Textile testing

Textile Testing I
Abdella Simegnaw
Ethiopian Institute of Textile and Fashion
Technology( EiTEX) Bahir Dar University, Bahir
Dar, Ethiopia

 Quality: Fitness for purpose
 List of requirements or
specifications
 Testing: determining/evaluating
the status of material against
quality standards
 Quality control:
The operational techniques and activities that are
used to fulfil requirements for quality and ensure
consistency in processes.
 Quality assurance: the planned and
systematic actions to provide adequate
confidence that a product or service will meet
customer satisfaction for quality
Introduction
 Difference between quality , testing, quality control and
quality assurance ?

Despite all the costs associated with it, testing is an important tool for the
following reasons:
1. Checking the quality of raw materials:
 spinning, weaving, chemical processing, garment…
Best quality raw materials will produce best quality product
 But how do you know the RM is best or bad quality?
2. Monitoring production
 Testing samples taken from the production line-quality control- controlling
the production process and the product not to go out of the specified
parameters .
1.1 Reasons For Testing (Objective of Testing)

3. Assessing the final product
 The test is done on the final product to check whether it meets the
requirements or not
 Alteration or correction of the production condition from the test
feedback is impossible
4. Investigation of faulty material
 If faulty material is discovered, the cause should be identified so as to
take corrective action to eliminate faulty production in future and so
provide a better quality product.
 Investigations of faults can also involve the determination of which
party is responsible for faulty material in the case of a dispute
between a supplier and a user, especially where processes such as
finishing have been undertaken by outside companies. Work of this
nature is often contracted out to independent laboratories who are
then able to give an unbiased opinion.
Cont. …

5. Product development and research
 In the textile industry technology is changing all the time,
bringing modified materials or different methods of
production.
 Before any modified product reaches the market place it is
necessary to test the material to check that the properties
have been improved or have not been degraded by faster
production methods. In this way an improved product or a
lower-cost product with the same properties can be provided
for the customer.
Cont. …

It is not possible or desirable to test all the raw material or all the final
output from a production process because of time and cost constraints.
Many tests are destructive so that there would not be any material left
after it had been tested. Because of this, representative samples of the
material are tested
Why do we sample materials for testing? Reasons for sampling:
 To minimize time requirement for testing.
 to asses Risk
 distractive nature of tests
Technical requirements of sampling process:
1. The sample should be a representative of the whole material
2. It should be unbiased; it should include all the varieties in the lot
Sampling

1. Consignment: the quantity of material delivered at the same
time. Can contain one or several lots.
2. Test lot or batch: this consists of all the containers of a textile
material of one defined type and quality, delivered to one
customer according to one dispatch note.
3. Laboratory sample: this is the material that will be used as a
basis for carrying out the measurement in the laboratory. This
is derived by appropriate random sampling methods from the
test lot.
4. Test specimen: this is the one that is actually used for the
individual measurement and is derived from the laboratory
sample.
Terms used in sampling

5. Package: elementary units (which can be unwound) within
each container in the consignment. They might be bump top,
hanks, skeins, bobbins, cones or other support on to which
have been wound tow, top, sliver, roving or yarn.
6. Container or case: a shipping unit identified on the dispatch
note, usually a carton, box, bale or other container which may
or may not contain packages.
Cont. …

A. RANDOM SAMPLE:
 In this type of sample every individual in the population has an equal chance of
being included in it. It is free from bias, therefore truly representative of the
population.
B. NUMERICAL SAMPLE:
Consider first a highly idealized, homogeneous strand of overlapping straight, and
parallel fibers .
A sample in which the proportion by number of, say, long, medium, and short
fibers would be the same in sample as in the population.
 its composition is the same at all parts along its length
TYPES OF SAMPLE
displacement =d
number of fibers =n,
length of the strand = L.
If n is small, then d is large compared with l and
there are gaps between the individuals, as at (a).
If, n is large enough, d is less than l and there is
overlapping, as shown at (b).
In either event and in the general case, the number
of whole fibers in any stream is given by: n=L/d

C. BIASED SAMPLE:
When the selection of an individual is influenced by factors
other than chance, a sample ceases to be truly representative
of the bulk and a biased sample results.
Causes of bias in sampling:
Bias due to physical characteristics: Longer fibers always have a
greater chance of being selected.
Position relative to the person: Lab assistant may pick bobbins
from top layer of a case of yarn (whether to save himself the
task of digging down into the case or because he has never
been told otherwise, we do not know), but the bobbin chosen
will be biased due to their position.
Subconscious bias: Person selecting cones will pick the best
looking ones free from ridges, cubwebbed ends, etc., without
thinking about it.

Zoning techniques
 Used for fiber bales where the properties may vary considerably from place
to place. (for raw cotton or wool)
 Steps in zoning technique
Fiber sampling from bulk

 Prepare tufts from the bulk.
 Divide this sample into four quarters.
 Take 16 small tufts at random from each quarter, the size
approximately 20mg.
 Each tuft shall be halved four times, discarded alternately with
right and left hands and turning the tuft through a right angle
between successive halving's. 16 'wisps' are thus produced from
each quarter sample.
 Combine each set of wisps into a tuft.
 Mix each tuft in turn by doubling and drawing between the
fingers.
 Divide each tuft into four parts.
 Obtain four new tufts by combining a part of each of former
tufts.
 Mix each new tuft again by doubling and drawing.
 Take a quater from each tuft to make the final sample.

Core sampling
Core sampling is a technique that is used for assessing the proportion of
grease, vegetable matter and moisture in samples taken from unopened
bales of raw wool. A tube with a sharpened tip is forced into the bale and a
core of wool is withdrawn.

Fiber sampling from combed slivers,
rovings and yarn
• The sample we get will be length extent biased. This is because unless special
precautions are taken, the longer fibers in the material being sampled are more likely
to be selected by the sampling procedures, leading to a length-biased sample.
• It is the fiber extent/location/ rather than the fiber length as such which determines
the likelihood of selection.

Approaches to solve the problem:
• Preparing numerical sample: In a numerical sample the percentage by
number of fibers in each length group should be the same in the sample as it
is in the bulk.
• Preparing Length biased sample: the percentage of fibers in any
length group is proportional to the product of the length and the
percentage of fibers of that length.
• If the lines A and B represent planes through the sliver then the
chance of a fiber crossing these lines is proportional to its length.
If, therefore, the fibers crossing this area are selected in some
way then the longer fibers will be preferentially selected..

• This type of sample is also known as a tuft sample and a similar method is
used to prepare cotton fibers for length measurement by the fibro graph.
• This can be achieved by gripping the sample along a narrow line of contact
and then combing away any loose fibers from either side of the grips, so
leaving a sample.
In sample the ratio of proportion of 10mm,
20mm, and 30mm would be 1:2:3.

