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ANNALS OF THE UNIVERSITY OF ORADEA
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SEWABILITY PROPERTIES OF GARMENT LEATHERS TANNED
WITH VARIOUS TANNING MATERIALS
ORK Nilay1, MUTLU Mehmet Mete1, YILDIZ Esra Zeynep2, PAMUK Oktay3
1 Ege University, Faculty of Engineering, Leather Engineering Department, 35100, Izmir, Turkiye, mete.mutlu@ege.edu.tr
2 Ege University, Emel Akin Vocational Training School, 35100, Izmir, Turkiye, esra.zeynep.yildiz@ege.edu.tr
3 Ege University, Faculty of Engineering, Textile Engineering Department, 35100, Izmir, Turkiye,
oktay.pamuk@ege.edu.tr
Corresponding author: Yildiz, Esra Zeynep, esra.zeynep.yildiz@ege.edu.tr
Abstract: Chromium tannage is the most used technology in processing of garment leathers. Due to
environmental requirements and demands on natural products there is an increasing interest on alternatives to
chromium tannage especially on vegetable tanned leathers. Leather properties vary in a very wide range
depending on the animal type it is obtained from and the process type and chemicals used in the
manufacturing. In this study, the effect of various tanning materials to the sewability of garment leathers was
investigated. For this purpose, vegetable, chromium and chromium-vegetable combination tanned garment
leathers from the same animal origin were supplied from a garment leather manufacturing factory. Needle
penetration force and the sewability values of these leathers were determined by using L&M Sewability Tester.
It was found that material properties and sewing properties showed differences regarding to the tanning
material used even in same type of raw material. Chromium tanned leathers had sewability values of 13.4%
horizontal and 14.2% vertical which are considered good to fair. Vegetable tanned leathers and chromium-
vegetable tanned leathers had sewability values of 38.2% horizontal, 49.2% vertical and 98% horizontal,
98.5% vertical respectively which are considered poor. The results of the study conclude that, there is a big
difference in material properties when the tanning technology and material is changed which also affects the
sewing properties.
Key words: Leather, Sewability, Garment, Tanning materials.
1. INTRODUCTION
Leather processing can simply be defined as, modification of hides/skins by a sequence of
chemical and physical treatments. Although leather processes and the preferred chemicals have big
contribution to designation of final leather characteristics, the type of the raw material, type and
amount of tanning material used, have the most important effect [1]. Modern tanning chemistry can
be classified by mineral, vegetable, oil, aldehyde, and organic tanning and syntans [2].
Chrome tanning is one of the most popular tanning systems because of the excellent
qualities of chrome tanned leather such as high hydrothermal stability, good dyeing characteristics
and softness [3]. Although vegetable tanning materials are generally used in production of saddlery,
harness, belt, shoe upper and sole leathers requiring less elasticity, high shape retention and
firmness; their use in garment leather production has increased due to natural look and feel they
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confer to leathers and high demands on natural products in last decades. The vegetable tanning
process is flexible, and can produce leathers with a very wide range of characteristics [4]. Besides,
combination of various tanning materials and chemicals provide a possibility to combine their
characteristics or even to enhance properties with their synergistic effect. This can lead to produce
leathers with better properties than the leathers tanned with a single type of tanning material.
Leather clothing differs in its origin, tannage and mechanical or physical properties. It is
necessary to distinguish between pig, goat and sheep leather, and cowhide, which differ both in their
properties and in their surface appearance. Leather clothing is affected both by its basic mechanical
properties and usage characteristics and by the manufacturing features of the leather [5].
Apparel making is the process of making shell structures from flat fabrics or leathers to
match the shape of human body. During this process, leathers are subjected to various types of
mechanical stresses, which are indispensable for the garment appearance [6]. In garment
manufacturing, a two dimensional structure is converted into a three dimensional structure. During
the process of sewing, the needle is subjected to repeated tensile stresses, heat, bending, pressure and
wearing. These stresses repeatedly act on the thread as a result of which leather is subjected to
various types of mechanical stresses which are low stress in nature [7].
