ISO 1973:2021 Textile fibres — Determination of linear density — Gravimetric method and vibroscope method.
5.2.2 Forceps, to apply the tensioning force to the individual fibre to be tested.
lithe apparatus can apply the tensioning force automatically (e.g. by a moving lower clamp and a upper clamp connected to a force measuring device, as mentioned in &2.3), forceps are not required.
6 Sampling
To ensure that the laboratory sample is representative of the material and that the test specimen is taken from the laboratory sample is representative of that sample, sampling shall be carried out in accordance with ISO 1130.
7 Conditioning and testing atmospheres
The atmospheres for preconditioning, conditioning and testing shall be in accordance with ISO 139.
8 Procedure
8.1 Gravimetric method
8.1.1 Condition the test specimens and carry out the tests in the standard atmosphere for testing as specified in Clause 6.
8.1.2 From the laboratory sample, take ten tufts having a mass of several milligrams and bring the fibres of each tuft into parallel alignment by carefully combing them several times with the comb sorter
8.1.3 Cut the middle part of each combed tuft to a given length (greatest possible), under the minimum tension necessary to remove crimp, by means of the cutting device (Mi). Take the necessary precautions so that there are no free fibre ends anywhere except at the two ends of the tuft bundle.
8.1.4 Place the ten bundles so obtained on the textile support fabric (514) and cover them with the glass plate (&L5) from the polished edge of which they shall protrude slightly.
8.1.5 From each of the ten bundles in turn, take out five fibres to form a bundle of 50 fibres, in each case drawing the fibres from one cut end. Make at least ten of these bundles. Recondition the specimen in the atmosphere specified in Clause 6, if necessary. Weigh these bundles individually, using the balance (5d.1), to an accuracy of ±1 %.
lithe bundle of 50 fibres cannot be weighed on the balance to the required I % accuracy. the number of fibres shall be increased accordingly (up to a maximum of 500).
8.2 Vibroscope method
8.2.1 Check the vibroscope, before examining the laboratory sample, as follows. Test 100 individual fibres using the vibroscope in question. Test these same fibres, for comparison, using the gravimetric method. Calculate the arithmetic mean and coefficient of variation of the vibroscope readings of linear density. lithe coefficient of variation of the vibroscope readings is larger than 10 %, the sample is not suitable for determination of linear density using this vibroscope.
Weigh the bundle of 100 fibres that have been tested with the vibroscope using the balance (511). Measure the length of all fibres in accordance with ISO 6989 with an accuracy of ±1 %. Or, where appropriate, cut the 100 fibres to a known length using the cutting device (5.12).
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