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Enhancing the mechanical properties of natural jute yarn suitable for
structural applications
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Mater. Res. Express 8 (2021) 055503 https://doi.org/10.1088/2053-1591/abfd5e
PAPER
Enhancing themechanical properties of natural jute yarn suitable for
structural applications
Md.Ashadujjaman1, Abu Saifullah2, Darshill U Shah3,Minglonghai Zhang4,Mahmudul Akonda5,
NazmulKarim6 and Forkan Sarker1
1 Department of Textile Engineering, DhakaUniversity of Engineering&Technology, Gazipur-1700, Bangladesh
2 Advanced Materials and Manufacturing (AMM) Research Group, School of Mechanical and Design Engineering, University of
Portsmouth, Portsmouth PO1 3DJ, UnitedKingdom
3 Department of Architecture, University of Cambridge, Cambridge, CB2 1PX,UnitedKingdom
4 Institute of Textile andClothing, TheHongKong PolytechnicUniversity, HongKong, People’s Republic of China
5 School ofMaterials. TheUniversity ofManchester,Manchester,M13 9PL, UnitedKingdom
6 Centre for Fine Print Research, University of theWest of England, Bristol, BS3 2JT,UnitedKingdom
E-mail: forkan@duet.ac.bd
Keywords:natural fibres, glycine, surface treatments, tensile properties
Supplementarymaterial for this article is available online
Abstract
Manufacturing natural-based high-performance composites are becoming of greater interest to the
compositemanufacturers and to their end-users due to their bio-degradability, low cost and
availability. Yarn based textile architecture is commonly used inmanufacturing these composites due
to their excellent formability. However, for using natural based yarn as a reinforcing architecture in
high load-bearing structural composite applications, a significant improvement inmechanical
performance is required. Particularly, jutefibre yarn suffers frompoormechanical properties due to
the presence of afibrillar network, polysaccharides and other impurities in the fibre. For achieving
this, we use aqueous glycine treatment (10%,W/V) on alkali(0.5%,W/V) and untreated jute yarns
for the first time. The glycine treatment on alkali-treated jute yarns (ATG) shows a huge improvement
in tensile strength and strain values by almost∼105%and∼50% respectively compared to untreated
jute yarns (UT) because of the strong interactions and bonds developed between glycine, alkali and
jute yarns. It is believed that the newly developed glycine treated jute yarns will be helpful to promote
jute yarns in composite industries where load-bearing is the primary requirement and replace their
synthetic counterparts.
1. Introduction
Fibre-reinforced composites have gained significant interests in recent years, due to their design flexibility,
durability, chemical resistance, and relatively higher strength and stiffness at a lowweight ratio. Traditionally,
fibre reinforced composites are composed of synthetic fibres including glass, carbon and aramid as
reinforcements in a polymermatrix [1]. However, synthetic fibres are not environmentally friendly as they are
manufactured from fossil fuels, associatedwith relatively higher energy consumption and carbon emission.
Naturalfibres reinforced composites can be an environmentally sustainable alternative to their synthetic
counterpart, due to lower environmental impacts including less carbon emission, less energy consumption and
biodegradability [2–5]. Themost promising natural plant fibres are jute, hemp, ramie, sisal,flax, and bamboo
which could potentially replace synthetic fibres for various applications. Arguably, jute is themost attractive
alternative amongst other natural plant fibres, due to its abundance, low production cost, lower density and high
individualfibre length, as well as reasonablemechanical properties [5, 6]. In addition, Jute is the secondmost-
produced natural fibre in theworld after cotton (∼3.63million tons), and at least∼50%cheaper than flax and
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other similar natural fibres. The use of jute for various applications could boost the farming economies of
developing countries such as Bangladesh and India, where it ismostly produced.
