performance of recycled high density polyethylene (hdpe)/ rice husk
TRANSCRIPT
PERFORMANCE OF RECYCLED HIGH DENSITY POLYETHYLENE
(HDPE)/ RICE HUSK COMPOSITE INJECTION GRADE IN
THERMOFORMING PROCESS
FATIMAH ZAHARAH BINTI CHE MOHAMAD
A report submitted in partial fulfillment
of the requirement for the award of the degree of
Bachelor of Engineering (Chemical-Polymer)
FACULTY OF CHEMICAL AND NATURAL RESOURCES ENGINEERING
UNIVERSITI TEKNOLOGI MALAYSIA
MAY, 2007
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Special dedication to my beloved mom and dad, also to my sisters and brother...
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ACKNOWLEDGEMENT
These five months had been quite tough and gave many challenging in finishing
the final year project. Without the help of the following individuals, this thesis will just
be a dream.
Firstly, I would to thank Universiti Technologi Malaysia, for giving me the
opportunity to carry out this final year undergraduate project and providing the useful
equipments.
Big thanks also go to my honourable supervisor, PM Dr. Wan Aizan Wan Abd.
Rahman, for helping and guiding me in various aspects through the progression of this
project. Also very thankful to Pn. Roshafima who supervised me during my supervisor
on leave. Not forgetting all staff and laboratory technicians for their willingness to help
and guide me during my research.
Finally, I would like to extend my heartfelt gratitude to all my course mate and
friends who offer needed tips, advice and endless cooperation. Without those helps, this
research report would not have been completed successfully. To my lovely parents and
family, thanks for the spiritually encouragement and very understanding.
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ABSTRACT
All thermoplastic polymers can be remelted and recompounded into a new
grade, but the presence of certain additives, blends, or fillers like glass fibers may
limit the application area of the recyclate. In this present study, it was my aim to
investigate the ability of recycled rice husk-filled-high density polyethylene (RHPE)
composite injection grade to be processed using thermoforming technique. Various
recycled RHPE composite injection grade, that is with composition 30%, 40% and
50% of rice husk were investigated in this study. These composites were first grinded
to a fine form using laboratory grinder machine before being melt-blended and
milled into sheets on a two-roll mill. Then, test specimens were prepared to study on
the mechanical properties that is tearing test and tensile test. The results showed the
tear and tensile strength were reduced significantly with the percentage increase of
rice husk contents. However, the Young modulus had increased. The MFI of the
recycled RHPE was determined to find its suitability in terms of flow behaviour and
compared to standard MFI for thermoform grade. MFI was found to decrease as
compared to the virgin HDPE, but is within the standard MFI for thermoforming
material grade. FTIR spectroscopy and DSC thermal analysis used to characterize the
recycled composite materials. FTIR analysis indicates that the major chemical
structure of rice husk filled in HDPE samples is not affected by recycling process
and also shows the rice husk contents was not undergo degradation during the
injection moulding process. While, melting temperature does not differ much from
the pure RHPE therefore recycled RHPE does not undergo much thermal
degradation. So, these shows the ability of recycled RHPE composite can be
reprocessed for other usage. Recycled RHPE composites containing 40% rice husk
exhibit good properties and showed high capability to be thermoformed.
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ABSTRAK
Semua polimer termoplastik boleh dilebur dan di sebatikan semula kepada gred
yang baru, tetapi dengan kehadiran bahan penambah, bahan campuran yang tertentu atau
pengisi seperti fiberglass, mungkin akan mengehad bidang aplikasi bahan yang dikitar
semula. Maka, objekif kajian ini adalah untuk menyiasat kebolehan komposit kitar
semula polietilena berketumpatan tinggi terisi sekam (RHPE) padi gred suntikan untuk
diproses pembentukan haba. Terdapat tiga komposisi produk komposit RHPE gred
suntikan ini digunakan dalam kajian ini, iaitu 30%, 40% and 50% kandungan sekam padi.
Produk komposit ini terlebih dahulu dikisar/ dihancurkan menggunakn alat pengisar
makmal bagi menghasilkan serbuk halus sebelum di adunleburkan dan menghasilkan
kepingan dengan menggunakan ‘two roll mill. Kemudian, specimen disediakan bagi
pengujian sifat-sifat mekanikal, iaitu ujian koyakan dan regangan. Keputusan yang
diperolehi menunjukkan kekuatan koyakan dan regangan, serta pemanjangan pada takat
patah menurun dengan penambahan peratusan kandungan sekam padi di dalam koposit
tersebut. Walaubagaimana pun, nilai modulus Young menunjukkan peningkatan bagi
keadaan yang sama. Sementara itu, indek aliran leburan (MFI) bagi komposit kitar
semula RHPE juga diperolehi bagi mendapatkan kesesuaian kelakuan kebolehaliran dan
seterusnya membandingkannya dengan nilai piawai MFI bagi proses pembentuksn haba.
Didapati nilai MFI komposit kitar semula RHPE menurun jika dibandingkan dengan nilai
MFI untuk HDPE tulen, tetapi nilainya masih dalam julat nilai piawai MFI untuk gred
pembentukan haba. Selain itu, analisis termal FTIR dan DSC turut dilakukan bagi
mengkaji sifat komposit kitar semula ini. Analisis FTIR menunjukkan struktur major
kimia dalam komposit RHPE tidak diberi kesan oleh proses kitar semula dan juga
menunjukkan kandungan sekam padi idak mengalami degradasi semasa proses acuan
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sunikan. Suhu leburan pula tidak manujukkan perubahan yang ketara jika dibandingkan
dengan komposit RHPE tulen (sebelum kiar semula), justeru itu komposit kitar semula
RHPE tidak banyak mengalami degradasi termal. Maka keadaan sebegini dapat
membuktikan kebolehan komposit kitar semula RHPE diproses semula untuk
aplikasi/kegunaan lain. Daripada ujian yang telah dibuat, komposit kitar semula RHPE
yang mengandungi 40% kandungan sekam padi memberikan sifat-sifat yang bagus
seterusnya menunjukkan kebolehan yang tinggi untuk dibentuk haba.
