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Journal of Natural Fibers
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/wjnf20
Thermo-physiological and Handle-related Comfort
Properties of Hemp and Flax Blended Denim
Fabrics
Nazan Okur
To cite this article: Nazan Okur (2021): Thermo-physiological and Handle-related Comfort
Properties of Hemp and Flax Blended Denim Fabrics, Journal of Natural Fibers, DOI:
10.1080/15440478.2021.1993488
To link to this article: https://doi.org/10.1080/15440478.2021.1993488
Published online: 31 Oct 2021.
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Thermo-physiological and Handle-related Comfort Properties of
Hemp and Flax Blended Denim Fabrics
Nazan Okur
Department of Textile Engineering, Istanbul Technical University, Istanbul, Turkey
ABSTRACT
This study investigated the use of ax and hemp bers in denim fabrics in
terms of thermo-physiological comfort and handle-related properties.
Cotton/ax and cotton/hemp blended fabrics with 2/1 twill and 3/1 twill
weaves were selected and evaluated compared to pure cotton fabric.
Besides, the eect of rinsing was examined. The ndings revealed that the
use of ax and hemp bers improved the thermo-physiological and handle-
related comfort properties of denim fabrics. Higher air permeability and
water absorbency along with quick-drying behavior could be achieved in
ax and hemp blended fabrics compared to pure cotton fabric. Handle-
related comfort properties of ax and hemp blended fabrics indicated soft
touch. Although the extension and formability values of the blended fabrics
were low, they were at an acceptable level and were improved after the
rinsing process.
摘要
本研究调查了亚麻和大麻纤维在牛仔布面料中的热生理舒适性和手感相关
性能. 选择了2/1斜纹和3/1斜纹组织的棉/麻和棉/麻混纺织物, 并与纯棉织
物进行了比较. 此外, 还考察了漂洗的效果. 研究结果表明, 亚麻和大麻纤维
的使用改善了牛仔布织物的热生理性和与手感相关的舒适性. 与纯棉织物
相比, 亚麻和大麻混纺织物具有更高的透气性, 吸水性和快干性能. 亚麻和
大麻混纺织物的手感舒适性表现为柔软触感. 虽然混纺织物的延伸率和成
型性值较低, 但它们处于可接受的水平, 并在漂洗过程后得到改善.
KEYWORDS
Flax; hemp; clothing comfort;
thermo-physiological
properties; handle
properties; denim
关键词
亚麻; 大麻; 服装舒适性; 热
生理特性; 处理属性; 蓝粗
棉布
Introduction
Environmental changes and damages with global economic and social impacts are among the biggest
challenges facing the world. As a response to this challenge, the materials used in textile and clothing
products tend to be renewable and environmentally friendly, and therefore a variety of natural fibers
have gained more importance in this sense. As the most emerging natural fibers, flax and hemp have
an increasing potential to be preferred in various products. Flax fiber is characterized by its perfor-
mance in terms of strength, appearance, touch, and comfort (Behera 2007), as well as antibacterial,
antistatic, and UV protection properties (Foksowicz – Flaczyk and Walentowska 2008; Jackowski et al.
2003). Hemp fiber, which is obtained from the stems of the industrial hemp plant (cannabis sativa), is
one of the oldest fibers used in textiles and clothing. However, it was not used for a long period, mainly
due to the prohibition of hemp cultivation and the rapid rise of synthetic fibers. Commercial
cultivation of hemp has emerged again since the 1990s and its use in textiles and clothing has gained
interest due to environmental considerations (Crini et al. 2020), and its inherent features such as
antibacterial and anti-static property, high moisture absorption, breathability, and UV protection
(Stanković et al. 2019). Its unique multi-layered fiber morphology ensures comfort in various
applications (Yang et al. 2013).
CONTACT Nazan Okur okurn@itu.edu.tr Department of Textile Engineering, Istanbul Technical University, Istanbul, Turkey
JOURNAL OF NATURAL FIBERS
https://doi.org/10.1080/15440478.2021.1993488
© 2021 Taylor & Francis
In the clothing industry, denim products, which are in all fashion trends, are among the most
popular products in the global market. While the use of cotton is common in the market, global
sustainable trends and differentiation in customer expectations have enforced the industry to search
and use new materials. Therefore, flax and hemp fibers have started to appear in denim products.
Especially since flax fiber is expensive and hemp fiber is newly used in textiles, these fibers can be
blended with cotton, and the advantages they offer in terms of product performance may increase their
use. As with all clothing products, in denim products, comfort has a critical role in customer
preferences as well as esthetic features. Although there are studies in which denim fabrics were
examined in terms of comfort (Babaarslan et al. 2018; Eryuruk 2019, 2020, 2021; Jamshaid et al.
