Materials Sciences and Applicatio ns, 2011, 2, 1724-1729
doi:10.4236/msa.2011.212230 Published Online December 2011 (http://www.SciRP.org/journal/msa)
Influence of Twisting Degree and Number of
Cords on the Structure of Silk
Dilfuza Khudayberdieva, Nodira Amirova, Mavjuda Abdukarimova, S. Khazova,
Nargiz Mirzahmedova
Tashkent Institute of Textile and Light Industry, Tashkent, Uzbekistan.
Received February 21st, 2011; revised April 1st, 2011; accepted April 29th, 2011.
ABSTRACT
Properties of the fibrous material which has oriented supermolecular formations are depended on such structural fac-
tors as morphology, inter position of structure elements, and their interaction. Influence of processing on changing
original structure of fibrous material during mechanical processing that causes deformation at loading is determined
by peculiarities of its structure. Reversible and irreversible changes of structural elements in fibrous material causes
changing of volume and sorption properties and will essentially influence on its chemical finishing processes. Influence
of twisting degree and number of silk cords on structure and physical mechanical properties. Changing of supermo-
lecular structure of thread in the process of its forming by X-ray graphic, sorption and focused beam electronic micro-
scopic methods was researched.
Keywords: Twisting, Cord of Threads, Degree of Crystallinity, Volume Properties
1. Introduction
In mechanical technology at rewinding, twisting and
weaving silk threads are subjected to deformation which
finally causes reconstruction of not only separate filaments
in threads but also of structural elements in amorphous and
crystalline parts of supermolecular silk structure.
The analysis of a priori and periodic literary sources
has shown that mainly the influence of twist and linear
density of crape threads on mechanical and working prop-
erties of crape fabrics were researched. The author of the
work [1] researched physical-mechanical and working
properties of crape threads samples with different linear
density, twisting and number of cords. Changing the
quantity of cords in crape threads with twist 2200 tw/m
causes increasing of breaking load of the fabric, durabil-
ity of angle fastening in the fabric, rubbing resistance and
fabric capillarity, as filling of the fabric and its thickness
increase. Increasing twists up to 3200 tw/m causes sig-
nificant decrease of rubbing resistance of the fabric, and
breaking load and durability of threads fastening in fab-
rics change very little.
Using natural silk for making knitted goods, the influ-
ence of cord and twist number on physical and mechanic-
cal properties of silk threads were investigated in the
work [2].
Increasing of twist up to 500 tw/m breaking load in-
creases, the same conformity with law can be seen in
changing cord of threads. These results are connected
with the changes that take place in the structure of silk
threads by the influence of mechanical forces in twisting.
H. Ito researched the influence of silkworm diet in
aseptic conditions on silk composition and its properties.
X-ray diffraction pattern and dyeing properties of the an
artificial diet fibroin were nearly the same as those of the
mulberry leaf diet fibroin. The artificial diet used in this
study affects the structure and properties of sericin pro-
teins, and a little those of fibroin proteins [3].
The works of scientists from Slovenia [4-6], both ex-
perimental and theoretical, are devoted to researching the
quality of coloring and reproduction the color depending
on fabrics structure.
Indian scientists [7] investigated the amino acid com-
position of five types of silk fibers obtained by feeding
silkworms with mulberry leaves of two types and three
types of other plants. The content of various amino acids
in the fiber obtained from the inner and outer layers of
the cocoon was compared. Difference between structure
and properties of silk fibers was determined. Strength
and density of the filaments by birefringence method
were researched. Coloring different types of fibers by
acid dyes is correlated with the content of terminal amino

