Influence of Twisting Degree and Number of Cords on the Structure of Silk

doi:10.4236/msa.2011.212230

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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.

E-mail: [email protected]

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.







Dc%100 %

ка





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

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)

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,

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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