Sugar Palm Tree: A Versatile Plant and Novel Source for Biofibres, Biomatrices, and Biocomposites
Sugar Palm Tree: A Versatile Plant
and Novel Source for Biofibres,
Biomatrices, and Biocomposites
J. Sahari1*, S.M. Sapuan1,2,3, E.S. Zainudin2,3, and M.A. Maleque4
1Laboratory
of Advanced Materials and Nanotechnology, Institute of Advanced
Technology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
2Department of Mechanical and Manufacturing Engineering, Universiti Putra Malaysia,
43400 UPM Serdang, Selangor, Malaysia
3Laboratory of Biocomposite Technology, Institute of Tropical Forestry and Forest
Products, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
4Department of Manufacturing and Materials Engineering, International Islamic
University Malaysia, 53100 Kuala Lumpur, Malaysia
Received: 19 January 2012, Accepted: 23 March 2012
SUMMARY
The use of green materials is a vital component in tackling problems of
environmental protection. At the same time, these materials help solve problems
arising from the shortage and undegradable nature of petroleum-based materials.
Among the numerous green material sources in Malaysia, the sugar palm tree
is a versatile plant that can produce biofibres, biomatrices, and biocomposites
for a wide range of applications. This paper focuses mainly on the significance
of the unutilised part of sugar fibres, as they are highly durable and easy to
process. Besides discussing recent advances in research into sugar palm fibres
and their biocomposites, this paper also addresses recent advances in research
into the development of new biodegradable polymers derived from sugar palm
starch. Fibre surface treatment, product development, and efforts to enhance
the properties of sugar palm fibre composites are also considered.
Keywords: Sugar palm tree; Biofibres; Biomatrices; Biocomposites
INTRODUCTION
The sugar palm tree is a member of the Palmae family and naturally a forest
species [1]. It belongs to the subfamily Arecoideae and tribe Caryoteae [2, 3].
*Corresponding
author.
E-mail address: [email protected]
©Smithers
Rapra Technology, 2012
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J. Sahari, S.M. Sapuan, E.S. Zainudin, and M.A. Maleque
Hyene [4] reported that sugar palm has around 150 local names, indicating its
multiple uses by the villagers. These names include Arenga pinnata, Areng palm,
black fibre palm, gomuti palm, aren, irok, bagot, and kaong [5]. In Malaysia, it
is known as either enau or kabung. The sugar palm plant was originally from
Assam, India, and Burma in the Indian subcontinent. It originates from an
area covering South-East Asia up to Irian Jaya in the east of Indonesia. The
sugar palm tree is available across the nation of Malaysia, Indonesia, and
other South-East Asian countries. Its is one of the most diverse multipurpose
tree species in culture. Figure 1 shows the sugar palm tree.
Figure 1. Sugar palm tree
There are several taxonomic names for sugar palm, such as Saguerus
rumphii, Arenga saccharifera Labill, etc. However, in 1917, Merill, through
the International Congress of Botany in Vienna, officially renamed it Arenga
pinnata [6]. Palms are among the oldest flowering plants in the world. For
centuries, many palm species have been tapped throughout the tropical
world in order to produce fresh juice (sweet toddy), fermented drinks (toddy,
wine), syrup (honey), brown sugar (jaggery), and refined sugar. Redhead [7]
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Sugar Palm Tree: A Versatile Plant and Novel Source for Biofibres, Biomatrices, and Biocomposites
reported that the sugar palm tree was the first source of sugar, fresh juice,
fermented drinks, and syrup. The fibres have been collected from the sugar
palm tree since 1416 during the Malacca Sultanate [8], with several names
such as aren, gomuti, and black palm fibre, and locally it is known as the ijuk
fibre. The British East India Company in Penang started to plant the sugar
palm tree to produce fibres owing to its high durability [8].
The sugar palm tree can be found at altitudes ranging from sea level up to
1400 m a.s.l. [4, 9, 10]. However, Johnson [11] stated that the sugar palm
tree could grow at 1200–1500 m a.s.l. and in areas where the rainfall was
500–1200 cm3. The sugar palm tree grows in the more humid parts of the
Asian tropics. Plantations are found from South Asia to South-East Asia and
from Taiwan to the Philippines, Indonesia, Papua New Guniea, India [9, 11],
North Australia, Malaysia [12], Thailand, Burma, and Vietnam [9].