2020; Kara and Akgun 2018; Karaca et al. 2012; Sabir and Kadem 2016; Sarıoğlu and Babaarslan 2019;
Uren and Okur 2019), any study was not investigated the comfort properties of flax and hemp blended
denim fabrics. Even, there is a limited number of studies examining non-denim fabrics made of flax
and its blends with other natural fibers in terms of thermo-physiological and/or sensorial comfort
(Behera 2007; Behera and Mishra 2007; Bilen 2021; Dalbaşi and Özçelik Kayseri 2021). The comfort
properties of hemp fiber were particularly investigated in knitted fabrics (Liu, Xu, and Zhang 2011;
Stanković and Bizjak 2014; Stanković et al. 2019; Stanković, Popović, and Poparić 2008), and among
the limited number of studies on woven fabrics (Jin Lee and Sun Ji 2017; Li et al. 2010; Petrulyte,
Velickiene, and Petrulis 2013), again, no study was specific to denim fabrics. Hence, the purpose of this
study is to investigate the effect of using flax and hemp fibers blended with cotton fiber on thermo-
physiological and handle-related comfort properties of denim fabrics. In addition, by investigating the
effect of the weave type and the rinsing process, it was aimed to make a significant contribution to the
literature with a comprehensive study on these promising blends that have recently been used in
denim products.
Experimental part
Materials
Commercially available denim fabrics in three different fiber compositions with two weave types were
supplied by a local manufacturer (Table 1). The warp yarns were 100% cotton, whereas 100% cotton
and blended yarns were used as the weft yarn. After weaving, the fabrics were processed by singeing,
mercerization, heat setting, and sanforizing as standard industrial finishing processes for denim
fabrics. Then they were grouped into two sets as untreated (not rinsed) and rinsed samples. The set
of the rinsed samples were treated in a rinsing process at 50°C for 10 minutes with 100 g dispergator,
200 g fixator, and 500 g softener in 80 liters of water.
Methods
Physical properties of the fabric samples in terms of yarn count, number of warp and weft yarns per
cm, mass per unit area, and thickness were determined according to the relevant standards (ISO 7211–
5; ISO 7211–2; ISO 3801; ISO 5084). The porosity of the samples was calculated from Equations 1 and
2 (Mukhopadhyay, Ishtiaque, and Uttam 2011). Densities of cotton, flax, and hemp fibers were
approximated as 1510 kg/m
3
, 1400 kg/m
3
, and 1500 kg/m
3
, respectively (Ticoalu, Aravinthan, and
Cardona 2013). The cover factor was calculated according to Equations 3–5, where K
1
and K
2
stand for
warp and weft cover factor, n
1
and n
2
are the numbers of warp and weft yarns per cm, and Nm
1
and
Nm
2
are the warp and weft yarn counts (Kara and Akgun 2018).
Porosity %ð Þ ¼ 1Density of fabric kg=m3
�=Density of fiber kg=m3
� � �x100 (1)
2N. OKUR
Table 1. Properties of fabric samples.
Sample
code Fiber composition Weave type Process Warp density (per cm) Weft density (per cm)
Fabric
square mass
(kg/m
2
) Thickness (mm)
Volume porosity
(%)
Cover
factor
Co 100% cotton 2/1 Z Twill Not rinsed 31 20 0.226 0.54 72.11 24.45
CoFlax 80% cotton/20% flax 37 25 0.198 0.43 69.02 25.11
CoHemp 60% cotton/40% hemp 34 19 0.176 0.39 69.46 23.18
Co 100% cotton 3/1 Z Twill 28 22 0.276 0.62 70.49 25.50
CoFlax 80% cotton/20% flax 27 21 0.271 0.63 70.98 25.43
CoHemp 60% cotton/40% hemp 33 25 0.264 0.56 68.56 25.77
Co 100% cotton 2/1 Z Twill Rinsed 30 19 0.220 0.84 82.61 24.02
CoFlax 80% cotton/20% flax 36 24 0.198 0.84 84.10 24.73
CoHemp 60% cotton/40% hemp 33 19 0.183 0.90 86.38 23.08
Co 100% cotton 3/1 Z Twill 28 21 0.266 0.93 81.03 25.39
CoFlax 80% cotton/20% flax 28 21 0.264 0.93 80.99 25.67
CoHemp 60% cotton/40% hemp 31 22 0.231 0.91 83.10 24.72
JOURNAL OF NATURAL FIBERS 3
Density of fabric kg=m3
� ¼Fabric square mass kg=m2
�=Fabric thickness mð Þ
� (2)
Cover factor Kð Þ ¼ K1þK2K1x K2
ð Þ=28ð ÞÞ (3)
K1¼3:3x n1=p1=10000 dtex1
ð Þ (4)
K2¼3:3x n2=p1=10000 dtex2
ð Þ (5)
The air permeability tests were conducted according to EN ISO 9237 by applying 100 Pa constant air
pressure to each sample attached to a 20 cm
2
circular holder. For measuring drying properties, the
method of Coplan (1953) and Fourt et al. (1951) was followed. The water absorbency was measured
following the method used by Mukhopadhyay, Ishtiaque, and Uttam (2011), and was calculated
according to Equation 6, where W
1
is the square mass of the dry fabric, and W
2
is the square mass
of the wet fabric.