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TABLE OF CONTENT
CHAPTER TITTLE ACKNOWLEDGEMENT iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS viii
LIST OF TABLES xi
LIST OF FIGURES xii
LIST OF SYMBOLS xv
LIST OF ABBREVIATIONS xvi
LIST OF APPENDIX xvii
1 INTRODUCTION
1.1 Background 1
1.2 Problem Statement 4
1.3 Objectives 5
1.4 Scope of Study 5
2 LITERATURE REVIEW
2.1 Thermoforming Process 7
2.2 Rice Husk 8
2.2.1 Background 9
2.2.2 General Features and Properties 10
2.2.3 Application 11
2.3 Processing of Natural Fiber Polymer 12
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3 METHODOLOGY
3.1 Material 23
3.2 Experimental Procedure 25
3.2.1 Samples Preparation 25
3.2.1.1 Grinding 25
3.2.1.2 Two Roll Milling 25
3.3 Material Characterization
3.3.1 Fourier Transform Infra-Red 26
3.3.2 Differential Scanning Calorimetry 27
3.3.3 Melt Flow Index 27
3.4 Material Performance Testing 28
3.4.1 Trouser Tear Resistance 28
3.4.2 Tensile Test 30
3.5 Product Thermoforming 31
4 RESULT & DISCUSSION
4.1 Introduction 32
4.2 Material Characterization 33
4.2.1 Fourier Transform Infra-Red 33
4.2.2 Differential Scanning Calorimetry 36
4.2.3 Melt Flow Index 38
4.3 Material Performing Test 40
4.3.1 Tearing Test 40
4.3.1.1 Tear Strength 40
4.3.2 Tensile Test 42
4.3.2.1 Young’s Modulus 42
4.3.2.2 Tensile Strength 44
4.3.2.3 Elongation at Break 46
4.4 Thermoforming Process 48
x
5 Conclusions and Recommendations
5.1 Conclusion 50
5.2 Recommendations 52
REFERENCES 53
APPENDIX 57
xi
LIST OF TABLES
TABLE NO. TITLE PAGE
1.1 Comparison between natural and glass fiber
(Wambua et. al, 1987) 2
3.1 Composition of rice husk in recycled composite 24
injection grade
3.2 Properties of pure HDPE injection grade (Naurah,2005) 24
3.3 Dimension of specimens Type V 30
4.1 Melting temperature of pure HDPE and recycled RHPE
composite 37
4.2 Mechanical properties of recycled RHPE composite
injection grade 41
xii
LIST OF FIGURES
FIGURE NO. TITLE PAGE
2.1 World rice production figures in 1999 9
(Chaoudhary et al, 2004)
2.2 Effect of rice husk content on mechanical
properties in polypropylene matrix
(Prachayawarakorn and Yaembunying, 2005) 13
2.3 FTIR spectra for (a) polypropylene (b) rice husk
and (c) rice husk-filled polypropylene.
(Prachayawarakorn and Yaembunying, 2005) 14
2.4 Elastic modulus vs. filler content for samples
with and without Licocene.
(La Mantia and Morreale, 2006) 17
2.5 Elongation at break vs. filler content for
samples with and without Licocene
(La Mantia and Morreale, 2006) 17
2.6 The effect of OPWF loading on the tensile
and tear strengths of the natural rubber composites
(Ismail and Jaffri, 1999) 22
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2.7 Relationship between the modulus at 100%
elongation (M100) and modulus at 300% elongation
(M300) with OPWF loading
(Ismail and Jaffri, 1999) 22
3.1 Recycled composite milled sheet 26
3.2 Trouser Tear Specimen 29
3.3 Trouser Tear Test 29
4.1 FTIR spectra for pure HDPE and recycled rice
husk-filled HDPE composite. 35
4.2 FTIR spectra for (a) polypropylene (b) rice husk
and (c) rice husk-filled polypropylene.
(Prachayawarakorn and Yaembunying, 2005) 35
4.3 Effect of rice husk loading on the melting
point for recycled RHPE composite injection
grade 37
4.4 Effect of rice husk loading on the flow
behavior for recycled RHPE composite injection
grade 39
4.5 Effect of rice husk loading on the tear strength
for recycled RHPE composite injection grade 42
4.6 Effect of rice husk loading on the Young’s
modulus for recycled RHPE composite
injection grade 44
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4.7 Effect of rice husk loading on the tensile strength
for recycled RHPE composite injection grade 46
4.8 Effect of rice husk loading on the elongation
at break for recycled RHPE composite
injection grade 47
4.9 Product from thermoforming process 49
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LIST OF SYMBOLS
% - Percentage oC - Degree celcius
N - Newton
MPa - Mega pascal (Pressure)
rpm - Rotor per minutes
s - Seconds
Tm - Melting temperature
Tg - Glass transition temperature
wt % - Weight percentage
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LIST OF ABBREVIATIONS
ABS - Acrylonitrile Butadiene Styrene
ASTM - American Society of Testing Materials
BS - British Standard
CCA - Chromated Copper Arsenate
DSC - Differential Scanning Calorimetry
EVA - Ethylene-Vinyl-Acrylic
FTIR - Fourier Transform Infrared
GSA - Grid Strain Analysis
HDPE - High Density Polyethylene
LTC - Lingnocellulosic-Thermoplastic Composite
MA - Maleic Anyhydride
MFI - Melt Flow Index
OPWF - Oil Palm Wood Flour
PC - Polycarbonate
PE - Polyethylene
PP - Polypropylene
PS - Polystyrene
PVC - Poly (Vinyl Chloride)
RHP - Rice Husk Powder
RHPE - Rice Husk Polyethylene (High Density) composite
SBR - Styrene Butadiene Rubber
SEM - Scanning Electron Microscopy
TGA - Thermogravimertric Analyzer
UF - Urea Formaldehyde
VP - Virgin Pine
xvii
LIST OF APPENDIX
APPENDIX TITLE PAGE
A Working Paper 58
CHAPTER 1
INTRODUCTION
1.1 Background
Composite materials are one of the most advanced engineering materials
today. The addition of high strength fibers to a polymer matrix can greatly improve
thermal and mechanical properties such as ultimate tensile strength, flexural
modulus, and temperature resistance (Herrera-Franco et al.,1996) Composite
materials made from plant fibers are receiving a great deal of attention today since
they are considered an environmentally friendly recourse. This kind of product,
lignocellulosic-thermoplastic composite (LTC) is a combination of any type of
natural fiber or wood waste and polymers, such as PE, PP, PVC in powder or pellet
or regrind, including additives, colourants, lubricants and binders (Naurah, 2005)
2
Fiber reinforced polymeric composite materials are widely used in aerospace
and automotive industries, sports products and medical equipment because of their
low density but high stiffness and strength. In the family of polymers for polymeric
composite materials, thermoplastic resins possess more toughness and better damage
band environmental resistance than thermosetting resins. Additionally, in contrast to
the crosslinkable thermosetting resins with chemical polymerization reactions in the
cure stage, the lack of chemistry in the thermoplastic composite manufacturing
substantially shortens the processing time. As a result, a simple physical process with
heat transfer can process the thermoplastic composite and shaping, making this
composite material suitable for the mass production of composite structures (Hsiao
and Kikuchi, 1999)
On the other hand, composites prepared from glass fibers are widespread
high-performance materials. Glass fibres are the most widely used to reinforce
plastics due to their low cost (compared to aramid and carbon) and good mechanical
properties. However, these fibres have serious drawbacks as indicated in Table 1.1.
