Indian Journal of Fibre & Textile Research Vol. 30, September 2005, pp. 273-277

Effect of thread structure and lubrication ratio on seam properties

B Meric" & A Durmaz

Department of Textile Engineering, Faculty of Engineering and Architecture, Uludag University, Bursa, Turkey

Received 17 September 2004; accepted 16 November 2004

The influence of thread structure and lubrication ratios on sew ing performance of polyester multifilament, staple and core-spun threads with 2%. 4% and 6% lubrication ratios has been studied. Three different twists (540 twists/m, 635 twists/m and I 060 twists/m) were applied to 100% polyester yarns to analyze the effect of twi st. The multifilament polyester yarns with 2 and 3 plies were used to study the effect of ply numbers. The effect on breaking elongation, coefficient of friction between thread and metal, and initial elasticity modulus has also been studied. The seam strength and seam slippage were measured to evaluate seams performance. It has been observed that the structure of threads affects the seam strength, whereas the lubrication ratio does not. The core-spun thread structure shows a great resistance against the seam opening.

Keywords: Breaking elongation. Breaking strength, Lubricat ion ratio, Seam strength, Seam slippage, Sewing thread

IPC Code: Int. Cl.7 D06H5/00; GOIN33/36

1 Introduction Sewing thread is one of the most important factors

which determines the seam strength, seam elasticity, durability and comfort as relevant to seam appearance and performance. A good sewing thread should give negl igible breaks and acceptable seam appearance and should not cause seam puckered 1.2.

The mechanical properties of sewing threads are very important for sewing performance. At higher stitching speeds, the sewing thread, especially the needle thread, is exposed to tensional and frictional forces. Various properties of threads influence their performance during sewing process3

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• These are: type of fibres, the structure of thread, count of sewing thread, number of twist and friction properties.

Generally, natural and synthetic fibres are used in sewing threads. Cotton is multipurposeful natural fibres while polyester and polyamide fibres are the mostly used synthetic fibres. Staple spun, core-spun, multifilament, monofilament, twisted, textured and air-jet sewing threads can be produced using these fibres .

Twisting process is the most important step of thread production. The optimum twist value of the thread produces a strong resistance against the dynamic loads in the needle thread. An excessive twist value can be the cause of critical lateral force and less breaking tenacity 1

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"To whom all the correspondence should be addressed. Phone: 4429193; Fax:+ 90-224-4428021; E-mail : bi nnaz@uludag.edu .tr

The friction between the machine components and the needle thread is also vitaly important. All sewing threads, especially the synthetics, need a lubrication process against the frictional forces. The lubrication process must ensure static friction properties. A regular coefficient of friction ensures a smooth transition of thread from inside of the guide components. It protects the thread against hi gh needle temperatures and reduces static electricity, especially on synthetic fibre threadsl.2·6·

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A high quality sewing thread must be selected according to fabric properties and sewing conditions. To get high efficiency from a thread during the sewing process, the thread must have high breaking tenacity, initial elasticity modulus, uniform friction and a resistance against the needle temperature and the abrasion.

In the present work, effects of sewi ng thread structures, twi st values, ply numbers and lubrication ratios on sewing thread properties and sewtng performance have been studied.

2 Materials and Methods To study the effects of lubrication process, thread

structures, twist and ply values on sewing thread properties and sewing performance, three different polyester thread structures (multifilament, staple and core-spun) with the same ticket number( 150 or 180), three different lubrication ratios (2. 4 and 6 %) and three different twist values (540. 635 and 1060 twtsts/m) were used . Two and three ply numbers were

274 INDIAN J. FIBRE TEXT. RES., SEPTEMBER 2005

also applied to the same sewing thread. The properties of the sewing threads are given in Table l.

