ASTM D2731-21 PDF

Overview

ASTM D2731-21: Standard Test Method for Elastic Properties of Elastomeric Yarns (CRE Type Tensile Testing Machines) is an internationally recognized standard developed by ASTM International. It establishes procedures for determining the elastic properties of “as produced” elastomeric yarns made from materials such as rubber and spandex. The key elastic properties evaluated by this method include force at specified elongations (FASE), permanent deformation (set), and stress decay. By providing a precise, repeatable methodology, this standard supports consistency in quality control across the textile and yarn manufacturing industry.

This method relies on CRE (Constant Rate of Extension) type tensile testing machines, ensuring reliable measurement of yarn performance parameters essential for acceptance testing of commercial shipments.

Key Topics

• Elastic Properties Measured: The primary properties assessed are:

  • Force at Specified Elongation (FASE): Indicates the tensile force when a yarn is stretched to defined elongation percentages (typically 100%, 200%, and 300%).
  • Permanent Deformation (Set): Measures the residual stretch in yarn after repeated stretching and relaxation cycles.
  • Stress Decay: Assesses the decrease in stress over time while the yarn is held at maximum extension.

• Applicable Materials: The standard covers elastomeric yarns, including those made from rubber or spandex, with a linear density ranging from 40 to 3200 dtex (36 to 2900 denier).

• Test Limitations: D2731-21 does not apply to covered, wrapped, or core-spun yarns, nor to yarns spun from elastomeric staple fibers.

• Uniformity and Bias Assessment: The standard includes recommendations for resolving discrepancies between laboratory results, such as conducting statistical analysis using samples from the same lot.

• International Relevance: Developed according to globally recognized standardization principles, this method is widely accepted for material acceptance testing in the textile industry.

Applications

• Quality Control in Yarn and Textile Manufacturing: ASTM D2731-21 is extensively used for acceptance testing of elastomeric yarn batches to ensure consistent performance and product quality before further processing or shipment.

• Product Development and Research: The standard supports research into new elastomeric yarns by providing quantitative data on key elastic characteristics, facilitating innovation in stretch fabrics and advanced textiles.

• Garment Performance Assessment: Since force at specified elongation relates to the resistance experienced by wearers, this test method helps predict garment comfort and durability, supporting specification development for stretch apparel, sportswear, and medical textiles.

• Interlaboratory Comparisons: The precision and repeatability guidelines in D2731-21 assist organizations in comparing test results among multiple laboratories, enabling more consistent manufacturing partnerships and supply chain quality assurance.

Related Standards

For comprehensive characterization and accurate testing of elastomeric yarns, the following related ASTM standards may be relevant:

• ASTM D76: Specification for Tensile Testing Machines for Textiles
• ASTM D123: Terminology Relating to Textiles
• ASTM D1776: Practice for Conditioning and Testing Textiles
• ASTM D2258: Practice for Sampling Yarn for Testing
• ASTM D2433: Test Methods for Rubber Thread (for rubber thread-specific procedures)
• ASTM D2591 and D6717: Test Methods for Linear Density of Elastomeric Yarns

These referenced standards together ensure a robust and harmonized approach to testing elastomeric yarn properties across varying applications within the textile industry.

Keywords: ASTM D2731-21, elastomeric yarns, elastic properties, CRE tensile testing, force at elongation, permanent deformation, stress decay, rubber yarn, spandex yarn, textile testing standards.