In Malaysia, sugar palm trees can be found widely along the rivers in the
rural areas of Bruas-Parit (Perak), Raub (Pahang), Jasin (Melaka), and Kuala
Pilah (N. Sembilan) [8]. Generally, it can be seen throughout Malaysia, as this
species grows wild in many places [6]. In Tawau (Sabah) there are around
809 ha of sugar palm plantation planted by Kebun Rimau Sdn Bhd, and at
Benta (Pahang) there are 50 ha of sugar palm tree plantation [13]. However,
the plantation area of this species is smaller compared with that of other palm
species, such as oil palm and coconut palm, as shown in Table 1.
Table 1. Plantation areas of the palm family [12]
Plantation
Hectares
Oil palm
1 359 691
Coconut
182 776
Sugar palm
892a
Sago
647
Pinang
445
Salak
41
a
Sahari [13]
APPLICATIONS OF THE SUGAR PALM TREE
Among the plants of the tropics, it is difficult to find a family of plants that can
produce more useful service to people than the sugar palm tree. Therefore,
this family has been identified as the most versatile plant owing to its many
applications such as neera sugar, fruits, fibres, etc.
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J. Sahari, S.M. Sapuan, E.S. Zainudin, and M.A. Maleque
Primary Applications
Neera sugar
More than 3000 palm species of the tropics and subtropics can be classified
as multipurpose trees, and the sugar palm tree is considered to be one of the
most diverse multipurpose tree species in culture [6]. This is because almost
all parts of the tree can be used for many important products, and it plays an
important economic role for the people of rural areas [12, 14–16]. Haris [17]
also reported that the sugar palm tree can be used in various applications in
the Philippines. Figure 2 shows the tapping process of neera sugar.
Figure 2. Tapping process
One of the most important products of the sugar palm tree is palm sugar,
locally known as neera sugar. It is sweet and brown in colour, as shown in
Figure 3. Neera sugar is normally used as a food sweetener in traditional
food. Palm sugar can be consumed freshly, or it can be allowed to ferment
for a while to become palm wine [12]. It has been reported that sugar palm
was the prime source of sugar, fermented drinks, and syrup [7].
Haris [17] stated that palm sugar can also be processed to make palm wine,
vinegar, and alcohol. In Tawau (Sabah), around 809 ha of sugar palm plantation
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Polymers from Renewable Resources, Vol. 3, No. 2, 2012
Sugar Palm Tree: A Versatile Plant and Novel Source for Biofibres, Biomatrices, and Biocomposites
Figure 3. Neera sugar
has been planted by Kebun Rimau Sdn Bhd to produce Arengga Pinnata
syrup, while at Benta (Pahang) there are 50 ha of sugar palm plantation to
produce brown sugar [13].
Nevertheless, in recent years the use of palm sugar has extended to another
level of application – to fermentation with yeast to produce alcoholic beverages.
Furthermore, advance fermentation processes can also be employed to produce
bioethanol. Bioethanol is used as a raw material for the production of a variety
of products such as chemical products, solvents, pharmaceuticals, cosmetics,
medicines, and beverages. It can also be used for the production of biofuel
as a renewable source of energy, like other bioethanol plant sources [18]. Of
more interest is the fact that sugar palm can yield the highest productivity
of bioethanol (20 160 L ha-1 year-1) compared with other sources such as
cassava (4500 L ha-1 year-1), sugar cane (5025 L ha-1 year-1), sago (4133 L
ha-1 year-1), and sweet sorghum (6000 L ha-1 year-1) [19]. Sugar palm is
scattered over almost all Indonesia, with a total area of around 70 000 ha, and
in about 13 provinces in particular: Papua, Moluccas, North Moluccas, West
Sumatra, West Java, Central Java, Banten, North Sulawesi, South Sulawesi,
South-East Sulawesi, Bengkulu, Kalimantan, and Nanggroe Aceh Darussalam.
The large-scale commercialisation of sugar palm plantations, ranging from
800 000 ha to 4 million ha, is going to be developed, especially in Indonesia,
to make use of this potential of the sugar palm tree.
Fruits
The sugar palm tree also can produce juices from its fruits. Figure 4 shows
the sugar palm fruits. The fruits are white in colour and are taken from its
fruit bunch. They can also be preserved in heavy syrup into a product called
Polymers from Renewable Resources, Vol. 3, No. 2, 2012
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J. Sahari, S.M. Sapuan, E.S. Zainudin, and M.A. Maleque
Figure 4. Sugar palm fruits
Figure 5. Products from sugar palm fruit
beluluk, which is also canned, and the fruits can be cooked with sugary syrup
for desserts [12], as shown in Figure 5.
