Characterization of Egyptian cotton fibres

Abstract

In this work, the quality of Egyptian cotton varieties has been studied in terms of a morphological investigation, single fibres tensile properties and other tuft properties determined by HVI. Finally, a new 'modified fibre quality index (MFQI)' for the characterization of the quality is presented and compared with the spinning consistency index. This index in most cases gives the real potential of the cotton variety according to its physical properties.

Full text

Indian Journal of Fibre & Textile Research
Vol. 38, March 2013, pp. 109-113
Characterization of Egyptian cotton fibres
Magdi El Messirya & Samar Ahmed Mohsen Abd-Ellatif
Textile Engineering Department, Faculty of Engineering,
Alexandria University, Egypt
Received 27 November 2011; revised received and accepted
29 March 2012
In this work, the quality of Egyptian cotton varieties has been
studied in terms of a morphological investigation, single fibres
tensile properties and other tuft properties determined by HVI.
Finally, a new ‘modified fibre quality index (MFQI)’ for the
characterization of the quality is presented and compared with the
spinning consistency index. This index in most cases gives the real
potential of the cotton variety according to its physical properties.
Keywords: Equptian cotton Fibre quality index, Spinning
consistency index, Tensile properties
Cotton species (Gossypium hirsutum) is native to
Mexico and Central America and has been developed
for extensive use in Egypt, accounting for more than
80% of Egyptian Production. This group is known as
long staple (LS) cotton. It varies in length from about
7/8 inch to 15/16 inch. Another group (Gossypium
barbadense), which makes up the most valuable and
the balance of the Egyptian production, is of early
South American origin, varying in length from 11/4
inch to 19/16 inch. It is commonly referred to as
extra-long staple (ELS)1. Egyptian cotton fibres are
composed mostly of α-cellulose (88-96.5% w/w). The
rest is non-cellulosic that are located on the outer
layers and inside the fibre lumen. The non-cellulosic
include proteins (1-1.9% w/w), waxes (0.4-1.2%
w/w), pectin (0.4-1.2% w/w), inorganic (0.7-1.6%
w/w), and other substances (0.5 to 8% w/w). The
specific chemical composition of cotton fibres varies
according to their varieties and growth conditions2.
The cotton classification is a system of standardized
procedures for measuring raw cotton properties
(physical attributes) that affect quality of processing
(spinning mainly) and quality of products (yarns).
Several standards as well as testing techniques are
available for the characterization of cotton fibres,
such as HVI and AFIS techniques. It is known that
there are some differences in the principles of
measurements and the results of AFIS and HVI
spectrum apparatus. Despite of these differences, it is
possible to specify basic cotton fibre properties
having potential influence on the cotton yarn
strength3. There are also differences between
measurements of fibre strengths based on bundle
concept and single fibre concept as described by
Militky and Kremenakova4. Equations relating single
cotton fibre strength to bundle strength are presented
but proved to be of limited success5. Many
research3,6,7 studies have been conducted to observe
the phenomenon of spun yarn failure which is found
to be strongly dependent on yarn structure, fibre
packing in the yarn cross section5,8 as well as the
cellulose accumulation inside the cotton fibres6.
Several studies have been published and different
formulas are suggested to define the cotton fibre
quality1,3,4,9,7. One of the first attempts to create
aggregated criterion of cotton fibre quality is fibre
quality index (FQI), as shown below:
FQI = (Fibre strength × Length)/Fineness
This is further modified by considering more fibre
properties, as shown below:
FQI = (Fibre strength × Length × Uniformity × Maturity
coefficient)/Fineness
For HVI results, FQI is expressed in the form of
FQI = UHM × UI × STR/MIC
Militky and Kremenakova4 described that the
procedure for the evaluation of cotton quality index
(U) can be simply modified for other selected
properties or other set of weights. Considering
different fibre properties and assuming linear
geometric properties, some criteria based on the
regression models connecting fibre properties with
parameters are used to characterize spinning ability or
quality of yarn (characterized by yarn strength)10. The
spinning consistency index (SCI) is connected with
cotton HVI properties through regression model3, as
given below:
SCI =-414.67 + 2.9 STR + 49.1 UHM + 4.74 UI - 9.32
MIC + 0.95 Rd + 0.36 b
However, for Egyptian cotton the value of SCI does
not accurately reflect the spinnability of the different
___________
aCorresponding author.
E-mail mmessiry@yahoo.com