The shortcomings have been highly exploited by proponents of natural fibre
composites.
Table 1.1: Comparison between natural and glass fiber (Wambua et. al, 2003)
3
Among all reinforcing fibers, natural fibers have gained their importance
especially for low load bearing applications. Natural fiber reinforced polymer
composites are superior over synthetic fiber reinforced composites in certain
properties like enhanced biodegradability, combustibility, lightweight, ease of
recyclability, etc. These advantages place the natural fibers composites among high
performance composites having economical and environmental advantages, with
good physical properties (Mehta and Parsania, 2006).
It is well known that there are environmental and economical advantages to
produce natural filler/thermoplastic elastomer composites. Cellulosic filler–
reinforced plastics materials are low cost, lightweight, free from health hazards, have
enhanced mechanical properties, and thus have the potential for structural
application. According to one research from Universiti Sains Malaysia that has been
done on Rice Husk Powder (RHP)–Filled Polystyrene/Styrene Butadiene Rubber
(PS-SBR) Blends, the tensile strength decreases with increased RHP loading.
Incorporation of filler in the polymer matrix will reduce the ability of the composites
to transfer applied stress, especially particulate filler of irregular shape. But when
adding the maleic anhydride–polypropylene (MA–PP) as a coupling agent in the
RHP/PS–SBR composites, it improved the interaction between filler and matrix,
causing a more effective transfer of the stresses from matrix to filler, thus increasing
the tensile strength of the composites (Zurina et al., 2004).
4
1.2 Problem Statement
Polymer composites have been a subject of research and utilization for some
decades. During the last years, the increase in environmental concern has become an
important issue as a result, it is also necessary to reduce and rationalize the use of
polymeric materials, not only due to their non-biodegradability, but due to their
production requires large amounts of oil, which is notoriously not renewable. All
these issues have induced researchers to look for alternatives. Thus, the interest
arises toward polymer composites filled with natural organic fillers, especially in
conjunction with recycled and/or recyclable polymer matrices. This class of
composites (sometimes indicated as “green composites”) shows other interesting
features (La Mantia and Morreale, 2006).
Besides, environmental legislation, consumer concern, and waste
management approaches based on concepts like the ‘polluter pays’ are all increasing
the pressure on manufacturers of materials and end-products to consider the
environmental impact of their products at all stages of their life cycle including
ultimate disposal, a ‘cradle to grave’ approach. At this moment, ‘designing for
recycling’ or ‘eco-design’ are becoming a philosophy that is applied to more and
more materials and products. Recycling must be an important part of our daily lives
if we are to preserve the natural resources of our planet.
Although, in theory, all thermoplastic polymers can be remelted and
recompounded into a new grade compound, the presence of certain additives, blends,
or fillers like glass fibers may limit the application area of the recyclate. Therefore,
in this present study, it was my aim to investigate the ability of recycled rice husk-
filled-high density polyethylene composite injection grade to be processed via
thermoforming process, to produce packaging product.
5
1.3 Objectives
The main objective of this research is:
1. To determine the suitability and optimal formulation of recycled HDPE/Rice
Husk (RHPE) composite injection grade for thermoforming process.
This objective is subdivided into:
a) To determine the characteristics and properties of recycled RHPE
composite and analyze its suitability for thermoforming process.
b) To study which composition based on mechanical properties of
recycled RHPE composite could be used for thermoforming process
according to packaging product.
1.4 Scope of Study
1. Samples preparations:
Recycled RHPE composite for thermoforming process.
i) Ground the composites
ii) Melted mix and sheeted by using two roll mills.
2. Materials characterizations
i) Fourier Transform Infra-Red (FTIR)
ii) Differential Scanning Calorimetry (DSC)
iii) Melt Flow Index (MFI)
6
3. Material performing testing
i) Tearing Test
ii) Tensile Test
4. Product thermoforming
Produce thermoformed product by using the optimal formulation of the
composites.
CHAPTER 2
LITERATURE RIVIEW
2.1 Thermoforming Process
Thermoforming is one of the most frequently used thermoplastic sheet-
forming techniques in food packaging because of ease of production, low cost, high
speed and high performance (Ahyan and Zhang, 2000). Polymers that are widely
thermoformed include polyethylene (PE), polypropylene (PP), polystyrene (PS),
polyvinylchloride (PVC), polycarbonate (PC), and acrylonitrile butadiene styrene
(ABS). These materials have difference in their thermoformability that stem from
differences in their mechanical, thermal and rheological properties (Morye, 2005).
Generally, the process consists of heating thermoplastic sheets to their
softening temperatures forcing the hot and flexible material against the contours of a
mould by mechanical, air or vacuum pressure. When held to the shape of the mould
and allowed to cool, the plastic retains the shape and details of the mould. Since the
sheet heats up, it softens and undergoes sag. Excessive sagging causes defect such as
localized thinning, sheet tearing, and webbing.
8
For each type of polymer, there is a different way to thermoform based on the
deformation temperature. Semicrystalline polymers need to be heated closed to their
melting temperature since this type of polymers maintain their rigidity even above
their glass transition temperature (Tg). Meanwhile, amorphous polymers become
sufficiently soft above their Tg and are therefore thermoformed by heating them
above their Tg (McConnell, 1994).
Morye, (2005) noted that, as semicrystalline polymers have a relatively sharp
melting point, the thermoforming temperature window for these polymers is usually
narrow. Also, the melt strength is typically low in semicrystalline polymers at higher
thermoforming temperatures. This causes excessive sagging in many instances.
However, amorphous polymers that are thermoformed above their Tg in the rubbery
plateau typically have a wide thermoforming temperature range due to the large
rubbery plateau region. Amorphous polymers are therefore generally easier to
thermoform than semicrystalline polymers.
