Introduction.pptx for yarn manufacturing

College of Engineering and Technology
Textile Engineering Program
Yarn Manufacturing-I
Wolkite University

2
 Yarn is a generic term for a twisted continuous strand of textile fibers, filaments or
material in a form suitable for knitting, weaving or otherwise intertwining to form
textile fabric.
 Yarn:
Introduction
 Refers to the conversion of a large quantity of individual unordered fibers of relatively
short length into a linear, ordered product of very great length by using suitable
machines.
 It is also called as spinning.
 Yarn Manufacturing:

3
Cotton Harvesting and Spinning
 Cotton was used as cloth raw material in
the old world at least 7,000 years ago.
 A machine that removes the cotton from the
boll without damaging the cotton plant.
 Cotton continues to be picked by hand
in developing countries.

4
 Cotton Grading
 The term cotton classification or cotton grading refers to;
 The application of standardized procedures developed by USDA for measuring
those physical attributes of raw cotton that affect the quality of the finished
product and/or manufacturing efficiency.
 Essential quality parameters for cotton grading are:
 Fibre length
 Length Uniformity Index (UI %)
 Fibre strength (g/tex)
 Micronaire (HVI
micronaire)
 Color (HVI color Rd, +b)
 Trash (HVI trash area %)

5
 Each cotton fruits consists of seeds,
leaf and about 3000 to 5000 fibers.
 The process of separating seeds from
the lint cotton in order to produce two
marketable products, fiber and seed
is called cotton ginning.
 Cotton Ginning
 The objective of cotton ginning is;
 To reduce moisture content and to remove foreign matter.
 These operations facilitate processing and improve fiber quality.

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Types of cotton ginning
I. Saw ginning:
 The cotton lint is removed from the seed by
pulling it with saw teeth through metallic ribs.
 It used for medium and short staple
varieties.
 Has higher extraction of fibers from seed but
also higher damage of fibers.

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II. Roller ginning:
 Roller ginning is the most primitive way of
removing lint from seeds.
 Separation is by means of roller & knife.
 It is used for long and extra long fibers.
 Has lower extraction of fibers from seed but also
lower harm of fibers than saw ginning.
Cont…

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 Cleaned cotton fibers are collected into a
hopper of a machine called bale press
machine.
 The fibers are converted into a compressed
bale, weighing 180 to 225 Kg each, with the
help of hydraulic pressure.
 Each bale is wrapped with cloth or plastic,
tied with iron or plastic strips.
Cotton Bale
Cotton Bales

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Cotton Spinning
 Cotton is a hygroscopic material and easily adopts to
the atmospheric humidity.
 So, air temperature inside blow-room area should
be more than 25ºC, and
 The relative humidity (RH%) should be around 45 to
60 %.
 Because, high moisture in the fiber leads;
 To poor cleaning, and
 Dryness in the fiber leads to fiber damages which
ultimately reduces the spinnability of cotton.
 Standard atmospheric conditions:
 Relative humidity = 65 ± 2% RH
 Temperature = 27 ± 2ºC
(tropical)
 Conditioning time = 24 hours
(cotton)

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 The variation of the following properties are worth considering during cotton
spinning:
Fiber micronaire
Fiber length
Fiber strength
 Variations in these properties result in dye absorption variation.
 Therefore, it’s a good practice;
 To check the properties of all the bales, and
 To maintain good bale management principles.
 To avoid dye pick-up variation and barrier in the finished fabric.
Cont…
Fiber color
Fiber maturity and trash

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Bale management (Engineered fiber selection system)
 Bale Management:
 It is defined as the process of sorting, mixing, and
testing of bales according to characteristics of the fibers
to produce good quality of yarn at low production cost.
 The main objectives of bale management are:
To compensate for the variation in properties of the raw
materials
To obtain required and uniform quality of yarn
To reduce shade variation of the finished fabric
To meet the functional and end use requirements.

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 Bale management process has done by following the below steps:
1.Selection of Raw cotton,
2.Testing moisture percentage in bales,
3.Collecting sample from each bale,
4.Testing of sample,
5. Classification of Bales,
6. Bale law down,
8. Mixing.
In a particular lot;
 Not to blend cotton type differing in staple length more than 1/16".
 Micronaire range and average of the cotton used should be same for all the
mixings of a lot.
 Range and average of color of cotton used should be same for all the mixings of a
lot.
Cont…

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Raw material as a factor influencing spinning
 Both natural and man-made fibers are used for spinning to produce yarn of
desired quality.
 The annual world fiber consumption in 2004 approximately 70 million tons;
 Synthetics: 38 mill tons,
 Cotton: 22 mill tons,
 About one third of the man-made fibers is processed as endless filament, still two
thirds or 67% come in staple fiber form.
 And, the greater part of the staple fiber is used in the production of yarn.
 The major raw materials used in a spinning mill are cotton, viscose and polyester.
 Characteristics of Raw Material:
 Cellulose fiber: 2.5 mill tons and
 Others: 7.5 mill tons.

