Overview
ISO 2403:2021 - Textiles - Cotton fibres - Determination of micronaire value defines a standardized laboratory method for measuring the micronaire of loose, disorientated cotton fibres (bale, lap, sliver or lint sources). The micronaire value is a primary cotton‑quality parameter related to the air permeability (packing density) of a compressed plug of fibres and is expressed on an arbitrary micronaire scale (typically about 2 to 8). ISO 2403:2021 updates procedures for instruments, sample preparation, calibration and reporting to ensure consistent, comparable micronaire results.
Key topics and technical requirements
- Measurement principle: Air is passed through a compressed plug of cotton; readings of airflow and/or pressure difference are converted to a micronaire value.
- Apparatus: Balance (±0.2 %), airflow instrument with compression cylinder, flowmeter and manometer or electronic sensors. Instrument volumes are specified so compressed specimen mass yields 0.16–0.30 g/cm3 packing range for prescribed masses.
- Conditioning: Samples conditioned in the standard atmosphere (ISO 139) - e.g., 4 h in moving air (or 12 h in still air) or shorter if mass change ≤ 0.25 % in 2 h.
- Specimen preparation: Two permitted methods:
- Method A - test specimen taken directly (no removal of foreign bodies)
- Method B - remove foreign matter (seed, sand, stalk pieces)
The chosen method must be recorded. Annex C compares these methods.
- Calibration and verification: Use International Calibration Cottons (USDA series) to calibrate and routinely check instruments. Instrument performance is acceptable when average calibration values deviate ≤ ±0.10 micronaire unit. Annex A describes calibration procedures.
- Procedure & precision: Pack specimen evenly, apply constant flow or pressure, record readings (±1 %). Annex B provides precision data from experiments.
- Test report requirements: Report must reference ISO 2403:2021 and include material source, specimen prep method, number of specimens/readings, instrument make/model, date, averages (to 0.1 unit), deviations from procedure and unusual observations.
Applications and users
ISO 2403 is used for:
- Quality control in ginneries, spinning mills and textile laboratories
- Cotton trading and classification where micronaire affects pricing and processing
- Instrument manufacturers and calibration laboratories
- Research on cotton fibre maturity, fineness and processing behavior
Keywords: ISO 2403, micronaire value, cotton fibres, cotton testing, airflow instrument, calibration, textile standards, cotton quality.
Related standards
- ISO 139 - Standard atmospheres for conditioning and testing (normative reference)
- ISO 1130 - Sampling methods for textile fibres (normative reference)
ISO 2403:2021 provides a clear, reproducible method for micronaire measurement so stakeholders across the cotton value chain can compare fibre quality and optimize processing and trading decisions.
