COMESA 268: Textile fibres - Determination of linear density - Gravimetric method and vibroscope method

2006·2.2 MB·English

by  Common Market for Eastern and Southern Africa (COMESA)

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and Southern Africa
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COMESA 268 (2006) (English): Textile fibres -
Determination of linear density - Gravimetric
method and vibroscope method

COMESA HARMONISED COMESA/FDHS
STANDARD 268: 2006

Textile fibres - Determination of linear density -
Gravimetric method and vibroscope method

REFERENCE: FDHS 268:2006
Foreword

The Common Market for Eastern and Southern Africa (COMESA) was established in 1994 as a regional
economic grouping consisting of 20 member states after signing the co-operation Treaty. In Chapter 15 of
the COMESA Treaty, Member States agreed to co-operate on matters of standardisation and Quality
assurance with the aim of facilitating the faster movement of goods and services within the region so as
to enhance expansion of intra-COMESA trade and industrial expansion.

Co-operation in standardisation is expected to result into having uniformly harmonised standards.
Harmonisation of standards within the region is expected to reduce Technical Barriers to Trade that are
normally encountered when goods and services are exchanged between COMESA Member States due
to differences in technical requirements. Harmonized COMESA Standards are also expected to result into
benefits such as greater industrial productivity and competitiveness, increased agricultural production and
food security, a more rational exploitation of natural resources among others.

COMESA Harmonized Standards are developed by the COMESA experts on standards representing the
National Standards Bodies and other stakeholders within the region and are approved after circulating
Final Draft Harmonized Standards (FDHS) to all member states for at least three months. The assumption
is that all contentious issues would have been resolved during the previous stages or that an international
or regional standard being adopted has been subjected through a development process consistent with
accepted international practice.

COMESA Standards are subject to review, to keep pace with technological advances. Users of the
COMESA Harmonized Standards are therefore expected to ensure that they always have the latest
version of the standards they are implementing.

This COMESA standard is technically identical to ISO1973:1995- Textile fibres - Determination of linear
density - Gravimetric method and vibroscope method