Water absorbency %ð Þ ¼ W2W1
ð Þ=W1x100 (6)
Alambeta instrument was used to measure thermal conductivity, thermal resistance, and thermal
absorptivity (Hes, De Araujo, and Djulay 1996). The relative water vapor permeability of the fabric
samples was measured on a Permetest instrument (Hes and De Araujo 2010). Handle-related comfort
properties were determined by using Fabric Assurance by Simple Testing (FAST) system. The
thicknesses measured at 2 g/cm
2
(T2) and 100 g/cm
2
(T100) using FAST-1 compression meter was
used for calculating the surface thickness (T2-T100), and the compressibility was defined as the surface
thickness in the percentage of fabric thickness at 2 g/cm
2
. The bending length was measured by using
FAST-2 bending meter. The bending rigidity was calculated by using Equation 7, where, W: fabric
square mass (kg/m
2
), c: bending length (m) (Varshney, Kothari, and Dhamija 2011), and the total
bending rigidity was calculated according to Equation 8 (Frydrych and Matusiak 2015).
B μN:mð Þ ¼ W x c3x9:81 x106(7)
Btotal μN:mð Þ ¼ pBwarpx Bweft
� (8)
The extension was measured by applying 5, 20, and 100 g/cm loads using FAST-3 extension meter.
The formability was calculated using Equation 9 where, F: fabric formability B: bending rigidity, E
20
:
extension at 20 g/cm, and E
5
: extension at 5 g/cm, and the shear rigidity was calculated using Equation
10 (Varshney, Kothari, and Dhamija 2011).
F mm2
�¼B x E20 E5
ð Þ =14:7 (9)
Shear Rigidity %ð Þ ¼ 123 =Bias extension at 5g=cm (10)
Table 2. Results of the variance analysis for the effects of fiber composition, weave type, rinsing, and their interactions on thermo-
physiological comfort properties.
AP WA RWVP DT DR TC TA TR
Fiber composition 0.000* 0.239 0.617 0.004* 0.026* 0.000* 0.112 0.000*
Weave type 0.000* 0.000* 0.450 0.021* 0.163 0.000* 0.219 0.000*
Rinsing 0.000* 0.000* 0.154 0.000* 0.630 0.000* 0.000* 0.000*
Fiber composition*Weave Type 0.000* 0.540 0.520 0.000* 0.744 0.025* 0.034* 0.001*
Fiber composition*Rinsing 0.000* 0.883 0.339 0.010* 0.718 0.638 0.248 0.881
Weave type*Rinsing 0.098 0.676 0.105 0.027* 0.935 0.037* 0.291 0.269
Fiber composition*Weave Type*Rinsing 0.866 0.172 0.000* 0.007* 0.170 0.009* 0.197 0.001*
* Significant at 95% confidence level (AP: Air Permeability, WA: Water Absorbency, RWVP: Relative Water Vapor Permeability, DT:
Drying Time, DR: Drying Rate, TC: Thermal Conductivity, TA: Thermal Absorptivity, TR: Thermal Resistance).
4N. OKUR
All tests were carried out under standard atmospheric conditions (20 ± 2°C and 65 ± 2% relative
humidity) after the samples were conditioned for a minimum of 24 hours. The analysis of variance was
performed on the test results to identify the main effects and their interactions by using the general
linear model (GLM) procedure on SPSS 27 software at a 95% confidence level. Student-Newman-
Keuls (SNK) post hoc tests and independent samples t-test were utilized to identify the differences
among sample means.