Influence of Twisting Degree and Number of Cords on the Structure of Silk 1725
groups in polymer molecules of silk.
In the process of mechanical technology under the in-
fluence of tension in fibrous materials changes of fibre
surface and structure take place, they lead to the changes
of cristallinity index [8].
Knitted goods made of cotton yarn with different type
of spinning, yarn counts, twist factors and structures have
various physical and mechanical quality indexes [9,10].
In literary sources there is no information about influ-
encing the conditions of processes in mechanical tech-
nology of textile materials on structural transformations
of fibers on supermolecular level and influencing these
changes on silk coloring.
2. Materials and Methods
The subjects of the research were: silk threads with dif-
ferent twist and different number of cords (n): 1-Thread
for han-atlas fabrics—total twisting 338 tw/m, linear
density 3.22 tex; n = 2.3 direction of twist S; 2-Thread
for shirt fabric—total twisting 700 tw/m, linear density
3.22 tex; n = 2.6 threads, direction of twist S; 3-Crape
thread—total twisting 2000 tw/m, linear density 3.22 tex;
n = 2.4 of thread, direction of twist S.
Twist was made on Composite Winder Type MT-CW-
D/T machine. Conformance of obtained and set twists
was determined on Twist Counter device. The obtained
twist was fixed in steam medium within 10 - 20 minutes
depending on thickness of winding threads on a bobbin
in autoclave.
Physical and mechanical properties of threads were
researched in an accredited educational-certification center
“CentexUZ” in TITLI on AUTOGRAPH AG-1 devices.
The sorption of water steams was investigated with the
help of Mc Ben spring tungsten scales with sensitivity
1.5 mg/mm at 25˚C ± 0.1˚C and residual pressure 10 - 5
mm. Hg. 5 parallel determinations were made. Relative
mistake in measurement was 1.5%. The evaluation of
magnitude pores radiuses, Å, was made according to the
method [11].
According to isotherms of sorption magnitude of spe-
cific surface was defined—Ssp, of silk. Ssp—of the silk
was calculated according to Brunauer—Emmet—Teller
(BET) equation according to the method.
Total volume of pores was calculated according to
formulae:
W0 = a/ρ; where,
a—adsorbent mass taken at impregnation Р/P0 = 1
ρ—adsorbent density
Average radius of capillaries was calculated from the
ratio
rn = 2W010–4/Ssp [11]
Radiographic investigation of the samples was made
on X-ray diffractometer “DRON-3Н” with monochro-
matized Cu K

—radiation at tension 22 kV and current
power 12 mА which were chosen depending on the
preparation. The samples were made by pressing poun-
ded preparations in the form of tablets. The survey was
made in the interval of 2θ = 10˚ - 35˚. Crystallinit de-
grees (Dc) were determined according to German—
Veidinger method. The evaluation of crystallinity de-
grees was made according to the ratio of peak intensity
for one of the main maximums the altitude of which was
proportional to crystallinity degrees, to so-called amor-
phous dispersal.



II
Dc%100 %
I
ка
к


where, Iк and Iа—intensity of crystal reflex and amor-
phous dispersal, accordingly [12].
The research was made on focused beam electronic
microscope REM-250. In order to exclude the electric
charge which is sharply accumulated on non-conducting
sample in scanning, the samples were covered with a thin
film. For this, the sample was placed in high-vacuum
evaporator VEP-4К and was covered with silver.
3. Experiment
In initial stage of the research physical and mechanical
properties of silk textile thread with different twist de-
gree and cord of threads were investigated (Table 1).
With increasing of twist, the durability of the thread
increases to some critical point, then strength properties
decrease. Increasing of elementary threads in textile
thread causes increasing of its durability.
For revealing changes in supermolecular structure
volume and superficial properties of threads with differ-
ent twist and number of threads cords using sorption,
X-ray methods were researched, and external surface of
the samples was researched by focused beam electronic
microscopy.
REM-researching of the Silk samples showed the fol-
lowing results: initial untwisted natural silk thread has a
smooth surface (Figure 1), here and there slightly coarse
with rare linear thin folds along the fiber axis.
Table 1. Physical and mechanical properties of silk textile
threads with different degree of twist and cord of threads.
Samples of
threads for fabric
Twist
tw/m
Number
of
cords, n
Linear
density
N, tex
Breaking
load,
Рр, cН
Elongation
at break L,
%
“Han-atlas” 338 2 5.14 122.91 8.33
700 2 5.0 204.84 17.41
“Shirt” 700 6 17.0 502.73 19.41
20002 5.5 144.91 14.82
“Crepe-de-chine” 20004 12.2 301.38 18.04

