Overview
ISO 4913:1981 is an international standard published by the International Organization for Standardization (ISO) that specifies a method for determining the length (span length) and uniformity index of cotton fibres. This standard applies exclusively to fibres taken from raw or partially processed cotton and excludes fibres from cotton blends or recycled from cotton yarns or fabrics.
The methodology described in ISO 4913:1981 uses optical instruments to measure the minimal lengths achieved by specified percentages of fibres in a test tuft (barbe d’essai). The uniformity index is then calculated as the ratio of these minimal lengths, providing a quantitative assessment of fibre length distribution. Accurate fibre length measurement is crucial for quality control in the textile industry, affecting yarn strength, appearance, and fabric performance.
Key Topics
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Scope and Application
Applicable to raw or partially processed cotton fibres only; not suitable for cotton blends or recycled cotton fibres.
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Definitions
- Barbe d’essai: A tuft of cotton fibres prepared by combing, intended for optical measurement.
- Span length: The minimal length of fibres reached by a specified percentage of the tuft.
- Uniformity index: Ratio (in percentage) of the smallest to largest span lengths measured at different fibre percentages, indicating fibre length uniformity.
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Sample Conditioning
Samples must be conditioned under standard atmospheric conditions of 65 ± 2% relative humidity and 20 ± 2 °C (or 27 ± 2 °C in tropical regions), as specified in ISO 139.
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Test Preparation
Two methods for sample preparation:
- Manual combing using specialized combs to create uniform tufts.
- Mechanical combing with an apparatus that distributes fibres consistently across pegs.
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Optical Measurement
Utilizes an optical measurement device designed for cotton fibres, measuring optical density distribution across the tuft length. Measurements are performed at specified density percentages to derive span lengths.
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Calculation
The uniformity index is calculated using the formula:
Uniformity Index (%) = (Minimum Span Length / Maximum Span Length) × 100
This index quantifies fibre length uniformity in the sample.
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Test Reporting
Test reports must include:
- ISO 4913:1981 reference
- Mean span lengths and uniformity index (rounded appropriately)
- Percentage of density optical chosen for measurement
- Type of test apparatus and method of combing used
- Origin of the cotton sample (raw, partially processed, or waste)
- Any operational details or incidents affecting results
Applications
ISO 4913:1981 is essential for textile manufacturers, quality control laboratories, and researchers who need reliable, standardized methods to:
- Assess fibre length and uniformity, which directly influence yarn quality and fabric properties.
- Monitor cotton fibre quality during different stages of processing.
- Compare raw cotton fibre batches for procurement decisions.
- Ensure consistency in cotton fibre measurement worldwide through standardized procedures.
- Support breeding and cultivation programs by providing objective fibre length data.
This standard enhances the precision of fibre quality assessments, contributing to higher efficiency in the textile production chain and improved end-product consistency.
Related Standards
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ISO 139: Textiles - Standard Atmospheres for Conditioning and Testing
Specifies the atmospheric conditions under which textile samples, including cotton fibres, should be conditioned and tested to ensure consistent results.
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ISO 1130: Textiles - Sampling Procedures for Testing
Defines sampling methods and guidelines to ensure representative cotton fibre samples are selected for analysis.
Adherence to ISO 4913:1981 in conjunction with these complementary standards enables reliable and reproducible testing, fostering international comparability and confidence in cotton fibre quality assessments.
Keywords: ISO 4913, cotton fibres, span length, uniformity index, textile testing, fibre length measurement, optical measurement, cotton quality standard, raw cotton testing, textile industry standards.
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