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D2591-07 – Standard Test Method Technical Guide
📐 Scope and Specimen Requirements
ASTM D2591-07 (Reapproved 2020) specifies a test method for determining the linear density of short lengths of “as produced” elastomeric yarns made from rubber, spandex, or other elastomers. It is applicable to yarns in the range of 40 to 3200 dtex (36 to 2900 denier). This method is not intended for covered, wrapped, or core-spun yarns, yarns spun from elastomeric staple, or elastomeric yarns removed from fabrics. For the determination of linear density using skeins, refer to Test Method D6717.
The values stated in SI units or U.S. Customary units are to be regarded separately as standard, and each system shall be used independently of the other.
| 🟦 Parameter | 📏 SI Range | 📐 US Customary Range |
|---|---|---|
| Linear Density | 40 – 3200 dtex | 36 – 2900 denier |
⚙️ Test Procedure and Calculations
The test method requires a pre-relaxed specimen to be fastened vertically in an apparatus under a specified tension. A specified length is then cut from the specimen and weighed. The linear density is calculated from the mass and length. Proper sampling according to Practice D2258 ensures representative results. Terminology relevant to this standard includes denier, elastomeric yarn, linear density, and tex, as defined in Terminology D4849.
| 🔍 Term | 📖 Definition (per D4849) |
|---|---|
| Denier | Linear density expressed in grams per 9000 meters |
| Tex | Linear density expressed in grams per 1000 meters |
| dtex | Linear density expressed in grams per 10,000 meters |
📊 Significance and Use
This test method is considered satisfactory for acceptance testing of commercial shipments because current estimates of between-laboratory precision are acceptable, and it is used extensively in the trade. Linear density of elastomeric yarns is used in calculations for tensile and elastic properties. If there are differences of practical significance between laboratories, comparative tests should be performed to determine if statistical bias exists, using competent statistical assistance.
💡 For accurate results, ensure specimens are pre-relaxed and the tension during mounting is consistent with the specified conditions.
⚠️ This test method is not applicable to covered, wrapped, or core-spun yarns. For such materials, alternative methods should be employed.
❓ Frequently Asked Questions
🔍 What is the linear density range covered by D2591? The method covers yarns from 40 to 3200 dtex (equivalent to 36 to 2900 denier).
💡 How is the specimen prepared for testing? The specimen must be pre-relaxed and then fastened vertically under a specified tension before cutting a defined length for weighing.
⚡ Can this test method be used for yarns removed from fabrics? No, it is only applicable to “as produced” elastomeric yarns, not those removed from fabrics.
📌 What standards are referenced for terminology? Terminology D4849 for yarn and fiber terms, and Terminology D123 for general textile terms.