 Take out fiber (2mm at each stage) and discard until a distance
equal to that of the longest fiber in the sliver has removed.
After that each draw will be of numerical samples.
RANDOM DRAW METHOD

 Cut all the projected fibers and discarded. The glass plate is then
moved back few mm, exposing more fibers with “natural length”
without cut. In each case projected fiber ends must be removed.
CUT SQUARE METHOD

 2. Atmospheric Condition For Testing
Atmospheric Condition
For Testing
2

2. Atmospheric Condition For Testing
o The properties of textile fibers are in many cases strongly
affected by the atmospheric moisture content.
o Many fibers, particularly the natural ones, are hygroscopic in
that they are able to absorb water vapor from a moist
atmosphere.
o If sufficient time is allowed, equilibrium will be reached.

o The amount of moisture that such fibers contain
strongly affects many of their most important
physical properties. The consequence of this is
that the moisture content of all textile products
has to be taken into account when these
properties are being measured
o Effects:
o Dimensional
o Mechanical
o Electrical
o others

• wool and viscose, lose strength when they absorb water
while cotton, flax, hemp and jute, increase in strength.
• Fibers that absorb water from 30 to 90%, the
approximate relation b/n electrical resistance and
moisture content is,
 RMn = k
 where R = resistance,
 M = moisture content (%),
 and n and k are constants.
 when fibers absorb moisture dimensionally they will get
swell which will increase their mass.

 Is a ratio, expressed in percent, of the amount of atmospheric
moisture present relative to the amount that would be present if
the air were saturated.
 Since the latter amount is dependent on temperature, relative
humidity is a function of both moisture content and
temperature.
Relative humidity

✓Standard asthenosphere for textile laboratories
✓Because of the important changes that occur in textile
properties as the moisture content changes, it is
necessary to specify the atmospheric conditions in which
any testing is carried out.
✓Therefore a standard atmosphere has been agreed for
testing purposes and is defined as a relative humidity of
65%+/-2 and a temperature of 2O0C+/-2.
✓In tropical regions a temperature of 27 ± 20C may be
used.

 Control of testing room atmosphere
✓ Testing laboratories require the atmosphere to be maintained at
65 ± 2% RH and 20 ± 2C in order to carry out accurate physical
testing of textiles.
✓ The temperature is controlled in the usual way with a heater and
thermostat, but refrigeration is necessary to lower the
temperature when the external temperature is higher than 2OC
as is usually the case in summer.
✓ The relative humidity is controlled by a hygrometer which
operates either a humidification or a drying plant depending on
whether the humidity is above or below the required level.

 The amount of moisture in a fiber sample can be expressed as either regain
or moisture content. Regain is the weight of water in a material expressed as
a percentage of the oven dry weight
 WATER CONTENT OR MOISTURE CONTENT is the quantity of water
contained in a material,
 MOISTURE REGAIN : is defined as the percentage of water present in a
textile material of oven dry weight.
 where D is the dry weight and W is the
weight of absorbed water.
Regain and moisture content
Moisture content is the weight of water expressed as a percentage of the total weight

 It can be measured in different
ways, the most widely used
being oven drier.
 1. By oven dry method
(Direct)
 A conditioning oven is used
which is a mesh container
suspended inside the oven from
one pan of balance, the
mechanism of which is outside
the oven.
 The dry mass is obtained by
drying the sample at a
temperature of 105 ± 2 0C.
 Constant mass is achieved by
drying and weighing repeatedly
until successive weighing differ
by less than 0.05%.
Measurement of moisture

 A continual flow of air at the correct relative humidity is passed
through the oven which is maintained at 105o C.
 The main advantage of using a conditioning oven for carrying our
regain determinations is that all the weighing is carried out inside
the oven.
 The method is based on the assumption that the air drawn into the
oven is at the standard atmospheric condition. If this is not the case
the correction has to be made
 aPercentage correction = 0.5 (1 - 6.48 x 104 x E x R) %
 Where R = relative humidity % / 100, and E = Saturation vapour
pressure in pascals at the temperature of the air enter the oven
(taken from a table of values)

• The accent on speed of testing is illustrated by the Townson and
Mercer instrument which employs an IR lamp to dry out the sample.
• A 5gram sample is used, a constant original weight which enables
the balance incorporated in the instrument to be graduated in
percentage of moisture instead of grams. Times quoted for the test
include 3min for viscose fiber and 8min for cotton.
• The accuracy claimed is that the results are reproducible to within
0.2 percent with unskilled operators.
2.IR drying method (Direct)

3. Capacitance/Resistance method (Indirect)
➢The measurement of resistance or capacitance changes
can be used to give an indirect method of regain
determination.
➢Two electrodes are pushed into a package of yarn and the
resistance between the electrodes is measured by suitable
electronics, the answer being displayed on a scale which is
directly calibrated in regain values.
Different electrode sets are used for different packages, for
example long thick prongs for bales and short needle like
probes for yarn packages.

 The instrument has to be calibrated for the type of probe, the
type of fiber and the expected regain range.
 Advantages :speed and ease of reading, the fact that they can
calibrate directly in regain units and it can be made portable.
 The disadvantages of electrical methods are the need to
recalibrate them as they are indirect methods, the variations in
readings due to packaging density, presence of dyes, antistatic
agents and also variations in fiber quality.

Spectroscopic Moisture Analysis
 Spectroscopic methods of determining moisture
content include infrared (surface
moisture), microwave (total moisture)
and nuclear magnetic resonance (NMR)
spectroscopy. These indirect measurement
methods can be quite complex and/or time
consuming because they require multiple
samples for calibration. For that reason they are
not widely used for moisture content quality
control checks along packaging lines.

 Time: A sample takes a certain amount of time to reach
equilibrium. This rate of conditioning depends on size and
from of material, the material type.
 Relative Humidity: Higher the RH Higher will be Regain.
 Temperature: No direct impact, but at high temperature
the atmosphere can hold more water.
 The previous history of sample: Bleached or scoured
cotton will absorb more moisture than untreated material.
Factors Affecting the Regain of
Textile Material:

 The most fiber characteristics is length strength and fineness.
Firstly, longer fibers
Easier to process.
More even yarns can be produced
a higher strength yarn
 Alternatively a yarn of the same strength can be produced but
with a lower level of twist, thus giving a softer yarn.
 The length of natural fibers varies greatly while manmade fiber
length can be controlled; for blending purpose it is dependent
on the length of natural fibers.
 The length and fineness are sometimes related in natural fibers
whereas for man-made fibers, length and fineness can be
controlled separately.
 For wool, longer fibers are coarser while long cotton fibers are
Fiber Length

 The average length of a spinnable fiber is called Staple
Length. Staple length is also most important fiber
characteristics.
It influences:
1. Spinning limit.
2. Yarn evenness.
3. Handle of the product.
4. Luster of the product.
5. Yarn hairiness.
6. Productivity.
 The Staple Length groupings are currently used in the trade
staple:
1. Short Staple: 1inch or less.
2. Medium staple: 1.03 to 1.125 inch.
3. Long staple: 1.16 to 1.38 inch.
4. Extra long staple: 1.09 and above.
1.Staple length

2. Mean length
 In the case of natural fibers the definition of mean length
is not as straight forward as it might be. This is because
natural fibers besides varying in length also vary in
diameter at the same time.
 If the fibers all had the same cross-section then there
would be no difficulty in calculating the mean fiber
length.
 However, if the fibers have different diameters then the
thicker fibers will have a greater mass so that there is a
case for taking the mass into account when calculating
the mean length. There are in fact three possible ways of
deriving the mean length:.