For lubrication process of threads, the Graff lubrication method was used. The Graff lubricant (dry emul sion) was applied hot on the thread using Graff appli ca tors . Since the lubrication process is carried out at hi gh temperatures, the affin ity of lubricant and homogeny dispersion o n the thread are better than the watery em ul sion8

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The count of sewing thread was tes ted on Mesdan Sartarius BL 60S, the ten sil e properties on Textechno Statimat II, the twist val ue on Omac SNC Btella and the yarn-to-metal surface friction o n Mesdan Attnftl II 233 B. The seam strength and seam slippage were tes ted accord ing to BS 3320 test method on an Titan Universal Strength Tester. The results of the experiments were evaluated with Costat Stati stics Program by means of SNK (Student-Newman-Keuls) tests and variance analyses .

3 Results and Discussion

3.1 Thread Properties

The mechanical properties of the sewing thread are g iven in Table 2 and the results of SNK test are g iven in Table 3. It is observed that the structure of thread affects the breaking tenacity and breaking extension but the lubrication ratio is not effective. For the different thread structures, the multifilament thread has the maximum breaking tenacity and the staple thread structure has the minimum breaking tenacity.

According to SNK test, the three different thread structures with same ticket number show s ignificant differences . The maximum extension-at-break is observed for core-spun thread. In this kind of thread, filament core ensures the necessary breaking tenacity . The staple coating increases the resistance against abrasion. It protects the thread against the dynamic and thermal loads .

If the yarn-to-metal friction coefficient of the first group threads are examined, it is observed that the fric ti on coefficient of multifil ament thread is more than those of the staple and core-spun threads . Fig. 1 shows metal friction coefficient for different thread structures. An increase in lubrication ratio causes a decrease in coefficient of friction . Since the surface is coated with staple, the coefficient 0f friction test results of the staple and core-spun threads are similar. In the spun thread structure, the lubricant stays on the surface and it produces better thermal resistance than the filament threads .

Table !- Properti es of threads

Thread type Lubricant Thread Thread Twist Ply ratio,% ti cket number twi sts/m number

number den

Multifilament 2 150 184 1060 z 2 4 150 188 1060Z 2 6 150 191 1060Z 2

Staple 2 150 189 1060Z 2 4 ISO 19 1 1060 Z 2 6 150 196 1060 z 2

Core-spun 2 150 205 I 060 Z 2 4 150 207 l060 z 2 6 150 207 1060Z 2

Multifil ament 2 150 178 540 Z 2 4 150 182 540 Z 2 6 150 190 540 z 2

Multifilament 2 !50 183 635 z 2 4 150 186 635 z 2 6 150 189 635 z 2

Multifilament 2 180 147 645 S-540 Z 2 4 180 149 645 S-540 Z 2 6 180 151 645 S-540 Z 2

Multifilament 2 180 147 645 S-540 Z 3 4 180 149 645 S-540 Z 3 6 180 15 ! 645 S-540 Z 3

The initial elasticity modulus of multi fil ament threads is found to be higher which produces better loop formation. When the needle moves dow n, a hig h moduled thread minimizes the value of thread extension . When the needle moves up , the thread relaxes and an appropriate loop formation appears. With the change in lubrication ratio, the initial elasticity modulus decrease6

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Twist value has great influence on break ing tenacity and breaking extension but the lubrication ratio has no effect. When the twist value increases, the breaking tenacity of thread decreases . According to SNK test, there are significant differences among the three twist values. A high twist value can be the cause of critical lateral forces and less breaking tenac it/ ·<J . If the change in breaking extension is studi ed, the threads which have 635 twists/m show higher extension values .

The effect of tv.- ist value on the friction coefficient shows that the increase in twi st value decreases the friction coefficient. Fig. 2 shows the effect of twis t value on thread-to-metal coefficient of friction . The twist process gives a circular ·cross-section to the thread and thus decreases the friction of coeffici ent. With the increase in lubrication ratio, the coefficient of friction decreases a little amount 12

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MERIC & DURMAZ: EFFECT OF THREAD STRUCTURE & LUBRICATION RATIO ON SEAM PROPERTIES 275

Yarn structure

Multifilament Ticket No: 150 ( I 060 twists/m )

Staple spun Ticket No: 150 ( 1060 twi sts/m)