Results and discussion
Fabric structural and physical properties
The test results of structural and physical properties of the fabric samples are given in Table 1. From
Table 1, it can be seen that warp density and weft density of the fabric samples were between 27–37 and
19–25 per cm, respectively. The square mass of 2/1 twill fabrics was around 200 ± 25 g/cm
2
, while it
was around 270 ± 25 g/cm
2
. While the thickness values of 2/1 twill fabrics varied between 0.39 and 0.54
mm, the thickness of 3/1 fabrics was measured between 0.56 and 0.63 mm. The volume porosity and
cover factors of all fabrics were close to each other and around 70% and 25, respectively. After rinsing
process, thickness of the samples increased significantly, whereas the fabric square mass and the
number of warp and weft yarns per cm generally decreased that caused the cover factors to decrease
slightly.
Thermo-physiological comfort properties
The results of the analysis of variance are given in Table 2. According to the air permeability values
(Figure 1), it was observed that cotton/flax and cotton/hemp blended fabrics had higher air perme-
ability. While cotton/hemp blended 2/1 twill fabric had significantly higher air permeability than
others, cotton/flax blended 3/1 twill fabric had significantly higher air permeability than the other
samples. Regarding the hemp fiber, multiscale structure like an assembly of many single fibers, and
hence holes between the fibers and high void rate can be stated as the reason for the higher air
permeability (Yang et al. 2013; Zhang, Zhong, and Feng 2016). Besides, earlier studies revealed that
flax blended fabrics allow more air to pass through the fabric compared to pure cotton fabrics since the
yarns are loosely packed due to the coarser fibers with a circular cross-section (Behera 2007). The
rinsed samples had higher air permeability, which confirms the earlier findings (Yıldırım, Üstüntağ,
and Örtlek 2014). Swelling of fibers and the shrinkage of the yarns during the rinsing process led to a
0
50
100
150
200
250
300
350
400
450
Co CoFlax CoHemp Co CoFlax CoHemp
2/1Z Twill 3/1Z Twill
Air permeability (mm/s)
not rinsed rinsed
Figure 1. Air permeability.
JOURNAL OF NATURAL FIBERS 5
marginal increase in the fabric thickness. The increase in the thickness of the fabrics laid in a range of
55% to 132%. On the other hand, the fabric square mass and the number of warp and weft yarns per
cm generally decreased that caused the cover factors to decrease slightly. These created more space
between the yarns. Hence, greater inter-yarn pores contributed to the higher porosity of the fabric
0%
50%
100%
150%
200%
250%
300%
350%
Co CoFlax CoHemp Co CoFlax CoHemp
2/1Z Twill 3/1Z Twill
Water absorbency (%)
not rinsed rinsed
Figure 2. Water absorbency.
Table 3. SNK post hoc test results for relative water vapor permeability, drying time, thermal conductivity, and thermal resistance.
RWVP DT TC TR
2/1 Z Twill Not rinsed Co 44.85 a 4.00 c 0.0617 c 16.22 a
Co/Flax 53.05 b 2.84 b 0.0550 b 18.21 b
Co/Hemp 62.80 c 2.32 a 0.0495 a 20.18 c
Rinsed Co 24.55 a 2.23 b 0.0489 b 20.43 a
Co/Flax 24.90 a 2.23 b 0.0452 a 22.11 b
Co/Hemp 23.57 a 2.00 a 0.0446 a 22.42 b
3/1 Z Twill Not rinsed Co 38.47 a 4.42 b 0.0640 a 15.55 a
Co/Flax 38.51 a 4.52 b 0.0633 a 15.84 a
Co/Hemp 40.79 a 4.25 a 0.0635 a 15.84 a
Rinsed Co 23.24 a 2.55 b 0.0531 b 18.82 a
Co/Flax 23.56 a 2.20 a 0.0525 b 19.06 a
Co/Hemp 22.58 a 2.17 a 0.0477 a 20.96 b
Values having the same letters are not different from each other at 95% significant level (RWVP: Relative Water Vapor Permeability,
DT: Drying Time, TC: Thermal Conductivity, TR: Thermal Resistance).
0
10
20
30
40
50
60
70
80
90
Co CoFlax CoHemp Co CoFlax CoHemp
2/1Z Twill 3/1Z Twill
Drying rate (g/h/m2)
not rinsed rinsed
Figure 3. Drying rate.
6N. OKUR
(Table 1), and fabrics became more permeable (Karaca et al. 2012). Besides, 2/1 twill fabrics had higher
air permeability values since lower thickness allows easier passage of air through the fabric in a shorter
time (Karaca et al. 2012).
The water absorbency was significantly influenced by the weave type and the rinsing process.
