Original Article

Journal of Reinforced Plastics

and Composites

Novel Aloe Vera fiber reinforced 0(0) 1–13

! The Author(s) 2016
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DOI: 10.1177/0731684416652739
Development and characterization jrp.sagepub.com

Saurabh Chaitanya and Inderdeep Singh

Abstract
In the current research enterprise, behavior of novel bio-composites incorporating Aloe Vera fibers in biopolymer matrix
(polylactic acid) has been experimentally examined in comparison to Sisal fiber reinforced bio-composites. These bio-
composites were melt blended using single screw extruder prior to injection molding. The effect of fiber weight fraction
(10–20–30%) and fiber surface modification on mechanical behavior of developed bio-composites was investigated.
Alkaline treatment using sodium hydroxide concentration of 5% was used for fiber surface modification. Both alkali
treated and raw fibers were characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis and
scanning electron microscope. Thermal stability of the fibers improved after alkaline treatment. The mechanical char-
acteristics of developed bio-composites exhibited an improvement with increasing fiber concentration. Alkaline treat-
ment of fibers further improved the tensile, flexural and compressive properties of developed bio-composites, while
their impact properties declined compared to raw fiber reinforced bio-composites. Moreover, from the results, it is
evident that the characteristics of Aloe Vera fiber reinforced bio-composites are comparable to Sisal fiber reinforced bio-
composites and the developed bio-composites have the potential to be used in various automotive, furniture and
architectural applications.

Keywords
Aloe Vera fiber, Sisal fiber, injection molding, thermal degradation, mechanical characterization, biocomposites

starch rich material.1–3 Owing to renewable and bio-

Introduction
degradable nature of PLA, it is often termed as
Squandered use of petroleum-derived polymers and ‘‘cradle-to-grave’’ material. At present, PLA is widely
polymer-based composites in the last few decades has being used by the packaging industry for the produc-
posed serious environmental concerns throughout the tion of biodegradable packing material.4 Nature Works
globe, citing its non-renewable and non-degradable LLC, Blair, USA is one of the largest manufacturers of
nature. Hence, an exigency in developing green prod- PLA in the world offering a family of commercially
ucts for a greener and sustainable future led to the available biopolymers with an annual production of
development of bio-composites consisting of a biopoly- 150,000 metric tons. PLA being developed has a
mer matrix reinforced with natural fibers. negligible carbon foot print as well as it is developed
Biopolymers have the ability to degrade naturally in
landfills or under certain forced environmental condi-
tions. For engineering applications, polylactic acid
(PLA) is one of the most promising and commercially Department of Mechanical and Industrial Engineering, Indian Institute of
available biopolymer today. PLA is a natural plant Technology Roorkee, Uttarakhand, India
sugar-derived sustainable biopolymer which is renew-
Corresponding author:
able as well as biologically degradable. It is a thermo- Inderdeep Singh, Department of Mechanical and Industrial Engineering,
plastic aliphatic polyester which can be derived from Indian Institute of Technology Roorkee, Uttarakhand 247667, India.
corn, rice, sugar cane, sugar beet, sweet potato or any Email: inderfme@iitr.ac.in

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2 Journal of Reinforced Plastics and Composites 0(0)