1.Mean length based on number of fibers
(unbiased mean length) L.
2.Mean length based on fiber cross-section
(cross-section biased mean length) Hauteur H.
3.Mean length based on fiber mass (mass-
biased mean length) Barbe B

It doesn’t consider the effect of fiber cross section and mass. Simply an
arithmetic mean and is unbiased mean length.
To see the effect of different fiber diameters on the mean length consider three
different fibers each with a different cross-sectional area a and a different length l
as shown in Fig. above. So, the mass W:
 ρ=fiber density
 In the calculation of mean length each fiber is given an equal weighting no
matter how large the diameter of the fiber is.
1. Mean length based on number of fibers

2. Cross-section biased mean length H (Hauteur)
 In this calculation of mean length each fiber is weighted according to its
cross-section, so that if a fiber has a cross-section a1,a2,a3 so the calculation
of the mean:
3. Mass-biased mean length B (Barbe)
 The Barbe is obtained when the fiber length groups from a comb sorter are
each weighed and the average length calculated from the data. The
Hauteur can be obtained from the data by dividing the mass of each length
group by its length and expressing the result as a percentage:
 w = alp, Therefore if density p is assumed constant then:

 The methods used to measure fiber length fall into
two main types:
 The direct measurement of single fibers mainly for research
purposes and
 Methods that involve preparing A tuft or bundle of fibers
arranged parallel to one another.
Methods of Fiber length
measurement

A. Hand stapling method : (By trained
classers):
 Selecting a sample and preparing the fibres by hand doubling
and drawing to give a fairly well straightened tuft of about ½
inch wide.
 This is laid on flat black background and the staple length is
measured.
 The shorter fibres will lie in body of the tuft and extreme ends
(tips) will not be the limits used for measurement of staple
length.
 The classer chooses the length where there are reasonably well
defined edges.
 Subjective in nature, so difference in results between classers.
Measurement of Individual Fibre
Length: (Cotton fibre length)

 In the diagram
 OQ = 1/2 OA
 OK = 1/4 OP
 KS = 1/2 KK’
 OL = 1/4 OR
 Short fibre percentage = (RB/OB) × 100%
 LL’ = Effective length (because many m/c settings are
related with this length)
 LL’-MM’ = NL’=Inter-quartile range
 Dispersion% = NL’/LL’

Span Length
Span length is the distance exceeded by a stated
percentage of fibers from a random catch point in
drafting zone. 2.5% and 50% span length are the most
commonly used by industry.
2.5% Span Length and 50% Span Length:
x % Span length is the distance spanned by x %of fibers
in the specimen being tested when the fibers are
parallelized and randomly distributed and where the
initial starting point of the scanning in the test is
considered 100%. This length is measured using “Digital
Fibrograph‘.

Uniformity Ratio
The ratio between 50% span length and 2.5% span length
is called uniformity ratio, express as a percentage.

Uniformity Index
UI Description
<77 VL
77-80 L
81-84 M
85-87 H
>87 VH

Upper Half mean length(UHML)
The 50% point of fibers and extrapolating to the
lengths axis indicates the Upper Half Mean length .

 Fibers in the drafting zone that are not clamped by
either of the pairs of rollers of drafting zone are
referred to as floating fiber index. It is expressed as
a percentage and calculated by the following
equation.
Floating Fiber Index (FFI):

 SFC can be calculated from the output of
the fibrogram
 SFC% = 50.01−( 0.766×2.5%SL) − (81.48× 50%SL)
Short Fiber Content (SFC)
amount of fiber shorter than 0.5in.
SFC Description
<6 VL
6-9 L
10-13 M
14-17 H
>17 VH

 Optical method of measuring the density along the
length of a tuft of parallel fibres. Samples are prepared
by “fibro sampler
C. Photoelectric method (Fibro
graph):

 The point where it is caught is at random along its
length.
 Distance traveled from base line
 Floating fibre (%) = [2.5%SL / L – 0.975} × 100
 U.R. = (50%SL / 2.5% SL) × 100 [apprx. 40-50%
for normal cotton]
 Where L = avg. length of fibre

An attempt to automate the process of
single fiber measurement and is intended
mainly for measuring wool fibers.
Rotating shaft with a spiral groove machined
in it. One end of the fiber to be measured is
gripped by a pair of tweezers whose point is
then placed in the moving spiral. This has the
effect of moving the tweezers to the right
and so steadily drawing the fiber through the
pressure plate. This ensures that the fiber is
extended under a standard tension.
D.WIRA fiber length machine

A fine wire rests on the fiber and is arranged so that when
the far end of the fiber passes under the wire it allows it to
drop into a small cup of mercury and thus complete an
electrical circuit. This causes the shaft to stop moving, so
halting the tweezers; at this point the tweezers are then
raised to lift the counter immediately above where it has
stopped. Finally measurement will be taken from the
counter.

 Tuft methods are often used for routine fiber length testing as they
are more rapid than the direct methods. The preliminary preparation
is directed towards producing a bundle of parallel fibers.
 Danger of fiber breakage
 Clamping.
 Combining to remove loose un gripped fibres.
 The protruding tufts are cut from edge of the clamp and weighed.
 The clamps then opened and fibres in side clamps are weighed
separately.
 where W is the width of clamp
E. Tuft methods

 For quicker measurement of length (staple length).
 Objective measuring technique of earlier staple length
measuring method. (Classer judges by eye).
F. Shirley photoelectric stapler

 Fringes of fibre are prepared by
hand and carefully placed over
black velvet pad
 The photoelectric stapler detects
the distance between where the
density gradient are maximum
(on either side).
 Two photoelectric cells connected
opposition to each other
 Depending on light intensity, the
opposed cells pass a current,
which is proportional to the
difference in the intensity.
 Variation in current is shown in
sensitive galvanometer.
 As the fringe is advanced inside
the instrument, two maximum
density gradient point will be there
and this distance is “staple length”
(max. deflection of galvanometer in
opposite direction)

FINENESS
➢Fineness describes the measurement of cross-
sectional area of fibers or yarns.
➢The finer the fiber, the finer is the yarn that can be
spun from it.
➢The spinning limit, that is the point at which the fibers
can no longer be twisted into a yarn, is reached earlier
with a coarser fiber.
➢ Coarser fiber is more rigid and stiff, difficult to twist
during spinning.
➢The stiffness of the fibers affects the stiffness of the fabric
made from it and hence the way it drapes and how soft it feels.

Why Fiber Fineness is so important:
1. It affects Stiffness of the Fabric
➢The fineness determines how many fibres are
present in the cross-section of a yarn of given
thickness. Additional fibres in the cross-section
provide not only additional strength, but also a
better distribution in the yarn.
As the fiber fineness increases, resistance to
bending decreases.
It means the fabric made from yarn of finer fiber
is less stiff in feel.It also drapes better.

2. It affects Torsional Rigidity of the Yarn
➢ Torsional rigidity means ability to twist.
As fiber fineness increases, torsional rigidity of the yarn
reduces proportionally.
Thus fibers can be twisted easily during spinning operation.
➢Also there will be less snarling and kink formation in the
yarn when the fine fibers are used.
3. Reflection of Light
Finer fibers also determine the luster of the fabric.
Because there are so many number of fibers per unit area
that they produce a soft sheen.
Also the apparent depth of the shade will be lighter in case
of fabrics made with finer fibers than in case of coarser
fibers.