Themechanical properties of jute are related to its relatively higher degree of crystallinity (∼58%), and
higher cellulose content (∼70%) (table S1, Supporting Information (available online at stacks.iop.org/MRX/8/
055503/mmedia)) [7]. Jute fibres have a ‘fringed fibrilmodel’, where the inter-fibrillarmatrix contains
hemicellulose within ultimate cells and themiddle lamella contains lignin between ultimate cells [8]. The
viscoelastic and tensile behaviour of jutefibre depends on such polysaccharides (e.g. hemicellulose, lignin and
pectin) and their relative proportion because they create links between the cellulosicmicrofibrils and are
responsible for stress transfer among them [9]. It has been reported in the previous study that the removal of
polysaccharides eliminates themicrovoids present between the ultimate cell andmiddle lamella of thefibre. As a
result,microfibrils present in thefibre becomemore parallel and homogeneity of the fibre improves which
results in improvement of the failure stress, failure strain and stiffness of jutefibres [9]. The alkali treatment is
themost commonly usedmethod to remove polysaccharides i.e. hemicellulose, lignin, pectin, which improves
the load-bearing capacity of jutefibre as a reinforcingmaterial forfibre reinforced composites [6, 9]. However,
jutefibre still containsmicro-voids among the fibrils which limit their load-bearing capacity and create a weak
fibre/matrix interface [6]. Previous studies have reported the removal of such defects via chemical [10–12],
physical [13] and nanomaterialsmodifications[5, 13, 14] of jute fibres, which are time-consuming and
expensive. Additionally, there are concerns with nanomaterials safety and their potential carcinogenic nature to
health. The alkali treatment is the commonly used chemicalmedication for naturalfibres as it removes surface
waxes and affects hemicelluloses. The alkali treatment (0.5wt.-%) of jute fibres with the prolonged exposure into
the alkali solution is considered to be themost effective way of removing hemicelluloses without affecting lignins
significantly [5, 15]. Further to alkali treatment, it is necessary tomodify jute fibre to remove theflaws
(microvoids) due to removal of lignins from the skin offibremay also generate stress concentration. As a result,
further chemicalmodification is necessary to solve these issues. However, the treatment should be cost-effective,
environmentally friendly and easy to scale up. At present nano surfacemodification is becoming popular in
modifying natural fibres in composites applications. However, dealingwith thesematerials are health hazardous
and costly.
For fibre-reinforced composites (FRC), yarn-basedmulti-axial textile architectures offer bettermechanical
properties including impact, compression after impact damage and interfacial strength, than themost popular
unidirectional yarn architectures [16–19]. Textile architectures aremainly inducedwith plain, twill, sateen, and
knitted derivatives which aremainlymanufactured from yarns. Therefore, there exists a growing demand for
FRC composite preforms comprised of woven fabric withmulti-axial yarn architectures. However, the use of the
jute yarn for structural FRC applications is limited due to its poor performance properties. The tensile strength
for jute yarnwas reported∼42–45MPa only. Such a lower tensile strength ismainly due to the fibre impurities
and the twist imparted to thefibre during spinning into yarn [20, 21]. In addition, the strain to failure of jute yarn
was found to be limited∼6.0%–7.5%with a large scattering in the value in those studies [19, 20]. Recently, few
studies have been carried out on the nano-modification of natural jute yarns to increase the strength and
interfacial performance of the composites [21, 22]. It was found that the lower value of strain% is responsible for
the amorphous phase’s viscoelastic shear deformation present in the cellulose of the fibre [23]. Such viscoelastic
shear deformation can be avoided by improving the crystallinity offibres. In addition, the tensile strength can be
improved by aligning themicrofibrils in parallel directions with the loading axis [10, 24]. However, the
improvement ofmechanical properties of natural jute yarns are still limited, and not yet well understood.
Nevertheless, it is well established that the deformation of natural fibres largely depends on the interphase of
elementaryfibres in the yarn. Recently, glycine-based proteinmaterials have been used in cellulosicmaterials to
improve strain to failure andwettability of cottonfibres. Glycinewasfirst applied on cottonfibres to improve
tensile properties. It was found that the glycine treatment improved the strain%offibres by 36% [25]. This is
mainly due to the interactions between the amino functional group of glycine and carboxylic groups present in
the amorphous region of the cellulosicfibres that creates a strong chemical bond; thus, improves themechanical
properties of cottonfibres. As jute has similar cellulosic structures to cotton, glycine is believed to have similar
effects to improve themechanical properties of Jute fibres, which has not been reported yet to the best of our
knowledge. In addition, glycine is an environmentally friendly simplest formof protein-based amino acid that
has been extensively used in the drug industry. The low price and nonhazardous feature of glycine and the
presence of amino-functional group havewidened the scope of using thismaterial inmany applications [26].
Here, we report for thefirst time the improvement of tensile properties of jute yarns including the tensile
strength and strain via a combination of alkali and aqueous glycine treatment.We optimize the processing
conditions and parameters for such treatment to achieve the bestmechanical properties of jute yarns. The
untreated jutefibreswere treatedwith a lower concentration (0.5wt.-%) of alkali treatment, followed by a
subsequent glycine treatment on the alkali-treated jute yarns. Surface topography of the treated and untreated
jute yarns was examined using optical and scanning electronmicroscopes (SEM). In addition, changes in the
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Mater. Res. Express 8 (2021) 055503 M.Ashadujjaman et al
diameter of the yarns were recorded using an opticalmicroscope, tensile properties were assessed via single yarn
testing for 50 samples.We usedWeibull statistics to analyse fibre failures after tensile tests. Chemical and
thermal analysis were performed using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron
spectroscopy(XPS) andThermogravimetric analysis (TGA), respectively.
