Composite Materials
Nowadays, composite materials are one of the important materials in life. They are widely used
in many sectors and applications such as transportation, medical, consumer products, building
and construction due to their specific mechanical performance, characteristic and properties
(Smith and Hashemi, 2006). Recently, growing awareness and social concerns towards
preserving and protecting the environment has spurred efforts to develop products compatible
with the environment. Therefore, interests to enhance polymer properties by employing
natural fibers to replace the existing synthetic fibers are reinforced.
1.1 Research Background
Natural fibers as reinforcements or fillers in polymer composites have received extra attention
over synthetic fibers because of their acceptable specific strength properties, locally abundant,
low cost, low density, nonabrasive, non-toxic, and biodegradable properties (Kalia et al., 2009;
Singha et al., 2011; Torres and Cubillas, 2005). Using natural 'bers from renewable resources to
replace the traditional synthetic 'bers such as glass 'bers, carbon 'bers, and aramid 'bers will
contribute to environmental sustainability. Furthermore, they are relatively abundant in nature
and the use of these lignocellulosic materials in polymer composites may assist to reduce waste
disposal problems in agricultural fields and also promote recycling activities. The inclusion of
natural fibers in polymer composites can also provide a cost reduction to the plastic industry.
Currently, numerous studies have been conducted related to the development of natural fibers
reinforced polymer composites (NFRPs). NFRPs have higher specific strength properties,
lightweight, low density, non-abrasive as well as low cost as compared to commercially
reinforced synthetic fiber composites (Ashori, 2008; El-Tayeb, 2008; Prachayawarakorn et al.,
2010). NFRPs had been identified to have extensive application in many industries including the
automotive industry, building, construction, packaging and furniture production. There are
various types of natural fibers that were utilized in polymer composites i.e. sisal (Almeida et al.,
2010; Li et al., 2008; Pimenta et al., 2008), jute (Kannappan et al., 2012; Lovdal et al., 2012;
Saha et al., 2010) , flax (Aydin et al., 2010; Foulk et al., 2006) , kenaf (Rashidi et al., 2009;
Thirmizir et al., 2010; Tawakkal et al., 2012), pineapple (Chollakup et al., 2010; Threepopnatkul
et al., 2009), bamboo (Gonzlez et al., 2011; Kang and Kim, 2011; Lee and Wang, 2006; Ochi,
2012), bagasse (El-Tayeb, 2008; Lu et al., 2006) fibers and many more.
There are many studies involving blending natural fiber with polymer matrix i.e. high density
polyethylene (HDPE) (Shang et al., 2012; Yao et al., 2008), low density polyethylene (LDPE)
(Obidiegwu, 2012; Shinoj et al., 2011), polypropylene (PP) (Asumani et al., 2012; Chakrabarty et
al., 2011), poly (lactic acid) (PLA) (Aydn et al., 2010; Tawakkal et al., 2012), epoxy (Khalil et al.,
2011; Maleque et al., 2007) and unsaturated polyester (Rashdi et al., 2009; Qiu et al., 2012). In
their work, they found that there is poor interfacial interaction between natural fiber and nonpolar polymer matrix. This is due to the hydrophilic nature of natural fiber and hydrophobic
character of polymer matrix. Therefore, in order to overcome this problem, modification and
treatment, i.e. mercerization, isocyanate treatment, acrylation, latex coating, permanganate
treatment, acetylation, silane treatment and peroxide have been used (Cristaldi et al.,2010;
Kalia et al., 2009; Lu et al., 2000; Torres and Cubillas; 2005).
Silane and maleic anhydride grafted polyolefins have been found to be the most effective
coupling agent and compatibilizer to improve adhesion between lignocellulosic fiber and
thermoplastic matrices (Bledzki and Gassan, 1999; Vilaseca et al., 2010). The alkali treatment
using sodium hydroxide (NaOH) has been reported as the most common method used to
remove the natural and artificial impurities of fiber surface (Bhat et al., 2011; Bachtiar et al.,
2010; Chakrabarty et al., 2011). Eco degradant has been used as additive in
polyethylene/chitosan composites and found to give a favorable impact on the thermal
properties of the composites (Azieyanti and Salmah, 2014).
Polyethylene is the most common thermoplastic used in polymer industries and widely used in
various applications include transportation, food packaging and building industries.
Polyethylene offers many advantages such as low price, excellent performance, chemical
inertness, good electrical resistance and processability, toughness, flexibility and recyclability
(Ahmad and Luyt, 2012). Polyethylene also has a low melting point of about 135 C, constitutes
compatible processing temperatures with lignocellulosic fibers, avoiding degradation of
cellulose (Nwabunma and Kyu, 2007). Thus, make it suitable to use as polymer matrix of natural
fiber composites.