4. Absorption of Dyes
The amount of dye absorbed depends upon the amount of
surface area accessible for dye out of a given volume of
fibers. Thus a finer fiber leads to quicker exhaustion of
dyes than coarser fibres.
5. Ease in Spinning Process
A finer fiber leads to more fibre cohesion because the
numbers of surfaces are more so cohesion due to friction
is higher.
Also finer fibers lead to less amount of twist because of
the same increased force of friction.
This means yarns can be spun finer with the same amount
of twist as compared to coarser fibers,

6. Uniformity of Yarn and Hence Uniformity in
the Fabric
Uniformity of yarn is directly proportional to
the number of fibres in the yarn cross section.
Hence finer the fiber, the more uniform is the
yarn. When the yarn is uniform it leads to other
desirable properties such as better tensile
strength, extensibility and luster.
It also leads to fewer breakages in spinning and
weaving

➢Fineness describes the measurement of cross-sectional area of fibers or
yarns.
➢It difficult to define a measure of fineness as a measure of its diameter
or x-section due to a number of reasons:
1. The cross-section of many types of fibers is not circular
Wool has an approximately circular cross-section but silk has a triangular
cross-section and cotton is like a flattened tube
2. The cross-sections of the fibers may not be uniform along the fiber
length. This is often the case with natural fibers.
the cross-sectional shape of the fibers may not be uniform from fiber to
fiber.
Fineness measurement

 For a given fiber (that is of a fixed density) its mass is
proportional to its cross-sectional area:
m=a*l*p
Mass of a fiber = cross-sectional area X length X density
 Therefore for a known length of fiber its mass will be
directly related to its cross-sectional area.
 The mass of a given length of fiber is used as a measure
of its fineness.
 The primary unit is Tex
tex (g/lOOOm),
So, there should be alternative measurement systems which indirectly can
measure the diameter or x-section of fibers.
1. Gravimetric or dimensional measurements

 Decitex = mass in grams of 10,000
meters of fiber
 Millitex = mass in milligrams of
1000 meters of fiber
 Denier = mass in grams of 9000
metres of fiber
 For fibers with a circular cross-section
such as wool the mass per length can be
converted into an equivalent fiber
diameter sometimes known as d(grav.)
using the following equation:

 The projection
microscope is the
standard method for
measuring wool fiber
diameter, and all other
methods have to be
checked for accuracy
against it.
 The method is also
applicable to any other
fibers with a circular
cross-section.
2. Fiber fineness by projection microscope

It involves preparing a
microscope slide of short
lengths of fiber which is
then viewed using a
microscope that projects
an image of the fibers onto
a horizontal screen for
ease of measurement.
Techniques are followed
that avoid bias and ensure
a truly random sample.

 This is an indirect method
 The airflow at a given pressure difference through a
uniformly distributed mass of fibers is determined by the
total surface area of the fibers.
3.Fiber fineness by the airflow method
 The surface area of a fibre (length X circumference) is
proportional to its diameter but for a given weight of
sample the number of fibres increases with the fibre
fineness so that the specific surface area (area per unit
weight) is inversely proportional to fibre diameter;

 The specific surface area which determines the flow of
air through a cotton plug, is dependent not only upon
the linear density of the fibres in the sample but also
upon their maturity.
 Hence the micronaire readings have to be treated with
caution particularly when testing samples varying
widely in maturity.
 Suitable for mill practice due to its speed of
measurement
 For a constant mass of fibre ( i.e. The actual volume)
the air flow is inversely proportional to the specific
surface area

Micronaire (MIC) is a measure of
the air permeability of compressed
cotton fibers. It is often used as an
indication of fiber fineness and
maturity.
Micronaire Description
<3 Very fine
3.1-3.6 Fine
3.6-4.7 Medium
4.8-5.4 Course
>5.5 Very Course

4.Vibration method
• Used for individual fibre (one fibre at a time)
• An indirect method of estimating the mass/unit length of
fibre, based on the theory of vibrating strings.
• . The natural fundamental frequency (f) of vibration of a
stretched fiber is related both to its linear density and to the
tension used to keep it tight:

➢one end of a weighted fiber is
clamped and the lower edge of the
fiber passes over a knife edge, thus
providing a fixed length of fiber
under tension.
➢The level of tension used is in the
range from 0.3 to 0.5 cN/tex
usually applied by hanging a
weighted clip on the end of the fiber.
➢The fiber is caused to vibrate either
by vibrating the top clamp or by
using acoustic transducers and the
amplitude of the vibration measured
over a range of frequencies.

F= (1/2l) ×√(T/M)
M= T x (1/2lf)2
Where,
F = natural fundamental frequency of
vibration (c/s)
T= tension
M= mass per unit length (gm/cm)
L= free length
l = wave length

 It is a non-microscopically
method of measuring fibre
diameter and operates by light
scattering. The fibre (cut into
snippets 1.8mm long) and
suspended in Isopropanol (to
give a slurry) are caused to
intersect a circular beam of
light in a plane at right angles
to the direction of the beam
(not greater than 200
micrometer dia).
 The intensity of scattered
light is proportional to the
projected area of fibre, i.e.
diameter
5. Light scattering method (OFDA: Optical Fibre
Diameter Analyzer):

 Only fibres that completely
cross the beam are recorded,
so that the scattered light
pulse is then proportional to
the fibre diameter.
 The flow rate and
concentration of the slurry
are such that fibre intersect
the beam one at a time. The
snippets which do not fully
intersect the beam are
rejected.
 The Capable of measuring
50 fibres per second. The
beam diameter is maximum
200 micrometer to reduce
the effect of any curvature
due to fibre crimp

Fiber Maturity
➢Cotton fiber consists of cell wall and lumen.
The maturity index depends upon the thickness
of the cell wall.
➢Unripe fibers have neither adequate strength
nor adequate longitudinal thickness. They lead
to loss of yarn strength, neppiness, high
proportion of short fibers, varying dyeability,
processing difficulties mainly at the card.

To measure maturity some method of measurement is
required. The degree of cell wall thickening may be expressed
as the ratio of the actual cross-sectional area of the wall to the
area of the circle with same perimeter (see figure)
Measurement of fiber maturity:

 A completely solid fiber would have a degree of thickening of 1.
Mature fibers have an average value of around 0.6 and immature
fibers have an average value of between 0.2 and 0.3.


1.Measurements of cotton maturity
by caustic soda
 It is most commonly used
 A thin tuft of fibre is drawn by means of tweezer from a sliver
help in a comb sorter.
 The tuft is laid on a micrroscope and a cover slip put over the
middle of the tuft.
There are two step involved in this method
 Treatment with 18% coustic soda
 The fibre on the microscope slide are then saturated with small
amount of 18% coustic soda solution which is swelling them.
 Examination under a microscope to count the mature, half mature
and immature fibre.
 The slide is then placed on stage of microscope and examined.