INDIAN J. FIBRE TEXT. RES., MARCH 2013
110
cotton varieties. The present study is therefore
undertaken to investigate the Egyptian cotton varieties
and to develop a modified fibres quality index (MFQI).
Cotton samples representing the different Egyptian
cotton varieties are prepared in order to perform
different fibre tests determining their physical
properties. Fibres from different ELS and LS
Egyptian cotton under investigation Giza 45, Giza 70,
Giza 87, Giza 88, Giza 80, Giza 85, Giza 86, Giza 89
and Giza 90. The single fibre properties are tested in
Department of Textile Materials, Textile Faculty, and
Technical University of Liberec Cz. Fibre bundle
measurements are performed on the HVI (high
volume instrument)at the laboratories of the Modern
Nile Cotton Co.
Structure and Morphology of Egyptian cotton
An analysis of the potential relationship between
the microstructure and the surface properties of
different cotton fibres has previously been performed
and proved to be of high importance11.
It is necessary to carefully analyse the structure and
the surface properties of cotton fibres in order to
enhance the performance of cotton based materials and
fabrics. In this context, the relationships between the
microstructure and the surface properties of different
cotton fibres should be thoroughly considered. Figure 1
shows the SEM images of grey cotton samples at
magnifications of ×1000 and ×10000 for different
cotton varieties. The samples were used without
treatment. The convolutions on the cotton fibres
surfaces are clearly shown and the fibre surface is
found to be different for each type tested. This certainly
reflects on their performance in the spinning process
and the quality of the yarns produced from the different
types of cotton. Efforts have been made to observe the
convolutions present on the surface of cotton fibres,
representing different cotton types and relating them to
their surface characteristics. Sinoimeri12 attempted to
group different types of cottons according to their inter-
fibre-friction properties. It is apparent that these
properties are mainly due to the surface properties of
the fibres including micro- or nano-scopic surface of
fibres. Fibre surface characteristics have a significant
influence on their frictional characteristics11.
Moreover, these frictional properties affect the
values and the variability of the drafting forces
applied on the fibres during their processing and are
considered to be one of the main factors determining
the unevenness of the products at different spinning
stages12. Furthermore, surface characteristics are
expected to have a considerable effect on the yarn
strength. Therefore, the analysis of the SEM for the
different varieties of Egyptian cotton considers the
relative number of convolutions, surface smoothness
and surface irregularity, which, in turn, should largely
affect fibres and yarn strength properties. Table 1
shows a comparative classification of the surface
characteristics of the different varieties of the
Egyptian cotton. The properties presented in Fig. 1
could be of a great significance regarding the single
fibre strength properties. It is expected that highly
convoluted fibres would give a less fibre strength.
Although the testing of single fibres is considered
to be exhaustive, demanding and difficult, it proves
sometimes to be of great use especially to breeders
and researchers with limited testing material available
or in the areas where the detailed data is able to justify
the investment in time and effort. In this research
work, a study on the single cotton fibres tensile
properties is conducted. Samples from five different
varieties of Egyptian cotton are drawn (Giza 86, Giza
87, Giza 88, Giza 90 and Giza 45), and 50
measurements are applied for each variety. The
Vibroscope, a device for the measurement of strength
characteristics of single fibres, is utilized. For each
sample, numerical values for fibre count, breaking
force, breaking elongation, tenacity and young
modulus are recorded. Table 2 shows the mean
values, CV%, minimum values and maximum values
of the single fibres strengths for the five cotton
varieties under investigation. The variation in
properties is related to genetic of the cotton verities10.
Fibres Tuft strength
Cotton fibres are usually tested in bulk form
utilizing a mass or beard of fibres to a test instrument
for measurement. There are many reasons for this, not
the least of which is that handling single cotton fibres
Table 1—Comparative classification of the different varieties of Egyptian cotton
Cotton type G45 G70 G87 G88 G80 G85 G86 G89 G90
Convolutions Low Low Low Low Medium Medium Medium Medium High
Surface smoothness Smooth Smooth Smooth Smooth Smooth Rough Rough Rough Rough
Surface irregularity Low Low Low Low Low Medium Medium High High

SHORT COMMUNICATIONS
111
is tedious and time consuming. Another argument for
the application of the tuft strength testing technique is
that cotton fibres are seldom used in the single fibre
form and the properties which are of interest are the
properties of a tuft of these fibres3,5. Several
investigators5,6,8,13 correlate the yarn tenacity by the
value of the bundle strength. However, the tuft testing
has many drawbacks especially while testing the
strength characteristics of the fibres. It is expected
that the strength of a yarn is not predicted accurately
by averaging the strength of the individual fibres. The
above results indicate high value of the coefficient of
variations for all the measured single fibre properties,
which is much higher than the tuft values.
Comparison between Single Fibre and Tuft Testing Techniques
In a further step, a comparison between the single
fibre tensile characteristics obtained from the
Vibroscope and the tuft fibre strength obtained by the
HVI is conducted. The summary of the results is
shown in Table 3.
A statistical analysis is then performed as a
comparison between the fibre strength values
obtained from the Vibroscope and those obtained
from the HVI. The value of R2 = 0.807 is found
Fig. 1—
SEM images of single raw cotton fibres [(a) G.45, (b) G.70, (c) G.87, (d) G.88, (e) G.80, (f) G.85, (g), G.86, (h) G. 89, and
(i) G.90] [(i) ×1000 and (ii) ×10000]