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 Understanding the influence of raw material is important both from the
technological as well as economic point of view.
 Raw material has significant effect on the yarn producer, because;
 Raw material accounts for about 80% to 90% of the yarn quality and 50% to
70% of the total production cost of a short-staple yarn.
Cont…
 Therefore, it’s very important to have a thorough understanding of;
 The quality parameters of the fibers and
 Their influence on the spinning process and yarn quality.

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 The optimal choice of cotton for producing yarns of desired property is rendered
difficult, because of two reasons:
 Raw material quality is determined by the interaction of several physical
properties of the fibers, and
 Inherent variation existing in all the properties among the fibers.
Cont…
 Therefore, the spinner should know those aspects of fiber quality which will enable him to choose,
 The material most suited for the intended purpose from a wide range of cottons that differ in
their physical properties.
 The three major fiber characteristics that influence the compatibility are:
 The Fiber Length, Fiber fineness and Fiber strength.

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Fiber Fineness:
 Fiber fineness is an important quality characteristic which plays a prominent part in
determining the spinning value of cottons.
 It determines how many fibers are present in the cross-section of a yarn of given
thickness.
 A multitude of fibers in the cross-section provide not only high strength, but also
better distribution in the yarn.
 Fiber fineness influences primarily:
Spinning limit;
Yarn strength;
Yarn evenness
Luster;
Handle; and
Productivity of the process.

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There are lower limits to the number of fibers in the cross-section, as follows (for
normal conditions).
About 30 fibers are needed at the minimum in the yarn cross-section, but there are
usually over 100.
Fibers on yarn cross-section of ring and rotor spun yarn
Cotton yarns
Ring-spun yarn Combed 33 fibers
Carded 75 fibers
Rotor-spun yarn Carded 100 fibers
Synthetic fiber yarns Ring-spun yarn Carded 50 fibers
Rotor-spun yarn Carded 100 fibers
The number of fiber can be calculated approximately by;
Cont…

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Blends of fine cotton fibers with coarse synthetic fibers would produce a yarn with
an externally synthetic fiber character.
Specification of fineness:
With the exception of wool & hair fibers, fiber fineness can not be specified by
reference to diameter.
Because, the cross-section is seldom circular and is not easily measurable.
Usually specified by the relation of mass(weight) to length.
Tex = or Dtex =
 Where as for man made fibers, dtex is used almost exclusively,
 The micronaire value is used worldwide for cotton.
Cont…

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Micronaire:
This is a measure of fiber fineness and maturity.
Low micronaire values indicate fine and/or immature fibers;
 High micronaire values indicate coarse and/or mature fibers.
Conversion factor:
 dtex = Mic × 0.394
Micronaire value Fineness
Up to 3.1 Very fine
3.1- 3.9 fine
4.0 – 4.9 Medium(premum
range)
5.0 – 5.9 Slightly coarse
Above 6 coarse
The fineness scale is as follows:
Cont…

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Example: A cotton yarn of 30s English cotton count (Ne) consists of cotton with a
micronaire value of 4
Calculate ‫ח‬F
inch
g

 Micronaire value does not always represent the actual fineness.
 Also it is dependent on the degree of maturity.
 In practice, maturity of cotton has a greater effect on micronaire than the fineness
for the same variety;
 Because, variation in fineness within variety is usually 5%
 Whereas, variation in maturity can be +10% and –20 %.
Cont…

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 Maturity:
Cotton fiber consists of cell wall and lumen.
 The maturity index is dependent upon the thickness of the cell wall.
Fiber maturity influences both the processing of cotton and quality of yarn in terms of
strength, evenness and appearance.
A fiber is to be considered as:
 Mature: cell wall of the moisture-swollen fibre represents 50 - 80% of the round
x-section.
 Immature: when it represents 30 - 45%, and
 Dead: when it represents less than 25%.
 Since some 5% immature fibers are present even in a fully matured boll.
 Cotton stock without immature fibers is unimaginable.