The 2/1 twill fabrics had higher water absorbency values, which can be attributed to the relatively
higher porosity of the fabrics since the amount of water absorbed by the fibrous materials increases
as the porosity increases (Das et al. 2009). Similarly, with the increase of porosity after rinsing, the
water absorbency properties of the fabrics increased. Although the effect of fiber composition was
found statistically insignificant, higher water absorbency values were achieved as a result of
blending the cotton fiber with flax and hemp fibers (Figure 2). The relative water vapor perme-
ability measurements showed that the permeability of the cotton/hemp blended fabric was the
highest, and it was followed by the cotton/flax blended fabric and pure cotton fabric, respectively,
in 2/1 twill untreated fabrics. In the rinsed samples, the lowest values were observed in cotton/
hemp blended fabrics. On the other hand, any significant difference was not detected among 3/1
twill untreated and rinsed fabrics. It was observed that the relative water vapor permeability values
of 2/1 twill fabrics were higher. Besides, rinsing process generally decreased the relative water vapor
permeability. The relative water permeability of the fabrics, which represents the cooling of the skin
by perspiration from the surface of the fabric, depends on the fabric square mass, fabric moisture
content and fabric thickness (Hes and De Araujo 2010; Havlová, 2020). The lower square mass of 2/
1 twill fabrics resulted in higher permeability. As a result of rinsing process, the thickness of the
fabrics increased. Since the water vapor passes through the yarn itself, but not through the inter-
yarn pores and the gaps inside the fabric, the increase in the fabric thickness makes the passage of
vapor difficult.
The drying time and drying rate of the samples are seen in Table 3 and Figure 3, respectively. The
shortest drying time was observed in cotton/hemp blended 2/1 twill fabrics in both untreated and
rinsed conditions. Besides, the drying time of cotton/flax blended fabric was significantly lower in
untreated 2/1 twill fabric than pure cotton fabric. Cotton/hemp blended fabric had a significantly
shorter drying time in 3/1 twill untreated fabrics, and both cotton/flax and cotton/hemp blended 3/1
twill weave rinsed fabrics had a significantly shorter drying time than cotton fabrics. Consequently,
lower drying times were achieved by blending the cotton fiber with flax and hemp, in conformance
with the earlier studies (Liu, Xu, and Zhang 2011). Moreover, the drying rate was higher in cotton/flax
and cotton/hemp blended fabrics. The findings also showed that 2/1 twill fabrics had shorter drying
times and higher drying rates. Regarding the rinsing process, the rinsed samples had shorter drying
times and higher drying rates. The effect of weave type and rinsing process on the drying behavior of
the fabric samples can be correlated to the higher porosity (Kim and Kim 2016).
0
50
100
150
200
250
300
Co CoFlax CoHemp Co CoFlax CoHemp
2/1Z Twill 3/1Z Twill
Thermal absorptivity (W. s1/2/m2.K)
not rinsed rinsed
Figure 4. Thermal absorptivity.
JOURNAL OF NATURAL FIBERS 7
Thermal conductivity, thermal absorptivity, and thermal resistance values are demonstrated in
Table 3 and Figure 4. According to the results (Table 3), the thermal conductivity value of the pure
cotton fabric was the highest that was followed by cotton/flax and cotton/hemp blended fabrics,
respectively, in 2/1 twill untreated fabrics. However, any significant difference was not observed
among 3/1 twill untreated fabrics. In the rinsed samples, the lowest values were observed in cotton/
hemp blended fabrics. When the main effect of fiber composition was analyzed for the group of
samples individually, thermal conductivity values were measured from highest to lowest in pure
cotton, cotton/flax and cotton/hemp blended fabrics, respectively. The results in the respective of
fiber composition are related to the thermal conductivity values of the fibers. The thermal conductivity
of cotton fiber is 0.071 W/mK (Morton and Hearle 2008), whereas, it varies from 0.035 to 0.045 W/mK
for flax fiber, and from 0.040 to 0.049 W/mK for hemp fiber (Vaitkus et al. 2014). Therefore, the lower
thermal conductivity of flax and hemp fibers presented matching results in the fabrics. Regarding the
weave type, 2/1 twill fabrics had lower thermal conductivity in the untreated condition. Besides, rinsed
samples had lower thermal conductivity. These results are related to the higher porosity and hence
higher amount of entrapped air in the fabric since the thermal conductivity of air is lower than the
fibers. Concerning the thermal absorptivity values (Figure 4), the pure cotton fabric had the highest
value in the 2/1 twill untreated fabrics; whereas, cotton/flax blended 3/1 twill fabrics had the highest
values in both untreated and rinsed conditions. Thermal absorptivity is related to the warm-cool
feeling of the fabrics and it depends on the contact area between the skin and the surface of the fabric.