1. Normal fibers are those that
after swelling appear as solid
rods and show no continuous
lumen.
2. Dead fibers are those that after
swelling have a continuous
lumen and the wall thickness is a
fifth or less than the ribbon
width.
3. Thin-walled fibers are those
that are not classed as normal or
dead, being of intermediate
appearance and thickening

 Around 100 fibers from Baer sorter combs are
spread across the glass slide and treated with
18% caustic soda solution viewed under
microscope and examined :
MATURITY CO-EFFICIENT

2. Measurements of cotton maturity by
Polarized Light

Category Range of maturity
coefficient
Very immature
Immature
Average maturity
Good maturity
Very high maturity
Below 0.60
0.60 to 0.70
0.71 to 0.80
0.81 to 0.90
Above 0.90

3. Mature and immature fibers differ in their behavior
towards various dyes. Certain dyes are preferentially taken
up by the mature fibers while some dyes are preferentially
absorbed by the immature fibers.
• It is developed in the United States of America for
estimating the maturity of cotton. In this technique, the
sample is dyed in a bath containing a mixture of two
dyes, namely Diphenyl Fast Red 5 BL and Chlorantine
Fast Green BLL.
• The mature fibers take up the red dye preferentially,
while the thin walled immature fibers take up the green
dye.
3. Measurements of cotton maturity by
dyeing methods:

 In addition to useable fibres, cotton stock
contains foreign matter of various kinds
 This foreign material can lead to extreme
disturbances during processing.
 Trash affects yarn and fabric quality. Cottons
with two different trash contents should not be
mixed together, as it will lead to processing
difficulties.
 Therefore it is a must to know the amount of trash
and the type of trash before deciding the mixing.

Measurements of trash
1.Shirley Trash Analyzer
 100g. of cotton sample ‘S’
to be analysed is weighed
accurately and is passed
through the Trash Analyser
giving L1g. of lint and T1g. of
trash. The trash T1 is
collected and again
processed giving L2g. of lint
and T2g. of trash. The lint
portions L1 and L2 are
weighed together and give
the total lint content in the
sample.

 If the Trash T2 is still
found to contain a sizable
amount of lint, it is passed
once again through the
Analyzer giving L3g. of lint
and T3g. of trash. Then lint
content L = L1 + L2 + L3
and Trash T = T3.
 In general, two such 100 g.
samples are analyzed and
the average calculated. It
is essential that the sample
processed must be fairly
representative of the bulk
sample.

2. optical – electronic trash analyzer
 One drawback of Shirley Analyzer method is that it
cannot provide information relating to the number or
size of non-lint particles. This has prompted the
development of various optical – electronic
techniques for measuring the number and physical
features of non-lint particles found on the surface of
raw cotton samples.

.
an instrument which employs a television camera
to view the sample to be analyzed and a specialized computer-
based signal analysis system to analyze the signal
from the camera. The signal analyzer can determine and
display information concerning the number, size distribution,
length and area of particles viewed by the camera. The
working group on "Dus tand Trash" at the International cotton
conference in Bremen(1990) recommended Shirley Analyzer
Mark II, Micro dustand Trash Monitor (MTM) from Uster
Technologies, USA and ITV Dust and Trash Tester from
Hollingworth as standard instruments.

 Measurement of trash, providing a measure of the sample
surface area (% AREA)covered by trash and the number
(COUNT) of particles.
 The two HVI system measure trash in a similar way,
although using different pixel spacing. A video camera
optically scan sample compressed against a viewing window
above the camera.
 In the Motion Control HVI systems the viewing area is
divided into a matrix of 59500 raster points (pixels) or248 x
240 raster lines. Dark trash particles (i.e. those whose color
value is 30% darker than the light cotton color of the
environment) are counted.
 The Area is calculated by the relationship,
 Where Nx is the number of pixels darkened by trash. The
COUNT is given by the relationship,

 The cleaning efficiency helps to evaluate the performance
of a machine. If it falls below a certain level the machine
needs to be checked. The removal of trash particles such as
seed & leaf particles, stalks, sand and dust from cotton is
quantitatively expressed as cleaning efficiency which can
be estimated as follow.
 About 200gm of sample is taken from the feed & delivery
of a machine like Blow room, Card or Beaters. These
samples are analyzed for trash content. This is done by
processing a 100gm of sample through a Trash Analyzer
and collecting the trash obtained & weighing it accurately.
Two samples must be analyzed and average trash content is
calculated.
The Cleaning Efficiency of a Machine:

Fiber quality measurements using
High volume instruments(HVI) ,
AFIS

HIGH VOLUME INSTRUMENT
TESTING (HVI)
ADVANTAGES:
 Following are the advantages of HVI testing:
 the results are practically independent of the
operator
 the results are based on large volume
samples, and are therefore more significant
 the respective fiber data are immediately
available
 the data are clearly arranged in summarized
reports
 they make possible the best utilization of raw
material data

 Problems as a result of fiber material can be predicted, and
corrective measures instituted before such problems can
occur cotton classification does not only mean how fine or clean, or
how long a fibre is, but rather whether it meets the requirements of
the finished product.
 To be more precise, the fibre characteristics must be classified
according to a certain sequence of importance with respect to the
end product and the spinning process.
 The ability to obtain complete information with single operator HVI
systems further underscores the economic and useful nature of HVI
testing.
 Two instrument companies located in the us manufacture these HVI
systems. Both the systems include instruments to measure
micronaire, length, length uniformity, strength, color, trash,
maturity, sugar content, etc.

 A system may include
any combination of the
following measuring
modules:
 Length/Strength
Module
 Micronaire Module
 Color/ Trash Module

Fiber length is measured by optically by the LEDs when the
fiber Beard entered the measuring zone

FLU Description
<77 Very low
77-80 Low
81-84 Medium
85-87 High
>87 Very high

 The amounts of fiber in the cotton sample shorter
than 0.5 inch or 12.7 mm
SFI
SFI% Description
<6 Very low
6-9 Low
10-13 Medium
14-17 High
>18 Very high

HVI uses the “Constant rate of elongation” principle while
testing the fibre sample. The available conventional
methods of strength measurement are slow and are not
compatible to be used with the HVI. The main hindering
factor is the measurement of weight of the test specimen,
which is necessary to estimate the tenacity of the sample.
Expression of the breaking strength in terms of tenacity is
important to make easy comparison between specimens of
varying fineness.
Principle of Measurement

Strength(g/tex) Description
<21 Very low
22-24 Low
25-27 Medium
28-30 High
>31 Very high

 Measurement of elastic behavior of fibers in the
bundle
 The distance the fiber extend before they break is
expressed as percent of elongation
Bundle fiber elongation

Rd =The whiteness of the light that reflected by the
cotton fiber
+b=Yellowness of the light that is reflected by cotton
fiber

 SCI=-414.67+2.9S-9.32M+49.17L+4.74UI+0.65Rd+0.36+b
SCI
it predicts the spinnablity of the fiber

 In textile industry raw material is the most dominant
factor as it contributes 50-75% in total manufacturing
cost.
 In quality conscious scenario, quality of raw material
plays a vital role. But the quality of raw material is
decided by measuring its properties.
 Now measurement through conventional techniques is
very laborious and time consuming.
 Hence the researchers focus their attention towards the
inventions of such instrument, which gives accurate and
quick result and one of the wonderful development is
AFIS - Advanced fibre information system.
ADVANCED FIBER INFORMATION
SYSTEM (AFIS)