from amply available starch rich resources.5,6 PLA pos- Aloe Vera (Aloe barbadensis Miller) has been used as
sesses higher strength and stiffness as compared to a medicinal plant for curing skin and other ailments
other renewable resource-derived biopolymers. since thousands of years. It is also widely used by cos-
However, high cost, low heat deflection temperature metic, food and pharmaceutical industries worldwide
and low elongation at break (brittle nature) of PLA is leading to its widespread cultivation.30 Aloe Vera
restricting its widespread usage in engineering applica- leaves are cut to extract Aloe Vera gel from them, leav-
tions.7,8 Incorporation of synthetic and natural fibers ing the outer leaf shell as a byproduct. Aloe Vera fibers
into PLA is explored as an effective way to overcome are thus easily extracted from these leftover leaf shells
these shortcomings to an extent.9–11 However, the use using retting process and are at present, majorly being
of synthetic fibers like glass or carbon fiber is costly and used by small textile units in southern India.31 Aloe
render partially degradable and non-recyclable nature Vera fibers are also lucrative from farmer’s point of
to PLA-based composites. Hence, the use of natural view as it gives them additional economic benefit.
fibers as a reinforcement becomes lucrative from eco- Sisal (Agave sisalana) plant is widely cultivated in
nomic as well as environmental perspective. many parts of the world for its fibers. Both Aloe Vera
Natural fibers are a renewable resource, light in and Sisal can be easily cultivated and are low mainten-
weight having high specific strength and stiffness, bio- ance plants which have the ability to survive through
logically degradable and abundantly available at low tough weather conditions in a rocky terrain. Although,
cost. Natural fibers are also processing friendly as Sisal plant is an Aloe Vera lookalike, but in reality,
they are non-abrasive as well as hypoallergenic.12–15 these plants are very different in nature. While, the
Natural fibers can be derived from plants, animals use of short Sisal fibers as a reinforcement into polymer
and minerals. Plant-derived natural fibers are cellulose composites has been investigated by few researchers,
based and are generally classified according to the part the use of Aloe Vera fibers as a reinforcement is yet
or type of plant from which they are extracted (as to be explored.
shown in Figure 1). Plant-derived natural fibers are In case of natural fibers, the presence of hemicellu-
also the most widely used natural fibers for fabrication lose, lignin and other waxes on the fiber surface hinders
of bio-composites. Several studies incorporating nat- the formation of an efficient bond between fibers and
ural fibers such as Jute,16,17 Hemp,18,19 Sisal,20,21 the polymer. Several chemical based, fiber surface
Banana,22 Coir,23 Bamboo,24 Flax,25,26 Kenaf27 and modification techniques such as alkaline treatment,
Abaca28,29 have been reported, exploring their potential silane treatment, acetylation treatment, peroxide treat-
as a reinforcement into different polymer matrices. ment and benzoylation treatment have been studied in

Figure 1. Classification of plant-derived natural fibers.