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Immature fibers have neither adequate strength nor adequate longitudinal stiffness.
Instead, they leads to :
Loss of yarn strength.
Nepinness.
A high proportion of short fibers.
Varying dyeability.
Process difficulties mainly at the card
Maturity Percent (Coefficient):
 Maturity Coefficient = (M + 0.6H + 0.4 I)/100
 Where; M is percentage of matured fibers,
 H is percentage of Half matured fibers and,
 I is percentage of Immatured fibers.
Classification of maturity Coefficient
Maturity coefficient Category
above 0.9 Mature
0.7- 0.9 Half mature
Below 0.7 immature
Cont…

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Cont…
Classification of maturity ratio
Maturity Ratio Category
1.00 and above Very Mature
0.95 - 1.0 Above Average
0.85 - 0.95 Mature
0.80 - 0.85 Below Average
Less than 0.80 Immature
 Maturity ratio = [(N – D)/200] + 0.70.
Where;
 N is percentage of normal (matured)
fibers and,
 D is percentage of dead (immature)
fibers.
Maturity Ratio:
Example: For the chosen standard, N = 67% D or I = 7% and H = 26%.
Mc = ( 67 + 0.6 (26) + 0.4 (7) ) / 100 = 0.85,
Calculate maturity ratio(M.r)???

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Fiber length:
 The "length" of cotton fibers is a property of commercial value as the price is
generally based on this character.
 If other factors being equal, longer cottons give better spinning performance than
shorter ones.
The fiber length influences:
Spinning limit
Yarn strength
Yarn evenness
Handle of the product
Lustre of the product
Yarn hairiness
Productivity

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 Productivity is influenced through:
The end breakage rate
The quantity of waste
 Fibers of under 4 - 5 mm will be lost in processing (as waste and fly)
 Fibers up to 12 - 15mm do not contribute to strength
 But, only to fullness of the yarn.
 Fibers above these lengths produce the other positive characteristics in the yarn.
 But, noticeable shortening of many fibers arises before the spinning process owing to
mechanical working, for example ginning and cleaning.
 The effect is such that fiber length exhibits the greatest irregularity of all the fiber
Cont…
The required turns of twist(which affects handle)
General spinning conditions.

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Cont…
Fig: The staple diagram by number Fig: The staple diagram by weight
 Staple Length (classers’ staple)
Staple length is length of clamped fiber, that exceed certain distance.
 It is measured by personal judgment of the appearance of a hand prepared sample.
 A sample of cotton contains fiber absolute minimum (2mm) up to absolute
maximum b/n 30 and 60 mm,

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 The length of cotton fiber can be determined by expert classers and measuring
instruments.
 The staple length (classer‘s staple) groupings for cotton:
 Short staple: 1’’ or less
 Medium staple: 1 1/32” - 1 1/8”
 Long staple: 1 5/32” - 1 3/8”
 Extra-long staple: 1 13/32” and above.
 In order to reduce the various errors and difficulties associated with personal
judgment, laboratory tests are desired.
 With the development of HVI, digital fibrograph and other instrument, possible to
measure important fiber characteristics easily.

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Various staple Diagram Forms
I. Rectangular Staple
Fig: Rectangular staple
 Achievable and Imaginable for synthetic (manmade) fibers.
 Since the fibers are all equally long;
 No length variation are present.
 However, the length evenness cannot be maintained into the yarn.
 Because, fibers are shortened during processing, mainly at the card.
 Spinning machines are not suited to processing of fibers having all the
same length.
 In the drafting arrangement, such fibers are not moved individually, but in
bunches, resulting a high degree of unevenness.

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Fig: Triangular staple
This permits better processing than the rectangular staple.
But, contains too many short fibers.
During movement, for example in the drafting arrangement the
fibers cannot be maintained under control.
They move freely and produce substantial unevenness.
They cannot always be bound into the body of fibers, so
that some of them are lost as waste and fly.
If a short fiber is bound-in, however, one end often
projects and results in a hairy yarn.
II. Triangular staple
Cont…

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III. Trapezoid staple IV.Stepped staple
 This is the ideal staple for processing
and more suitable the flatter the curve.
 However, a flat curve often means a
high price.
 This diagram is typically for cotton.
 The stepped staple curve can arise;
 When fiber materials of very
different lengths are mixed in
the wrong proportions.
 As with a rectangular staple, the
fibers can be moved only in groups.
Cont…

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Fibrogram
 In addition to the staple diagram, the fibrogram is available.
 In the staple diagram the fibers are aligned at one end.
 In the fibrogram they are arranged by clamping randomly distributed fibers of a
cotton sample.
 The fibers protruding from the clamps are straightened by a brushing process
and measured optically.
 It gives a good representation of the drafting operation and of the
arrangement of the fibers in the yarn.
 The lengths are stated as span-lengths, that is lengths which span a certain
distance.

