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D4031-07 – Standard Test Method Technical Guide
The ASTM D4031-07 (Reapproved 2018) standard provides a standardized methodology for measuring the bulk properties of textured yarns. By evaluating the change in length of a tensioned skein subjected to specific environmental and loading conditions, this test method quantifies critical yarn characteristics such as skein shrinkage, crimp contraction, bulk shrinkage, and crimp recovery.
📐 Scope and Specimen Requirements
This test method is specifically designed for crimped, continuous multifilament yarns. It measures the length changes in a tensioned skein when its crimp characteristics are altered by exposure to wet or dry heat. The standard applies to yarns ranging from 1.7 to 88.9 tex (15 to 800 denier). Three distinct conditions for crimp development mediums and several loading routines are provided to allow determination of yarn bulk by several different procedures.
Values are stated in both SI units and inch-pound units. According to the standard, each system shall be used independently of the other, as the values stated in each system are not exact equivalents. Combining values from the two systems may result in nonconformance with the specification.
⚙️ Test Procedure and Loading Routines
A skein of yarn of a prescribed linear density is prepared and subjected to a crimp development medium using a specific loading routine. As the crimp is developed or shrinkage occurs in the yarn, the skein changes in length. The lengths of the skein under specified tension forces are used to calculate the value of bulk shrinkage, crimp contraction, skein shrinkage, or crimp recovery.
⚠️ Important Note: The loading routines consist of low-tension forces (light loads of 0.04 to 0.98 mN/tex (0.5 to 11 mgf/den)) that extend the yarn without removing crimp, and high-tension forces (heavy loads of 8.8 mN/tex (100 mgf/den)) that remove crimp without elongating the yarn. A list of weights to be used is given in Table 1 of the standard.
| 🔧 Loading Type | ⚡ Tension Range (mN/tex) | ⚡ Tension Range (mgf/den) | 🎯 Purpose |
|---|---|---|---|
| Light Load (Extending Load) | 0.04 – 0.98 | 0.5 – 11 | Extend yarn without removing crimp |
| Heavy Load (Removing Load) | 8.8 | 100 | Remove crimp without elongating yarn |
📊 Key Measured Properties and Significance
The test method allows for the calculation of several important properties depending on the loading routine and crimp development medium used.
| 📊 Measured Property | 📐 Description |
|---|---|
| Skein Shrinkage | Irreversible reduction in skein length after exposure to heat. |
| Crimp Contraction | Reversible measure of the yarn’s potential to retract as crimp is developed. |
| Bulk Shrinkage | Change in length due to the development of crimp characteristics from heat. |
| Crimp Recovery | Extent to which the yarn returns to its original crimped state after deformation. |
💡 Tip on Significance: The values obtained by this test method should not be used to predict similar properties in fabricated structures except in narrow well-defined comparisons, such as 16.7 tex (150-denier) polyester from the same feed yarn merge and textured on the same machine type.
❓ Frequently Asked Questions
🔍 What types of yarn are covered by ASTM D4031?
This test method applies specifically to crimped, continuous multifilament yarns ranging from 1.7 to 88.9 tex (15 to 800 denier).
💡 What are the standard tension ranges for the loading routines?
Light loads range from 0.04 to 0.98 mN/tex (0.5 to 11 mgf/den), and heavy loads are 8.8 mN/tex (100 mgf/den).
⚡ How should the units in this standard be handled?
Values are stated in both SI units and inch-pound units. These two systems of units are not exact equivalents and shall be used independently of one another.
📌 What are the primary properties measured by this test method?
The method provides calculations for skein shrinkage, crimp contraction, bulk shrinkage, and crimp recovery, depending on the specific procedure employed.