The term sewability can be defined as the ability and the ease with which the 2-D fabric
components can be qualitatively and quantitatively be seamed together to 3-D garment [8]. Better
sewability means greater ease of formation of shell structures and styles with the absence of fabric
distortion and seam damage. The appearance and durability of seams form an important component
of the quality of the finished product [9]. Damage of the structure of the fabric occurs when the
fabric is penetrated by the needle. The needle can penetrate at any point in the fabric. The structure
of the fabric can be deformed beyond its elastic limit or can literally be destroyed [10].
The sewing needle penetration force which is one of the most significant technical parameter
in the sewing process is the quantitative measure of the damage that appears in a garment as the
result of the sewing process [11]. A high penetration force means a high resistance of the fabric and
thus a high risk of damage [12]. The sewing needle penetration force is affected by various factors
such as type and amount of layers of the sewing material, needle size, shape of needle point, stitch
speed of the sewing machine, and treatment of the sewing material, among others [13]. The fabric
should withstand the needle penetration without any damage to the fabric [10].
Although many sewability studies have been carried out on textile fabrics, there is not much
study related to sewability of garment leathers. It is accepted that leather as a material needs more
penetration force for the needle. However leather properties vary in a very wide range depending on
the animal type it is obtained from and the process type and chemicals used in the manufacturing.
The present work aims determination of the sewability properties of garment leathers tanned with
various tanning materials which are chromium, vegetable and chromium-vegetable combination.
Sewability of these garment leathers were compared with each other in terms of the average needle
penetration force (gf) and the sewability value (%). A good seam is a measure of quality in leather
garments. The results of this study will give data to be considered in sewing to obtain better seams
for manufacturing of high quality leather garment products.
2. MATERIAL AND METHOD
2.1 Material
In this research 3 chromium, 3 vegetable and 3 chromium-vegetable combination tanned
garment leathers (English origin sheep skins) obtained from a garment leather manufacturing factory
were used. The samples were analyzed by using L&M Sewability Tester as three parallels vertically
and horizontally.
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2.2. Method
Sampling of leathers were done according to TS EN ISO 2418. The tests were carried out at
the same conditions according to TS EN ISO 2419. The thicknesses of test samples were measured
according to TS 4117 EN ISO 2589. Apparent density of leathers was calculated according to TS
4121 EN ISO 2420 [14-17].
Fig.1: L&M Sewability Tester
The sewability properties of the leathers were determined by using L&M Sewability Tester
(Fig. 1). It enables consecutive readings of force for penetration of the fabric by a selected needle to
be measured on a small sample of fabric at a rate of 100 penetrations/min [18]. This device measures
the penetration force exerted by a sewing needle on the fabric. A strip of fabric passes through a
zone in which a sewing needle operates. A nominal value (threshold) of penetration force is
determined based on the fabric mass per unit area according to the fabric type, and then the number
of times this value is exceeded is recorded. Fabric sewability corresponds to the number of points
that exceed the threshold previously set, related to the over-all tested points and expressed as a
percentage. The sewing operation will be more difficult as the sewability parameter increases [19].
In this study the device setting was maintained constant for all the tests; the total count per
leather was 100; the force range chosen was 500gf, and the threshold value for sewability
determination was 150gf. The number of high recordings which exceed the threshold value, which is
called the “sewability value”, was also recorded.
3. RESULTS AND DISCUSSION
The weight and thickness properties of garment leathers tanned with chromium, vegetable
and chromium-vegetable combination were determined and are given in Table 1. Vegetable tanned
leathers are known to give denser and thicker leathers; contrary chromium tanned leathers are
famous with their light, soft and thinner character. Apparent density of chromium tanned leathers
and vegetable tanned leathers vary between (0,680 - 1,000 g/cm3) and (0,780 - 1,150 g/cm3)
respectively [20]. When the apparent density figures in Table 1 are considered, they are in
accordance with the reference limits. Although thickness of leathers are adjusted by mechanical
operations to give a uniform distribution across the whole area; vegetable tanned leathers were found
thicker than chromium-vegetable combination tanned leathers and chromium-vegetable combination
tanned leathers were found thicker than chromium leathers.
Table 1: The properties of garment leathers.