2.1 Rice Husk
Rice husk is a waste from agriculture activities and is abundant in Malaysia
and neighboring countries. The present technique of disposing of this material is by
opening burning, which has now become an environmental issue because it
contributes to air pollution. The use of rice husk as a filler in polymer matrices has
become one of the alternative methods for using this waste material and at the same
time overcoming environmental problems. (Zurina et al., 2004)
9
Figure 2.1 World rice production figures in 1999 (Chaoudhary et al., 2004)
2.2.1 Background
The rice grain, commonly called a seed, consists of the true fruit or brown
rice (caryopsis) and the hull, which encloses the brown rice. The hulls are a by-
product of the rice-mills, and are separated from the husked rice through aspiration.
The husks are about one-fifth by weight of the harvested and dried crop, and contain
about 20% silica and the rest being lignin and cellulose (Chaudhary et al., 2004).
Hull is consisting of organic and inorganic component, which 70-80% of hull dry
weight is organic content (Nurhumaiza, 2001). This hull also called as rice husk,
where these materials contribute to environment contamination.
10
Rice husk ash or silica ash, as it is commonly called and referred to
henceforth, is obtained after burning the rice husks and has attracted much attention
in the past decades. It is classified as an industrial waste and depending upon the
combustion conditions, contains approximately 55–97% silica in partly crystalline
and amorphous forms, the rest being an amalgamation of carbon impurity and a
small fraction of metal oxide impurity (Chaudhary et al., 2004).
2.2.2 General Features and Properties
Generally, rice husk is a part of natural fiber source and as natural fibers, they
are relatively abundant in nature and, therefore, can be obtained from renewable
resources. They can also be recycled. The main disadvantages of natural fibres are:
their low permissible processing temperatures, their tendency to form clumps, and
their hydrophilic nature (Torres and Cubillas, 2005).
Rice husk roughly contains 35% cellulose, 35% hemicellulose, 20% lignin and
10% ash (94% silica), by dry weight basis (Prachayawarakorn and Yaembunying,
2005). As a result of much contents of cellulose, rice husk also can be considered as
cellulosic fiber. The cellulosic fiber tends to degrade at about 200°C and quick
become friable with loss of water (Shanks et al, 2004). Besides, these natural fibers
are presence of large amounts of hydroxyl groups, which then make the properties of
rice husk very much in category of hydrophilic.
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2.2.3 Application
Nowadays, many researchers are interested to study on rice husk as a fiber
composite. Then they are looking to the effect and successful of this kind of fiber
composite as filler in polymer thermoplastic material to reduce the consuming of the
material. This filler is also performed as reinforcement in polymer thermoplastic or
thermosetting to improve their properties. This happened since the cost of polymer
now is now very costly due to the increment of oil price. Rice husk is well referred to
as organic filler.
As a filler, the main cause exist is poor compatibility between hydrophilic
natural fillers and hydrophobic polymers used as matrix. Similar surface tension and
similar polarity of matrix and fillers are required for good interfacial adhesion in
natural filler–reinforced polymer composites. To produce reactive hydroxyl groups
and a rough surface for adhesion with polymeric materials, plant fibers need to
undergo physical and/or chemical treatment to modify the surface structure. The
performance and stability of composite reinforced natural fillers depend on the
development of strong interfacial bonding between fiber and matrix various
composite products such as laminates/panels, doors, roofing sheets, shuttering and
dough moulding compound (Chaudhary et al., 2004)
In addition, the advantages of rice husk used as filler over their traditional
counterparts include relatively low cost, low weight, less damage to processing
equipment, improved surface finish of moulded parts (compared to glass fibre
composites), and good relative mechanical properties (Wambua et al., 2003)
12
2.3 Processing of Natural Fiber Polymer Composites
Many researches had been done in order to improve the thermoplastic
mechanical properties, including blending this polymer with another polymer as well
as with agricultural fibers. These combinations of two or more materials are called
composite. Nowadays, recyclablility of composites also concerned in many research
since the recycling materials in our daily lives is very important consequence to
preserve the natural resources of our planet.
Prachayawarakorn and Yaembunying (2005) did one of the researches that
based on the recylability of composite. They have studied the effect of recycling on
properties of rice husk/polypropylene composite. Rice husk (200 mesh and 40% by
weight) and polypropylene were compounded in a twin-screw extruder and injection
moulding technique was applied in order to obtain testing specimens. It was found
that tensile, flexural strength and % yield elongation of the rice husk-filled
polypropylene were only slightly dropped compared to unfilled polypropylene as
Figure 2.2. The cause in decrease of these properties is due to the immiscibility
between rice husk and polypropylene phase, causing voids or weak point inside the
specimens. Because of the greater stiffness of rice husk than that of polypropylene,
this brings about the improvement in specimen Young's modulus and flexural
modulus that determine stiffness of the specimen. For impact strength, the addition
of rice husk into polypropylene matrix can increase impact strength of the sample
since rice husk can absorb and transfer impact force.
13
0
10
20
30
40
50
60
Mechanical properties
PPPPRH
Tensile strength Flexural strength Elongation at yield
Mpa
Mpa
%
Figure 2.2: Effect of rice husk content on mechanical properties in polypropylene
matrix (Prachayawarakorn and Yaembunying, 2005)
However, when the recycled time of this composite increase, tensile strength,
Young's modulus, flexural strength, flexural modulus and impact strength are found
to be slightly decreased, whereas % elongation at yield seems to be slightly extended.
In general, mechanical behaviour of a polymer is a function of its microstructure or
morphology. The drop in the sample mechanical properties is because the specimens
experience repeated thermal processes, leading to the deterioration of rice husk
component as seen from FTIR spectra (referred Figure 2.3), TGA thermograms and
SEM micrographs. Moreover, enhance in melt flow index (MFI) of the samples was
also obtained when increase the recycled time. Nevertheless, MFI of polypropylene
are greater value than those of the composite specimens. This is attributable to the
rice husk can interrupt the molten polymer to be extruded from the capillary
rheometer (Prachayawarakorn and Yaembunying, 2005).
14
In addition, SEM micrographs revealed the reduction of rice husk particle
size by the recycling process, leading to better phase compatibility between rice husk
and polypropylene. Then, when the rice husk specimen is recycled, % water
absorption of the specimen seems to be reduced with increasing numbers of recycled
times. This is due to the partial removal of cellulose and hemicellulose (as observed
from FTIR and TGA technique), major components in rice husk, bringing about the
reduction of hydrophilicity of rice husk, the main source for absorbing water
(Prachayawarakorn and Yaembunying, 2005).