BASICS PRINCIPLE:
 A fibre sample is introduced into
the system and is processed
through a fibre individualizer,
which aero mechanically
separates the sample into three
components consisting of
cleaned fibre, micro dust, and
trash.
 Each of these components is
transported in a separate
pneumatic path and analyzed
electro-optically or by other
means.
 The data processing and
reporting are handled by an
industrialized PC.

 uses unique cleaning and separating
techniques to present the fibres
pneumatically to the electro-optical
sensor.
 A specimen of fibre is hand teased into a
sliver-like strand and is inserted into the
feed assembly
 The fibres are opened and cleaned using
pinned and perforated cylinders,
 Airflow into the perforations of the
cylinder allows for thorough engagement
and efficient dust and trash removal.
 Trash is released after the carding action
by the "counter flow" separation slot.
 Heavy trash particles are separated from
fibres and transported out of the system,
whereas, the smaller dust and fibres are
returned to the cylinder aerodynamically
by the air drawn into the slot, thus the
term "counter flow slot".
Fibre individualizer:

 The electro-optical (E-O)
sensors consist of three
basic elements tapered
entrance and exit nozzles
(on Version 4 lint sensor, a
single piece accelerating
nozzle) beam forming
and collection optics.
Electro-optical sensors:
Generally, rectangular waveforms are
produced by the light scattered by
individual fibres. Nep signals are
much greater in magnitude and
duration and generate a characteristic
nep "spike". Trash particles produce
smaller spiked waveforms, which are
distinguishable from neps in
magnitude and duration.

Linear Density
 The thickness or diameter of a yarn is one of its most
fundamental properties. However, it is not possible to
measure diameter of a yarn in any meaningful way.
 A system of denoting the fineness of a yarn by weighing a
known length of it has evolved. This quantity is known as
the linear density and it can be measured with a high
degree of a accuracy if a sufficient length of yarn is used.
YARN COUNT

 There are two systems of linear density designation in
use: Direct and Indirect system
1. Direct system
 The direct system of denoting linear density is based on
measuring the weight per unit length of a yarn.
 It is fixed length system.
 Finer the yarn, lower the count number.
The main systems in use are:
 Tex - Weight in grams of 1000 meters
 Denier - weight in grams of 9000 meters
 Decitex - weight in grams of 10000 meters

2.Indirect system
 This is the traditional system of yarn linear density
measurement.
 The indirect system is based upon the length per unit
weight of a yarn and is usually known as count.
 It is based on the fixed weight system.
 Finer the yarn, higher the count number.
 The main system in use are,
1. Worsted count Ne w = number of hanks all 560 yards
long in 1 pound Cotton
2.Count Nec (english count Ne) = number of hanks all 840
yards long in 1 pound Metric
3.Count Nm = number of kilometer lengths per kilogram

Ne=(length in yd *)/(840yd*wt lb)
NeW= =(length in yd )/(560yd*wt lb
Nm=(length in meter)*wt in kg*100
I.e 1, lb = 453g

Example 1: If the metric count is given 50 then
what will be the English cotton count?
Solution:
We know that, Ne=0.5905 X Nm
Where, English cotton count is expressed as Ne
And Metric count as Nm
So English count will be Ne=0.5905 X 50=30
 Ans. 30 Ne

Measurement of yarn number or count
 Two basic requirements for the determination of the yarn
number are
A. An accurate value for the sample length
B. An accurate value for its weight
.
1. Yarn in package form
➢When the yarn is in package form, such as
ring bobbins or cones, it is usual to wind a
number of skeins by means of wrap reel.
This is a simple machine consisting of a reel,
yarn package creel, a yarn guide with
traverse, a length indicator, and a warning
bell.
Length measurement

 For cotton yarns the reel has a girth (circumference of
reel) of 54 inch, so that 80 revolution of the reel as skein
of 120 yard, or a lea.(i.e1yd=36 inch)and(1m=1.093yd)
 The same lea will be weighed accurately to calculate the
count.
2.Yarn in short length (from fabric)
 The determination of the yarn count of yarn in fabric is
usually made on a comparatively short sample length
because the piece of fabric available.
 After conditioning in the testing atmosphere, two
rectangular warp way strip and 5 weft way strips are cut
from the cloth.
 In length, the strips should be about 20 inch and wide
enough to allow fifty threads to be removed from each
strip.

Weight Measurement
1.Balances
 The analytical balances and any other special yarn balances
used in the determination of count must be accurate, and it
is essential that they are well maintained.
 The weight should be capable of giving a result to an
accuracy of not less than 1 in 500.
 The yarn removed from fabric will have crimp. So it is
measured first and length should be calculated.
C=(l-p)/p*100%
 where, c = crimp, l = uncrimped length and p = crimped
length.

Regain Measurement
 The problem of accounting for the presence of moisture in
the sample can be tackled in several ways, two of which
are considered here.
 1)Determine the oven dry weight and multiply by

Example 1.
Textile technologies measure cotton yarn length and mass by
using wrap reels which have a circumference of 1.09361 yard
with 100 revolution and the oven dry weight is 2.9525 gram
by electronic balance respectively. Calculate the yarn count in
Tex system?
Sol/n
1 yd=0.9144m
100*1.09361yd=109.361yd
109.361yd*0.9144m/yd=99.999 m
Tex= m(g) *1000
l(m)
=32 Tex

 2)Allow the sample to condition in the testing
atmosphere long enough to reach equilibrium, and
then weigh in the same atmosphere.
 Among the two, the first method will give accurate
result than second method.

 When testing spun packages,
sixteen are randomly chosen
and a lea from each wrapped
on the reel at the correct
tension.
 The leas are taken to constant
weight in the drying oven.
 The official regain is added to
the oven dry weights and the
individual counts are
recorded. The mean count is
then calculated.
Count testing methods
1.Wrap reel, drying oven, analytical balance

 It is used to read count system
directly
 beam balance is used, behind
which is a separate rod of
hexagonal section with five of the
faces lettered from A to E and
engraved with a count scale to
cover a certain range.
 Face B of the scale is turned to the
front, weight B is placed in the left-
hand pan, and rider B put on the
beam.
 The position of the rider to be
adjusted until the beam is balanced.
 This balance can be, of course, be
designed to suit count systems other
than that of cotton.
2.Wrap reel and a Knowles balance

direct reading instrument
 A given length is measured out and suspended from
the hook, the count is then read directly from the
quadrant scale.
 The versatility of this type of balance is improved by
engraving the scale with more than one series of
values.
 For example, one scale may read from 0.1 to 1.0 to
give the hank of a 4 yard sample of sliver.
 Second scale may read from 0.1 to 0.6 for 20 yard
samples of roving.
 Third scale may read from 4s to 80s for 840 yard
samples of yarn.
 The scales just mentioned are in the cotton count
system, but other quadrant balances are available for
different ranges and different systems.
3.Wrap reel and a quadrant balance

A). Normal count
 It is direct measurements of sliver,
roving and yarn count and give
statistical data and graphs.
B).Nominal count;
It is direct measurements of sliver,
roving and yarn count and give
statistical data and graphs with
comparison of the nominal or
theoretical count number..
4.Fast count analyzer

1.based on the linear density of the
constituent yarns and
2. based on the resultant linear density of
the whole yarn.
 In the first way the tex value of the single
yarns is followed be a multiplication sign
and then the number of single yarns
which go to make up the folded yarn, e.g.
Measuring folded yarns counts
 For example, 2/24s cotton count system implies a yarn
made from two 24s count cotton yarns twisted together;
1/12s cotton count means a single 12s count cotton yarn.
➢In the tex system there are two possible ways of referring
to folded yarns:

1. 80 Tex x 2: This indicates a yarn made from twisting together two
80 Tex yarns. This type of designation is generally used with woolen
yarns.
2. R 74 Tex/2: This indicates a yarn made from twisting two yarns
together whose resultant count is 74 Tex. This type of designation is
generally used with worsted yarns.