Core spun Ticket No: 150 ( I 060 twi sts/m)

Multifilament Ticket No: 150 (540 twi sts/m)

Multifilament Ticket No: 150 (635 twi sts/m)

Multifilament Ticket No: 180 (2 ply)

Multifilament Ticket No: 180 (3 ply)

Factor

Group I Thread structure

Multifilament Staple spu n Core-spun

Group II Twist value

540 twists/m 635 twi sts/m I 060 twi sts/rn

Group III Lubrication ratio

2 % 4 % 6 %

Ply number 2 3

Table 2- Mechanical properties of threads

Lubrication ratio,%

2 4 6 2 4 6 2 4 6 2 4 6 2 4 6 2 4 6 2 4 6

Breaking tenacity, cN/tex

54.99 53 .29 55. 18 33.37 3 1.94 31.89 52. 10 51.88 51.83 61.58 63 .09 6 1.68 56.72 55.40 57.81 56.88 58.99 59.13 49 .34 53.56 54.24

Break ing extension, %

11.43 11.82 11.79 11.65 11.24 11.04 17.93 18.31 17.96 10.46 I 1.1 I 11 .25 14.00 13 .32 12.89 11.6 1 12.00 12.03 11.89 13.23 13.37

Friction coeffic ient, J..l

0.1549 0. 1194 0.1177 0.0609 0.0607 0.06 13 0.0749 0.0783 0 .0679 0.2658 0.2249 0.2041 0.2492 0.2109 0.2050 0.1840 0.1694 0.1 6 13 0 .2 190 0 .2292 0.2257

Table 3--Student-Newman-Keul s results Breaking

tenacity, cN/tex

54.488 " 32.4 c

51.934 b

62.115 a

56.647 b

54.42 c

53.109 b 56.277 " 56.685 a

58.331 " 52.382 b

Breaking ex tension, o/o

ll.68b 11.308 c

18.065 "

10.941 c

13.401 " 11.68 b

11.479 b 12 .6 14 " 12.698 a

11.876 b 12.829"

Seam strength kgf

.!8.956 a

16.403 b 17.64 1 ah

19.474 a

33.1 12" 18.956"

15.288 a

14 . 191 b

16.103"

14.666 b 15 .72 1"

In iti al elastic ity modulus, cN/ tex

5 12.53 478.69 471.25 259.74 263.09 250.44 35 1.1 8 338.16 338.16 707.78 692.38 62 1.74 553.35 544.27 505.95 571.54 532.82 484.2 1 574.1 1 523 .66 490.78

Seam opening kgf

10.8 18 " 10.505 a

16.986"

10.821" 18.060 " 10.8 18"

11. 57 " 11.006 " 11 .405 "

11.396 a

11.258 a

a.b.cSignificant difference levels

0.2

c .~ 0.15 u ii: Q)

8 0.1 c 0

~ 0.05 lL

0

Lubrication 'atio !'a 2 % [) 4 % 1>16%

Multiflarrent Staple Core-spun Thread structure

Fi g. l- Thread-to- metal fr ictio n coefficient values for different thread structures and lubricat ion ratios

0,3

c 0.25 <ll

Lubrication ratio

ii:~2 o/oo4o/o~6%

B 0.2 w

0 u <.: 0.15 0

~ ~ 0.1

540 635 1060 Twist number, twists/m

Fi g. 2-Thread-to-metal friction coeffic ient va lues for different twi sts and lubri cation ratios

276 INDIAN J. FIBRE TEXT. RES ., SEPTEMBER 2005

When the relationship between twist value and initi al modulus is studied, it is observed that the increase in twist value decreases the initial modulus. The decrease in initial modulus shows the increase in ex tension capabilit/ 1• This kind of threads extends during the sew ing and causes seam puckering.

Both lubrication ratio and ply value influence the breaking tenacity and breaking extension. An increase in lubrication ratio causes increase in breaking tenacity and breaking ex tension . According to the SNK test, there are no significant differences between 2% and 6% of the lubrication ratios.

