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Significance and Use
This test method for the determination of evenness of textile strands is used extensively for acceptance testing of commercial shipments of filament or spun staple yarn, comber laps, roving, sliver, or tops. 6.2 6.3 6.4 6.5 Evenness values obtained on different instruments will be comparable for strands from the same sample provided the following parameters are the same in all cases: (1) the measure of evenness used; (2) the capacitive length zone L (see 3.1.5 and 18.104.22.168); (3) the sample length, Ls (see 3.1.8); (4) instrument test speed, (5) laboratory temperature and humidity conditions (see 12.1 and 12.1.1); and (6) test specimen variation. When different models of an instrument are used, and one or more of the six parameters are not identical, test results may differ.
Values of strand evenness are also used in quality control, process optimization, and together with yarn strength measurements, is the first appraisal of a strand's quality. A low evenness value is, in general, preferred. Higher evenness values generally indicate difficult spinning, lower yarn strength, and poorer fabric appearance. Experience has shown that the relationship of evenness to the prediction of yarn performance and to fabric appearance is not a simple one. An evenness value must, therefore, be used cautiously and be supplemented by additional evenness information, such as mid-term and long-term mass variations, thin, thick, and nep imperfection counts, diagram chart spectrogram chart, length variation curve, and histogram analyses.
Continuous filament yarns should be tested for mass variation on instruments specifically designed to them.; failure to do so will result in inaccurate test results. Further, low-twist, continuous yarns tend to flatten to a ribbon configuration while passing through the condenser of a capacitance instrument. These specific instruments are designed to insert false twist in the condenser during testing to overcome the flattening effect and may result in false variation readings.
6.4 Strands made from fiber blends should be tested only if the different fibers are uniformly distributed throughout the strand. Non-uniform blending may cause a higher reading of mass variation than the true value if the component fibers differ in dielectric constant (see 3.1.1 and 22.214.171.124).
6.5 Evenness values obtained on different instruments will be comparable for strands from the same sample provided the following parameters are the same in all cases: (1) the measure of evenness used; (2) the capacitive length zone L (see 3.1.5 and 126.96.36.199); (3) the sample length, Ls (see 3.1.8); (4) instrument test speed, (5) laboratory temperature and humidity conditions (see 12.1 and 12.1.1); and (6) test specimen variation. When different models of an instrument are used, and one or more of the six parameters are not identical, test results may differ.
6.6 If there are any differences of practical significance between reported test results for two (or more) laboratories, comparative test should be performed using competent statistical assistance and an agreed upon number of samples that are homogeneous and randomly assigned, should be used to determine if there is a statistically significant difference between them. If a bias is found, either its cause must be found and corrected, or future testing for that material must be adjusted in consideration of the statistically significant differences found.
1.1 This test method covers the indirect measurement of evenness (mass variation) of non-conductive textile strands, including top, comber lap, sliver, roving, and yarn produced from staple fibers and continuous filament yarns, by means of capacitance testing equipment.
1.2 Strands made from fiber blends can be tested using this test method only if the different fibers are uniformly distributed throughout the strand.
1.3 The test method provides numeric values for the measurement and evaluation of short-, mid-, and long-term mass variations of the tested strand in terms of frequently occurring faults classified as thin places, thick places, and neps and graphical representations of evenness values in the form of diagram charts, spectrograms, length variation curves, and histograms.
1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
D123 Terminology Relating to Textiles
D1776 Practice for Conditioning and Testing Textiles
D2258 Practice for Sampling Yarn for Testing
D4849 Terminology Related to Yarns and Fibers
ICS Number Code 59.080.50 (Ropes)