Figure 2.3: FTIR spectra for (a) polypropylene (b) rice husk and (c) rice husk-filled
polypropylene. (Prachayawarakorn and Yaembunying, 2005)
15
Besides, in different ways of research, Chu and Sullivan (2004) has
investigated about recyclability of a continuous e-glass fiber reinforced
polycarbonate composite. Fiber reinforced plastics are multi-component materials for
which physical properties are strongly dependent on fiber and resin structure. Despite
the disruptive nature of recycling methods on such structures, these materials
nevertheless can be recycled. In this research, they have been studied about the
recyclability of a fiber-reinforced cyclic BPA polycarbonate. It is found that ground
up composite is recyclable and possesses properties as good as or better than a
comparable commercial composite. The processing techniques investigated herein
are injection, extrusion compression, and compression molding. As expected,
processing technique and parameters are important in determining the mechanical
properties of the molded regrind. The results show that injection and extrusion
compression-molding yield recycled composites with good tensile properties, though
the impact strengths are relatively low. This is due to high fiber orientation and fiber
bundle dispersion. On the other hand, compression molded samples, which show
random fiber orientation and low fiber bundles dispersion have relatively low tensile
properties, but excellent impact strength.
Meanwhile, Singleton et al., (2003) were studied on the mechanical
properties, deformation and fracture of a natural fibre/recycled polymer composite. A
composite laminate based on natural flax fibre and recycled high density
polyethylene was manufactured by a hand lay-up and compression moulding
technique. The mechanical properties of the composite were assessed under tensile
and impact loading. Changes in the stress–strain characteristics, of yield stress,
tensile strength, and tensile (Young's) modulus, of ductility and toughness, all as a
function of fibre content were determined experimentally. A significant enhancement
of toughness of the composite was explained in terms of the principal deformation
and failure mechanisms identified by optical microscopy and scanning electron
microscopy. These mechanisms were dominated by delamination cracking, by crack
bridging processes, and by extensive plastic flow of polymer-rich layers and matrix
deformation around fibres. Improvements in strength and stiffness combined with
high toughness can be achieved by varying the fibre volume fraction and controlling
the bonding between layers of the composite.
16
The use of natural organic fillers in addition to post consumer recycled
polymers is getting a growing interest during the last years; this is due to many
advantages they can provide in terms of cost, aesthetic properties, environmental
impact. So, La Mantia and Morreale, (2006) were investigated about the mechanical
properties of recycled polyethylene ecocomposites filled with natural organic fillers.
Several types of wood flour (differing each other with regard to production source
and particle size) were added to a recycled polyethylene coming from films for
greenhouses and the effects of filler type, content, and size were investigated.
Investigation was then focused on the improvement of mechanical properties,
through the addition of polar copolymers (ethylene-co-acrylic acid, ethylene-vinyl
acetate) and a maleic anhydride-grafted-grafted polyethylene in order to try to
overcome the poor adhesion between polar filler particles and nonpolar polymer
chains. Investigation was also based on SEM micrographs. An overall positive
influence of these additives was observed. The addition of organic fillers to post-
consumer recycled polymer matrices causes an increase of elastic modulus (and thus
of rigidity) and of thermo mechanical resistance, while a reduction of ductility is
observed. These effects were more remarkable upon increasing the filler content. The
addition of polar polymers like the EVA copolymer, or the ethylene-co-acrylic acid
copolymer imparted little improvements to the overall properties of the final
composites as shown in Figure 2.4 and 2.5, but slightly lower than expected.
17
Figure 2.4: Elastic modulus vs. filler content for samples with and without
Licocene. (La Mantia and Morreale, 2006)
FIG. 2.5: Elongation at break vs. filler content for samples with and without
Licocene (La Mantia and Morreale, 2006)
18
Moreover, other researches were done by Kamdem et al., (2001). They have
studied on properties of wood plastic composites by compression molding using
particles from virgin pine (VP), recycled urea formaldehyde (UF) bonded (PB) and
recycled chromated copper arsenate (CCA)-treated utility poles retired from services
and virgin and recycled HDPE powder. Wood particles contract from red pine
lumber. The red pine lumber were treated using CCA afterwards removed from
service after 21 years utilization was Wiley milled to wood flour and blended with
recycled high-density polyethylene (HDPE) at 50:50 wood flour-to-plastic weight
ratios in 10 minutes to produce homogenous mixture. The blended materials were
compression molded into panels and the physical and mechanical properties
characterized. Samples containing particles from recycled CCA-treated pine
exhibited flexural bending properties higher than those made with either particle
from virgin pine or recycled urea formaldehyde bonded particleboard. The higher
modulus of elasticity and modulus of rupture from CCA-treated material were
attributed to the increased thermal coefficient of the solid deposits rich in copper
chromium and arsenic present in the cell wall of the recycled CCA-treated wood.
The biological durability and the photo-protection properties were improved for
samples containing recycled CCA-treated wood. The increase in strength properties
was due to the increase in heat diffusion attributed to the presence of copper
chromium and arsenic complexes in the CCA-treated wood.
19
Another research had been carried out by the different researchers;
Bhattacharyya et al., on 2005 that merit attention is that studies of formability
analysis for woodfiber-polypropylene composite sheet retaining their highest
possible aspect ratios. Thermoforming of woodfibre–polypropylene composite sheets
made without any modification of the fibres or the polymer is the focus of this paper,
the emphasis being on their formability and the associated issues. Both the degree to
which a material conforms to the desired part geometry after deformation and the
extent to which a sheet material may be deformed before unacceptable defects occur
are considered. Four thermoforming processes such as V-bending, die-match
forming, air pressure forming and deep drawing have been utilised to examine both
single-curvature and double-curvature deformation conditions. The technique of Grid
Strain Analysis (GSA) has been applied to quantify differences in strain distributions
during sheet deformation.
The effects of thermoforming process parameters and sheet composition on
sheet formability are also discussed. Notably, this study considers composite sheets
reinforced with wood fibres rather than wood flour, enabling the study of fibre lay up
and fibre interlocking effects. While the tensile strengths of the composite sheets
increase marginally, the stiffness increase significantly compared to those of
unreinforced polypropylene. The key deformation mechanism for layered
woodfibre–polypropylene composite sheets is inter-ply shear while intra-ply shear
dominates the deformation of homogeneous sheets. Forming temperature and blank
size have the most pronounced effects on the formability of these composite sheets
(Bhattacharyya et al., 2005)
20
Peterson et al., (2002) were studied on forming performance and
biodegradability of natural fiber polymer composite. A Taguchi approach to
experimental design has been used to analyse the hotpressing and vee-bending of
woodfibre–Biopole composites. Taguchi analysis of the hotpressing process
evidently shows the following manufacturing parameters produce the best tensile
strength and modulus results for this specific study: 210°C platen temperature, 0.5
MPa consolidation pressure, 3 min consolidation time and the application of pressure
once the Biopole melting point (160 °C) has been attained. Analysis of the
hotpressing process clearly shows that platen temperature is the parameter with the
most influence on tensile performance of the composite sheet produced, and
therefore must be most carefully controlled. Notable is the interaction between platen
temperature and consolidation time. Increasing the consolidation time at higher
platen temperatures leads to a significant drop in the tensile performance, which
indicates that a form of thermal degradation might be occurring, in either the fibre or
the polymer itself. Interaction effects also highlight the improved stability of tensile
test results when shorter consolidation times are used.
