ISO 5079:2020

Overview

ISO 5079:2020 - Textile fibres: Determination of breaking force and elongation at break of individual fibres specifies a laboratory method to measure the breaking force and elongation at break of single textile fibres in the conditioned or wet state. The standard restricts testing to a constant‑rate‑of‑extension (CRE) testing machine to ensure comparable results across laboratories. It applies to all fibres (including crimped fibres) provided the specimen length allows the specified gauge length.

Key topics and technical requirements

• Test principle: Individual fibres are extended at constant rate of extension until rupture; record maximum force and elongation at break.
• Equipment: CRE tensile testing machine with suitable clamps, capability for 5–40 mm/min extension rates, and data recording for force/elongation curves.
• Metrological requirements: Machine accuracy to at least ISO 7500‑1 class 1 and ISO 10012 measurement confirmation. Specific limits include:
  • force error ≤ ±1%
  • extension error ≤ ±0.1 mm
  • gauge length accuracy ≤ ±0.2 mm
  • clamp displacement rate accuracy ≤ ±5%
• Rates of extension: Select based on expected elongation at break:
  • 50% gauge length/min for mean elongation < 8%
  • 100% gauge length/min for 8% ≤ elongation < 50%
  • 200% gauge length/min for elongation ≥ 50%
• Gauge length: 20 mm (10 mm allowed if fibre is too short, with reduced accuracy).
• Pretension: Specified per unit linear density (cN/dtex) with values for staple and filament tests (e.g., 0.10 ±0.01 cN/dtex for most staple fibres; 0.050 ±0.005 cN/dtex for filaments).
• Specimens and sampling: Follow ISO 1130; test ≥50 fibres unless agreed otherwise. Limit fibre slippage/jaw breaks to ≤ 20% of specimens.
• Wet testing: Use distilled or grade 3 water (ISO 3696) at (20 ± 2) °C with non‑ionic wetting agent ≤ 0.1%.
• Results: Report breaking force, elongation at break, and calculate breaking tenacity if linear density (ISO 1973) is known.

Applications and users

ISO 5079:2020 is used by:

• Textile testing laboratories and QC teams verifying fibre strength and extensibility
• Fibre and filament manufacturers for product development and specification
• R&D groups assessing effects of treatments, wetting or conditioning on single‑fibre performance
• Instrument manufacturers and calibration labs ensuring compliance with CRE test methods

Practical uses include comparing raw material batches, validating fibre modification processes, and generating data for yarn and fabric performance models.

Related standards

• ISO 139 - Standard atmospheres for conditioning and testing
• ISO 1130 - Sampling fibres for testing
• ISO 1973 - Determination of linear density
• ISO 3696 - Water for analytical laboratory use
• ISO 7500‑1, ISO 10012 - Machine calibration and measurement management
• ISO 3060 and IWTO 32‑82 - bundle tests for natural fibres (referenced in Scope/bibliography)

Keywords: ISO 5079:2020, textile fibres, breaking force, elongation at break, CRE testing machine, tensile testing, gauge length, breaking tenacity.