2.Materials andmethods
2.1.Materials
The jute yarns were kindly donated byUMC JuteMills Ltd, Narsinghdi, Bangladesh. Jute (CorchorusOlitorius)
plants were harvested in Bangladesh via traditionalmethods and then processed in jutemills. Thefibres used in
themanufacturing of jute yarnwere pretreatedwith vegetable oil tofibrillate the technical jute fibres to improve
the spinnability of the fibre (figures 1(a) and S1(a), Supporting Information). As supplied jute yarns have a linear
density of∼9.5 lbs/spindle and aTPI of∼4.09 (Table S2, Supporting Information). Sodiumhydroxide
(EMSURE® ISO,>99%) pellets were supplied byMerck (Germany). Glycine (AminoAcetic Acid,
NH2CH2COOH99.88%awhite crystalline powder, Laboratory Reagent LR grade) used in this studywas
supplied by FineChemical Industries, India.
2.2. Alkali treatment
The untreated jute yarn (UT)were treatedwith 0.25%, 0.5%, 1%NaOHat room temperature for 24 h, and 2%
NaOHat room temperature for 2 h atmaterial to liquor ratio (M:L) of 1:30 (figures 1(c) and S1(b), Supporting
Information). The optimized alkali concentrationwas selected based on the results obtained from the tensile test
of alkali-treated fibres, whichwas then used for glycine treatment. After alkali treatment, all samples were
thoroughlywashedwith distilledwater until all the alkali traces were removed from treated yarns. Then all the
samples were air-dried overnight at 50 °C in an oven. The optimized alkali-treated fibreswere labelled as AT.
2.3. Glycine treatment
Alkali treated (AT) and untreated jute yarnswere treatedwith aqueous glycine at different concentrations (5, 10,
15 and 20 g l−1) at 100 °Cand pH7 for 1.5 hwith anM:L ratio of 1:20 in an infrared lab dyeingmachine (
figures 1(d) and S2(a)–(b), Supporting Information). In addition, four pH levels (3, 5, 7 and 11)were also
selected for 10 g l−1 aqueous solutions of glycine to see their effect on alkali-treated jute yarns. All of the treated
Figure 1. (a)Untreated jute yarns, (b) chemical interaction of jutefibrewith glycine, (c) alkali treatment of jute yarn and (d) glycine
treatment of jutefibre.
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Mater. Res. Express 8 (2021) 055503 M.Ashadujjaman et al
samples were thoroughly washedwith distilledwater and dried at 50 °C for at least 5 h in the oven.Here,
untreated jute yarnwith glycine treatment is labelled asUTG,while alkali-treated jute yarnwith glycine
treatmentwas identified as ATG.
2.4.Optical and scanning electronmicroscope (SEM)
Anopticalmicroscope (JiusionOriginal 40-1000X, China)was used to observe thefibre surface at different
magnifications, andmeasurement of the yarn diameter (figure S3, Supporting Information). A Scanning
ElectronMicroscope (SEM,Model-SU 1510, Brand-Hitachi, Japan)was used to characterize the fibrillar
packing of jute yarn. The samples were observed under SEMwithout any further coating on their surface using a
low accelerating voltage (∼2 kV).
2.5. Chemical and thermal characterization
The surface chemical composition of untreated and treated jute yarns were analyzed using aKratos axis X-ray
photoelectron spectroscopy (XPS) and a Fourier transform infrared spectroscopy (FTIR). The thermal
decomposition of untreated and glycine treated jute yarnwas analyzed using a TA instrument (TGAQ50,UK)
from room temp to 600 °C in a nitrogen atmosphere at a 10 °C/min heating rate.
2.6. Tensile test
For the tensile testing, yarn samples were taken randomly from the spool of alkali (UT, AT) and glycine-treated
(UTG, ATG) jute yarns, and conditioned in a standard laboratory atmosphere (65% relative humidity and
20±2 °C) for 24 h before thefinal testing. AUniversal Strength Tester (TestometricModel-M250-3CT,UK),
was usedwith a load cell capacity of 25KG tomeasure the breaking force and elongation at break of jute yarn
according to the ASTMD2256-01 standardmethod. Single yarns were tested using a 50mmgauge length at a
cross-head speed of 2mm/min as reported in the previous work [27]. The yarnwas set on themachine using a
special pneumatic yarn gripper supplied by Testometric, which ensures no slippage during testing (figures
S4(a)–(b), Supporting Information). The tensilemodulus of the yarnswas calculated from the slope of 0.1%–
0.3% strain of the yarn.
2.7.Weibull statistical analysis
The tensile properties of natural fibres (strength,modulus and strain%) are often described by theweakest link
theorywhich is based on the statement that thematerials aremade of small elements and the elements are linked
together. Amaterial is considered to have failed if any of these small elements have failed [28]. The cumulative
probability of failure for tensile and interface properties are given by the following formula:
⎜ ⎟⎜ ⎟
⎛
⎝
⎛
⎝
⎞
⎠
⎞
⎠
( )P 1 exp 1
o
ms
s= -
⎜ ⎟⎜ ⎟
⎛
⎝
⎛
⎝
⎞
⎠
⎞
⎠
( )P E
E
1 exp 2
o
m
= -
⎜ ⎟⎜ ⎟
⎛
⎝
⎛
⎝
⎞
⎠
⎞
⎠
( )P 1 exp 3s
o
me
e= -
where, s is the tensile strength; os is theWeibull scale parameter andm is theWeibull shape parameter.