Meanwhile, in bending (a common manufacturing situation), geometric
conformance is maximised when forming time is 60 s, forming rate is 250 mm/min
and forming radius/thickness ratio is 2 for the composite sheets studied in this paper.
A study of the influence of fibre volume fraction on the biodegradability of these
sheets shows that these composites are highly biodegradable, often degrading at a
rate greater than that of pure Biopole. The results also suggest that a woodfibre mass
fraction of, 15% maximises the degradation of the woodfibre–Biopole. This is
because the woodfibres are believed to act as conduits for the bacteria, thus enabling
greater access and improved degradation rates (Peterson et al., 2002)
21
Different research that has been done by Ismail and Jaffri (1999), were
reported on the physico-mechanical properties of Oil Palm Wood Flour (OPWF)
filled natural rubber composites. The composites were prepared with a laboratory
two roll mill and hot press. Increasing OPWP loading in natural rubber compounds
resulted in reduction of tensile strength, tear strength, and elongation at break but
increased tensile modulus and hardness. The incorporation of OPWF has also
resulted in the reduction of fatigue life. As the filler loading increases, the poor
wetting of the OPWF by the rubber matrix gives rise to poor interfacial adhesion
between the filler and rubber matrix (as evidenced by the scanning electron
microscopy fatigue fracture surface)
As illustrated in Figure 2.6, it shows the effect of OPWF loading on tensile
and tear strength of the composites. Incorporation of filler into a polymer matrix may
increase or decrease the tensile and tear strength of the composites. Unlike fibres,
which have uniform circular cross-section and certain aspect ratios, which normally
improve the strength, the irregular shape of fillers decreases the tensile strength of
the composite due to the inability of the filler to support stresses transferred from
polymer matrix. Also can be seen in Figure 2.7 that the tensile modulus, modulus at
100% elongation (M100) and modulus at 300% elongation (M300) increase with the
increase of filler loading. This observation indicates that the incorporation of OPWF
into the rubber matrix can improve the stiffness of the composites as usually defined
(Ismail and Jaffri, 1999)
22
Fig. 2.6:. The effect of OPWF loading on the tensile and tear strengths of the natural
rubber composites (Ismail and Jaffri, 1999).
Figure 2.7: Relationship between the modulus at 100% elongation (M100) and
modulus at 300% elongation (M300) with OPWF loading (Ismail and Jaffri, 1999).
24
CHAPTER 3
METHODOLOGY
3.1 Material
The raw material that was used in this research was Rice husk- High Density
Polyethylene (RHPE) composites injection grade, where HDPE as a matrix while
rice husk as filler or fiber reinforcement in this composite. This material was
prepared in the project research done by a Master student for injection moulding
process. The compositions of the composites are shows in Table 3.1.
Table 3.1 Composition of rice husk in recycled composite injection grade
Number of Sample
Composition of Rice
Husk (%)
Composition of HDPE
(%)
1 30 70
2 40 60
3 50 50
24
Besides, the properties of pure HDPE injection grade, HD5218AA that produced the
composite was also tabulated in Table 3.2.
Table 3.2 : Properties of Pure HDPE Injection Grade ( Naurah Mat Isa, 2005)
Property Value Unit
Melt Flow Index (2.16kg load) 18 g/10min
Density (annealed) 952 Kg/m2
Tensile Strength at Yield 29 MPa
Elongation at Break 300 %
Flexural Modulus 1050 MPa
Impact Strength (Charpy) 5 kJ/m2
Hardness (Shore D) 65 -
Melting Temperature, Tm 130 °C
Vicat Softening Point (1kg) 123 °C
Thermal Conductivity 0.48 W/m°C
25
3.2 Experimental Procedure
3.2.1 Samples Preparation
3.2.1.1 Grinding
The materials provided, samples of RHPE composites injection grade, were
ground using grinder/crusher machine in the polymer laboratory to form find
particles, so as the next processing stage can be easily performed. The condition of
this process was in room temperature.
3.2.1.2 Two Roll Milling
The crushed recycled composites were mix blended together by means of two
roll mills. The compounding of this composite was set up at 135° C for 7 to 10
minutes excluded 10 minutes of cooling time. This two toll mills has a function to
blend the materials in melt state as well as forming sheet as in Figure 3.1. The
purpose of this melt blending is to ensure the materials are well dispersed and to
homogenize them. The milled sheets were then used for the test samples preparation
for, that are tearing and tensile tests. The amount required to form a sheet were 30
grams.
26
Figure 3.1 Recycled composite milled sheet
3.3 Materials Characterizations
3.3.1 Fourier Transform Infra-Red (FTIR)
The chemical components of pure HDPE injection grade and one of the
compositions of recycled composites were studied by using FTIR spectrometer.
Samples were pressed in thin disc to get the thickness of 10-100 µm for FTIR
measurements. The FTIR spectra were recorded on a Spectrum 2000 GX
spectrometer (Perkin-Elmer) using KBr disc technique for 16 scans. The resolution
was 4 cm-1 and the spectra scanned range was 4000-370 cm-1.
27
3.3.2 Differential Scanning Calorimetry (DSC)
Thermal analysis of the recycled composites was carried out using
Differential Scanning Calorimetry (DSC 7 – Perkin Elmer). The samples were placed
in sealed 10 mg aluminium pans under constant nitrogen flow. DSC was performed
by heating a recycled composite sample of about 5-12 mg from 80 to 160°C. The
heating rate used was at 5 °C/min. The objective from this measurement was to study
the melting points of those composites. Melting temperature, Tm was obtained from
the peak value of the endothermic graph. Thermal analysis results provide process
parameters for thermoforming, and two-roll milling, thus making processing easier;
example processing temperature was predicted from Tm.