INDIAN J. FIBRE TEXT. RES., MARCH 2013
112
between the single fibre and bundle strength for the
different varieties (Fig. 2). Thus, the tenacity of single
fibre from the Egyptian cotton can be obtained using
the following equation:
STRf = 5.705 TSt − 170.24 ... (1)
where STRf is the single fibre tenacity in cN/tex; and
TSt, the tuft strength measured HVI in cN/tex.
However, no reasonable correlation is observed
between the single fibre and the bundle elongations.
Cotton Fibre Quality
Hunter14 study was to predict the most important
yarn quality characteristics derived from cotton fibre
properties that were measured by means of an HVI
system. Linear multiple regression methods were used
for the estimation of yarn quality characteristics. More
recently, many approaches including artificial neural
networks and fuzzy logic have been used for
predicting textile products quality from fibre
properties. However, Hunter14 concludes that, until
now, there is no viable solution. Such and Sasser7
have reviewed the impact of HVI systems on both the
domestic and world cotton textile industries. Several
formulas have been suggested for defining the cotton
fibre quality. Considering other fibre properties and
assuming linear geometric properties, a modified
formula is presented as:
MFQI = [UHM × UI × STRf × (1+EL) × (1-SF)]/ MIC
… (2)
The fibre length is expressed by upper half mean
UHM (mm), UI (%) stands for the fibre length
uniformity index, STRf (cN/tex) stands for the single
strength, EL (%) stands for the fibre elongation at
break, (MIC) stands for the micronaire value
representing the fibre fineness and maturity and
SF(%) stands for the short fibre content. Taking into
consideration the variability in the fibre length, the
term FQI represents the specific work of rupture
which is defined as the amount of energy needed to
break a material and is represented by the area under
the stress strain curve. It measures the ability of a
material to withstand a given energy. In order to
compare different materials, work of rupture should
be normalized to take account of the various masses
of different materials. Hence, specific work of
rupture, which is the amount of energy needed to
break a material of unit mass, should be used. Thus,
MFQI is more consistent for the comparison between
different types of cotton. The MFQI given in the
Table 3—Tuft fibre strengths measured by HVI
G.45
G.87
G.88
G.86
G90 Parameter
Strength
g/tex
Elongation
%
Strength
g/tex
Elongation
%
Strength
g/tex
Elongation
%
Strength
g/tex
Elongation
%
Strength
g/tex
Elongation
%
Mean 42.3 6 45.2 6.5 45.1 5.1 43.1 5.8 33.5 7.7
CV% 3.3 3.2 3.6 3.1 3.91 3.05 4.9 3.5 4.02 3.89
Table 2—Characteristics of cotton varieties
Cotton
Parameter
Fibre count
dtex
Tenacity
cN/tex
Elongation
%
Young
modulus
g/den
Mean 1.33 37.88 9.24 32.11
CV% 20.97 34.59 26.86 39.83
Min. 0.76 9.3 4.1 11.05
G.45
Max. 1.7 65.3 13.6 71.83
Mean 1.51 37.13 6.53 42.59
CV% 17.52 41.17 33.43 41.46
Min. 1.06 9.47 1.9 17.91
G.87
Max. 2.14 74.09 10.9 115.29
Mean 1.62 35.55 6.32 43.55
CV% 21.04 41.89 26.92 34.9
Min. 1.07 7.66 3.1 16.81
G.88
Max. 2.4 72.66 10.7 88.85
Mean 1.76 39.01 8.69 42.09
CV% 17 29.73 27.17 43.2
Min. 1.05 12.65 4.2 20.08
G.86
Max. 2.38 68.11 14.2 87.31
Mean 1.64 32.75 8.51 34.3
CV% 21.39 29.99 30.17 32.62
Min. 1.1 13.19 3.9 14.58
G.90
Max. 2.33 59.36 14.2 63.95
Fig. 2—Correlation of single fibre and tuft tests