Similarly,E is the tensilemodulus of the fibre; Eo is theWeibull scale parameter andm is theWeibull shape
modulus, where, se is the tensile strain, oe is theWeibull scale parameter andm is theWeibull shape parameter.
Based on equations (1)–(3) a double natural logarithm is taken on both sides, which is shown in equations (4)–
(6):
( ( )) ( ) ( )P m mln ln 1 ln ln 4os s- - = -
( ( )) ( ) ( )P m E mln ln 1 ln ln E 5o- - = -
( ( )) ( ) ( )P m mln ln 1 ln ln 6oe e- - = -
Where the cumulative probability of failure is related to the tensile strength ( ),s tensilemodulus (E), tensile
strain ( ),e theWeibullmodulus (m) and E ando o o, es are the scale parameters of strength, the tensilemodulus of
thefibre and tensile strain of the yarn.
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Mater. Res. Express 8 (2021) 055503 M.Ashadujjaman et al
3. Results and discussion
3.1. Surfacemorphology
Figures 2(a)–(c) show optical images of untreated and treated jute yarns (figure S5a, Supporting Information).
UT jute yarns show a loose appearance of technical fibres in the yarn,figure 2(a). The presence of impurities such
as hemicelluloses and lignins in the interfibrillar network offibres increase fibre irregularitymay cause the loose
appearance offibres in the yarn.
However, after the alkali treatment, a noticeable change in thefibre packing of AT yarn (figure 2(b))was
observedwhich could be related to the removal of hemicelluloses after alkali treatment. As a result, yarn
diameters were slightly reduced from∼0.92mm to∼0.71mm (Table S4, Supporting Information), which is in
agreementwith the results obtained in previous studies [6, 28, 29]. Glycine treatment on untreated jute fibre
(UTG) slightly improved the packing of technical fibre in jute yarnwhile no change in the diameter was observed
forUTG jute yarn (figure S5(a) andTable S4, Supporting Information).
However, glycine treatment on alkali-treated jute yarn (ATG) enabled a significant tight packing of thefibre
in the jute yarn. As a result, a uniform reduction of yarn diameter (see figure 2(c) andTable S4, Supporting
Figure 2. (a)Opticalmicrograph ofUT jute yarn (X20), (b)Opticalmicrograph of AT jute yarn (X20), (c)Opticalmicrograph of ATG
jute yarn (X20), (d) SEMmicrograph ofUT jute yarn (X250), (e) SEMmicrograph of AT jute yarn (X250), (f) SEMmicrograph of ATG
jute yarn (X250), (g) FTIR spectra of untreated and treated jute yarns, (h)TGA curves of untreated and treated jute yarns and (i)
Derivationweight%Vs temperature profile curves of untreated and treated yarn.
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Mater. Res. Express 8 (2021) 055503 M.Ashadujjaman et al
Information)was observed throughout the length of the yarn, due to the technical fibrefibrillation via alkali
treatment, and suitable bonding between the functional group of glycine and jutefibres. A scanning electron
microscope (SEM)was used to investigate thefibrillar arrangement and surface smoothness of the fibre after
alkali and glycine treatments. (figures 2(d)–(f) and S5(b), Supporting Information). Figure 2(d) shows scattered,
non-uniform and uncleaned technical fibre surfaces in theUT yarn. The top surface ofUT yarn is coveredwith
foreignmatters such as oil, waxes, and bindingmaterials such as lignin and hemicelluloses. Alkali treatment
removed such impurities and improved the fibre surface roughness [6, 30, 31] (see figure 2(e)). In addition,
alkali-treated fibres show grooved appearances which clearly indicates the presence of individual fibre cells
(figure 2(e)) and in agreementwith previous studies [9, 32]. It could be explained by the fact that hemicelluloses
that are located in the inter-microfibrillar region are sensitive to alkali solutions and can easily be removed
during the alkali treatment, which causes individual fibrefibrillation in the yarn. The application of glycine on
untreated yarn (UTG) improved the connection of technical fibres,figure 2(f). However, glycine treatment on
alkali-treated yarns (ATG) increases not only thefibre packing but also the interconnection between the
fibrillatedfibres created by alkali actions (figure 2(f)). Such improved interconnections create tightfibre packing,
and ultimately reduce the yarn diameter similar to theATG yarn.
