The Influence of Stitch Density and of the Type of Sewing Thread on Seam Strength



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The Influence of Stitch Density and of the Type of Sewing Thread on Seam Strength
Daniela Barbulov – Popov1, Nenad Cirkovic2, Jovan Stepanović2
1Technical faculty “Mihajlo Pupin”, Zrenjanin, University in Novi Sad, Serbia

2Technological faculty, Leskovac, University in Nis, Serbia


Abstract – Having in mind the complex problems of technological process of sewing, as well as general demands for seams produced in garment production, this research should contribute the development of sewed seams breaking forces. Thus, many measurements of seam breaking forces have been conducted. These measurements enable us to define optimal strength of seam strength that improves the compliance of sewed seams parameters. This paper deals with the influence of the thread type and stitch density on the seam strength. The breaking forces and elongations at break were determined by the standardized method (SRPS 2062) and fabric (tape method) according to SRPS EN ISO 13934-1. Fabric samples used for seam testing were sewed by seam (1.01.01) and stitch type 301 with stitch densities 3, 4 and 5 cm-1. Optimal seam strength (130.9 Ncm-1) on the fabric T71, and at the same time the highest strength, has been noticed at the samples with seam line in weft direction with stitch density 5 cm-1, sewed with polyester thread 20x2 tex count, while on fabric T71 that value is 115.9 Ncm-1. According to obtained results, it can be concluded that stitch density (3 cm-1 ÷ 5 cm-1) and the type of sewing thread (cotton and polyester, K1 ÷ K5) have great influence on defining seam sttrength, their inconsistency may lead to great differences in seam behavior.

Keywords – Seam Strength, Seam Breaking Force


  1. Introduction

The seam characteristics include: strength, elasticity, durability, safety, and appearance. Inconsistency of these characteristics can lead to significant differences in seam behavior and it also affects their deformation characteristics. During the process of clothes exploitation, sewed seams and materials are subjected to different loads, which are usually very variable, leading to different deformations. Seam strength should correspond to material strength in order to obtain product uniformity which will be capable to endure all forces which is that product subjected to [1,2]. During wearing, stitch bonded parts of clothing are subjected to different stresses. In order to improve seam endurance, seam elasticity should be a little stronger than material elasticity. Thus, the material would also mitigate the effect of the forces that affect clothing product during wearing. The seam elasticity depends on material that is stitch bonded, stitch type, seam type, stitch density, etc. Seam durability depends on its strength and on relationship between seam and material elasticity [3,4]. Seam safety depends mainly on sewing width, slippage of fabric wires as well as on stitch type. It is crucial to prevent its slitting and breaking during the wearing process.




  1. Defining seam strength

One of the most important indicators of the sewed products quality is seam strength, which depends on different technical-technological parameters, such as: fabric type, type and sewing thread count, sewing needle count, stitch type, stitch density, seam type, etc. According to definition, strength and elasticity of sewed seam should be made in such a way that they do not allow seam breakage upon normal stresses of garment products, but also it cannot allow the fabric deformation [1,4]. The seam strength can be determined experimentally (by defining the force which the seam can withstand). Defining breaking force, the point when deformation, seam breakage and elongation at break occur, i.e. when the sewed sample changes its length, is based on measurements related to force and elongations under constant direct stress.

On the dynamometer, during the testing fabric samples with seam in transverse direction in relation to the seam, the stress (loading) q at mobile pirn clamp is evenly applied (Figure 1a). Furthermore, we can notice q reaction at fixed pirn clamp which is also evenly applied stress even to q (N/cm), i.e. q = q.


Figure 1. Seam stress at transverse tension a) sample on dynamometer, b) and c) application of the stress in a stitch
For the value of the applied force on the lower mobile pirn clamp, the loading q will be:
[N/cm] (1)

Where:


q – stress of the sample at mobile clamp (N/cm),

q' – the reaction to the stress q (N/cm),

F – drawing off force of lower mobile clamp (N),

b - the sample’s width on the dynamometer(cm).