Secondary Applications
Sugar Palm Fibre (ijuk)
Sugar palm fibre, known locally as ijuk, has been one of the most popular
fibres among researchers over the past decade. Ijuk is black in colour, and up
to 0.50 mm in diameter [20]. According to Siregar [1], ijuk is heat resistant up
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Sugar Palm Tree: A Versatile Plant and Novel Source for Biofibres, Biomatrices, and Biocomposites
to 150°C, and its flash point is around 200°C . It has been reported that ijuk
fibre is up to 1.19 m in length [21], with 1.26 kg m-3 density [22]. Traditionally,
ijuk has been used in the manufacture of ropes, filters, broom, and roofing,
and in handicraft applications such as for making kopiah [22, 23]. Tomlinson
[24] reported that ropes made from sugar palm fibre have better performance
than ropes made from rattan fibre (Calamus sp.). The main advantages of ijuk
are its durability and good resistance to sea water. It is also unaffected by
heat and moisture compared with coir fibre. Unlike other natural fibres, ijuk
can be obtained from the trees directly without secondary processes to yield
the fibres [25]. Therefore, ijuk should be a good material in the development
of new ‘green’ materials.
The fibre is originally wrapped along the sugar palm trunk [12]. The tree can
grow up to 12.3 m tall and has a thick, black/brown, hairy, fibrous trunk, with
a dense crown of leaves, which are white on the outside. The tree begins to
produce black sugar palm fibre after about 5 years, before flowering, and the
type of fibre is dependent upon the age and altitude of the sugar palm tree
[2]. The fibres that are taken after flowering will produce fibre approximately
1.4 m long. Each tree can yield about 15 kg, and around 3 kg is the very best
and stiffest fibre (unpublished data, 2007). In Malaysia, black sugar palm
fibre started to be used in 1416 during the Malacca Sultanate [8]. In 1800,
the sugar palm tree was planted by the British East India Company in Penang
to yield high-durability rope made from black sugar palm fibre [8]. Figure 6
shows the sugar palm fibre.
Figure 6. Sugar palm fibre
The characterisation (tensile and chemical properties) of single fibres from
different morphological parts of the sugar palm tree, i.e. the sugar palm frond
(SPF), sugar palm bunch (SPB), ijuk, and sugar palm trunk (SPT), has been done
Polymers from Renewable Resources, Vol. 3, No. 2, 2012
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J. Sahari, S.M. Sapuan, E.S. Zainudin, and M.A. Maleque
by Sahari [13]. From the investigation it was found that the tensile strength of ijuk
was 276.64 MPa, and the tensile modulus was 5.86 GPa, as shown in Figure 7.
The elongation at break of ijuk was 22.3%, which was approximately the same
as that of oil palm and coir fibres, thus showing similar physical and mechanical
properties of members of the same palmae family [26]. For the chemical analysis
it was shown that ijuk has a high cellulose content of 52.29% (Table 2). Thus,
the mechanical properties of sugar palm fibre are strongly influenced by the
cellulose content [27]. Cellulose was the main structural component, providing
strength and stability to the plant cell walls and the fibres [28]. Generally, ijuk
can be used as reinforcement in composites owing to its higher tensile strength
and cellulose content in comparison with other established natural fibres such
as kenaf, pineapple leaf, coir, and oil palm bunch.
Figure 7. Tensile stress–strain curve of fibres from different morphological parts of the
sugar palm tree [13]
Further characterisation of the tensile properties of sugar palm fibres was
conducted, and results are shown in Figure 8 [29]. The fibres were obtained
from different heights of the sugar palm tree (1, 3, 5, 7, 9, 11, 13, and 15 m)
and subjected to single-fibre tensile testing. The results showed that the fibres
obtained from the bottom part demonstrated inferior tensile strength, modulus,
elongation at break, and toughness to fibres obtained from the upper part.