EX.3 A resultant two ply yarn count of 16 worsted has one
component yarn of 36 worsted. What is the count of the other
component?
EX.2 A two ply yarn in Tex is composed of one thread 40 Tex,
one thread unknown count and has a resultant count of 100
Tex. What is the count of the other component yarn??

EX.4 A three ply yarn is composed of one thread of 56
worsted, one thread of 48 worsted and one thread of 2/80
cotton. What is the count of resultant yarn?

Count calculation for ply yarn with contraction:
Normally, when two single yarns are twisted together one
should expect some contraction or some increase in
length depending on the twisting direction. A contraction
will result in a yarn slightly coarser than the estimated
value. In order to correct for this difference, typically 5%
to 10% contraction or extension should be accounted for.

EX.5 Suppose two yarns of 24/1 Nm are going to be
plied with 4% contraction. Find its resultant count
in metric system.

EX.6 Suppose you are provided a cotton yarn of 1500 km of
2/24s found at completely dry condition. Calculate the
resultant count in Tex at standard atmospheric condition with
7% contraction.

 Let,
The yarn count be= N tex.
Tex= m(g) *1000
l(m)
And specific volume of yarn= 1.1
So, 1.1 cm^3 yarn has the weight of = 1 gm.
And yarn diameter= d cm.
Now,
N tex. Yarn has a length = 1000 m.
1 tex. Yarn has a length = (1000/N) m. = 10^5/N cm.
Relation ship between yarn count(Tex) and
yarn diameter

 Again
 Volume = Cross sectional area × length
or, 1.1 = (πd²/4) × ( 10^5/N )
or, d² = (4× 1.1 × N) / (π×10^5)
or, d = √{4.4/ (π×10^5 ) × √N
or, d = (0.375/ 100) × √N
∴ d = (0.375/ 100) × √tex.
This is the relation between yarn diameter
(cm) and yarn count in Tex system.

 Converting cm to inches and tex to
cotton count:
Diameter in inch, d = (0.375/ 100) × √tex.
Or, d = (0.375/ 100) × √(590.5/Ne) ×
(1/2.54) [Tex = 590.5/Ne]
Or, d = (0.375 × √590.5) / (100 ×√Ne ×
2.54)
Or, d = 3.6 / (100 × √ Ne)
∴ d = 1/ (28√Ne) inch.
This is the relation between diameter and
yarn count in cotton count (Ne) system.

Introduction:
 Twist is the measure of the spiral turns given to yarn in
order to hold the fibres or threads together.
 Twist is primarily instructed in to a staple yarn in order to
hold the constituent fibres together, thus giving strength
to the yarn.
 Twist is necessary to give a yarn coherence and strength.
Real twist::
To insert a real twist into a length of yarn, one end of the yarn should
be rotated relative to the other end, Spun yarns usually have real twist.
False twist:
When inserting false twist into a length of yarn, both ends of the
yarn are clamped, usually by rollers, and twist is inserted with a false
twister between the clamping points.

 In practice, yarn twist is described using three
main parameters:
A. Twist direction
B. Twist level (turns/unit length).
C. Twist factor or twist multiplier

The effects of the twist on strength
1.As the twist increases, the lateral force holding the fibres
together is increased so that more of the fibres are
contributed to the overall strength of the yarn.
 2.As the twist increases, the angle that the fibres make with
the yarn axis increases, so prevents them from developing
their maximum strength which occurs when they are
oriented in the direction of the applied force. As a result, at
certain point the yarn strength reaches a maximum value
after which the strength is reduced as the twist is increased
still further (Fig).

filament yarn will be stronger than the equivalent staple
fibre yarn as a comparatively large amount of twist is
always needed in a staple yarn. Sometimes
intermingling is used instead of twist

Factors affect by Twist properties
(a) Handle:
 As the twist level is increased it becomes more compact
because the fibres are held more tightly together, so
giving a harder feel to the yarn.
 Because of decrease in the yarn diameter, its covering
power is reduced.
 A fabric produced from a low-twist yarn will have a soft
handle but at the same time weaker yarn thus resulting in
pilling and low abrasion resistance of fabric.

(b) Moisture absorption:
 High twist holds the fibres tight thus restricting
water to enter
 Such a high twist yarn is used where a high degree of
water repellency is required, e.g. in gabardine fabric.
 Low twist yarn is used where absorbency is required.
(c) Wearing properties:
 With an increase in twist level wearing properties
(abrasion and pilling) are improved.
 High level of twist helps to resist abrasion as the
fibres can’t easily pulled out of the yarn.
 The same effect also helps to prevent pilling (which
result from the entanglement of protruding fibres).

(d) Aesthetic effects :
 The level of twist in yarn alters its appearance both by
changing the thickness and light reflecting properties.
 Different patterns can be produced in a fabric by using
similar yarns but with different twist levels; a shadow stripe
can be produced by weaving alternate bands of S and Z twist
yarns
 Level of twist can also be used to enhance or control twill
effect: a Z-twill fabric produced by weaving Z-twist yarns
will have enhanced Z-twill effect. Same is the case for S-
twill.

Twist Applications:
 Georgette is made of highly twisted yarn (up to 1000 TPM) by
weaving S and Z twisted yarns alternately both in warp and
weft direction.
 Chiffon is made in the same way but yarn is more twisted (up
to 2000 TPM) and finer than that used in georgette-
Cupramonium rayon is used.

 Herringbone is made by using yarns of different types
and levels of twists.