The decrease in the contact area decreases the thermal absorptivity, and the lower the thermal
absorptivity, the warmer the feeling during the short thermal contact of the skin with the fabric
Table 4. Results of the variance analysis for the effects of fiber composition, weave type, rinsing, and their interactions on handle
related properties.
ST C
BR
warp
BR
weft TBR
EX
warp
EX
weft
FA
warp
FA
weft SR
Fiber composition 0.003* 0.000* 0.000* 0.000* 0.000* 0.037* 0.000* 0.000* 0.002* 0.000*
Weave type 0.000* 0.000* 0.000* 0.602 0.000* 0.003* 0.000* 0.000* 0.037* 0.000*
Rinsing 0.000* 0.000* 0.012* 0.026* 0.021* 0.392 0.201 0.841 0.175 0.000*
Fiber composition *Weave Type 0.672 0.013* 0.002* 0.001* 0.082 0.000* 0.006* 0.840 0.010* 0.347
Fiber composition *Rinsing 0.820 0.208 0.000* 0.020* 0.036* 0.000* 0.005* 0.076 0.131 0.027*
Weave type*Rinsing 0.026* 0.002* 0.541 0.186 0.000* 0.105 0.341 0.018* 0.532 0.000*
Fiber composition *Weave Type *
Rinsing
0.002* 0.013* 0.111 0.102 0.002* 0.000* 0.000* 0.010* 0.115 0.588
*Significant at 95% confidence level (ST: Surface Thickness, C: Compressibility, BL: Bending Length, BR: Bending Rigidity, TBR: Total
Bending Rigidity, EX: extension at 100 g/cm, FA: Formability, SR: Shear Rigidity).
Table 5. SNK post hoc test results for surface thickness, compressibility, total bending rigidity, extension (warp and weft), and
formability (warp).
ST C TBR
EX
warp
EX
weft
FA
warp
2/1 Z Twill Not rinsed Co 0.15 a 23.12 a 14.97 b 4.34 c 4.30 c 1.61 b
Co/Flax 0.16 b 28.69 b 16.91 b 3.08 b 1.85 b 0.84 a
Co/Hemp 0.17 b 32.26 b 12.72 a 1.98 a 0.70 a 0.65 a
Rinsed Co 0.26 a 30.91 a 8.68 a 3.63 b 4.70 c 0.81 a
Co/Flax 0.28 b 37.58 b 13.19 b 2.80 a 2.55 b 0.73 a
Co/Hemp 0.27 b 35.60 b 12.94 b 2.88 b 1.35 a 0.66 a
3/1 Z Twill Not rinsed Co 0.11 a 16.35 a 19.77 a 3.53 a 4.20 c 1.66 b
Co/Flax 0.14 b 20.08 b 27.74 b 4.03 b 3.10 a 1.03 a
Co/Hemp 0.13 b 20.38 b 16.85 a 4.54 c 3.60 b 1.14 a
Rinsed Co 0.25 a 28.01 a 15.34 b 3.47 a 5.30 c 1.61 b
Co/Flax 0.26 b 28.49 a 19.66 b 4.11 b 4.45 b 1.31 a
Co/Hemp 0.26 b 31.54 b 11.61 a 3.43 a 3.60 a 0.99 a
Values having the same letters are not different from each other at 95% significant level (ST: Surface Thickness, C: Compressibility,
TBR: Total Bending Rigidity, EX: Extension at 100 g/m, FA: Formability).
8N. OKUR
Table 6. Bending, extension, formability, and shear properties of the fabric samples.