3.2. Chemical and thermal characterizations of treated jute yarns
Figure 2(g) shows the FTIR spectra of UT, AT,UTG andATG jute yarns, which demonstrates four
characteristics peaks forUT jute yarns [6, 33]. The peak located at∼3400 cm−1 is responsible for the stretching
of hydrogen bond, which is originated from the hydroxyl groups present in the cellulose, hemicellulose and
lignin of jute fibres. The peaks between 2900 and 2700 cm−1 are for theC-H stretching of alkyl groups of
cellulose, lignin and hemicelluloses present in jute fibres. In addition, the FTIR spectrumof untreated jutefibres
shows peaks at∼1738 and∼1249 cm−1 band. The peak at∼1738 cm−1 is for C–Ostretching of carboxylic and
ester groups fromhemicelluloses presents in the interfibrillar region ofUT jute fibres. Furthermore, the band at
1249 cm−1 is for theC–Ostretching of acetyl groups from lignins of untreated jutefibres. After alkali treatment,
these peakswere disappearedwhich is in agreementwith a previous study [6]. The disappearance of such peaks
clearly confirms the removal of hemicellulose and lignin from the bundle of technical jute fibres after alkali
treatment, which is evident from the optical and SEM images of AT jute yarns (figures 2(b), (e)), and could be
explained by the formation ofNa-cellulose from the reaction between the cellulose andNaOH, figure 3.
For glycine treatment onUT jute yarn, no additional absorption peakswere observed, whichmay be due to
the presence of impurities in jute fibre that restricts the reaction between the glycine compound and jute fibre.
However, ATG jute yarns show slightly extended peaks at∼1540 cm−1 and∼570 cm−1, which is possibly due to
the formation of an amide bond between the amine groups of glycine and carboxylic acid groups of jutefibres.
Such observation is further supported by the elimination of the carboxylic ester peak at∼1732 cm−1 after glycine
treatment. In addition, the peak at 570 cm−1 indicates the formation ofN–C=Obending [34] again possibly due
to the interaction between amine functional groups of glycine and carboxyl groups of jute fibres, (figure 2(g))
Furthermore, the broadening of the peak at∼3200 cm−1may be due to the formation of hydrogen bond
between the functional groups of glycine and alkali-treated jute fibres.
The thermal gravimetric analysis (TGA) ofUT and treated jute yarns showup to 4%–5%mass loss at∼100
oC, which indicates the evaporation of water presents in jute fibre (up to 15%) [6]. UT yarns showed two
decomposition peaks at∼298 oC and∼349 oC,which are related to the de-polymerization of hemicelluloses, and
the decomposition of cellulose after heating, respectively [30]. However, AT jute yarns show a reduction in the
onset decomposition temperature to∼272 °Cand increment in the end-set decomposition to∼356 °C
(figure 2(h) andTable S3, Supporting Information), maybe due to the removal of polysaccharides, and the
increment of crystallinity for the alkali-treated AT jute yarns [6]. In addition, the higher percentage of residues in
the AT yarns indicate the improvement of thermal stability of thefibre[35]. BothATGandUTGyarn show
significant improvement in the on-set and end-set decomposition temperature of the jute yarns. For example,
ATGyarns exhibit an onset temperature of∼306 oC and an end-set decomposition temperature of∼361 oC
(figure 2(h)). Such improvement in the decomposition temperatures is related to the improvement of
crystallinity of jute fibre after the reaction taking place between the glycine and cellulose of jute fibres.
Furthermore, the derivatives of TGA curves for untreated and treated jute yarns show three peaks, where the
first peak at 290 °C indicates the onset of decomposition offibre; the second peak at 345 °C indicates the
decomposition of hemicellulose and celluloses, and the third peak at 440 °C indicates the presence of
polysaccharides in the fibre (figure 2(i)). After these peaks, the stability in the curve presents the percentage of ash
after the decompositions [36]. For ATGyarns all of the three peaks significantly improvewhich can also be
regarded as the reflection of thermal stability improvement of the yarns.
We also performedXPS analysis to quantify the atomic content of carbon, oxygen, nitrogen on the fibre
surfaces, and theC/O ratio for different treatment conditions. XPS analysis shows that the untreated yarn (UT)
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Mater. Res. Express 8 (2021) 055503 M.Ashadujjaman et al
has a higher C/O ratio of∼3.93 (figure 4(a)) due to the abundance of natural binding components such as waxes,
lignin and hemicelluloses on the surface of untreated jutefibres. TheC/Oratio confirmed the agreement with
other natural reinforcing fibres like jute andflaxwere also found to be 5.45 and 4.03, respectively [6, 37]. After
alkali treatment (AT)C/Oratiowas reduced slightly to∼3.44 due to the decomposition of bindingmaterials
(waxes and hemicelluloses) on the jute fibre surface. C/Oratio reduces significantly to∼2.36 after glycine
treatment (ATG) on alkali-treated jutefibres, whichmay be due to the increase of oxygen and nitrogen-
containing functional groups on glycine-treated jute yarns, figure 4(a).