It was concluded by Ishak et al. [29] that the variation in tensile properties was
due to the varying chemical composition of the fibre, which was affected by
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Sugar Palm Tree: A Versatile Plant and Novel Source for Biofibres, Biomatrices, and Biocomposites
Table 2. Chemical composition of fibres from different morphological
parts of the sugar palm tree [13]
Description (%)
Sugar palm frond Sugar palm bunch
(SPF)
(SPB)
Moisture, %
2.74
Extractive, %
Holocellulose, %
2.70
Ijuk
Sugar palm
trunk (SPT)
7.40
1.45
2.46
2.24
4.39
6.30
81.22
71.78
65.62
61.10
Cellulose, %
66.49
61.76
52.29
40.56
Lignin, %
18.89
23.48
31.52
46.44
3.05
3.38
4.03
2.38
Ash, %
Table 3. Chemical composition of sugar palm fibre obtained from
different heights of the sugar palm tree [29]
Composition (%)
Cellulose
Height (m)
1
3
5
7
9
11
13
15
37.3
49.36
55.28
56.55
56.8
55.75
54.42
53.41
6.11
Hemicelluloses
4.71
7.36
7.68
7.93
7.92
7.89
7.45
Lignin
17.93 18.941 20.89
20.45
23.6
22.96
24.27
24.92
Ash
30.92
14.04
5.8
4.23
2.06
4.09
3.98
4.27
Extractive
2.49
2.019
1.71
1.41
1.35
1.48
1.21
0.85
Moisture content
5.36
8.64
7.92
8.37
8.19
7.72
8.12
8.7
Figure 8. Tensile strength of sugar palm fibre obtained from different heights of the
sugar palm tree [29]
ageing, especially at the bottom part of the tree. Table 3 shows the chemical
composition of sugar palm fibre obtained from different heights of the sugar
palm tree. It was observed in this study that the cellulose, hemicellulose,
and lignin contents increased with increase in tree height. As fibres at 1 m
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J. Sahari, S.M. Sapuan, E.S. Zainudin, and M.A. Maleque
height were near to the ground, they contained a great quantity of impurities
such as silica, and their ash content was found to be much higher (30.92%)
compared with fibres obtained from the upper parts (5–15 m), where the ash
content range was 2.06–5.84%.
Sugar Palm Starch (SPS)
The sugar palm tree is one of multipurpose trees grown in Malaysia. Besides
yielding neera sugar, it also provides a great variety of products such as ropes,
filters, brooms, and roof materials (Mogea, 1991). Nowadays, researchers focus
more on the production of bioethanol, which can be derived from neera sugar
[18, 30]. The inner part of the sugar palm stem contains starch. It has been
used as raw material for starch and glue substances [17]. For the production
of 1 t of starch, 10–20 trees are needed, which suggests that one tree can
produce 50–100 kg of starch [31]. This accumulated starch is harvested from
the trunk of matured palms and can be applied as ‘green’ material. Starch will
act as a biopolymer in the presence of a plasticicer such as water, glycerol,
and sorbitol at high temperature.
In recent years, owing to the unique behaviour of plasticised starch, many
researchers have been using it as a biomatrix. Teixeira et al. [32] used plasticised
cassava starch as a biomatrix, employing either glycerol or a mixture of glycerol/
sorbitol (1:1) as the plasticicer, and combined them with cassava bagasse
cellulose nanofibrils as reinforcing materials. Development of corn-starchbased ‘green’ composites reinforced with graft copolymers of Saccharum
spontaneum L. (Ss) fibre was carried out by Kaith et al. [33]. Prachayawarakorn
et al. [34] prepared a biodegradable polymer from thermoplastic rice starch
(TPRS), and cotton fibre and low-density polyethylene (LDPE) were added to
the TPRS matrix in order to improve the poor tensile properties and high water
absorption of TPRS. Recently, Vallejos et al. [35] applied corn and cassava
starches plasticised with 30 wt% glycerin as biomatrices, using fibrous material
obtained from ethanol–water fractionation of bagasse as reinforcement. Other
important research based on starch materials was carried out by Duanmu et
al. [36]. They determined the moisture absorption, dimensional stability, and
mechanical properties of wood-fibre-reinforced allyl glycidyl ether (AGE)–potato
starch composites. However, no research has been carried out to evaluate
the potential of sugar palm starch (SPS) as biopolymer.
Sugar-Palm-Fibre-Reinforced Polymer Composites
Research into natural fibre has become most popular among scientists and
technologists in view of environmental concerns. The need for ‘green’ material
prompts researchers to seek opportunities to develop new material on the
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Sugar Palm Tree: A Versatile Plant and Novel Source for Biofibres, Biomatrices, and Biocomposites
basis of environmentally friendly criteria. This has opened up alternative ways
to solving agricultural residue problems. On account of their better mechanical
properties, sugar palm fibres are used as reinforcement in concrete and road
construction [17]. These fibres which are known as gomuti or gomutu and
are also used as coating material in India [12].
The utilisation of sugar palm fibre progressed one step further with its use as
a reinforcing agent in polymer composites. An enormous amount of research
is currently being done to study the properties of sugar palm fibre and its
composites. Previous research claimed that sugar palm fibre showed promising
utilisation in many composite applications [6, 37, 38].
Owing to its good mechanical properties, ijuk fibre could be used as reinforcment
material in polymer composites. The mechanical properties of ijuk-fibrereinforced polymer composites have been studied for cases of chopped,
long, and woven ijuk fibre using various polymer matrices [1, 20, 39, 40–42].