 Twist is usually expressed as the number of turns
per unit length, e.g. TPM or TPI.
 However the ideal amount of twist varies with the
yarn thickness i.e., the thinner the yarn, the greater
is the amount of twist that has to be inserted to give
the same effect.
 The factor that determines the effectiveness of the
twist is the angle that the fibers make with the yarn
axis.
Level of Twist:

a fibre taking one full turn of
twist in a length of yarn L. the
fibre makes an angle with the
yarn axis.
For a given length of yarn,
the angle is governed by the
yarn diameter D:
tan θ = пD/L
The greater the diameter of the
yarn, the greater the angle of
twist (for same twist level).As
1/L is equivalent to turns per unit
length then:
tan θ ∞ D x turns/unit length

➢In the indirect system for measuring linear density the
diameter is proportional to 1/√count. Therefore
tan θ ∞ (turns / unit length ) / √ count
➢Twist factor is defined using this relationship:
K=(turns / unit length ) / √count (K is the twist factor)
Value of K differs with each count system.
(a) In case of Tex (direct system):
K= TPM x √count
(b) For indirect:
K= TPI (or TPM or TCM)/ √count
(Value of K ranges 3.0—8.0 from softer to harder)

Sampling :
 2-5% random sample is taken from bags that are selected
from the consignment. Say if there are 100 bags, then select
5 bags randomly for testing. From each bag select one cone
for testing and from each cone 10 tests are to be made thus
total 50 testing.
Specimen :
 After conditioning, outer few layers from cone are removed.
Then it is side-end withdrawal and mounted on the tester.
Test methods :
 Following methods are used to test the twist.
MEASURING TWIST:

Techniques of twist measurements
1) Direct count/straightened fiber technique
methods
2) Twist contraction/ Untwist re twist
methods
3) Twist to breack methods
4) Microscopic methods

1) Direct counting method :
 This is the simplest method of twist measurement.
 The method is to unwind the twist in a yarn and to count how many turns
are required to do this.
 A suitable instrument has two jaws at a set distance apart. One of the jaws
is fixed and the other is capable of being rotated.
 A counter is attached to the rotating jaw to count the turns. Samples are
conditioned in standard testing atmosphere before starting the test.
 Twist = No. of Turns/specimen length

A standard tension (0.5cN/tex) is used when the yarn is being clamped in
the instrument.
The twist is removed by turning the rotatable clamp until it is possible to
insert a needle between the individual fibres at the non-rotatable clamp
end and to traverse it across the rotatable clamp.
Single spun yarns : a minimum of 50 tests should be made. Specimen
length for cotton is 25mm and woollen or worsted yarns, is 50mm.
Folded, cabled and single continuous filament yarns : a minimum of 20
tests should be made with specimen length of 250mm.

 This tester has the extra advantage of allowing twist tests at fixed
intervals.
 The straightened fibre principle is still used for the actual
measurement of the twist.
 The yarn passes from the sample package, through a guide, through
non-rotating jaw, then through rotating jaw and finally wound on to a
(clockwork-driven) drum.
2) Continuous twist tester

 3) Untwist-twist method or Twist contraction
method :
 This method is based on the fact that yarns contract in
length as the level of twist is increased and it increases in
length on twist removing, at last reaching a maximum length
when all the twist is removed.
 The yarn is first gripped in the left-hand clamp which is
mounted on a pivot and carries a pointer.
 After being led through the rotating jaw, the yarn is pulled
through until the pointer lies opposite a zero line on a small
quadrant scale; jaw is then closed.
 At this stage the specimen is under a small tension and has a
nominal length of 50cm
 As the twist is removed, the yarn extends and the pointer
assumes a vertical position, so removing the tension.

 The image processing system working with a video
camera gives a new and exact way for determining the
diameter of fibres or yarns or the twist angle of yarns.
This method compared with the conventional method is
very quick. The report of the measurements with the
results is printed
4.Image processing system

Higher twist multipliers are used,
 To increase yarn tenacity and yarn elongation;
 To produce lean yarns with low hairiness;
 To improve spinning stability;
 To obtain a clean-cut fabric appearance; and
 To improve the shifting resistance of the yarns.
Lower twist multipliers are selected,
 To achieve a soft hand in the final fabric;
 To produce bulky and more hairy yarns;
 To reduce a yarn‘s tendency to snarl; and
 Increase output with the same rotor speed.
Twist multipliers
The twist factor or twist multiplier is a measure of twist, which
accounts for the yarn radius as well as the twist level.

 Fibre strength is generally considered to be next to
fibre length and fineness in the order of importance
amongst fibre properties.
 Fibre strength denotes the maximum tension the
fibre is able to sustain before breaking.
 It can be expressed as breaking strength or load,
tenacity etc.
 Elongation denotes elongation percentage of fibre at
break.
TENSILE TESTING

There are three types of tensile strength:
 Yield strength - The stress a material can withstand
without permanent deformation
 Ultimate strength - The maximum stress a material
can withstand
 Breaking strength - The stress coordinate on the
stress-strain curve at the point of rupture.
Tensile strength is the ability of a material to withstand a pulling
(tensile) force

 Molecular structure
 No. and intensity of weak places
 Coarseness or fineness of fibre
 Relative humidity
 Elasticity
Factors affecting the strength of
fibres:

a) Specimen length:
 Breaking strength is the “load to break” at the
“weakest” point of a specimen of a specified
length.
Factors affecting tensile results:
c) Capacity of machine:
 If a very weak specimen is tested in a machine with very
high capacity, the time to break will be short, so
optimistic result will be produced.

b) Rate of loading and time to break:
 Most textile materials show an increase in breaking
strength with increasing rate of extension together
with a decrease in extension.
 Due to visco-elastic nature of textile material, they
require certain time to respond to the applied stress.
 Different types of textiles (fibres/yarns/fabrics)
respond differently depending on the structure.

D). Previous history of the specimen: Specimen have
been strained beyond the yield point earlier. Specimen
have been subjected to any chemical treatment before test
Effect of humidity and temperature:
 Behavior of textile material changes with the relative
humidity of the atmosphere.
 Temperature, although have not much effect, but at very
high temperature fibre may be degraded.
 Also at very low temperature fibres may be brittle.
E) Clamping problem:
 Jaw slip -----> Too low clamping pressure
 Jaw damage ------> Too high clamping pressure

Three ways to carryout tensile test:
1. CRT: Pulling one clamp at a uniform rate and the load is
applied through the other clamp. Which moves appreciably
to actuate a load measuring mechanism so that the rate of
increase of either load or elongation is usually not constant.
2. CRE: Rate of increase of specimen length is uniform with
time (the load measuring mechanism moves a negligible
distance).
3. CRL: Rate of increase of the load is uniform with time and
rate of extension is dependent on the load-elongation
characteristics of the specimen.
Principles of Tensile Testing

 F*r=W*x=mg*Rsinθ
 mgR/r =K
 F=Ksin θ
1. CRT
Pendulum leaver principles..

TENSORAPID (CRE Principle): For tensile testing of single and ply
yarn.
 Testing of slivers, leas and fabrics is also possible.
 Force measurements up to 1000N without exchanging the force
transducer.
 The clamping force, the yarn tensioners and the suction-off of the yarn
can be programmed.
 All numerical and graphical results are displayed on a video screen.
(Histogram, L-E curve, tables, etc.)
 Package creel for the automatic measurement up to 20 packages.
 Calling-up of test parameters of frequently tested yarn types from the
memory (up to 40).
 Pneumatically-actuated yarn clamps ; the clamp pressure is
programmable.
 Electronic elongation measurement.
 Test speed – Continuously adjustable between 50 and 5000mm/min.
2.CRE
Universal strength tester

 In constant rate of loading
(CRL) tests, the specimen is
loaded at a constant rate and
the elongation is a
dependent quantity.
 The oldest methods of
measurement system
 It is not possible in constant
rate of loading tests for load
to decrease. Load must
3.CRL

Textile testing

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