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Chaitanya and Singh 3

the past.32 Alkaline treatment (using NaOH) of natural effect of alkaline treatment of novel Aloe Vera fibers
fibers is the most extensively used treatment for deligni- has been investigated on the behavior of developed bio-
fication of natural fibers. Alkaline treatment is expected composites. The effect of fiber content on the mechan-
to remove the lignin and waxes off the fiber surface as ical behavior of developed bio-composites has also been
well as roughen it, enabling better interlocking and experimentally investigated.
bonding between fibers and the matrix.33–35 Alkaline
treatment of fibers beyond optimum level has been
reported to decrease the strength of the bio-compo-
Materials and methods
sites.32,34 This delignification technique substitutes the A new high performance, injection molding grade of
hydroxyl groups (OH group) present in the natural PLA (Ingeo 3260HP) was procured as a sample quan-
fibers with –ONa group as represented in equation (1). tity for academic research from NatureWorksTM LLC,
Alkaline treatment using NaOH has been reported to Blair, USA. The polymer was supplied in pellet form
significantly enhance the degradation rate of bio- having a density and melt flow rate of 1.24 g/cm3 and
composites.36 65 g/10 min (210 C, 2.16 kg), respectively. No compati-
bilizer was added in PLA-based bio-composites as
Natural Fiber  OH þ NaOH ¼ Natural Fiber  O Naþ natural fibers as well as PLA are hydrophilic in
þ H2 O þ impurities nature and have affinity for each other.2,8,29 PLA pellets
being hygroscopic were dried in a hot air oven at 60 C
ð1Þ for 6 h prior to processing.
PLA and PLA-based bio-composites can be conveni- Commercially available Aloe Vera fibers were pro-
ently processed via traditional polymer processing cured from Anakaputhur Weaver Association,
routes such as melt mixing,7 compression molding,20 Chennai, India. The fibers were supplied in strand
injection molding2 and resin transfer molding.37 form. Aloe Vera fibers were then chopped to a length
Injection molding is, however, considered as the most of 5 mm. Sisal fibers were supplied in chopped form
appropriate processing route by the plastic industry to (5 mm) by Women’s Development Organization,
fabricate small- to medium-sized parts rapidly with pre- Dehradun, India. Chopped Aloe Vera and Sisal fibers
cision. Moreover, to commercialize bio-composites, were washed with hot water at 80 C to remove undesired
rapid processing routes like injection molding are pith/dirt and any parenchyma cells present on the fiber
advisable and more economical compared to other surface. The fibers were then dried in a hot air oven for
polymer processing routes.38 However, injection mold- 8 h at 100 C to remove excess moisture.
ing process using a commercial scale injection molding
machine to develop bio-composites has not been inves-
tigated much.8
Fiber surface modification
For bio-composites to be used for varying commer- Fiber surface modification was done using alkaline
cial applications, mechanical characterization of the delignification method. Sodium hydroxide (NaOH)
developed bio-composites is inevitable. Mechanical was supplied in pellet form by Sisco Research
properties in terms of tensile, flexural and impact Laboratories Pvt. Ltd., India. Aloe Vera and Sisal
strength have been widely studied in the recent past. fibers were soaked in sodium hydroxide (5% NaOH
However, to the best of author’s knowledge, studies (m/v)) solution for 5 h. Fiber-to-liquid ratio of 1:15
on compressive properties of short fiber reinforced (w:w) was used. The fibers were then filtered and
PLA-based bio-composites are not available in litera- washed under running distilled water to neutralize the
ture. Baets and colleagues39 recently reported the com- fibers and restore a pH of 7. Fibers were then dried in a
pressive properties of flax, coir and bamboo fiber hot air oven at 100 C for 8 h. The Treated Aloe Vera
reinforced epoxy-based composites. Bos et al.40 exam- Fibers (TAF) and Treated Sisal Fibers (TSF) are
ined the effect of fiber surface modifications on the labeled as TAF and TSF, respectively in the following
compressive behavior of unidirectional flax fiber rein- sections. Similarly, Untreated Aloe Vera Fibers (UAF)
forced epoxy-based composites. and Untreated Sisal Fibers (USF) are labeled as UAF
Hence, in the present experimental investigation, the and USF, respectively.
feasibility of using novel Aloe Vera fibers derived from
the waste, as a reinforcement into PLA matrix using
injection molding process has been examined. For com-
Fourier transform infrared spectroscopy
parative analysis, the mechanical properties in terms of Fourier transform infrared spectroscopy (FTIR) ana-
tensile, flexural, compressive and impact strength of the lysis of the fibers was done to determine the effect of
Aloe Vera fibers reinforced bio-composites were com- alkaline treatment, using FTIR spectrometer (Thermo
pared with Sisal fiber reinforced bio-composites. The Nicollet, Model Magna 760). The fibers were grinded

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4 Journal of Reinforced Plastics and Composites 0(0)