According to Sastra et al. [40], composites made from woven fibre have much
better mechanical properties than chopped and long fibres. Suriani et al. [43]
studied the interfacial adhesion of ijuk-fibre-reinforced epoxy composites,
while Leman et al. [39] studied the impact properties and water absorption
of ijuk-reinforced epoxy composites. A small boat has also been fabricated
from hybrid-woven-glass/ijuk-reinforced unsaturated polyester composites
using the lay-up technique [44]. Figure 9 shows ijuk composite products.
Figure 9. Composite products manufactured from ijuk. (a) ijuk composite boat; (b)
ijuk composite rod
In order to enhance the interfacial properties of natural fibre composites, surface
treatment of natural fibres is needed. Bachtiar [45] and Bachtiar et al. [42]
studied the effects of alkaline treatment of sugar palm fibre on the mechanical
properties of sugar-palm-fibre-reinforced epoxy composites. The results verified
that the mechanical properties (tensile, flexural, and impact) of the composites
were improved, particularly the tensile modulus, with the treatment.
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J. Sahari, S.M. Sapuan, E.S. Zainudin, and M.A. Maleque
Ishak [46] also looked into the potential of sea water treatment for surface
modification of woven-sugar-palm-fibre-reinforced unsaturated polyester
composites. It was interesting to note that the opposite result was obtained by
Leman et al. [25], where sea water treatment resulted in a significant reduction
in the tensile strength, tensile modulus, elongation at break, flexural modulus,
and impact strength of composites.
The effects of impregnation modification via vacuum resin impregnation on
the physical and mechanical properties of sugar palm fibres were investigated
[47]. From the investigation, the physical properties of impregnated fibres
showed significant improvement when the moisture content of the fibre was
dropped from 8.19 to 0.75–0.46% for impregnation with phenol formaldehyde
(PF), and to 0.87–0.44% for impregnation with unsaturated polyester (UP).
Meanwhile, water absorption of impregnated fibre was reduced from 116.82 to
61.64–22.52% for PF and to 63.49–23.31% for UP. It was observed that fibre
impregnated with thermoset polymer resin (PF and UP) at an impregnation
pressure of 600 mmHg for 5 min showed a notable improvement in physical
properties, and that PF was superior. Figure 10 shows impregnated sugar
palm fibre.
Figure 10. Impregnated sugar palm fibre [47]. (a) unimpregnated fibre; (b) impregnated
fibre
Other Applications
The sugar palm tree also has many traditional applications. For example,
the young leaves can be eaten fresh or cooked. However, the harvesting of
young leaves will shorten their lifetime. Thus, they are taken only when really
needed. The leaves are usually eaten immediately after harvesting to avoid
irritation of the mouth area. Their sweet flavour when cooked is like that of
young coconut [12]. In Indonesia, young leaves, petiols, and core stems are
cooked for soup or fried [9]. Moreover, the young leaves are traditionally
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Sugar Palm Tree: A Versatile Plant and Novel Source for Biofibres, Biomatrices, and Biocomposites
used for making cigarette wrappings or consumed as salads [9]. The leaves,
similarly to coconut leaves, are used for thatch, for weaving into baskets, for
band matting, and for roofing [12].
The midribs of the leaflets are used for making high-durability brooms and
fishing tools [12, 17]. The outer part of the stem consists of wood, which is
extremely hard and durable. It can be processed for flooring, furniture, and
the hand grips of tools [17]. Its roots are useful for medicine and fishing tools.
When it is boiled with water, it can break down stones within the bladder.
Palm sap can be used for indigestion, rashes, and pulmonary irritation [12]. In
the Philippines, it is used to avoid tuberculosis by the fermentation process.
CONCLUSIONS
The use of ‘green’ materials has rapidly evolved owing to health and
environmental issues and the shortage of petroleum resources. This review
outlines the research carried out and the significant advances made in the field
of biofibres, biomatrices, and biocomposites from a renewable resource, i.e.
the sugar palm tree. Nevertheless, a deeper understanding of their chemical,
mechanical, and thermal properties is still needed in order to produce desirable
and competitive materials derived from sugar palm fibre and sugar palm
starch. The use of these unutilised materials as biofibres, biomatrices, and
bicomposites will open up another avenue for the large-scale utilisation of
the sugar palm tree.
ACKNOWLEDGEMENTS
Special thanks to the Ministry of Agriculture and Agro-Based Industry of
Malaysia for financial support through its Science Fund (project number 0301-04-SF0246). Special thanks also to the Ministry of Higher Education for
the MyPhD Financing Programme under the Tenth Malaysia Plan (RMK-10),
and to Universiti Putra Malaysia for providing the research facilities.
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