High-resolutionC1sXPS spectra of untreated and treated jute fibres show threemain peaks: C-Cbond
(∼284.5 eV), C−Oepoxy and alkoxy groups (∼286.4 eV), andC=Ocarbonyl groups (∼288 eV),figures 4(b)–(e).
The epoxy and alkoxy functional groupswere increased significantly after glycine treatment on untreated fibres,
which is similar to the results obtained in previous studies [5, 24].
3.3. Tensile properties
Jute yarns, usually brittle, show a sudden decrease in loadwhich corresponds to the failure strain of the yarn as
reported bymany other researchers whoworkedwith naturalfibres [6, 9, 33, 38]. To analyze the tensile
behaviour ofUT and surface treated-jute yarn, a single yarn tensile test was conducted. Figure 5 shows a large
variation in tensile properties which could be due to the variations in the fibrefineness. Therefore, 50 single yarn
tests for each type of treated and untreated jute yarnswere tested in this work. The values of tensile properties
(tensile strength,modulus and strain%)were statistically analyzed using a two-parameterWeibull statistical
distribution (Table S6, Supporting Information). Here, we optimize the alkali concentration, the glycine
percentage and the effects of pH for surface treatments of jute yarn. These results are listed in (Table S4,
Supporting Information). For alkali treatment, 0.5% concentrationwas found to themost effective in the case of
10 g l−1 glycine concentrations which is considered the best-suited glycine concentration in this study (see Table
S4, Supporting Information). The effects of glycine percentage on the alkali-treated jute fibrewere studied and
optimized as 10 g l−1 (Table S4, Supporting Information). The effect of pHon the tensile properties of optimized
glycine-treated (10 g l−1) jute yarns were studied in order to understand the intensity of interaction between the
glycinemoieties and cellulose functional groups at different pH levels. The neutral pH (7) of glycine solutions
was found to be good enough to improve the tensile properties of ATG jute yarns (Table S4, Supporting
Information). Based on the obtained results, here we used 0.5% alkali concentration and 10 g l−1 glycine
solutionwith pH (7) for AT,UTG andATG yarns. For tensile testing results, UT yarns show relatively lower
tensile strength of∼42MPa, the tensilemodulus of∼324MPa and tensile strain of∼7.7%,figures 5(d)–(f),
Figure 3.Possible interaction between the jutefibrewith sodiumhydroxide and glycine.
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Mater. Res. Express 8 (2021) 055503 M.Ashadujjaman et al
which is also an agreement with the previous studies related to natural fibres [20, 21]. These lowermechanical
properties ofUT ismainly due to thewaxy cementing layer on the fibre surface composed of lowmolecular
weight fats, lignin, pectin and hemicelluloses [6]. After alkali treatment the values of tensile strength, tensile
modulus and tensile strain increase to∼70MPa,∼290MPa and 9.7%, respectively for AT yarns (figure 5(d) and
Table S5, Supporting Information ). Though no improvement in tensilemodulus observed after alkali
treatment, however, the tensile strength and strain% increased by∼70%and∼26%, respectively, whichmay be
due to the improvement in the packing order of cellulose chains [39]. Alkali solutions are commonly used as a
scouring agent in textile processing to remove the impurities from the fibre surfaces and the hemicellulose
located in the interfibrillar region of thefibre[6, 33, 39]. As a result, an excessive number offibrillations is
occurred in that region, which enables the improvement in the packing order.
In addition, the orientation of the elementaryfibre located in the jute yarn can re-arrange themselves and
parallel along the length of the yarn during tensile loading (figure 2(b)). The alkali treatment on natural fibre
reduces the spiral shape of cellulosemicrofibrils that allow the re-arrangement of the cellulose chains and
improve the tensile properties of thefibre [39]. Similarly, the alkali treatment of abacafibre-enabled higher
tensile properties than the untreated one, due to the rearrangements of cellulosemicrofibril along the
longitudinal axis [40]. In addition, the alkali treatment canmake a better arrangement of the cellulose chain in
thefibrewhich is responsible for the release of internal strain that leads to improving the strength and strain%of
jutefibre [41]. Further glycine treatments on alkali-treated jute yarns improve tensile properties significantly
(Table S5, Supporting Information),figures 5(d)–(f). The tensile strength and strain%of AT jute yarns increase
from∼70MPa and∼0.7% to∼86MPa and 11.5% for ATG yarns, respectively, which are almost∼105%and
∼50% increment in strength and strain values respectively compared to theUT yarn. The enhancement in the
tensile strength is supported by the stress-strain curves forUT andATGyarns infigure 5(b), (c). The possible
reason for the improvement in the tensile properties of ATG yarn is related to the strong connection between the
AT jutefibres in the yarnwith the functional group of glycine via suitable chemical or physical bonding. The
proposed reactionmechanism is provided infigure 3. In addition, the abundance of oxygen functional group
and possible formation of hydrogen bonds have been byXPS and FTIR analysis (figures 4(e) and 2(g)). Thereby,
the amorphous region present in the jute fibre cellulose is reduced andmorefibrils can pack together to print in
the parallel direction to carrymore loads. This is in agreement with a previous study [25], where they treated
cellulosic cottonfibrewith glycine and found a significant increment in the tensile properties due to the bonding
Figure 4. (a)Wide-scanXPS spectra of untreated, alkali and glycine treated jute yarns; (b) high-resolution (C1s)XPS spectra of
untreated jute yarn; (c) high-resolution (C1s)XPS spectra of alkali-treated jute yarn; and (d) high-resolution (C1s)XPS spectra of
untreated and glycine applied jute yarn; (i) high-resolution (C1s)XPS spectra of alkali and glycine treated jute yarn.