It is observed that for the same ticket number the breaking tenacity of 2 plied thread is higher but the breaking extension is less for 3 plied thread. The 3 plied thread has a hi gher coefficient of friction. However, for the initial modulus similar results are obtai ned.

When the threads with same ply value and the same twist value but the different ticket numbers (!50 and 180) are compared, the 180 ti cket numbered thread, which is thinner, has less coefficient of friction. This can be explained by the little contact area between the material s. 3.2 Sewing Properties

3.2.1 Effect of Thread Type on Seam Strength and Seam Opening

In the analysis of variance, it is observed that the structure of thread affects the seam strength but it does not affect the seam opening. The lubrication ratio also does not affect the seam strength and the seam opening. According to SNK test, multifilament thread structure has the highest seam strength. However, the staple thread structure has the minimum seam strength. When a comparison is made on values

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20 rn .I<:

18 ..c '5I c:

16 (l) .... Vi E 14 Sl (f)

12

10 MUitifilam:mt Staple Core-spun

Thread structure

Fig.3-Seam strength for different thread structures and lubrication ratios

of the thread breaking tenacity , it is observed that the multifilament threads have higher seam strength . When the results of seam slippage are studied , the maximum resistance against the seam opening is observed for the core-spun threads. The seam strength test results of the three different thread structures are given in Fig. 3.

3.2.2 Effect of Twist 011 Sewing Strength and Seam Opening The twi st value and the lubrication ratio do not

affect the seam strength and seam slippage. Fig. 4 shows seam strength at diffe rent twist values and lubrication ratios.

According to SNK test, there is no significant difference between the values of seam strength. As it can be seen from Fig . 4, the results are·,s imilar. The seam strength of the thread which has 635 twists/m is found to be higher.

3.2.3 Effect of Ply Number on Seam Strength and Seam Opening

The lubrication ratio and ply number affect the seam strength but do not affect the seam opening. According to SNK results, there is no significant difference between 2 % and 6 % lubrication ratios.

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20 OJ .I<:

18 ~

~ 16 (l) .... Vi

14 E m

12 (f)

10 540 635 1060

Twist number, twists/m

Fig. 4-Seam strength for different twists and lubricati on ratios

18

~ 16 ..c

~ 14 Vi E 12 m (/) 10

8

Lubrication ratio ~2 % 04% !SI6 %

2 Ply nurrber

3

Fi g. 5-Seam strength for different ply numbers and lubricati on ratios

MER!C & DURM AZ : EFFECT OF THREAD STRUCT URE & LUBRICATION RATIO ON SEAM PROPERTI ES 277

There is signifi cant difference between 2 and 3 plied threads and the seam strength of 3 pl ied thread is higher. Fig. 5 shows seam strength values with di fferent ply numbers.

The ply number also affec ts the level of strength loss whi ch occurs during the sewing process. When the pl y value increases, the strength loss decreases . If the break ing tenacity va lues of 2 and 3 plied sewing threads are examined, in spite of the high breaking tenac ity of 2 pli ed threads, seam strength of 3 plied threads is found higher. The results of the seam opening are found similar.

4 Conclusions T hread structure, twist and ply number affect the

th read properties and seam strength. The multifilament thread structure g ives the bes t results on the thread breaking tenacity and seam strength . The twist number affects the thread properties but it has no effec t on the seam strength and seam opening. Ply nu mber also affects the thread properties ·and seam strength . The seam strength of 3 pl ied thread is found to be higher.

Seam opening is more related to the fabric structure. Thread structures, twist value and ply nu mber do not affect the seam slippage. However, the core-spun thread structure shows a great resistance against the seam opening.

The yarn-to- metal fri cti on coefficient decreases with the increase in lubrication ratio and twist values . The lubrication process has a little affec t on the fibres.

The initi al modulus of thread is an important property for the loop formation and a higher initia l

modulus produces a better loop formation . The results show that the multi f ilament threads have higher initi al modulus. With th~ increase in twist value, the initi al modulus decreases and the thread ex tension increases. T his situation causes a problem during the sew tng process .

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