ISO 16549:2021 Textiles — Unevenness of textile strands — Capacitance method

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INTERNATIONAL STANDARD ISO 16549:2021

Textiles — Unevenness of textile strands — Capacitance method

1 Scope

This document describes a method, using capacitance measuring equipment, for determining the unevenness of linear density along the length of textile strands.

The method is applicable to tops, slivers, rovings, spun yarns and continuous filament yarns, made from either natural or man-made fibres, in the range of 4 tex (g/km) to 80 ktex (kg/km) for staple-fibre strands and 1 tex(g/km) to 600 tex (g/km) for continuous-filament yarns. It is not applicable to fancy yarns or to strands composed fully or partly of conductive materials such as metals; the latter requires an optical sensor (see A.4), and to raw silk filaments which are tested according to a specific standard.

The method describes the preparation of a variance-length curve, as well as the determination of periodicities of linear density. It also covers the counting of imperfections in the yarn, namely of neps and of thick and thin places.

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

3 Terms a nd definiti ons

For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https://www.iso.org/obp

— IEC Electropedia: available at http://www.electropedia.org/

3.1

unevenness

variation of linear density along the length of a continuous strand or yarn

Note 1 to entry: The term is also used occasionally for the variation of yarn diameter.

3.2

c o ef f ic ient- of-v a r i at ion u neven ne s s

CV

u

value of unevenness (3.1) expressed as a coefficient of variation

Note 1 to entry: The coefficient-of-variation unevenness is expressed in percent, for example CV = 18,3 %.

u

Note 2 to entry: See also 4.6 and 4.7.

ISO 16549:2021

3.3

me a n- dev i at ion u neven ne s s

U

u

value of unevenness (3.1) expressed as an average mean deviation

Note 1 to entry: The mean-deviation unevenness is expressed in percent, for example U = 14,6 %.

u

3.4

capacitor length

effective length of the capacitor in the direction of the specimen movement, usually 8 mm to 20 mm

3.5

length between

L

b

length of the test specimen for which the instrument takes an individual reading of mass

Note 1 to entry: The unevenness value decreases as L is increased.

b

Note 2 to entry: In the capacitance method, L is normally the capacitor  length (3.4) but it can be increased b

electronically.

Note 3 to entry: L is sometimes referred to in the literature as B.

b

3.6

length within

L

w

length of the test specimen for which an individual value of evenness is determined, and a reading is given

Note 1 to entry: The unevenness value increases as L is increased. When L is more than 100 m or so, then a w w

further lengthening of L increases CV (or U ) only slightly.

w u u

Note 2 to entry: L is sometimes referred to in the literature as W.

w

3.7

total measured length

sum of all lengths within, L (3.6)

w 3.8

nep

tightly tangled knot-like mass of unorganized fibres

3.9

package

yarn wound to a shape, which can be supported (for example, bobbins, cones) or unsupported (for example, skeins, cakes), suitable for conditioning and testing

3.10

spectrogram unit

attachment to unevenness testers for the calculation and presentation of periodic variations in the strand

3.11

thick place

yarn defect with linear density substantially (at least 50 %) greater than that of the adjoining segments of the yarn and extending for at least 5 mm

3.12

thin place

yarn defect with linear density substantially (at least 50 %) smaller than that of the adjoining segments of the yarn and extending for at least 5 mm

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