into a powder form and mixed with KBr in the ratio of Table 1. Nomenclature of developed PLA-based
1:200 by weight. The mixture, thus, obtained was biocomposites.
pressed to form pellets for testing. The FTIR spectra
Fiber
were recorded in the range of 4000 to 500 cm1 in the Fiber concentration (%) Label
transmittance mode.
UAF 10 PL/UAF/10
UAF 20 PL/UAF/20
Thermal characterization
UAF 30 PL/UAF/30
Thermal characterization of treated and untreated fibers TAF 10 PL/TAF/10
was performed using a Thermo-gravimetric Analyzer TAF 20 PL/TAF/20
(Make: EXSTAR 6300). Thermo-gravimetric analysis TAF 30 PL/TAF/30
(TGA) tests were performed at a heating rate of 10 C/ USF 10 PL/USF/10
min (up to a maximum temperature of 550 C) under
USF 20 PL/USF/20
nitrogen atmosphere with a gas flow rate of 200 ml/min.
USF 30 PL/USF/30
TSF 10 PL/TSF/10
Bio-composite fabrication TSF 20 PL/TSF/20
Dried PLA pellets and fibers were melt blended at a TSF 30 PL/TSF/30
temperature of 180 C using a single screw extruder.
The extrudate in the form of a strand of 4 mm diameter
was cooled in water and subsequently pelletized into determined by placing the flexural test specimens
5 mm long pellets using a pelletizer. Fiber reinforced under flexural loading using a three-point bending fix-
PLA pellets, thus, obtained were dried in hot air oven ture. The flexural tests were performed in accordance to
at 100 C for 8 h prior to injection molding. Dried fiber ASTM D790-10. During flexural test, a span length of
reinforced pellets were then injection molded using a 64 mm was chosen for 4 mm thick specimen, and the
commercial scale injection molding machine (Make: tests were carried at crosshead speed of 2 mm/min.
Electronica-Endura-60) to fabricate test specimens in Compressive strength of the developed bio-compo-
accordance to respective testing standards. sites was determined in accordance to ASTM D3410
Bio-composites incorporating Aloe Vera and Sisal using a modified University of California, Santa
fibers of varying fiber content (10%, 20%, 30% and Barbara (UCSB) fixture.41 The UCSB fixture does not
40% by weight) were developed during pilot experi- require additional tabs, eliminating the errors occurring
mentation. However, beyond 30 wt.% of fibers, high due to improper or flawed tab installation. Moreover, it
volume of fibers resulted in agglomeration of fibers, ensures efficient loading of the specimen, subjecting the
leading to feeding and blending difficulties during pro- test specimen to combined end and side loading; 4 mm
cessing. Hence, test specimens incorporating varying thick, compression test specimens were clamped in
fiber weight fraction up to 30% were developed. The UCSB fixture and placed between two flat plates on
nomenclature of bio-composites developed using trea- an UTM. The specimens were compressed at a cross-
ted and untreated fibers with varying fiber concentra- head speed of 1 mm/min.
tion is given in Table 1.
Impact testing. The resistance to impact of the developed
bio-composites was determined in accordance to
Mechanical characterization ASTM standard for Notched-Izod Impact Test
Tensile, flexural and compression testing. Tensile, flexural (ASTM D256-10) using a low energy impact tester
and compression tests were performed on universal (Make: Tinius Olsen-IT504).
testing machine (UTM) (Make: Instron-5982). Tensile
properties in terms of tensile strength and modulus of
the developed bio-composites were determined in
Morphological examination
accordance to ASTM D3039M-14. During tensile test, Morphological examination of treated and untreated
to efficiently calculate the tensile modulus, an extens- fibers was performed using a scanning electron micro-
ometer (Make: Instron) having a span length of 50 mm scope (SEM) (Make: LEO 1550). The fractographs of
was used to measure strain at a crosshead speed of the failed tensile and impact test specimens of the devel-
1.5 mm/min. oped bio-composites were also observed using SEM.
Flexural properties in terms of flexural strength and The samples to be examined were gold sputtered prior
modulus of the developed bio-composites were to SEM examination.

