BS ISO 2403:2021 pdf download – Textiles — Cotton fibres — Determination of micronaire value
This document specifies a method of determining the micronaire value of loose disorientated cotton fibres taken from bales, laps and slivers, or other sources of lint cotton.
2  Normative references
The following documents are referred to in the text in such a way that some or all of their content  constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 139, Textiles — Standard atmospheres for conditioning and testing
ISO 1130, Textile fibres — Some methods of sampling for testing
3  Terms and definitions
For the purposes of this document, the following terms and definitions apply.
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micronaire value
measure for the air permeability of a mass of cotton under specified conditions
Note 1 to entry: The micronaire scale is based on a range of cottons to which micronaire values have been assigned by international agreement.
Note 2 to entry: It is expressed in terms of an arbitrary scale, the so-called micronaire scale.
4  Principle Air is passed through a test specimen consisting of a plug of fibres. The permeability is indicated on a scale for recording variations in either the rate of flow through, or the pressure difference across, the plug. The mass and volume of the test specimen are either a constant for a given type of instrument or varied appropriately in relation to each other. The scale indicating variations in permeability can be calibrated in arbitrary units of micronaire value or marked in the appropriate absolute units of rate of flow or of pressure difference and a table or graph provided for conversion of the observed readings into micronaire values.
5  Apparatus and materials
5.1  Balance, of sufficient capacity to weigh the test specimen required for the airflow instrument used, with an accuracy of ±0,2 %.
to be tested to determine whether or not the instrument is correctly adjusted and is giving results on the correct level (for more information, see Annex A).
8.1.1  Consider the performance of any instrument to be within the requirements of this document if the average results for each such calibration cotton do not differ from its corresponding established values by more than ±0,10 micronaire scale unit.
8.1.2  Re-test, by the above procedure, cottons giving differences greater than ±0,10 micronaire scale unit between the average of the two tests and the established value. Accept the results if the difference between the two new micronaire values for such a cotton does not exceed ±0,10 micronaire scale unit. If the difference continues to be greater than ±0,10 micronaire scale unit, either re-adjust the instrument and repeat the above check procedure or apply, on the basis of the established differences referred to above, an appropriate correction or adjustment to test values for subsequent samples submitted for testing.
8.2  Pack the test specimen evenly into the compression cylinder, a small portion at a time, fluffing the fibres with the fingers in order to break up any lumps and taking care that all the fibres are inserted in the cylinder. Put the compression plunger in position and lock it.
8.3  Cause the air to flow through the test specimen at the appropriate constant flow (or pressure) and note the reading on the pressure difference (or airflow) scale of the instrument to an accuracy of about ±1 %.
8.4  If a second measurement is required for the same test specimen, remove the cotton from the instrument, taking care not to lose fibre, and repeat the procedure given in 8.2 and 8.3.
8.5  Test the number of test specimens per sample. Annex B provides additional information and precision data.BS ISO 2403 pdf download