If we observe the application of the force in one stitch, 301 type, (Figure 1b), it is obvious that, ideally, threads will be stressed at elongation in each stitch. Due to the fact that q = q, stitch stress will not cause the thread migration at entangle points. Because of that, we must define reactions that occur at side stitches (Figure 1c). In that case, if we apply the force of lower clamp movement and the theory of material resistance, we can find values of reaction forces A(N) and B(N), which would refer to the strength of thread built in the seam:

=[N] (2)
Where: d-stitch length (cm).
If we change the values for the stitch length that is d= b/n, in the last formula, the seam breaking force F, which is bonded with stitch type 301, can be expressed as follows:

(N). (3)
Where:
FP – thread breaking force (N),

n – number of stitches in sewed material sample

If we know the initial thread breaking force and the coefficient of strength loss of thread in the process of stitch making , the previous formula is changed into:

(N), (4)

Where: FP1 - initial thread breaking force (N),

 - Coefficient of strength loss of thread.

If we want to use this formula, it is necessary to determine the value of coefficient of strength loss of thread experimentally under the different conditions of stitch formation. On the basis of these experimental data relating to different fabrics sewed by lockstitch of different densities, the value of this coefficient is between 0,8 and 1,2.


Methods used for testing seam strength are based on testing thread slippage or thread breakage in the seam area. According to tt.Coats method, the seam breaking force is defined at one cm of seam length, i.e. by defining relative breaking force, in transverse direction in relation to seam line. The relative seam breaking force is calculated on the basis of average value of breaking force and seam length (the width of test tube used for testing) according to the expression [3,5]:

(5)

Where: Fr – relative seam breaking force (Ncm-1)

F – breaking force of test tube seam (N),

b – the width of sewed sample test tube (cm).

As the stitch density and breaking force of used thread have great influence on breaking characteristics if seams, it is necessary for this paper to introduce parameter called “seam strength factor”, which is calculated according to the following equation:
(6)

Where: fk – seam strength factor (Ncm-1)

FP – thread breaking force (N)

gu – stitch density (cm-1)

Havin in mind the analysis of seam breaking forces testing and the instability of wire system of the fabric and thread system in the seam (due to the stress), it is necessary, for projecting sewed seams breeaking forces, introduce appropriate correction coefficients that would take this fact into consideration. In this case, correction coefficient k is defined throug the relationship between seam breaking force (Fr) and seam strength factor (fk).


  1. Experiments

Two types of fabrics were used for sample seam bonding (Figure 1), which were bonded by sewing machine (PFAFF company), class 461 (sewing speed 2500 min-1), stitch type 301 (Figure 2) [6].


dani-1_0

Figure 2. The shape of seam sample used for testing breaking characteristics
The machine is equiped with upper and lower transport, pedal and needle positioning and automatic thread cutting. Fabric samples, tape shape (two pieces), dimensions 185 mm x 50 mm, were sewed by the seam mark 1.01.01 (Figure 3) [7], at the distance of 10mm from the edge, with the needle 90 (normal needle point), and stitch density 3 cm-1, 4 cm-1 and 5 cm-1.
clip_image002

Figure 3. Lockstich type 301 ( 1- upper needle thread, a- lower thread-shuttle thread)

Breaking characteristics of threads were tested on dynamometer USTER TENSORAPID 4, according to standardized method SRPS 2062 [8], while breaking characteristics of fabrics were tested on dynamometer ZWICK, according to SRPS EN ISO 13934-1 [9]. The processing of research data was carried out by mathematical statistics.





  1. Results and discussion

Table 1 presents basic fabric characteristics that were used for making seam samples, while table 2 presents the characteristics of used sewing threads.



Table 1. Basic characteristics of fabrics used for making seam sample.


Fabric characteristics

T21

T71

Weave

Five wired sateen weave

Five wired sateen weave

Raw material content (%)

50/50; PES/Co

50/50; PES/Co

Surface mass (gm-2)

280

315

Warp yarn count (tex)

25x2

25x2

Weft yarn count (tex)

25x2

25x2

Warp density (cm-1)

30

37

Weft density (cm-1)

22

26

Breaking force in warp direction (N)

1672

1727

Breaking force in weft direction (N)

1305

1298

Elongation at break in warp direction (%)

19

19

Elongation at break in weft direction (%)

15

15

Table 2. Characteristics of used threads for sample seams sewing.