A COMESA Harmonized Standard does not purport to include all necessary provisions of a contract. Users are
responsible for its correct application.
INTERNATIONAL ISO
STANDARD 1973
Second edition
1995-11-01
Textile fibres - Determination of linear
density - Gravimetric method and
vibroscope method
Fibres textiles - Determination de Ia masse lin6ique - Methode
gravimk Pique et methode au vibroscope
Reference number
ISO 1973: 1995(E)
ISO 1973:1995(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide
federation of national Standards bodies (ISO member bodies). The work
of preparing International Standards is normally carried out through ISO
technical committees. Esch member body interested in a subject for
which a technical committee has been established has the right to be
represented on that committee. International organizations, governmental
and non-governmental, in liaison with ISO, also take part in the work. ISO
collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard ISO 1973 was prepared by Technical Committee
ISO/TC 38, Textiles, Subcommittee SC 6, Fibre testing.
This second edition cancels and replaces the first edition
(ISO 1973:1976), which has been technically revised.
Annexes A and B of this International Standard are for information only.
0 ISO 1995
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronie or mechanical, including photocopying and
microfilm, without Permission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-l 211 Geneve 20 l Switzerland
Printed in Switzerland
INTERNATIONAL STANDARD 0 ISO ISO 1973:1995(E)
Textile fibres - Determination of linear density -
Gravimetric method and vibroscope method
1 Scope ISO 6989: 1981, Textile fibres - Determination of
length and length distribution of staple fibres (by
This International Standard specifies a gravimetric measuremen t of Single fibres).
method and a vibroscope method for the determi-
nation of the linear density of textile fibres applicable
3 Definitions
respectively to:
For the purposes of this International Standard, the
a) bundles of fibres;
following definitions apply.
b) individual fibres.
3.1 tension: Forte tending to Cause the extension
of a body.
Useful data tan be obtained on man-made fibres and,
with less precision, on natura1 fibres.
NOTE 2 In textile testing, the tension applied is based on
the linear density or Cross-sectional area.
The procedures tan be applied only to fibres which
tan be kept straight and, in the case of bundles, par-
3.2 tensioning forte: Forte effective on a fibre
allel, during test preparation. These methods are
specimen during the vibroscope test.
properly applicable when the fibres are readily freed
of crimp. They are not applicable to tapered fibres.
4 Principle
NOTE 1 The vibroscope method may not be applicable
to hollow and flat (ribbon-like) fibres.
Two methods for determining linear density are de-
scribed:
2 Normative references
4.1 Gravimetric method (direct method by
weighing), for bundles of fibres
The following Standards contain provisions which,
through reference in this text, constitute provisions
Spetimens of a given length are weighed on a bal-
of this International Standard. At the time of publica-
ante. This method is applicable to bundles of fibres.
tion, the editions indicated were valid. All Standards
are subject to revision, and Parties to agreements
based on this International Standard are encouraged 4.2 Vibroscope method, for individual fibres
to investigate the possibility of applying the most re-
cent editions of the Standards indicated below. Individual fibres of a given length and under specified
Members of IEC and ISO maintain registers of cur- tension are subjected to Vibration at resonance fre-
rently valid International Standards. quency. The linear density is determined from the
conditions of the resonance state, i.e. the resonance
ISO 139: 1973, Textiles - Standard atmospheres for frequency, the length of the fibre and the tensioning
conditioning and testing. forte. The linear density is read directly on the scale
of the vibroscope apparatus. This method assumes
ISO 1130:1975, Textile fibres - Some methods of that the linear density of the tested length of the fibre
sampling for tes ting. is constant.
ISO 1973:1995(E) CJ ISO
NOTE 3 For high-modulus fibres (e.g. aramid fibres) the the laboratory Sample is representative of that sam-
use of the vibroscope method should be agreed on by the ple, sampling shall be carried out in accordance with
interested Parties, because the high stiffness of such fibres ISO 1130.
may influence the results.
8 Procedure
5 Apparatus
8.1 Gravimetric method
5.1 Gravimetric method
8.1.1 Condition the test specimens and carry out the
5.1.1 Balance, suitable for weighing the bundles of
tests in the Standard atmosphere for testing as spec-
fibres to an accuracy of at least -+ 1 %.
ified in clause 6.
5.12 Device for cutting the bundles under tension
8.1.2 From the laboratory test Sample, take ten tufts
to a length known within an accuracy of +- 1 % and
having a mass of several milligrams and bring the fi-
allowing an adjustment of the tension of the bundles
bres of each tuft into parallel alignment by carefully
to be tut.
combing them several times with the combsorter
(5.1.3).
For example, two razor blades set parallel in a suitable
holder may be used.
8.1.3 Cut the middle part of each combed tuft to a
given length (as great as possible), under the mini-
5.1.3 Combsorter, for preliminary alignment of fi-
mum tension necessary to remove crimp, by means
bres.
of the cutting device (5.1.2). Take the necessary
precautions so that there are no free fibre ends any-
5.1.4 Textile support fabric, of a colour contrasting
where except at the two ends of the tut bundle.
with th at of the fibres to be teste d .
8.1.4 Place the ten bundles so obtained on the tex-
5.1.5 Glass plate, measuring approximately
tile support fabric (5.1.4) and cover them with the
100 mm x 200 mm, with one polished edge.
glass plate (5.1.5) from the polished edge of which
they shall protrude slightly.
5.1.6 Forceps.
8.1.5 From each of the ten bundles in turn, take out
5.2 Vibroscope method
five fibres so as to form a bundle of 50 fibres, in each
case drawing the fibres from one tut end. Make at
5.2.1 Vibroscope ‘1, having the following accuracy:
least ten of these bundles. Recondition the specimen
in the atmosphere specified in clause 6, if necessary.
a) The applied tensioning forte shall be within the