Influence of Twisting Degree and Number of Cords on the Structure of Silk
1726
(a) (b)
(c) (d)
Figure 1. REM surveys of samples with different twist: (a) untwisted; twisted x; (b) With twist 338 tw/m; (c) With twist 700
tw/m; (d) With twist 2000 tw/m silk thread.
The silk thread which has twist 338 tw/m × 2 differs
very little (Figures 1(a) and (b).) from initial silk by sur-
face structure, but when twist increases (700 tw/m × 2)
micro- and macro-defects appear on the surface (Figures
1(c) and (d)). Significant superficial change takes place
at high twisting of textile thread. For the fabric of crape
assortment (2000 tw/m × 2) twist can be seen clearly,
practically we can’t see fibril elements (Figure 1(d)).
When twist increases we can see significant superficial
change and also micro- and macro-defects, twistedness,
bends, breaks, elementary fibre fibrilization. Changing of
thread surface, appearing of cracks and fractures un-
doubtedly influence on volume properties of the threads.
In connection with this sorption and volume properties of
natural silk threads samples with different twist and cord
were researched (Table 2).
According to the results of researching sorption prop-
erties it was determined that in the result of twisting
compared with initial untwisted silk all the samples of
silk threads for corresponding fabrics with different cord
of threads indexes of specific surface decreasing—Ssp,
and at the same time radius of pores—rп of the fiber in-
creases. Changing of pores total volume—W0, Ssp and rп
differs depending on the number of cords of threads. At
the same number of filaments W0 and rп fibers increase
(338 tw/m), then sharply decrease. Ssp at twisting degree
of 338 tw/m decreases compared wilh initial silk, then at
700 and 2000 tw/m it increases again. If number of cords
and twist degree are different at changing from 338 tw/m
to 700 and 2000 tw/m Ssp, W0 decrease, and rп for threads
700 tw/m in 6 cords—is the largest.
Crystallinity degree of textile thread for defining
structural changes in result of twisting was evaluated .
Comparing crtystallinity degree for the samples ob-
tained by combining in two threads with different num-
ber of twist its Cd decreases when number of twist in-
creases. However, intensive twist with large number of
threads causes increasing of crystallinity degree signify-
cantly (Table 3).
4. Results and Discussion
Density of packaging structural elements is one of the

Influence of Twisting Degree and Number of Cords on the Structure of Silk 1727
Table 2. Water stems sorption by silk samples at 25˚C.
Water stems sorption in % by threads will different cards number
Relative wetness of water
steams, %
initial 3.23 × 2S338 3.23 × 2S700 3.23 × 2S20003.23 × 6S700 3.23 × 4S2000
10 1.1 1.0 1.2 1.0 0.5 0.7
30 2.5 2.3 2.9 2.4 1.1 1.6
50 3.3 3.1 4.0 3.3 1.7 2.4
65 4.2 3.7 5.1 3.9 2.6 3.3
80 6.0 4.9 6.4 4.8 4.9 4.5
90 7.8 6.40 7.5 5.6 5.0 5.9
100 10.8 13.9 10.5 7.5 7.6 8.5
Table 3. Superficial and volume properties of silk threads.
Sample of thread for
fabric
Twist,
tw/m
Number of cords,
n
Specific surfac
(Ssu, м2/gr)
Total volume of
pores (Wp, sm3/gr)
Radius of pores
(rp, Å)
Crystal linity
degree, %
Initial untwisted
thread 0 1 83.712 0.108 25.8 62.0
“Han-atlas” 338 2 78.177 0.139 35.56 64.0
700 2 84.763 0.075 17.7 61.0
“Shirt” 700 6 36.034 0.076 42.18 67.0
2000 2 102.990 0.109 21.1 58.7
“Crepe-de-chine” 2000 4 54.093 0.085 25.8 68.8
most important physical characteristics which stipulate
the complex of structural-mechanical and sorption prop-
erties of fiber material.
Extreme nature of dependence of textile threads twist
and durability can be explained by increasing friction
forces between fibers at twisting to the values that exceed
fibers durability. At further of increasing yarn twisted-
ness breaking of fibers increases because of twisting de-
formation and pressing and in the result yarn durability
decreases [13].
Textile thread must have system of submicroscopic
pores that form developed inner surface with active cen-
ters which provide diffusion and fixation of the dye dur-
ing coloring. Effective free volume can change in the
processing and chemical finishing of the fiber.
In initial silk undense packing of structural elements
may take place because of steric obstacles of big side
substitutes and also in the result of thermal motion of
macromolecules.
Emptinesses that appear are approximately equal to the
volume of statistic polypeptide segment cause undensity
of packing in amorphous parts. The larger emptinesses
and pores in the fiber are determined by the peculiarities
of packing different fibrillar structures on all levels of
supermolecular formations of fibroin [14]. These correla-
tions obviously change in the process of deformation,
decrease or increase depended to loading regime. The
changes are the result of the action of several opposite
factors which cause:
 Increasing or decreasing of pores sizes, that promote
to appearance of micro and macro defects by the in-
fluence of tension in the process of twist;
 Crystallity degree and regulation of fibroin macro-
moleciles, that promote to increasing intensity of in-
termolecular interaction.
These facts allow to make the conclusion that the
changes in supermolecular structure of twisted silk threads
must influence on kinetic and thermodynamic characteris-
tics in dyeing process.
On the basis of these data the influence of these changes
on the quality of dyeing was researched. For dyeing active
vinylsulfon dyes Ostacolor Ostazin VR blue and yellow
Ostazin VGR were used. The kinetics of dyeing threds
samples with different twist, at 65˚C, 75˚C, 85˚C (Table
4) was investigated.
Determining the quantity of adsorbed and fixed dye on