Thread characteristics

K1

K2

K5

K3

K4

Raw material content (%)

100; Co

100; PES

60/40;

PES/Co


100; Co

100;PES

Count (tex)

8.9x3

8.3x2

12.5x3

19.4x3

20x2

Number of twists for single wired yarn (m-1)

S 1267

S 1039

S 1026

S 845

S 681

Number of twists at plying (m-1)

Z 875

Z 1010

Z 780

Z 690

Z 727

Breaking force (cN)

787

1204

1264

2051

2091

Elongation at break (%)

4.74

14.22

22.95

6.11

13.94

Breaking force at loop (cN)

1072.2

1646.1

1805.3

2546.7

3080.3



Table 3 shows the results of testing breaking characteristics of sewed seams.


Table 3. Results of testing seam breaking forces on fabric T21:


Stitch density

Thread

Fabric T21

Seam line in warp direction

Seam line in weft direction

Seam breaking force

Relative seam breaking force

Seam strength factor

Correction coefficient

Seam breaking force

Relative seam breaking force

Seam strength factor

Correction coefficient

F

(N)


Fr

(Ncm-1)



fk

(Ncm-1)





F

(N)


Fr

(Ncm-1)



fk

(Ncm-1)





3 cm-1

K1

124.9

24.9

23.58

1.0559

125.1

25.0

23.58

1.0602

K2

179.1

35.8

36.12

0.9911

199.9

39.9

36.12

1.1046

K5

201.2

40.2

37.90

1.0607

246.7

49.3

37.90

1.3008

K3

282.4

56.4

61.53

0.9166

288.3

57.7

61.53

0.9377

K4

398.2

79.6

62.79

1.2677

413.4

82.7

62.79

1.3171

4 cm-1

K1

150.8

30.2

31.44

0.9605

181.9

36.4

31.44

1.1578

K2

236.8

47.4

48.16

0.9842

257.4

51.5

48.16

1.0693

K5

274.2

54.8

50.56

1.0838

295.1

59.0

50.56

1.1669

K3

334.8

66.9

82.04

0.8154

368.7

73.7

82.04

0.8983

K4

447.2

89.4

83.64

1.0688

483.2

96.6

83.64

1.1549

5 cm-1

K1

190.1

38.0

39.30

0.9699

221.8

44.4

39.30

1.1297

K2

309.1

61.8

60.20

1.0265

310.1

62.0

60.20

1.0299

K5

338.9

67.8

63.20

1.0727

368.3

73.7

63.20

1.1661

K3

436.9

87.4

102.55

0.8522

444.2

88.8

102.55

0.8659

K4

537.5

107.4

104.55

1.0272

579.4

115.9

104.55

1.1085



Table 4. Results of testing seam breaking forces on fabricT71:

Stitch density

Thread

Fabric T71

Seam line in warp direction

Seam line in weft direction

Seam breaking force

Relative seam breaking force

Seam strength factor

Correction coefficient

Seam breaking force

Relative seam breaking force

Seam strength factor

Correction coefficient

F

(N)


Fr

(Ncm-1)



fk

(Ncm-1)





F

(N)


Fr

(Ncm-1)



fk

(Ncm-1)