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 2.5% Span Length (SL):
Distance from the clamp on a fiber beard to a
point up to which only 2.5% of the fibers extend.
 Defined as the length of fiber at which only 2.5%
of long fibers are excluded.
 Distance from the clamp on a fiber beard to a point up to which only 50 % of the
fibers extend.
 Defined as the length of fiber at which only 50% of long fibers are excluded.
 50% Span Length (SL):
Cont…

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 This is defined as the mean length of the
longer half (50%) of the fiber distribution by
weight.
 Mean length of the fibers is defined as “the
average length of all fibers in the test
specimen based on weight – length data”
 Upper-half-mean length (UHML):
 Length Uniformity Ratio (UR):
UR = *100
 This is often used by digital fibrograph users.
Cont…

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SFI = 122.56-(12.87UHML) - (1.22UI)
= 90.34- (37.472.5% SL) - (0.90UR)
 Length uniformity Index (UI):
UI = *100,
 This is commonly preferred by HVI users.
 Short Fiber Index (SFI):
Cont…

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 Fiber Strength:
 Fiber strength is very often the predominant characteristic.
 A numerous types of fibers are not usable for textiles,
 Because of inadequate strength.
 Minimum strength for a textile fiber is approximately 6 cN/tex.
 Since binding of the fibers into the yarn is achieved mainly by twisting, and thus can exploit at most
30 - 70% of the strength of the material.
 A lower limit of about 3 cN/tex is finally obtained for the yarn strength, which varies linearly with the
fiber strength.
 Some significant breaking strengths of fibers are:
 Polyester fiber…….35-60cN/tex.
 Cotton……………………..15-40cN/tex.
 Wool………………………...12-18cN/tex.

36
 The strength characteristics can be determined either on individual fibers or on
bundle of fibers.
 Some standards of fiber strength
Pressley (g/tex) HVI mode (g/tex) Stelometer (g/tex)
Very Weak 21 and less 17 and less 17 and less
Weak 21-23 8-21 17-19
Average 24-26 22-25 20-22
Strong 27-29 26-29 23-26
Very Strong 30 and more 30 and more 26 and more
Cont…

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 Short Fiber Content:
 Usually percentage of fibers less than 12.7 mm, is referred to as the short fiber content
(SFC).
 The negative effect of a high percentage of short fibers are:
Extreme drafting difficulties
Increased number of neps and yarn irregularity, and
 Ends down which reduce quality and increase processing costs
 Higher wastage in combing and other operations.
 Sources of short fibers are:
i. Seed cotton and Variety of cotton
 There are not much variations in cotton fiber inside the ball.
 But, variety plays some part as weaker fibres tend to break down in processing.

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II. Growing conditions
 Growing conditions affect the maturity of cotton.
 Immature fibers break up easily during harvesting, ginning and other processing.
III. Harvesting
 Manual harvesting still adopted in developing countries cause less impurities,
less harsh treatment in ginning, opening and cleaning.
 However, mechanical harvesting results the opposite and all cotton balls
including unopened balls are collected at a time.
 As the result more immature fiber, so result for more fiber breakage.
Cont…

39
IV. Ginning
 The marketing of cotton emphasizes clean cotton (higher
grades) and the higher grades bring higher prices.
 The requirement of very clean cotton without dust for
open-end spinning has resulted in hard ginning, and
more intense cleaning in blow room machines.
 Effect of lint cleaners on
short fiber content
V. Blow room machines
 Each operation in the blow room and subsequent machines stresses and breaks fibers increasing
short fiber content.
Cont…

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 Trash Content:
Trash is a measure of the amount of non-lint materials in cotton, such as leaf and
bark from the cotton plant.
Trash affects yarn and fabric quality.
Therefore, it is very important to know the amount of trash and the type of trash
before deciding the mixing.
The scale below represents the degree of contamination:
Up to 1.2% Very clean
1.2 – 2.0% Clean
2.0 – 4.0% Medium
4.0 – 7.0% Dirty
7.0 % and above Very dirty

41
 Therefore, mixing of cottons having a trash content differing by more than 3% is
not advisable.
 The average level of trash in the mixing for producing a card sliver of good quality
for a specified count is given below.
Ne 20 30 40 60 80 100
Average Trash (%) in mixing 5.0 4.0 3.5 3.0 2.5 2.0
Cont…

42
 Neps:
 Neps are small entanglements or knots of fibers.
 In general, two types of neps can be distinguished.
 Fiber neps which are small knots that consist only of fibers, and
 Seed-coat neps which contain foreign particles such as seed or leaf
fragments.
 A large proportion of neps in raw cotton is produced by the processing method
such as;
 Plucking,
 Hard ginning, and
 The nep count is substantially increased in the blow room.

