ISO 2321:2017

Overview

ISO 2321:2017 - Rubber threads - Methods of test specifies standardized laboratory methods for determining the physical and mechanical properties of rubber threads (elastic threads). The standard addresses both general properties and specific behaviours of rubber threads in contact with fabrics. It is intended primarily for natural and synthetic polyisoprene rubber threads; some tests are not fully suitable for other elastomers (for example, urethane-based threads). The standard also stresses that comparisons are valid only for new threads or threads with identical processing histories, and that previous processing (spooling, fabrication) and any relaxation treatments must be reported.

Key topics and technical requirements

ISO 2321:2017 organizes test methods and reporting requirements that cover:

• Conditioning of samples and test-piece preparation prior to testing
• Count (sectional and conventional/size number) and metric yield determination
• Density measurement (two alternative methods)
• Tensile strength, modulus and elongation at break, with loop-formation testing procedures
• Schwartz value (SV) determination
• Elongation under a specified load, stress retention, and tension set tests
• Accelerated ageing of relaxed threads and dry-heat resistance testing
• Adhesion/ribbons testing to assess bonding between threads and fabrics
• Resistance to copper staining during laundering, effect of washing, and resistance to atmospheric fume staining
• Detailed apparatus, procedures, expression of results, and test reporting requirements

Applications and practical value

ISO 2321:2017 is used to:

• Establish quality control criteria for elastic threads in manufacturing
• Provide reproducible methods for R&D and material comparison (when processing histories match)
• Define test requirements for product specifications, procurement, and supplier acceptance
• Assess durability and compatibility of rubber threads in textiles, garments, medical elastics, and technical textiles where thread‑fabric interaction is critical
• Evaluate ageing, laundering behaviour, and staining risks in end‑use conditions

Who should use this standard

• Elastic thread and rubber thread manufacturers
• Textile and rubber testing laboratories and quality assurance teams
• Garment and hosiery producers specifying elastics for apparel
• Product developers, material scientists, and procurement specialists seeking consistent test methods

Related guidance

Refer to other ISO and national standards covering rubber and textile testing for complementary test methods and cross-references when building a full testing program. For reliable comparisons, ensure sample histories and conditioning are documented as required by ISO 2321:2017.