3 cm-1

K1

138.6

27.7

23.58

1.1747

156

31.2

23.58

1.3231

K2

194.0

38.8

36.12

1.0741

203.8

40.7

36.12

1.1267

K5

212.3

42.5

37.90

1.1213

254.5

50.9

37.90

1.3430

K3

295.8

59.2

61.53

0.9621

325.9

65.2

61.53

1.0596

K4

405.1

81.0

62.79

1.2900

416.9

83.4

62.79

1.3279

4 cm-1

K1

160.0

32.0

31.44

1.0178

184

36.8

31.44

1.1704

K2

247.3

49.5

48.16

1.0278

272.1

54.4

48.16

1.1295

K5

265.8

53.2

50.56

1.0522

301.7

60.3

50.56

1.1926

K3

353.9

70.8

82.04

0.8592

377.7

75.5

82.04

0.9202

K4

538.8

107.7

83.64

1.2876

563.0

112.6

83.64

1.3462

5 cm-1

K1

212.0

42.4

39.30

1.0788

234.3

46.8

39.30

1.1908

K2

311.8

62.4

60.20

1.0365

334.0

66.8

60.20

1.1096

K5

314.3

62.9

63.20

0.9952

371.3

74.3

63.20

1.1756

K3

438.9

87.8

102.55

0.8561

464.8

93

102.55

0.9068

K4

570.2

114

104.55

1.0903

654.7

130.9

104.55

1.2520




The graph shows the results of testing seam breaking forces according tables 3 and 4. These results are presented in figure 5.



Seam sample

Fr

(Ncm-1)



Statistical data of correlation and regression analysis

( Y = A + B · X)



R

A

B

SD

Fr= A+B·fk

In warp direction of fabric T21

59.20

0.94927

4.93548

0.91715

7.86325

4.93548+0.91715·fk

In weft direction of fabric T21

63.77

0.93973

8.52728

0.93374

8.79279

8.52728+0.93374·fk

In warp direction of fabric T71

62.13

0.93021

4.58683

0.9725

9.93144

4.58683+0.9725·fk

In weft direction of fabric T71

68.18

0.91797

6.87083

1.04624

11.70005

6.87083+1.04624·fk


Figure 5. Changes of seam breaking forces depending on thread type and stitch density, a) for fabric T21 and b) for fabric T71 (O – seam line in warp direction,

P – seam line in weft direction)
The analysis of obtained results of breaking forces shows:

  • Increased stitch number improves the strength of analyzed seams, i.e. their breaking and relative breaking force. This improvement can be noticed for all samples, regardless to the type of used thread.

  • Comparing fabrics T71 and T21, the bigger breaking force can be noticed at fabric T71, which is caused by fabric construction itself. As these fabrics are in the same weave and of the same raw material content, the seam breaking force is influenced by the density of weft and warp wires in the fabric (Table 1). The seams in weft direction have bigger breaking force comparing to seams in warp direction, which can be explained as a result of structural solution of woven fabric and its bigger breaking force in warp direction.

  • Seam samples were sewed by PES threads (K2, K4) that, thanks to better mechanical characteristics, have bigger values of breaking forces in relation to samples sewed by cotton threads (K1, K3).

Statistic data processing proves the validity of results obtained by the influence of stitch density and sewing thread type on seam strength. This also confirms mutual dependance of seam relative breaking force, as dependance variable, and stitch density and sewing thread type, as independant variable, during which correlation coefficient R is determined.

Table 5 shows correlative and regression analysis of results, which are obtained by testing relative breaking force of seam and stitch density for seam samples with used stitch 301 type.


Table 5. Correlation and regression analysis of results obtained by testing the influence of seam strength factors on relative seam breakin force.

Note: Fr –average value of relative breaking force of seam force, R – correlative coefficient, A and B – coefficients of regression (linear) equation, fk –seam strength factor (Ncm-1)

Linear regression of dependence between relative breaking force and seam strength factor is shown in figures 6 and 7. These regressions are valid for stitch density interval from 3 cm-1 to 5 cm-1.





(a) seam in warp direction



(b) seam in weft direction
Figure 6. Linear regression between relative breaking force and seam strength factor for samples used on fabric T21, a) seam in warp direction and b) seam in weft direction.



(a) seam in warp direction


b) seam in weft direction
Figure 7. Linear regression between relative breaking force and seam strength factor used for samples on fabric T71, a) seam in warp direction and b) seam in weft direction
On the basis of results shown in tables and graphs, it can be noticed that optimal seam strength on fabric T71 with 4 cm-1 has the value 70.8 Ncm-1 for the seam in the warp direction, and 75.5 Ncm-1 for seam in weft direction, with 5 cm-1 , it is 114 Ncm-1 for the seam in warp direction and 130.9 Ncm-1 for the seam in weft direction.
It acan also be concluded that change of seam breaking force (results referring to stitch densities in itnterval from 3-5 cm-1) gains aproximative functional dependance. Higher values of stitch density cause damaging of above mention dependance.
Dependence correlation between parameters, in an interval, besides information on the type of dependence, can also be used for calculating values of one parameter for appropriate value of other one. Understanding dependence between some parameters of sewing process is of great importance in quality control and in the process of textile processing.