Influence of Twisting Degree and Number of Cords on the Structure of Silk
1728
the fiber in identical conditions of dyeing for all the
samples showed that the filament “Han-atlas”338 kr/m
× 2 absorbs more dye than “Shirt” and “Crepe-de-
chine” of the same cord. Sorption of “Crepe-de-chine”
thread (2000 tw/m × 4) is less than of “Shirt” (700 tw/m
× 6) ones. The same effect can be seen at fixation of the
dye on the threads. Twist degree of threads doesn’t in-
fluence significantly on the dye sorption, but the fixa-
tion of the dye doubles with increasing degree of
threads twist. On the basis of kinetic curves values of
diffusion coefficients in dyeing process (Tables 5 and 6)
were calculated.
Threads for “Han-atlas” have pores with a large radius
and total pore volume, therefore the dye diffuses into the
fiber easier. The values of the diffusion coefficient of
dyeing “Han-atlas” threads are higher compared with other
samples. When temperature increase the diffusion coeffi-
cient of dyeing Ostazin blue VR increases, then it de-
creases a little, while the Ostazin yellow VGR uniformly
increases. Differences between changes in diffusion co-
efficient and the type of dye are probably connected with
the structure of the molecule.
5. Conclusions
With increasing of twist thread durability of increases to
some critical value and causes significant surface changes.
In the result of twisting Ssp increases and at the same
time rп of the fiber decreases. Conformity to some estab-
lished law of Ssp and rп changes to some extent differs
depending on the number of threads cords At high twist
degree of (2000 tw/m) Ssp, W0 decrease and rп for threads
changes little.
Table 4. Influence of dyeing temperature on the equilibrium sorption and fixation of the dye by silk threads with different
twist degree and with the cord of 2 threads.
Ostazin blue VR Ostazin yellow VGR
338 tw/m 700 tw/m 2000 tw/m 338 tw/m 700 tw/m 2000 tw/m
Temperature, ˚C
С* С** С* С** С* С** С* С** С* С** С* С**
45 17.0 12.9 16.4 12.6 14.1 10.2 13.6 10.5 13.5 9.9 12.4 8.95
65 17.9 14.4 17.8 14.05 17.8 14.0 15.8 13.5 15.4 13.4 15.2 13.2
85 16.0 10.6 14.5 8.6 12.5 7.0 13.6 10.8 13.1 10.8 13.0 10.2
С* amount of sorbed dye gr/kg, С** of dye fixation gr/kg.
Table 5. Influence on equilibrium sorption and fixation of the dye by silk threads with different twist, and with cord of
threads.
Ostazin blue VR Ostazin yellow VGR
Thread sample with twist (tw/m) and the
number of cords С* С** С* С**
338 × 2 16.65 4.95 16.6 4.1
700 × 6 15.85 5.85 15.2 5.2
2000 × 4 15.55 8.05 13.75 8.75
Table 6. Dependence of diffusion c oe ffic ie nt D·10 12 m2/sec on twist degree and temperature of dyeing.
Ostazin blue VR Ostazin yellow VGR
Samples of threads for fabric Twist, tw/m Number of
cords, n 45˚C 65˚C 85˚C 45˚C 65˚C 85˚C
“Han-atlas” 338 2 16.8 19.0 18.0 12.2 12.5 14.0
“Shirt” 700 6 14.0 16.1 14.0 11.0 10.0 13.3
“Crepe-de-chine” 2000 4 13.0 15.0 12.0 8.3 9.8 11.7

Influence of Twisting Degree and Number of Cords on the Structure of Silk 1729
Crystallinity degree of the thread with increasing twist
at identical number of cords decreases. However inten-
sive twist with large number of threads cord causes in-
creasing of crystallinity degree, that makes difficult dye
diffusion inside the fibre.
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