3.3.3 Melt Flow Index (MFI)
Melt Flow Rate measures the rate of extrusion of thermoplastics through an
orifice at a prescribed temperature and load. It provides a means of measuring flow
of a melted material that can be used to differentiate grades as with polyethylene, or
determine the extent of degradation of the plastic because of moulding. Degraded
materials would generally flow more as a result of reduced molecular weight, and
could exhibit reduced physical properties.
Approximately 7 grams of the material were loaded or fully loaded into the
barrel of the melt flow apparatus. Melt flow index was performed according to
ASTM D 1238, in melt flow indexer with the temperature of 190°C. The weight of
2.16 kg was applied to a plunger and the molten material was forced through the die.
The extrudate was cut manually referred to Procedure A at the time of 30 sec then it
was weighed. Then, melt flow index was reported as g/10min.
28
3.4 Material Performance Testing
For this section, the performances of materials were studied by doing
mechanical tests, which includes tear and tensile tests. These entire mechanical tests
were carried out according to ASTM. Thus, the optimal composition of recycled
RHPE composite could be determined for producing a good thermoform product.
3.4.1 Trouser Tear Resistance
Tear resistance measures the ultimate force required to tear film or sheet at a
constant tearing speed across a specimen divided by the specimen thickness. It often
used for quality control checks or for material comparison where tear failures are
possible. In addition, this testing is used for films and sheeting with a thickness less
than 1 mm by a single-tear method.
The specimen was cut to the appropriate shape from a sheet. The shape of the
specimen designed as in Figure 3.2 to create a tear when the specimen pulled in
tension. This testing was carried out according to BS2782 Method 360 B, Part 3 by
using a tensile test machine, which is Instron Machine Model 5567. The average
thickness of the specimen was measured for ten test specimens. Then the specimen
was placed in the grips of the testing machine and pulled at a rate of 20 mm per
minute as in Figure 3.3 with 10 N load until rupture.
29
T= 1.5 inch
L= 3 inch
Figure 3.2: Trouser Tear Specimen
Figure 3.3: Trouser Tear Test
30
3.4.2 Tensile Test
The tensile test was performed by elongate a specimen and measuring the
load carried by the specimen. From knowledge of the specimen dimensions, the load
and deflection data could be translated into a stress-strain curve. A variety of tensile
properties could be extracted from the stress-strain curve.
The sheet produced was cut into tensile test samples. The tensile tests were
carried out according to ASTM D-683 Type V on samples were tested at the constant
room temperature (23 ± 2°C). The dimensions of specimen Type V are shown as in
Table 3.3. Ten specimens were tested in unidirections, and then the average of width
and thickness of specimens were measured. Load of 100 N at 5 mm/min were
applied to the specimens. The tensile property measurements (tensile strength,
percent of elongation at yield, and Young’s modulus) from dumbbell specimens were
carried out in a Universal Testing Machine, that is Instron Machine Model 5567.
Table 3.3: Dimensions of specimens Type V
Dimensions Thickness, T, mm (in)
Width of narrow section 3.18 (0.125)
Length of narrow section 9.53 (0.375)
Width overall, min 9.53 (0.375)
Length overall, min 63.5 (2.500)
Gage length 7.62 (0.300)
Distance between grips 25.4 (1.0)
Radius of fillet 12.7 (0.5)
31
3.5 Product Thermoforming
After getting the optimal formulation of recycled RHPE composite based on
the best mechanical properties performance, this composite then were precede for
thermoforming process. This stage of process was done only to prove the capability
of recycled RHPE composite injection grade to be thermoformed to produce product
through thermoforming process.
CHAPTER 4
RESULT AND DISCUSSION
4.1 Introduction
In this research, the samples were studied on for their thermal characteristics
for the pre-determination of the processing parameters as well as melt flow
behaviour for standard thermoform grade range suitability, and the molecular
structure degradation determination. Two mechanical tests, tearing and tensile tests
were carried out to study the performance of the samples for packaging suitability.
The tensile and tear analysis concentrated only on:
1. Tear strength
2. Tensile modulus
3. Tensile strength
4. Elongation at break
33
4.2 Material Characterization
4.2.1 Fourier Transform Infrared
In general, FTIR (Fourier Transform Infrared) Spectroscopy, or simply FTIR
Analysis, is a failure analysis technique that provides information about the
chemical bonding or molecular structure of materials, whether organic or inorganic.
The technique works on the fact that bonds and groups of bonds vibrate at
characteristic frequencies. A molecule that is exposed to infrared rays absorbs
infrared energy at frequencies, which are characteristic to that molecule. During
FTIR analysis, a spot on the specimen is subjected to a modulated IR beam. The
specimen's transmittance and reflectance of the infrared rays at different frequencies
is translated into an IR absorption plot consisting of reverse peaks. The resulting
FTIR spectral pattern then is analyzed and matched with known signatures of
identified materials in the FTIR library.
FTIR spectra of recycled rice husk-filled- HDPE composites injection grade
are presented in Figure 4.1. The spectrum shows the wave numbers in the region of
2600-3100 cm-1 and 1375-1465 cm-1. These wave numbers illustrating the metil
upon saturated hydrocarbon that is produced from C-H stretching of aliphatic
carbon, and CH2 and /or CH3 deformation respectively which present the chemical
group in HDPE molecules. While, peak position also shows the stretching of
aromatic carbon upon C=C at 1529.889 cm-1, 3114.832 cm-1 and 3440.191 cm-1
assigned to O-H stretching of hemicullose and 1705.638 cm-1, which is assigned to
C=O stretching of lignin in rice husk component (Prachayawarankorn and
Yaembunying, 2005).
34
Even the material used in this study was a recycled composite, but it can
retain the existing of rice husk component in the composite. This can be proved by
the comparison between the FTIR analysis of recycled RHPE composite and rice
husk-filled polypropylene as in Figure 4.2 (c). It clearly shows the vibrational bands
of compositions from rice husk that presents the wave numbers in region of 3250-
3500 cm-1, 1700-1750 cm-1 and 1400-1600 cm-1 with respect to hemicellulose,
lignin and aromatic carbon stretching.
Therefore, it indicates that the major chemical structure of rice husk filled in
HDPE samples is not affected by recycling process. It also shows the rice husk
contents was not undergo degradation during the injection moulding process, as well
as not formed thermoset composite product. As a result, this shows the ability of
recycled RHPE composite can be reprocessed or recompounded into other grade
compound/product.
35
Figure 4.1: FTIR spectra for pure HDPE and recycled rice husk-filled HDPE
composite.