Sample
code
Weave
type Process
Bending
length
- warp
(mm)
Bending length
- weft (mm)
Bending rigidity
- warp
(µNm)
Bending rigidity
- weft
(µNm)
Extension
at 100
g/cm
- warp
(%)
Extension
at 100
g/cm
- weft
(%)
Bias
extension
(%)
Formability
- weft
(mm
2
)
Shear
rigidity
(N/m)
Co 2/1 Z Twill Not rinsed 23.00 15.50 27.06 08.28 4.34 4.30 1.72 1.01 87.13
CoFlax 19.38 21.83 14.13 20.23 3.08 1.85 1.73 0.41 69.58
CoHemp 19.13 19.75 12.12 13.35 1.98 0.70 3.63 0.25 36.91
Co 3/1 Z Twill 23.49 16.00 35.21 11.11 3.53 4.20 0.73 1.16 148.06
CoFlax 21.50 22.17 26.49 29.04 4.03 3.10 1.30 1.14 107.16
CoHemp 19.50 17.85 19.24 14.75 4.54 3.60 1.05 0.32 98.56
Co 2/1 Z Twill Rinsed 18.25 13.83 13.15 05.73 3.63 4.70 2.73 0.33 47.27
CoFlax 18.50 19.33 12.34 14.09 2.80 2.55 2.65 0.32 46.70
CoHemp 17.75 21.00 10.05 16.65 2.88 1.35 3.80 0.30 34.30
Co 3/1 Z Twill 23.25 14.00 32.84 07.17 3.47 5.30 2.15 0.53 59.90
CoFlax 20.50 18.83 22.33 17.31 4.11 4.45 2.63 1.09 49.17
CoHemp 19.00 15.63 15.57 08.66 3.43 3.60 3.75 0.25 36.65
JOURNAL OF NATURAL FIBERS 9
(Hes and Dolezal 1989). The independent samples t-test results showed that the untreated fabric
samples had higher thermal absorptivity. Thermal absorptivity is measured based on thermal con-
ductivity, density, and specific heat capacity (Hes, De Araujo, and Djulay 1996). Hence, the change in
thermal conductivity also affects the thermal absorptivity. Besides, as the porosity increases, the yarns
are not closely packed, and the contact area between the skin and the fabric decreases. As a result, the
thermal absorptivity decreases and the fabric gives a warmer feeling. The thermal resistance values of
the samples with lower thermal conductivity were higher as expected (Table 3) (Karaca et al. 2012).
Since the thickness of the rinsed fabric samples was higher, higher thermal resistance values were
measured, as thermal resistance is given by thickness divided by thermal conductivity of the fabric
(Stoffberg, Hunter, and Botha 2015)
Handle-related comfort properties
The results of the variance analysis are given in Table 4. The blended fabrics had higher surface
thickness and higher compressibility than pure cotton fabric (Table 5). This can be attributed to the
loosely packing of the flax and hemp fibers in the yarns since they are coarse fibers by nature with a
circular cross-section (Behera 2007; Stanković and Bizjak 2014). Thus, free spaces between the fibers
and the bulky structure of the yarn increased the compressibility, so it can be concluded that cotton/
flax and cotton/hemp blended fabrics have soft handle (Varshney, Kothari, and Dhamija 2011). Also,
2/1 twill fabrics and the rinsed fabrics were observed to have higher compressibility. The higher
porosity in 2/1 twill fabrics and the increase in porosity of the fabric after the rinsing process led to
greater free space for easier movement of yarns and further increased the compressibility of the fabric.
As seen in Table 6, blending cotton with flax and hemp fiber gave lower bending rigidity values in
the warp direction. Besides, although the yarns have more free space in 3/1 twill fabrics because of the
longer yarn floats and fewer intersection points in comparison to 2/1 twill fabrics, the higher thickness
of 3/1 twill fabrics exhibited higher bending rigidity (Kar and Pandharpure 2019). After rinsing,
fabrics had lower bending rigidity in the warp direction. Blending cotton with flax and hemp fibers
significantly increased the bending rigidity of the fabric samples in the weft direction. While bending
rigidity in the warp direction was higher than in the weft direction in pure cotton fabric, the opposite
was observed in blended fabrics. Considering that the blended yarns were used as the weft yarns in
blended fabrics, it can be concluded that flax and hemp increased the bending rigidity of the fabric.
This is because flax and hemp fibers are stated as stiff fibers (Sfiligoj Smole et al. 2013). Bending rigidity
in the weft direction was independent of the weave type, whereas rinsed fabrics were observed to have
lower bending rigidity in the weft direction. Since there were different trends in the warp and weft
directions, it was significant to examine the total bending rigidity values of the fabric samples. The
most outstanding result regarding the total bending rigidity was that the cotton/flax blended fabrics
had high total bending rigidity values (Table 5). In garments, low bending rigidity is preferred to
achieve softness (Behera 2007). Therefore, increasing the amount of flax and hemp in the fabric can
negatively affect the handle. It is also noteworthy to state that the rinsing process decreased the total
bending rigidity, indicating less stiff fabrics.