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Mater. Res. Express 8 (2021) 055503 M.Ashadujjaman et al
between glycine and cellulosic fibres. In addition, glycine can form zwitterion, which is a compoundwith no
electrical charge since it has both positively and negatively charged functional groups. Interaction between the
glycinemoieties with the hydroxyl groups of jute fibre takes place in the amorphous region offibrewhich
renders in absorbingmore energy during themechanical loading of the fibreswhich ultimately improves the
overall tensile properties of ATGyarn [25, 41].
The improvedmechanical properties could also be described based on the SEM image observations found in
figure 2(f) of this studywhere an excellent fibre packing and the paralleled, fibrillated fibres interconnection
were achieved for ATGyarns. As a result, therewas no stress decay to print the fibre in the parallel direction
leading to improve stress carrying capacity of ATG yarn during tensile loading applications. BetweenATG and
UTGyarns, ATGyarns showed better tensile strength and strain properties, because ATG yarns containmore
hydroxyl groups for the alkali treatment which enables better interactionwith the functional groups of glycine
compared toUTGyarns. However, ATG yarns exhibited a lower tensilemodulus value, this is possibly due to the
newbonds formed in the ATG yarnswhich increases the fibrillar cohesion to enhance the strainwith respect to
the increase of stress (seefigure 5(e)). Stress-strain curves of ATGyarn showedmore improvement compared to
UT yarns (seefigure 5(c)).
Here, improvement in tensile properties of jute yarn is related to the better packing offibrils in the fibre due
to strong chemical interactions after glycine treatments. Besides this, we observe diameter of the yarns have
changed after glycine treatment which also resulted in improving tensile properties of jute yarn is also shown in
Figure 5. (a)Typical stress-strain curve ofUT, AT,UTG andATG single jute yarn, (b) stress-strain curve of untreated jute yarn, (c)
stress-strain curve of alkali glycine treated jute yarn, (d)The tensile strength of untreated and treated jute yarn; (e)The tensilemodulus
of untreated and treated jute yarn, (f)The tensile strain%of untreated and treated jute yarn, (g)Tensile strength versus diameter
distribution of untreated and alkali glycine treated jute yarn, (h) )Tensilemodulus versus diameter distribution of untreated and alkali
glycine treated jute yarn, and (i)Tensile strain versus diameter distribution of untreated and alkali glycine treated jute yarn.
9
Mater. Res. Express 8 (2021) 055503 M.Ashadujjaman et al
figures 5(g)–(i). This result can be supported from the SEMand optical image observations (figure 2(c) and (f))
that yarnwith a smaller diameter have reduced porosity and fewer impurities in the fibre.We conduct statistical
analysis to validate the data obtained after tensile experiments (see Table S6, Supporting Information).Weibull
statistical distributionwas performed to evaluate the scale parameter (α) and shape parameter (β) of the
scattered tensile results
Hereαpredicts the experimental results andβ indicates themodulus ofWeibull distributionmainly known
asWeibullmodulus. Higher the value inWeibullmodulus better the improvement in the scattering effect in the
results. Figures 6(a)–(f) shows theWeibull distribution for tensile strength,modulus and strain of jute yarns as
the probability of failure (figures 6(a)–(c)) and ln curve (figures 6(d)–(f)). It is seen that this statisticalmodel
provided an excellent fitting of the data for the tensile properties of the yarns.Moreover,Weibull distribution
calculated a reasonable numerical prediction of the experimental data, provided in (Table S6, Supporting
Information). It was found that tensile strength and strain values (scale parameter) of the yarnwere improved
after introducing the alkali and glycine treatments on jute yarn (ATG). In this case, both the probability of failure
and ln curves were seen to shift from left to right significantly whenATGyarns were comparedwithUT jute
yarns. TheWeibullmodulus was obtained from the ln curve of the untreated and treated yarns as shown in
(Table S6, Supporting Information). UT yarn showed relatively lower value inWeibullmodulus (∼3, 4.5 and 4.8,
Figure 6. (a)Tensile strength datafitted to a two-parameterWeibull probability distribution as a function of surface treatment; (b)
tensilemodulus datafitted to a two-parameterWeibull probability distribution as a function of surface treatment; (c) tensile strain
data fitted to a two-parameterWeibull probability distribution as a function of surface treatment; (d) ln curves ofWeibull parameter
plot distribution considering the tensile strength; (e) ln curves ofWeibull parameter plot distribution considering the tensilemodulus;
(f) ln curves ofWeibull parameter plot distribution considering the tensile strain; (g) SEM fracture of untreated jute yarn after tensile
test at X250magnification; (h) SEM fracture of alkali treated jute yarn after tensile test at X250magnification and (i) SEM fracture of
alkali glycine treated jute yarn after tensile test at X250magnification
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Mater. Res. Express 8 (2021) 055503 M.Ashadujjaman et al
for tensile strength, tensilemodulus and tensile strain respectively)due to the high scattering ofUT yarns linked
to the presence of impurities in thefibre located in the yarn.However, theWeibullmodulus was increased to 6.1
for tensile strength, 5.9 for tensilemodulus and 6.1 for failure strain of the ATG jute yarnwhich could be because
of the better bonding between the jute fibre and the glycine, as we discussed in the earlier sections of this work.