43
 The card is the first machine to reduce the nep count to a usable level, and
 Nep-reduction at the card is achieved primarily by disentanglement rather than
by elimination.
 Neps not only create disturbance in themselves as thick places,
 But, also dye differently from the rest of the yarn and thus become clearly visible in
the finished fabric.
FIG: Shade variation in dyeing due to the presence of nep in the yarn
Cont…

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 Dust consists of small and microscopic particles of various substance.
 Are present as suspended particles in gases and sink only slowly.
 So that they can be transported in air over substantial distances.
Dust
Particle size (µm)
Trash Above 500
Dust 50 -500
Micro dust 15 - 50
Breathable dust Below 15
 Problems created by Dust:
i. Additional stress on personnel
 Dust is unpleasant, e.g. for eyes and nose
 It can induce allergies  It can induce respiratory disease (Byssinosis)

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2. Environmental problems
 Dust deposits
 Dust accumulations which can fall into the machines.
 loading of the air-conditioning equipment.
3. Effects on the product
 Quality deterioration directly, or indirectly through machine faults.
4. Stressing of the machines
 Dust accumulations lead to operational disturbances.
 Increased yarn unevenness.
 More end breaks.
 Rapid wear of machine components.
Cont…

46
 Color
 Color grade is determined by the degree of reflectance (Rd) and
 yellowness (+b) as established by official standards and measured by HVI.
 Reflectance indicates how bright or dull a sample is, and yellowness indicates
the degree of color pigmentation
 The color of cotton fibers can be affected by rainfall, freezes, insects and fungi,
and
 By staining through contact with soil, grass, or cotton plant's leaf.
 Color also can be affected by excessive moisture and temperature levels while
cotton is being stored, both before and after ginning.

47
 As cotton used in mixing come from different parts of the country,
 It may contain different levels of moisture at the time of mixing.
 Moisture Regain( R): is defined as the mass of water in a material expressed as
a percentage of the oven dry weight.
 R = (W/D) x 100
 Moisture content (M): is the mass of water in a material expressed as a
percentage of the total weight.
 M = W x 100
W+D
 Moisture:
 W = the weight of absorbed water
 D = oven-dry weight of the material
Where:
 Example: Let's suppose that a piece of fiber weighs 125.6 grams initially and 109.4 grams
after oven-dry weight.

48
 The measurement of fiber moisture is very important for a spinning factory,
because;
 It helps to decide on correct invoice weight,
 It is important in controlling count variation by maintaining consistency in
moisture content in mixing, and
 Almost all physical properties are affected by moisture, moisture
measurement helps to properly assess other fiber quality parameters.
 It is the weight of the material at standard moisture regain.
 Where;
 D = oven dry mass of the sample
 R = commercial moisture regain

49
 Three concepts must be clearly distinguished
 Permanent elongation: It is the extension of the fiber does not return to its
original state upon relaxation (removal of the load).
 Elastic elongation: That part of extension through which the fiber does return
to its original state upon relaxation.
 Breaking elongation: The maximum possible extension of the fiber until it
breaks.
 It is the permanent elongation and the elastic elongation together.
 Elongation:

50
 The following scale represents the cotton fiber elongation:
 Below 5.0% Very low
 5.0 – 5.8% Low
 5.9 – 6.7% Average
 6.8 – 7.6% High And
 Above 7.6% Very high
 Man-made fibers have higher elongation.
 For normal textile goods, higher elongations are neither necessary nor desirable.
 They make processing in the spinning mill more difficult, especially in drafting
operations.
 But, higher elongations may be needed for sportswear, stretch products and etc.

51
 Stickiness:
 The sticky substance (chemical deposit) is one of a group of sugars of the most
variable composition (saccharides), produced by
 Insects, or
 The plants themselves, depending upon the influence on the plants prior to picking.
 Honeydew secretion of white fly is known sticky substance on cotton fibers.
Types of sticky substances are given below:
 Secretions by whitefly: honeydew
 Fungus and bacteria: decomposition products
 Vegetable substances: sugars from plant juices
 Fats, oils: seed oil from ginning
 Synthetic substances: insecticides, fertilizers, oil from harvesting machines.

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Dry and mature cotton fibers contain less plant sugar, whereas immature fibers
contain more.
 During spinning of sticky cotton, the relative humidity (RH %) and ambient
temperature should be low as much possible.
An effective way to control cotton stickiness in processing is to mix sticky and non-
sticky cotton.
 Sticky cotton percentage in mixing should be less than 25%.

53
Reading Assignment
 Woolen and worsted spinning
 Processing of manmade fibers
N.B: It is part of exam

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