Weigh these bundles individually, using the balance
range of $- 0,5 % of the specified value;
(5.1 .l ), to an accuracy of 1 %.
b) The error in the vibroscope reading of resonance
NOTE 4 If the bundle of 50 fibres cannot be weighed on
frequency measured or applied shall not exceed
the balance to the required 1 % accuracy, the number of fi-
+- 0,5 %; bres may be increased up to 500.
c) The error in the vibroscope reading of Vibration
8.2 Vibroscope method
length of the fibre shall not exceed -+ 1 %.
8.2.1 Check the vibroscope, before examining the
6 Conditioning and testing atmospheres
laboratory test Sample, as follows. Test 100 individual
fibres using the vibroscope in question. Test these
The atmospheres for preconditioning, conditioning
Same fibres, for comparison, using the gravimetric
and testing shall be in accordance with ISO 139.
method. Calculate the arithmetic mean and coefficient
of Variation of the vibroscope readings of linear den-
7 Sampling sity. If the coefficient of Variation of the vibroscope
readings is larger than 10 %, the Sample is not suit-
To ensure that the labora tory sam ple i s represe ntative able for determination of linear density using this
of the material and that t he test s men take n from vibroscope.
1) For a list of suppliers of suitable vibroscope equipment, apply to the Secretariat of ISO Technical Committee 38.
2
0 ISO ISO 1973:1995(E)
Weigh the bundle of 100 fibres that have been tested 9 Expression of results
with the vibroscope using the balance (5.1 .l). Meas-
ure the length of all fibres in accordance with Examples of calculations of mean linear density are
ISO 6989 with an accuracy of + 1 %. Or, where ap- given in a nnex A.
propriate, tut the 100 fibres to a known length using
the cutting device (5.1.2).
9.1 Gravimetric method
Calculate the mean linear density, p, b, of the fibre,
9.1.1 For each bundle, calculate the mean linear
expressed in decitex, using the following formula:
density (p, b) of the fibre, and calculate the mean linear
=mb density ($, expressed in decitex, of the fibre in all
p1.b 100 x IO4 bundles tested, to three significant figures.
c 4
l.= ” I 9.1.2 Calculate the coefficient of Variation of the
mean linear density (pl), expressed as a percentage to
the nearest 0,l %.
is the mass, in milligrams, of the fibre
mb
bundle; 9.1.3 Calculate the 95 % confidence interval of the
mean linear density (p,), expressed in decitex, to the
is the length, in millimetres, of the ith fibre same precision as the mean linear density value.
in the bundle.
9.1.4 Calculate the 95 % confidence interval ex-
Compare this mean linear density with the mean
pressed as a percentage of the mean linear density
value of the linear density readout on the vibroscope.
value (pl).
The relative differente shall not exceed +- 3 % of the
mean value of the vibroscope readings. If the value of the confidence interval expressed as a
percentage of the mean is within -+ 2 %, the number
of bundles tested is adequate and the mean of the
8.2.2 From the laboratory test Sample, take ten tufts linear density shall be taken as the mean linear den-
having a mass of several milligrams and with these sity of the laboratory Sample.
form a bundle by repeated halving and doubling. From
this bundle take a tuft of at least 50 fibres and condi- If the value of the confidence interval expressed as a
tion them as specified in clause 6. percentage of the mean is above -+ 2 %, the number
of bundles tested shall be increased until the value
of the confidence interval is within + 2 %.
8.2.3 Fix each of the fibres to the vibroscope under
the applied tensioning forte, which shall be sufficient 9.2 Vibroscope method
to remove the crimp, using forceps (5.1.6) and taking
care to avoid any darnage or distortion of the fibre. 9.2.1 Calculate the mean of the vibroscope readings
of linear density of the fibres tested, expressed in
Calculate the tensioning forte to be applied from the
decitex to three significant figures.
nominal linear density. If the nominal linear density is
not known, an approximate value of the linear density
9.2.2 Calculate the coefficient of Variation of the in-
shall be established by preliminary tests, recorded
dividual values for the linear density, expressed as a
from the scale of linear density readings.
percentage to the nearest 0,l %.
Once this tensioning forte has been selected, it shall
9.2.3 Calculate the 95 % confidence interval of the
be applied and maintained with the required accuracy
mean linear density in decitex to the Same precision
(see 5.2.1).
as the mean linear density value.
Normally tensions Chosen within the range
(0,6 +- 0,06) cN/tex are suitable. 9.2.4 Calculate the 95 % confidence interval ex-
pressed as a percentage of the mean linear density
For highly crimped fibres, increase the tension to re- value.
move the crimp but not to stretch the fibre, in ac-
cordante with the vibroscope manufacturer’s The mean of the linear density values obtained shall
specifications. Alterations in tensioning forte shall be be taken as the mean linear density of the fibres in
stated in the test report. the Sample, provided that the value of the confidence
3
ISO 1973:1995(E) 63 ISO
interval expressed as a percentage of the mean linear f) test method (gravimetric or vibroscope) and type
density is less than +- 2 %. of tester used;
If the value of the confidence interval is too high, the 9) anY deviation, bY agreem ent or otherwise, from
number of fibres tested shall be increased until the the procedure spe cified.
value of the confidence interval, expressed as a per-
centage, lies within +- 2 %. IO.2 Gravimetric test results
10 Test report a) Length of the tut bundle;
The test report shall include the following information. bj number of bundles tested;
c) mean linear density of the Sample, in decitex;
10.1 General
d) coefficient of Variation, as a percentage;
a) Reference to this International Standard and date
of test;
ej 95 % confidence interval, in decitex.
b) complete identification of the Sample tested;
10.3 Vibroscope test results
c) type of package, its condition (e-g. raw, bleached,
dyed); a) Number of fibres tested;
d) conditioning and testing atmosphere used; b) tensioning forte used;
e) sampling scheme used, number of specimens c) mean linear density of the Sample, in decitex;
tested;
d) coefficient of Variation as a percentage;
ej 95 % confidence interval, in decitex.
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