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Chaitanya and Singh 5

Results and discussion (around 3424 cm1) representing free hydroxyl groups
broadened (Figure 2(b) and (d)), indicating toward an
Effect of fiber surface modification increased availability of hydroxyl groups on the fiber
Aloe Vera and Sisal fibers were characterized before surface for bonding with the matrix.43 The absorption
and after alkaline delignification treatment. FTIR spec- peaks around 1250 and 1739 cm1 completely dis-
troscopy, morphological examination and thermogravi- appeared from the FTIR spectra of treated fibers.
metric analysis of treated and untreated fibers were This disappearance of peaks may be attributed to the
conducted. removal of non-cellulosic contents such as hemicellu-
lose and waxes from the fiber surface.44,45
FTIR analysis of fibers
Morphology of fibers
Figure 2(a) to (d) represents a comparative FTIR spec-
trum of untreated and treated Sisal and Aloe Vera Modified surface of treated fibers was observed using
fibers. The peaks found around 3424 cm1 represent SEM micrographs depicted in Figure 3. In Figure 3(a)
characteristic absorption peaks of free hydroxyl and (c) representing UAF and USF, respectively, the
groups (OH stretching) present in natural fibers. presence of parenchyma cells and other non-cellulosic
The peaks at 2920 cm1 corresponding to characteristic content can clearly be observed at the fiber surface,
–CH stretching of methyl and methylene groups were rendering it a rough surface appearance. However,
observed for both treated and untreated fibers.42 The post alkali treatment, the fiber surfaces depicted in
absorption peaks around 1250 and 1739 cm1 asso- Figure 3(b) and (d) appeared to be cleaner with
ciated with CO and C¼O stretching, respectively, increased aspect ratio compared to untreated fibers.22
indicating the presence of non-cellulosic materials This increased aspect ratio is a result of fibrillation of
such as hemicellulose, pectin and lignin were observed fibers which is caused by delignification and removal
for both UAF and USF. However, post alkaline treat- of parenchyma cells and other impurities from the
ment, it was observed that the absorption peaks fiber surface.46 These observations substantiate the

Figure 2. FTIR spectrum of (a) USF, (b) TSF, (c) UAF, and (d) TAF.

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6 Journal of Reinforced Plastics and Composites 0(0)

Figure 3. SEM micrographs depicting (a) UAF, (b) TAF, (c) USF and (d) TSF.

observations made during FTIR analysis in the previ- from fiber surface after alkali treatment. Also, an
ous section. increase in the degradation starting temperature for
second step of thermal degradation was observed for
TAF (225 C) compared to UAF (185 C) widening the
Thermogravimetric analysis of fibers processing window for TAF. Similar observations were
Derivative thermogravimetric (DTG) curves of also recorded from thermographs of Sisal fibers.
untreated and treated Aloe Vera and Sisal fibers are TGA results of untreated and treated fibers in terms
depicted in Figure 4. The first step of weight loss for of degradation temperature (T5, T25, T50 and T75) at
all the fibers occurred between 45 C and 100 C due to different weight loss levels (5%, 25%, 50% and 75%)
loss of absorbed moisture by the fibers. The maximum are given in Table 2. It can be observed that the deg-
degradation rate of TAF was observed around 352 C radation temperatures (at all selected levels) of UAF
while for UAF it was observed at 341 C. This degrad- and USF are lower than the degradation temperatures
ation is attributed to pyrolysis of cellulose within the of TAF and TSF, respectively. This indicates toward an
fibers.47 A degradation peak was observed around improvement in the thermal stability of fibers post
215 C and 292 C for UAF and USF, respectively. alkali treatment.
This peak depicts the pyrolysis of non-cellulosic sub-
stances such as hemicellulose and waxes present in the
Mechanical characterization
fibers.45 However, this peak was found absent from
DTG thermographs of TAF and TSF, indicating Tensile and flexural properties. Comparative graphs
toward effective removal of non-cellulosic substances depicting tensile strength and modulus of treated and

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Chaitanya and Singh 7

Figure 4. DTG thermographs of Aloe Vera and Sisal fibers.

