GB/T 3292.1-2008Textiles -- Unevenness of textile strands -- Part 1: Capacitance method (English PDF)

1 Scope

This Part of GB/T 3292 specifies the method for determining the unevenness of linear density along the length of textile strands (including yarns, rovings and slivers) by using capacitance method.

This Part applies to staple-fibre strands and continuous filament yarns. The test range, for staple-fibre strands, is 4 tex ~ 80 ktex; the test range, for filament yarns, is 10 dtex ~ 1 670 dtex. This Part does not apply to fancy yarns and yarns containing conductive materials (such as metal wires); the latter can be measured by the photoelectricity method (see Part 2 of GB/T 3292).

This Part describes the generation process of the CVm-length curve, as well as the determination of periodicities of linear density. This Part also includes the counting of imperfections in the yarn (namely thin places, thick places and neps).

2 Normative references

The terms in the following documents become the terms of this Part by reference to this Part of GB/T 3292. For dated references, all subsequent amendments (not including errata content) or revisions do not apply to this Part.

However, parties to agreements that are based on this Part are encouraged to study whether the latest versions of these documents can be used. For undated references, the latest edition applies to this Part.

GB/T 6529, Textiles - Standard atmospheres for conditioning and testing (GB/T 6529-2008, ISO 139:2005, MOD)

3 Terms and definitions

The following terms and definitions are applicable to this Part of GB/T 3292.

3.1

Unevenness

The unevenness of linear density along the length of the sliver.

One of the time-domain representations of yarn linear density changes. The abscissa represents the length that is calculated from the starting end of the tested yarn; the corresponding ordinate represents the relative size of the linear density of the tested yarn at that point.

3.13

CVm-length curve

The CVm value under normal circumstances, which refers to the CVm value of the capacitor length. Use the electronic method to extend the length of the measuring field; calculate the CVm value under different cutting lengths (this method corresponds to the early cutting and weighing method). Several CVm values under different cutting lengths constitute the CVm-length curve.

4 Principle

6 Standard atmosphere

The standard atmosphere for preconditioning, conditioning and testing shall be in accordance with the standard atmosphere specified in GB/T 6529. Generally, unsupported packages shall be conditioned for 24 h; supported packages shall be conditioned for 48 h.

7 Sampling

7.1 Select laboratory samples according to one of the following methods:

-- according to the relevant specification of the product standard;

-- by agreement between the relevant parties.

7.2 Recommended sampling amount:

-- slivers and tops: 3 packages;

Generally, select the running speed according to the yarn bearing capacity and the needs of test analysis. The following running speeds are recommended.

Other speeds, if used, shall be stated in the test report:

-- slivers and tops: 25 m/min;

-- rovings: 50 m/min;

-- yarns: 400 m/min.

9 Calculations and expression of results

9.1 The test results of yarn unevenness mainly include the following indicators:

coefficient of variation unevenness CVm, yarn imperfections per kilometer, evenness diagram, spectrogram, CVm-length curve, etc.

10 Test report

The test report shall contain the following contents:

a) number of this Part;

b) test date;

c) description of the sample, including type of package;

d) instrument model;

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