In this research, natural fibers from galangal plant (Alpinia galanga fiber) were used as fillers in
polyethylene based composites. To date, there has been no study on the use of Alpinia galanga
fibers in thermoplastic based composites. Alpinia galanga fibers are waste of galangal
cultivation. Hence, Alpinia galanga fibers can be obtained for without additional costs. They are
locally available and have annual renewability. This plant is widely available in India, Thailand,
Indonesia, China and Malaysia and is extensively used in applications such as medicine, food
and cosmetics (Chudiwal et al., 2010). In Malayisa, based on data from the Department of
Agriculture, Malaysia, the annual production of Alpinia galanga between 2007 and 2011 was
approximately 1251, 1518, 1565, 13568 and 1980 metric tons respectively and shown in Table
1.1. The Alpinia galanga cultivation is expected to increase for years to come. Thus, this
agricultural crop-residue can be a valuable source of natural fibers as an alternative to
substitute synthetic fibers as well as to promote recycling.
1.2 Problem Statement
Conventionally, synthetic fibers such as glass, carbon and aramid 'bers are widely used as
reinforcements and fillers in polymer composites due to its role as reinforcing materials in
order to improve strength and stiffness of polymer composites. These synthetic fibers were
produced from petrochemical products, i.e. not sustainable and not eco-friendly products. The
continued reliance on this material might result in diminishing petroleum resources in the
future and cause adverse effects mainly towards the environment and human health. Besides,
these materials are also relatively expensive.
The other problems arise with the use of synthetic fiber in polymer composites is related to the
disposal system. This is because the use of incinerator for disposal of synthetic composites
would result in negative effects towards the environment by increasing number of air
pollutants in the atmosphere due to the carbon dioxide emissions (Gomes et al., 2007;
Wambua et al., 2003). Therefore, the study on natural fibers as reinforcement in polymer
composites to substitute synthetic fibers is a significant contribution to protect the
environment.
The increased amount of solid waste, particularly plastic wastes also becomes the key issues to
worry about. Therefore, the employment of eco degradant as an additive in polyolefins
composites is necessary. Eco degradant play a role to degrade polyolefin composites to the
basic elements, i.e. water, carbon dioxide and biomass by microorganisms (Ismail et al., 2009).
Among various natural fibers, Alpinia galanga seems to have a potential as reinforcement in
polymer composites. Alpinia galanga fibers are obtained from galangal stalks, the products of
agricultural waste after the galangal cultivation. In Malaysia, there is approximately 1000-2000
metric tons of galangal plant produced yearly and the total plantation of galangal has increased
on yearly basis. For example, the plantation area of galangal in 2010 and 2011 are 222 and 225
ha, respectively. This availability of galangal wastes creates a motivation for turning these
agricultural wastes into value added industrial products such as natural fiber composites.
However, lignocellulosic fibers are incompatible with nonpolar polymers causing limitations for
the successful utilization of natural fiber composites. Therefore, several chemical treatments
and compatibilizers have been employed to improve the compatibility between lignocellulosic
fiber and polymer matrix. The chemical treatments that have been chosen are sodium
hydroxide (NaOH) as well as coupling agent treatment using 3-aminopropyltriethoxysilane (3APE) and p-toluenesulfonic acid (PTSA). The maleic anhydride-graft-polyethylene (MAPE) and
eco-degradant PD04 also are the compatibilizer and commercialized additive to improve the
properties of the composites.
1.3 Research Objectives
The objectives of this study are listed below:
1. To study the effects of Alpinia galanga (AG) fiber loadings and addition of eco degradant
(eco) and maleic anhydride-graft-polyethylene (MAPE) on tensile and thermal properties,
morphology as well as water absorption of AG-high density polyethylene (HDPE) composites.
2. To investigate the effects of sodium hydroxide (NaOH), 3-aminopropyltriethoxysilane (3-APE)
as well as p-toluenesulfonic acid (PTSA) treated AG fiber loadings with addition of MAPE on
tensile and thermal properties, morphology as well as water absorption of AG/HDPE
composites.
3. To investigate the effects of NaOH, 3APE as well as PTSA treated AG fiber loadings with the
addition of eco degradant (eco) on tensile and thermal properties, morphology as well as water
absorption of AG/HDPE composites.
1.4 Scope of the study
In order to achieve the objectives of the research, the followings are scopes of this study:
1. Preparation of untreated AG/HDPE composites with and without addition of MAPE or eco
degradant by using injection molding with various AG fiber loadings (3, 6, 10 and 15 wt %).
2. Mechanical testing of untreated AG/HDPE composites with and without addition of MAPE or
eco degradant by using tensile testing machine.
3. Characterization of untreated AG/HDPE composites with and without addition of MAPE or
eco degradant on the thermal and the moisture absorption ability.
4. Morphological study of untreated AG/HDPE composites with and without addition of MAPE
or eco degradant using scanning electron microscope (SEM).
5. Preparation of NaOH&3-APE and PTSA treated AG/HDPE composites with addition of MAPE
or eco degradant by using injection molding with various AG fiber loadings (3, 6, 10 and 15 wt
%).
6. Mechanical testing of NaOH&3-APE and PTSA treated AG/HDPE composites with addition of
MAPE or eco degradant by using tensile testing machine.
7. Characterization of NaOH&3-APE and PTSA treated AG/HDPE composites with addition of
MAPE or eco degradant on the thermal and the moisture absorption ability.
8. Morphological study of NaOH&3-APE and PTSA treated AG/HDPE composites with addition
of MAPE or eco degradant using scanning electron microscope (SEM).
Source: Essay UK - http://www.essay.uk.com/free-essays/engineering/composite-materials.php