stiffness is an evidence of efficient stress transfer

Table 2. TGA results of Aloe Vera and Sisal fibers. between stiffer fibers and the matrix,7 along with
better distribution of natural fibers within the
Degradation temperature ( C)
matrix.8,48 Moreover, post alkali treatment, the
Specimen T5 T25 T50 T75 removal of non-cellulosic content from the fiber surface
leads to increased molecular orientation and better
UAF 72.5 285.1 336.2 429 packing of the cellulose chains. Cellulosic fibers
TAF 76.2 320.5 349.7 440.6 having high molecular orientation compared to less ori-
USF 77.1 305.2 345.2 426.0 ented fibers exhibit significant improvement in the
TSF 77.4 324.6 353.1 448.3 modulus.49
The tensile strength of PL/UAF/10 and PL/USF/10
bio-composites incorporating untreated fibers margin-
untreated fiber reinforced bio-composites with varying ally declined compared to tensile strength of neat PLA
fiber concentration are represented in Figure 5(a) and (43.9 MPa). However, with an increase in fiber concen-
(b), respectively. It can be clearly observed that the tration the tensile strength improved. Maximum tensile
tensile modulus significantly improved for all the devel- strength was observed for fiber weight fraction of 30%,
oped bio-composites with increasing fiber concentra- for both Aloe Vera and Sisal fiber reinforced bio-
tion. The tensile modulus for untreated fiber composites. Compared to neat PLA, tensile strength
reinforced PL/UAF/30 and PL/USF/30 bio-composites of untreated fiber reinforced PL/UAF/30 and PL/
surged by 177% and 237.9%, respectively, compared to USF/30 bio-composites imperceptibly improved by
neat PLA (1997.4 MPa). An elevated modulus clearly 5.3% and 12.1%, respectively. However, after the
indicates toward an increased stiffness of the developed incorporation of alkali treated fibers into PLA, the
bio-composites, due to the addition of Aloe Vera and bio-composites exhibited significant improvement in
Sisal fibers. Moreover, with the incorporation of alkali the tensile strength of PL/TAF/30 and PL/TSF/30
treated fibers, the tensile modulus of PL/TAF/30 and bio-composites by 18.1% and 14.8% compared to ten-
PL/TSF/30 bio-composites further increased by 28.6% sile strength of PL/UAF/30 and PL/USF/30 bio-com-
and 13.7% compared to tensile modulus of PL/UAF/30 posites, respectively. Flexural strength of developed bio-
and PL/USF/30 bio-composites, respectively. The flex- composites also improved with increasing fiber concen-
ural modulus of the developed bio-composites also tration for both untreated and treated fibers reinforced
increased with the addition of Aloe Vera and Sisal bio-composites (Figure 6 (a)). Compared to neat PLA,
fibers. An improvement in the flexural modulus of the flexural strength of PL/UAF/30 and PL/USF/30
bio-composites incorporating treated fibers, PL/TAF/ bio-composites surged by 27.5% and 40.3%, respect-
30 and PL/TSF/30 by 114% and 135% was observed ively. The incorporation of treated fibers resulted in fur-
(Figure 6 (b)), compared to flexural modulus of neat ther improvement in the flexural strength, which
PLA (3395.7 MPa). The significant improvement in the increased by 21.7% and 19.3% for PL/TAF/30 and

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8 Journal of Reinforced Plastics and Composites 0(0)

Figure 5. Tensile properties of PLA-based bio-composites; (a) tensile strength and (b) tensile modulus.

Figure 6. Flexural properties of PLA-based bio-composites; (a) flexural strength and (b) flexural modulus.

PL/TSF/30 bio-composites. Alkaline treatment leads to developed bio-composites increased with increasing
removal of weak and amorphous non-cellulosic content fiber concentration. The compressive strength for PL/
which binds the fibers into bundles.50,51 Removal of UAF/30 and PL/USF/30 bio-composites increased by
these binders leads to fiber fibrillation resulting in an 15.1% and 20.8% compared to compressive strength of
increased fiber aspect ratio and surface area available neat PLA (81.4 MPa). An increase in the compressive
for bonding with the matrix. An increased surface area strength of untreated fiber reinforced bio-composites
ensures better wettability of the fibers by the matrix was observed, despite low interfacial adhesion between
leading to an efficient load transfer between the the fibers and the matrix. During compression of nat-
two.52,53 Also the fibrils obtained post alkali treatment ural fiber reinforced polymer composites, fibers under
are more likely to arrange themselves along the direc- compressive load tend to buckle; however, the matrix
tion of applied load compared to untreated fiber bundle surrounding the fibers strain hardens upon yielding,
ensuring improved load carrying capacity.49 preventing the fiber buckling and hence, improving its
load carrying ability.54 Moreover, during compression,
Compressive strength. The compressive strength values of critical micro-cracks which appear early in brittle PLA
developed bio-composites are depicted in Figure 7. It are presumably closed, delaying the specimen failure.39
can be observed that the compressive strength of The incorporation of alkali treated fibers further