SHORT COMMUNICATIONS
113
formula is calculated for different Egyptian cotton
varieties and the results are given in Table 4. The
values obtained are compared with the values of the
spinning consistency index given by the HVI. In spite
of the relatively high degree of conformation between
the two indices, it is noticeable that the MFQI is more
relevant representing the differences between the
behaviour of the different varieties in spinning mills.
The performance of Giza 87 is found to be better than
that of Giza 88 during the different stages of the
spinning process. This is shown clearly by the value
of MFQI where the SCI failed to predict it. Same for
the Giza 45, whose spinnability is by far better than
Giza 88. This could also not be clearly detected by the
SCI but could be identified by the MFQI. Values of
MFQI also clearly differentiate between the ELS and
LS Egyptian cotton varieties.
In a subsequent step, the modified index is
compared with other global cultivars15, 16 to check its
efficacy (Table 5). High conformation between the
values of both MFQI and SCI could be detected as in
the case of the Egyptian cotton. Nevertheless, the
calculated value of the MFQI is more efficient in
showing the superiority of the spinning performance
of the Sovin compared to the spinning performance of
the US Pima. The SCI values are failed to show this
superiority. Both indices give acceptable classing for
the Chinese 132. On the other hand, both indices are
failed to show the expected superiority of the spinning
performance of the DCH32 over the Barakat.
In this work, the problem of the determination of
the cotton fibres quality has been studied. The
morphology of the Egyptian cotton fibres shows a
relationship between the surface structure and the
tensile properties of single cotton fibres, where high
convolution, rough and irregular surfaces lead to a
lower strength of the fibres. The extensive study of the
single fibre tensile properties has also been carried out.
The results for different cotton fibre varieties have been
presented. A comparison between single fibre tensile
behaviour and tuft fibre tensile behaviour has also been
performed giving a correlation factor of 0.807 between
both values. No relationship is observed between single
fibres and tuft fibres elongations. Finally, a term for the
characterization of cotton quality (MFQI), as a function
of fibre length, fineness and strength has been
introduced and compared with the SCI. The MFQI is
proved to be better than SCI in describing the
performance of cotton fibres.
References
1 Classification of cotton, (Cotton Incorporated);
http://www.cottonic.com/CottonClassification, (2012).
2 Phillip J Wakelyn , Noelie Bertoniere , Alfred Dexter French,
Devron Thibodeaux , Marie-Alice Rousselle , Barbara Triplett,
Wilton Goynes , J Vincent Edwards, Lawrance Hunter, David
McAlister & Gary Gamble Lewin, Cotton Fibre Chemistry
and Technology (CRC Press, Taylor & Francis Group), 2006.
3 High Volume Instrument for Fiber Testing, Application
Handbook of Uster HVI Spectrum (Zellweger Uster), 1999.
4 Militky J & Kremenakova D, Comparison of Complex Indices
for Cotton Fibre Quality Characterization; http://www.
icac.org/meetings/wcrc/wcrc4/presentations/data/papers/
Paper1097.pdf, (2012).
5 Frydrych I, Text Res J, 65 (9) (1995) 513.
6 Shu Hongmei, Wang Youhua, Chen Binglin, Hu Hongbiao,
Zhang Wenjing & Zhou Zhiguo, Acta Agronomica Sinica, 33
(6) ( 2007) 921.
7 Suh MW & Sasser, J Text Inst, 87(3) (1996) 43-59.
8 Ghosh A, Ishtiaque S M & Rengasamy R S, Text Res J, 75
(10) (2005)731&741.
9 Majundar A, Autex Res J, 5 June (2005) 71.
10 Asif M, Mirza J I & Zafar Y, Pak J Bot, 40 (3) (2008)1209-
1215.
11 Rjiba N, Nardin M, Drean J-Y & Frydrych R, J Colloid
Interface Sci, 314( 2007) 373-380.
12 Sinoimeri A, Wear, 267 (2009) 1619–1624.
13 Maria Cybulska, Goswami Bhuvenesh C & David MacAlister,
Text Res J, 71(12) (2001) 1087-1094.
14 Hunter L, Predicting cotton fibre properties from yarn
properties in practice, Proceedings, the 27th International
Cotton Conference (Faser Institute, Bremen), 2004, 62-70.
15 Indian cotton information; Suvin, www.cotton/ici , (2012).
16 Indian cotton information; DCH-32 Average, www.
cotton/ici, (2012).
Table 4—Values of MFQI and SCI for different Egyptian cotton
varieties
Cotton MFQI SCI
Giza 45 411.67 214
Giza 87 352.56 217
Giza 88 288.13 218
Giza 86 262.47 204
Giza 90 193.21 146
Table 5—Values of MFQI and SCI for different global cotton
cultivars
Cotton MFQI SCI
Barakat (Sudan) 261.1 162.79
US Pima (USA) 312.07 196.54
Sovin (India) 355.17 176.78
DCH32 (India) 257.45 145.04
132 (China) 302.41 173