.3.1) | A suspension of a finely divided polymer in a plasticizer, together with a volatile organic liquid. |
| 🎯 Apparent Viscosity (3.3.5) | The ratio of shearing stress to the rate of shear. Varies with shear rate for plastisols and organosols. |
| 📌 Scope (1.1) | Measurement of viscosity at high shear rates via an extrusion viscometer. |
✅ Regulatory Note: As an international standard, D1823-24 adheres to the World Trade Organization’s principles on international standardization issued by the TBT Committee. This standard and ISO 4575-2007 address the same subject matter, but differ in technical content.
⚙️ Referenced Standards and Material Specifications
The execution of D1823-24 draws directly on a network of parallel ASTM standards. The density of the liquid plastisol or organosol, an essential input for calculating volumetric flow rates, is determined according to Test Method D1475. The poly(vinyl chloride) resins used in formulating the test materials are expected to conform to Specification D1755.
Temperature control is paramount for accurate viscosity measurement. The standard mandates the use of thermometers that conform to Specification E1 for ASTM Liquid-in-Glass Thermometers. Statistically, the precision of the entire test method is established through interlaboratory studies conducted according to Practice E691, and any comparison of testing processes follows Practice E2935.
| 🟦 Standard | 📏 Function in D1823-24 |
|---|---|
| 📐 D1475 | Specifies density measurement for liquid coatings. |
| ⚡ D1824 | Defines the complementary procedure for low shear rate viscosity. |
| 🎯 E691 | Interlaboratory study practice for determining precision. |
| 📌 E2935 | Evaluating equivalence of two testing processes (e.g., vs. ISO 4575). |
📊 High Shear Viscosity and Precision Characteristics
The core measurement in D1823-24 is the resistance to flow exhibited by plastisols and organosols under high shear stress. The extrusion viscometer forces the material through a capillary die, and the resulting flow characteristics are used to calculate the apparent viscosity. The method explicitly discusses the non-Newtonian nature of these systems, where the viscosity coefficient (η) varies with the rate of shear, making the reporting of shear rate alongside the apparent viscosity a critical practice.
This method, originally approved in 1961 and revised in April 2024, provides a robust framework for quality control. Precision and bias are rigorously defined through the framework of Terminology E456 and Practice E691. Users are encouraged to rely on these defined protocols to establish the statistical validity of their test results.
💡 Critical Distinction: The behavior discussed in this test method is non-Newtonian. The “apparent viscosity” is strictly valid only for the specific shear rate at which it was determined. Always report the shear rate used. It is the responsibility of the user to establish appropriate safety, health, and environmental practices prior to use.
❓ Frequently Asked Questions
🔍 What is the designated apparatus for this test method?
The test method specifically requires an extrusion viscometer, commonly known as a Severs rheometer. This apparatus forces the test material through a calibrated capillary die at a controlled rate or pressure.
💡 How does this test method relate to D1824?
D1823-24 is specifically designed for measuring apparent viscosity at high shear rates, while Test Method D1824 covers measurements at low shear rates. They are explicitly designated as complementary standards for a full rheological profile.
⚡ Are the units strictly specified in the standard?
Yes. Section 1.3 explicitly states: “The values stated in SI units are to be regarded as standard. The values in parentheses are given for information only.” Full compliance requires reporting in SI units.
📌 What is the relationship between this standard and ISO 4575?
D1823-24 states it addresses the same subject matter as ISO 4575-2007, but the two standards differ in technical content. Practice E2935 is the prescribed method for formally evaluating the equivalence of results between the two testing processes.