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Chaitanya and Singh 9

Figure 7. Compressive strength of PLA-based bio-composites. Figure 8. Impact strength of PLA-based bio-composites.

enhanced the compressive strength of treated fiber rein- strength of PL/UAF/30 and PL/USF/30 bio-compo-
forced bio-composites. Compressive strength for PL/ sites, respectively. During impact test, a large amount
TAF/30 and PL/TSF/30 bio-composites increased by of energy is dissipated when a crack meets the fiber. If
19.3% and 9.4% compared to untreated fiber rein- the interfacial bonding between the fiber and the matrix
forced PL/UAF/30 and PL/USF/30 bio-composites, is good (as in case of treated fiber reinforced bio-
respectively. This increased ability to carry more load composites), the fiber breaks, dissipating low energy.
under compression may be attributed to the improved However, if the interfacial bonding is medium or low
interfacial strength with the removal of non-cellulosic (as in case of untreated fiber reinforced bio-
content from the fiber surface.55 Moreover, alkali treat- composites), increased number of fiber pullouts occur
ment apart from improved chemical binding is assumed instead of fiber breakages. As a consequence of this
to give rise to sites of mechanical interlocking,56 leading phenomenon, the path length of the crack is signifi-
to an increased matrix-fiber interpenetration resulting cantly enhanced leading to increase in the amount of
in an increase in the compressive strength values. energy required to break the sample.29 Hence, during
this experimental investigation, it was observed that,
Impact strength. Impact strength of bio-composites relies comparatively lower interfacial bonding was helpful
majorly on factors such as individual and combined in dissipating more energy due to fiber pullouts.
toughness of matrix and fiber, matrix-fiber adhesion
and distribution of the fibers within the matrix.
Morphological examination of fractured surfaces
Energy during fracture of the specimen subjected to
impact load is absorbed mainly during fiber fracture, The SEM images depicting fractographs of failed ten-
fiber-matrix debonding and fiber pullouts.57,58 The sile test specimens of neat PLA, PL/UAF/30 and
notched impact strength values of the developed bio- PL/USF/30 are shown in Figure 9(a)–(c), respectively.
composites are depicted in Figure 8. Compared to neat Figure 9(a) depicts a flat surface failure, indicating brit-
PLA, the impact strength improved for all the devel- tle nature of neat PLA. PL/UAF/30 fractographs
oped bio-composites and increased with increasing fiber depict a failure due to fiber pullouts as pulled out
concentration. The impact strength of PL/UAF/30 and fibers as well as fiber pullout regions are observed
PL/USF/30 improved by 165.4% and 142.3%, respect- throughout the fractured surface, pointing toward low
ively, compared to neat PLA (16.3 J/m). Similar interfacial bonding between UAF and PLA matrix.
improvements in impact strength of injection molded, However, in case of PL/USF/30 bio-composite, the fail-
Sisal and Kraft fibers reinforced PLA bio-composites ure mode was similar but fewer fiber pullouts along
were reported by Gonzalez et al.59 with some fiber breakages are observed, indicating
However, in case of treated fiber reinforced bio- toward imperceptibly better adhesion between the
composites, a decrease in the impact strength was untreated Sisal fiber and PLA compared to PL/UAF/
observed for all the fiber loadings. The impact resist- 30 bio-composites.
ance of PL/TAF/30 and PL/TSF/30 bio-composites SEM micrographs depicting fractographs of failed
declined by 27.2% and 13.2% compared to impact tensile test specimens of treated fiber reinforced

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10 Journal of Reinforced Plastics and Composites 0(0)

Figure 9. Tensile test fractographs of (a) PLA, (b) PL/UAF/30 and (c) PL/USF/30.