Leather type
Weight (g/m2)
Thickness (mm)
Apparent density (g/cm3)
Chromium
290,62
0,52
0,71
Chromium-Vegetable combination
363,96
0,59
0,79
Vegetable
420,95
0,61
0,87
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Fig. 2: Average Needle Penetration Force of Different Tanned Leathers.
As it can be seen from Fig. 2, the values of needle penetration force were varied between
111 gf and 284 gf.
Vegetable tanned leathers had higher needle penetration force and sewability values than
chromium tanned leathers. However semi-vegetable leathers had the highest needle penetration force
and sewability values in both directions. These findings could be related to physical properties of the
used leathers. Ork et al. (2014) also found that semi-vegetable tanned leathers came into prominence
with their high strength and low extension set properties which are important for garment leathers.
When physical test results of leathers tanned with different tanning types were statistically
evaluated, it was concluded that tanning type has important effect on the physical properties of
leathers even from the same origin. Physical properties of the leathers were varied due to the tanning
material used in their production [1].
Fig. 3: Sewability values of Different Tanned Leathers
When sewability values ranged between 0 and 10%, the fabric sewability was considered
good; between 10 and 20% sewability was considered to be only fair even though no great
difficulties arose during sewing [21].
As it can be seen in Fig. 3, sewability values of chromium tanned leathers were found 13.4%
horizontal and 14.2% vertical which could be accepted a fair value close to good. However
vegetable tanned leathers and chromium-vegetable combination tanned leathers had sewability
values of 38.2% horizontal, 49.2% vertical and 98% horizontal, 98.5% vertical respectively. So the
sewabilities of these samples are considered poor. This means that an extra attention is required to
obtain seam quality in production of garment leathers tanned with vegetable or vegetable-chromium
combination tannage.
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Ork et al. (2014) found stitch tear values of chromium, vegetable and chromium-vegetable
tanned leathers as 334 N/cm, 518 N/cm and 786 N/cm respectively [1]. Although stitch tear
resistance test is a static test which is done in tensile testing equipment and sewability test is a
dynamic test done with L&M sewability tester, there seems a consistent relation between the results
as seen Fig. 4.
Fig. 4: Average Needle Penetration, Stitch Tear Resistance and Sewability values of Leathers
5. CONCLUSIONS
In the last decades there is a demand on natural products in leather industry as in many
industries. Vegetable tannins which are known to give heavy, strong and durable leathers are now
being used in the production of soft, light and elegant garment leathers either alone or in
combination with mineral tanning materials. Undoubted, tanning materials have a significant effect
on the material properties of leathers produced. In this study, sewability of garment leathers tanned
with chromium, vegetable and vegetable-chromium combination tanning agents has been
determined and the following conclusions have been found:
Chromium leathers were found having the lightest weight, the thinnest and the less apparent
density followed by chromium-vegetable combination and vegetable tanned leathers.
Vegetable tanned leathers had come closer to the characteristics of chromium tanned
leathers; however there are still some differences in properties.
Average Needle Penetration Force was found lowest for chromium tanned leathers, followed
by vegetable and chromium-vegetable tanned leathers in order. That means chromium
tanned leathers can be sewn with a less needle force, and more needle force is required for
vegetable and chromium-vegetable tanned leathers.
Chromium tanned leathers had sewability values of 13.4% horizontal and 14.2% vertical
which are considered good to fair. Vegetable tanned leathers and chromium-vegetable
tanned leathers had sewability values of 38.2% horizontal, 49.2% vertical and 98%
horizontal, 98.5% vertical respectively which are considered poor.
When the results of dynamic sewability test are compared with static stitch tear test, the
relation among the data was found consistent, even the tests have totally different principles.
Leather is a luxury product due to limited supply, high cost of material and labor. This
luxury product should maintain all the quality and environmental requirements. Besides; garment
design and manufacturing quality have also big importance. The design should meet the fashion,
comfort, aesthetic expectations of the consumer. Leather garments contain many joining and
ornament seams due to small patterns related to animal size. These seams should be proper to meet
the quality aspects. The results conclude that, there is a big difference in material properties when
the tanning technology and material is changed which also affects the sewing properties.
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