The higher value inWeibullmodulus for the jute yarnwas found in similar to synthetic fibres reported in the
literature. Chawla et al [42] experimented with the value of 4.6 for theWeibullmodulus of ceramic fibre,
whereas this study calculated theWeibullmodulus of 6.1 of ATGyarns which confirmed theweakest link in the
fibre caused byflaws present in thefibrewas reduced significantly after introducing alkali and glycine treatment
on jute yarns.
3.4. Fractographic study of jutefibre yarn
We investigated the fracture specimen of different treated jute yarns using SEM. In this investigation, we
observed that bundles ofmicro-fibrils are present in the yarnwhich can be seen infigures 6(g)–(i). In the case of
the broken specimen fromUT yarn, a very uneven fracture of jute fibre bundles with fibre pull-out from the skin
ofUT yarn is visible infigure 6(g). Thismight be due to the presence of impurities into the interfibrillar network
ofUT yarnwhich is also supported by other studies [6, 43]. Fibre splittingwas observed as the dominant fracture
featurewith a small amount offibre pull-out for AT yarns (see figure 6(h)). The dominance offibre splitting
might be related to the improvement in the crystallinity of AT jute fibres and removal of the hemicelluloses
which act as the stress concentration points of jute fibres. The brittle fracture occurred in the transverse direction
of theUTGyarns to some extent for the glycine treatment whereas in (figure S6, Supporting Information). ATG
yarn showed a vivid brittle fracture surface without any fibre pull-out (seefigure 6(i)). For ATGyarns, fibrils in
the yarnwere broken in the same order along the transverse direction indicating that the improved packing of
microfibrils createdwith both alkali and glycine treatments evenly distributed along the length of the fibre.
3.5. Comparative studywith the literature
A comparisonwas tried tomake in (Table S7, Supporting Information) for the tensile properties particularly on
tensile strength and strain observed between this study and other natural fibre based (flax, hemp and jute) yarns
studies reported in the literature. The studies of jute yarnmechanical properties are very limited in the literature.
A direct comparison is difficult as the experimental conditions in those studies are different from this study. In
addition, differentfibres have different constituents’ ratios, which have a direct impact on themechanical
properties. As found in the comparison, the alkali glycine treated jute yarns (ATG) showed an excellent and huge
improvement both in tensile strength and strain properties in this study compared to any other reported tensile
properties of jute yarns found in the literature.
4. Conclusions
In this study, aqueous glycine treatment was applied on untreated and alkali-treated jute yarns, and their
influences on the chemical, thermal,morphological andmechanical properties of jute yarnwere evaluated. The
results indicate an extremely positive effect of glycine treatment on jute yarn towards structural properties
improvement. Glycine treatment on alkali-treated jute yarns (ATG) brought a remarkable improvement by
almost∼105%and∼50% increment in tensile strength and strain properties respectively compared to
untreated jute yarns. The significant improvements in themechanical properties of newly developed glycine and
alkali-treated jute yarns (ATG) achieved in this workwill be helpful to develop the use of jute yarn-basedwoven
ormulti-axial textile architectures as reinforcing elements inmanufacturing natural plant-based composites for
structural applications.
Acknowledgments
The authors kindly acknowledgeUMC jutemills for supplying jute fibre to conduct this researchwork.
Data availability statement
The data that support thefindings of this study are openly available at the followingURL/DOI:https://doi.org/
10.21203/rs.3.rs-151073/v1.
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Mater. Res. Express 8 (2021) 055503 M.Ashadujjaman et al
Funding information
This research did not receive any external funding.
ORCID iDs
Forkan Sarker https://orcid.org/0000-0002-6504-6822
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