Figure 10. Tensile test fractographs of (a) PL/TAF/30 and (b) PL/TSF/30.

PL/TAF/30 and PL/TSF/30 bio-composites are shown Figure 11. Figure 11(a) and (c) depicts fractured
in Figure 10(a) and (b), respectively. It can be clearly micrographs of untreated fiber reinforced PL/UAF/
observed that significantly better fiber matrix adhesion 30 and PL/USF/30 bio-composites, respectively, in
existed between treated fibers and PLA matrix, result- which a lot of fiber pullouts can be observed after
ing in fiber breakages during tensile fracture. Hence, impact failure. Fiber pullouts indicate toward low or
fiber surface treatment using alkaline solution was medium interfacial adhesion between the untreated
found to be effective in improving the interfacial adhe- fibers and the PLA matrix, due to the presence of
sion between the fibers and PLA matrix, leading to waxes and other non-cellulosic content on the fiber
improvement in tensile properties.60 surface. In Figure 11(b) and (d), depicting treated
SEM micrographs of fractured impact test speci- fiber reinforced PL/TAF/30 and PL/TSF/30 bio-
mens of developed bio-composites are shown in composites, respectively, a lot of fiber breakages

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Chaitanya and Singh 11

Figure 11. Impact test fractographs of (a) PL/UAF/30, (b) PL/TAF/30, (c) PL/USF/30 and (d) PL/TSF/30.

and a few fiber pullouts can be observed, indicating . An optimum fiber concentration of 30 wt.% for both
toward improved interfacial adhesion between fibers treated and untreated fiber reinforced bio-compo-
and the matrix. However, this improved adhesion, sites was recorded during experiments.
leads fibers to break, dissipating less energy compared . Beyond 30 wt.% of fiber reinforcement, it became
to energy dissipated during fiber pullouts as discussed difficult to feed the fibers and process the bio-com-
earlier. posites using extrusion–injection molding process.
. Mechanical performance in terms of tensile, flexural
and compressive behavior of the developed bio-com-
Conclusions posites improved after alkaline treatment of fibers.
In the present experimental investigation, novel Aloe However, the incorporation of treated fibers caused
Vera and Sisal fibers have been used to reinforce PLA the impact strengths of bio-composites to decrease as
matrix using extrusion–injection molding process. An compared to the untreated fiber reinforced bio-
exhaustive characterization of the fibers (treated and composites.
untreated) as well as the developed bio-composites
has been conducted. The following conclusions can be From the present investigation, it can be further con-
drawn: cluded that the properties of Aloe Vera and Sisal fiber
reinforced bio-composites are comparable. Hence, Aloe
. FTIR and morphological analysis (SEM) confirmed Vera fibers have a strong potential to be used as a
the partial dissolution of hemicellulose and lignin reinforcement in polymer matrix composites used in
from the fiber surface. Thermal stability of both various structural and non-structural applications.
Aloe Vera and Sisal fibers improved post alkaline
treatment. Declaration of Conflicting Interests
. It was found that the incorporation of both types of The author(s) declared no potential conflicts of interest with
fibers (Aloe Vera and Sisal) significantly improved respect to the research, authorship, and/or publication of this
the mechanical behavior of neat PLA. article.

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12 Journal of Reinforced Plastics and Composites 0(0)

Funding 15. Faruk O, Bledzki AK, Fink HP, et al. Biocomposites

The author(s) received no financial support for the research, reinforced with natural fibers: 2000–2010. Prog Polym
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