As seen in Table 6, while the extension of pure cotton fabric was higher in 2/1 twill fabrics, it was
higher in 3/1 twill blended fabrics in the warp direction. This result applies to both untreated and
rinsed samples. In the weft direction, the highest extension values were obtained in pure cotton fabrics,
whereas extension of the fabrics made of blended yarns was lower in both weave types and in untreated
and rinsed samples due to the lower elongation of flax and hemp fibers than that of cotton fiber (;
Sfiligoj Smole et al. 2013). Concerning the weave type, the extension was higher in 3/1 twill fabrics in
both warp and weft directions. Because of fewer intersection points, 3/1 twill weave provides more
mobility to the yarns and hence facilitates the extension (Behera and Sharma 1998). The high
extensibility is considered a positive feature in terms of sensorial comfort (Behera 2007). The extension
was low in blended fabrics, especially in the weft direction. However, statistical analysis revealed that
the rinsing process imparted a significant increase to the extension of the blended fabrics. The
10 N. OKUR
formability values in the warp and weft directions are demonstrated in Table 5 and Table 6,
respectively. The formability of pure cotton fabrics was higher than that of cotton/flax and cotton/
hemp blended fabrics. In general, slightly lower formability values were calculated for the rinsed
fabrics. In addition, the formability values of 3/1 twill fabrics were higher in the warp direction. In the
weft direction, cotton and cotton/flax blended fabrics had similar formability values, whereas cotton/
hemp blended fabric had lower formability. Regarding the weave type, 3/1 twill fabrics had higher
formability values. Formability is the measure of the ability of a fabric to absorb compression on its
own plane without buckling (Wang, Postle, and Zhang 2003). The higher the formability, the
smoother sewing process and hence better garment appearance (Frydrych and Matusiak 2015). In
the present study, the formability values of blended fabrics were lower than pure cotton fabrics. On the
other hand, all fabrics had a value above the lower limit, which is 0.25 mm
2,
stated in the literature
(Wang, Postle, and Zhang 2003). This means that the fabrics can accommodate the compression
applied during the sewing process and would probably not pucker.
The shear rigidity values are shown in Table 6. The highest shear rigidity values were obtained in
pure cotton fabrics, followed by the cotton/flax and cotton/hemp blended fabrics, respectively. The
smooth surface of flax and hemp fibers (Behera 2007; Zhang, Zhang, and Gao 2014) facilitates the
movement of the warp and weft yarns over each other at the intersection points in the fabric, and
consequently, higher bias extension and lower shear rigidity were obtained. Concerning the weave
type, 2/1 twill fabrics demonstrated lower shear rigidity values and the rinsing process resulted in
lower shear rigidity values that mean they would have better handle behavior (Behera 2007).
Conclusion
In this study, the effects of blending cotton with flax and hemp fibers on the comfort properties of
denim fabrics were deeply investigated. The results showed that blending flax and hemp with cotton
increased the air permeability, water absorption, and drying rate of the samples. These features were
higher in 2/1 twill fabrics due to their lower thickness and slightly higher porosity. In addition, 2/1
twill untreated fabrics were found to have higher relative water vapor permeability values for flax and
hemp blended structures. On the other hand, cotton/flax and cotton/hemp blended fabrics, in
particular 2/1 twill fabrics, had lower thermal conductivity, resulting in high thermal resistance and
keeping the wearer warmer as well as being warmer to initial touch due to lower thermal absorptivity.
However, the more permeable structures with high absorbency, high water vapor permeability and
breathability when sweating occurs, as well as the quick drying behavior, will enable these fabrics to be
defined as comfortable fabrics suitable for hot weather conditions. The findings of the study helped to
conclude that after the rinsing process, the thickness and porosity of the fabrics increased and the
fabrics had higher water absorbency and faster drying properties along with higher permeability.
Moreover, using flax and hemp fibers resulted in a similar or even softer feeling compared to pure
cotton fabrics due to their higher compressibility, lower shear rigidity, and similar total bending
rigidity. On the other hand, cotton/flax and cotton/hemp blended fabrics had lower extension and
formability values, which may worsen the appearance of the garment. It was also concluded that 2/1
twill fabrics would have a softer feeling, whereas lower extension and formability became more critical.
Besides, the rinsing process improved the handle-related properties. After the rinsing process, fabrics
with different fiber compositions had similar extension and formability values, even rinsing had a
significant impact on improving the extension of the blended fabrics.
From the sustainability perspective, the use of flax and hemp fibers has been increasing gradually in
the sector. However, researches are still very limited. This study provides useful information about the
use of these fibers regarding comfort in denim fabrics. Further studies investigating the blends of these
fibers with various regenerated cellulosic fibers and elastane, and the effects of different washing
processes will undoubtedly expand the knowledge on the use of these fibers in denim fabrics.
JOURNAL OF NATURAL FIBERS 11
Acknowledgments
The author(s) would like to appreciate Maritaş Denim for supplying the fabric samples, Kipaş Denim for carrying out the
rinsing process and Yünsa Yünlü Sanayi ve Ticaret A.Ş. for providing opportunity for the measurements of handle-
related comfort properties.
Disclosure statement
No potential conflict of interest was reported by the author.
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