  1. Conclusion

According to the results from this experiment, it can be concluded that seam strength depends on used fabric (structural and construction parameters), type of used thread (raw material content, count), as well as on stitch density per cm of the seam. Optimal seam strength (130.9 Ncm-1) on fabric T71, which is at the same time the highest strength value, was seen at samples with seam line in weft direction with stitch density 5 cm-1, sewed by poliester thread 20x2 tex count, while, for fabric T21, that value is 115.9 Ncm-1.


Having analyzed dependency of relative breaking force and seam strength factor on stitch density, as well as having applied given correlative relationships, it can be concluded that there is connectivity between parameters. It is approved by the values of correlation coefficient. On the basis of this analysis, it is possible to predict seam-breaking force for stitch density interval from 3 cm-1 to 5 cm-1 for all above mentioned sewing threads.
Taking into consideration numerous parameters influencing the seam quality (type of material, type and thread count, seam type, stitch type, stitch denstiy, etc.) , there are many possibilities for combining them with different final characteristics of seams. The main purpose of these combinations is defining the appropriate technical-technological parameters of sewing process in order to improve productivity and seam quality.


References

[1] J. Geršak, B. Knez: Određivanje čvrstoće šivanih šavova na odjeći , Tekstil 40 (8), 361-368, (1991).

[2] D.B–Popov, V. Petrović, N. Ćirković:Analiza utjecajnih parametara na jačinu šivanih šavova, IV Znanstveno-stručno savjetovanje „Tekstilna znanost i gospodarstvo“, Zagreb, januar (2011).

[3] P. Prvanov, B. Knez: Utjecaj tkanine, tipa šivanog šava i finoće konca na čvrstoću šavova na odjeći, Tekstil 42 (10), 539-545, (1993).

[4] N. Ćirković, J. Stepanović, V. Petrović, D.B.-Popov: Projecting breaking forces of sewed seams, 4th TEXTEH International conference,23-24 jun 2011, Bukurešt, Rumunija,( rad štampan u Zborniku radova u elektronskoj formi, str.304 - 313).

[5] Nähfaden und Nähte-Tehnologie; tt. Coats Glasgow, str. 102.

[6] ISO 4915: Textiles, Stich types – Classification and terminology, 1981.

[7] ISO 4916: Textiles, Seam types- Classification and terminology, 1982.

[8] SRPS 2062: 2002

[9] SRPS EN ISO 13934-1:2008

[10] J. Stepanovic, D. Radivojevic, V. Petrovic, C. Besic, Projecting of deformation characteristics of single and twisted wool yarns, Industria textila, No. 3, 99-105, (2010).

[11] J. Stepanovic, Z. Milutinovic, V. Petrovic, M. Pavlovic, Influence of relative density on deformation characteristics of fabrics in plain weave, Indian Journal of Fibre & Textile Research, No.1 , 76-81, (2009).

[12] D.T.Stojiljkovic, V.Petrovic, S.T.Stojiljkovic, D.Ujevic: Defining of memory function for tension and deformation of linear textile products on the basis of their rheological models, Industria Textila, No. 6, (2009).

[13] B. Kordoghli, M. Cheikhrouhou, C. Kacem Saidene: Mechanical behaviour of seams on treated fabrics, AUTEX Research Journal, Vol. 9, No3, 87-92, (2009).

[14] D.B.- Popov, D.Đorđić, N.Kaplanović: Analiza promene jačine konca u procesu šivenja, Tekstil i praksa, Vol. 47, No.1, 16-22, (2010).

[15] A.Kunštek: Čvrstoća šivanih šavova odjeće, Zbornik Simpozija SITTH i ITO, februar (1989).


Corresponding author: Daniela Barbulov – Popov

Institution: Technical faculty “Mihajlo Pupin”, Zrenjanin, University in Novi Sad, Serbia.

E-mail: diiv1@open.telekom.rs



TEM Journal – Volume 1 / Number 2 / 2012.

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