Figure 4.2: FTIR spectra for (a) polypropylene (b) rice husk and (c) rice husk-filled
polypropylene. (Prachayawarakorn and Yaembunying, 2005)
36
4.2.2 Differential Scanning Calorimetry Analysis
The change of the melting point of the polymers is due to the incorporation of
fibers (Manikandan et al., 1996). The DSC results are summarized in Table 4.1 as
the melting temperature of the materials used. The comparison between the various
percentage of rice husk in the recycled RHPE composite injection grade are
illustrated in Figure 4.3. During the DSC heating scan, the recycled RHPE
composites injection grade show only one endothermic peak that occurred in the
melting region. Thus the peak indicates the melting temperature, Tm of the materials.
The melting temperature of pure HDPE injection grade was found to be
130°C (Naurah, 2005). The incorporation of 30%, 40%, and 50% of rice husk
contents in that composite had reduced the Tm of pure HDPE to 128°C, 127°C and
125°C respectively. It can be seen that Tm of pure HDPE was depressed by about 2-
5°C by the addition of certain percentages of rice husk. The addition of rice husk in
HDPE lowered the Tm of HDPE and shifted to further lower temperatures when the
amount of rice husk contents was increased. However, for the curve of RH40PE,
there are two peaks observed. The second peak occurs may be due to the presences
of impurity during the samples preparation or high molecular weight HDPE. This is
possible because the temperature range over which a mixture of compounds melts is
dependent on their relative amounts, consequently, will broadened the melting.
Since temperature does not differ much from the pure RHPE therefore
recycled RHPE does not undergo much thermal degradation, thus can be reprocessed
for other usage. The predetermined Tm for the thermoform processed parameter
using recycled RHPE are 128.16 ◦C, 127.16 ◦C and 125.95 ◦C with respect to 30%, 40
%, 50 % rice husk contents.
37
Table 4.1: Melting temperature of pure HDPE and recycled RHPE composites
Figure 4.3: Effect of rice husk loading on the melting point for recycled RHPE
composite injection grade.
Material
Melting Temperature, Tm (°C)
Pure HDPE injection grade
130.03
Recycled RH30PE composite
128.16
Recycled RH40PE composite
127.95
Recycled RH50PE composite
125.95
38
4.2.3 Melt Flow Index
Melt flow index values of pure HDPE injection grade and various
compositions of rice husk contents in recycled RHPE composite injection grade are
shown in Figure 4.4. It can be seen that the melt flow index of pure HDPE injection
grade gave greater value than other recycled RHPE composites injection grade. As
the rice husk content increases, the MFI value decreases for all composites. This is
expected since the addition of fillers or fibers i.e rice husk to the HDPE restricts
molecular motion, imposing extra resistance to flow (Ahmad Fuad et al., 1997).
While, according to Prachayawarakorn and Yaembunying, (2005), the lower MFI
value is due to the interruption of rice husk particle in the molten polymer to be
extrudate from the capillary rheometer.
The molecular structure of samples composites has an influence on its
properties and processing characteristics. The MFI value gives a rough indication of
molecular weight or chain length. A material with a high melt index has shorter
chains and a lower molecular weight or smaller molecules, and vice versa. This
corresponds to the general deterioration in physical properties such as melt viscosity,
heat softening point, tensile strength at rupture and others, as the MFI increases or
decrease. Therefore, the lower MFI value indicates that greater melt viscosity in the
filled samples. The usual trend of decreasing melt index values to filler content is
reversed and the melt index actually increases with filler contents. While, the
observation shown that resin degradation is expected to result in lowering the
molecular weight, easing material flow and thus higher MFI values (Ahmad Fuad et
al., 1997).
According to Bruins, the range of MFI value for the standard thermoform
grade is 2-10 g/10 min. Therefore, from this MFI analysis, only recycled RHPE
composite with 40 % and 50 % rice husk contents were fell in this standard MFI
values. So, these recycled composite have show their suitability to be thermoformed.
39
0
2
4
6
8
10
12
14
16
18
20
0 30 40 50
Percentage of Rice Husk (%)
MFI
Val
ue (g
/10m
in)
Figure 4.4: Effect of rice husk loading on the flow behavior for recycled RHPE
composite injection grade.
40
4.3 Material Performing Test
4.3.1 Tearing Test
4.3.1.1 Tear Strength
` In tearing test, the most important property that would be considered is tear
strength. The tear strength is a measure of the resistance of a material to tear forces.
Tear resistance involve a predominantly effect by interfacial bonding in flexible
composite. As in impact resistance testing, where area under the stress-strain curve is
proportional to toughness or the energy to fracture the specimen, tear resistance is a
measure of crack or slit propagation (Harry and John, 1988). While, according Dilara
and Briassoulis (1998), tear resistance of plastic films is a complex function of its
ultimate resistance to rupture. Tear resistance of plastic films is very important with
regard to their overall mechanical behavior and a common failure mechanism for
agricultural plastic films.
Table 4.2 shows the mechanical properties of recycled RHPE composites
injection grade. While, Figure 4.5 shows effect of rice husk loading on the tear
strength for recycled RHPE composite injection grade. Incorporation of filler into a
polymer matrix may increase or decrease the tear strength of the composites.
Referring to Figure 4.5, the tear strength was decreased with the increase in the
percentage of rice husk filled in the composites. The decreased tear strength of the
composite was due to the inability of the filler to support stresses transferred from
polymer matrix.
41
This has been attributed to the incapability of rice husk fibers to dissipate
stress through the shear yield prior to fracture, and they hindered the local chain
motions of the HDPE molecules that enable the matrix shear yield. Since the fiber-
matrix, interfacial strength is too low, poor stress will then occurs and a weak
composite were resulted. Then, it decreases the ability of composite to resist the
stress during slit propagation (Nurfatimah, 2006).
Based on research by Ismail and Jaffri, 1999, the maximum tear strength for
film composite is 20 N/mm. Therefore, when this value is compared with tear
strength of the recycled RHPE composite, it shows that the suitability of recycled
RHPE composite to be used as thermoform packaging product.
Table 4.2: Mechanical properties of recycled RHPE composites injection grade
Samples
RH30PE
RH40PE
RH50PE
Tear strength
(N\mm)
5.5064 ± 0.41
4.6244 ± 0.08
3.8051 ± 0.09
Young’s
modulus (GPa)
1.232 ± 0.98
2.347 ± 0.83
1.842 ± 1.11
Tensile
strength (MPa)
16.258 ± 0.98
13.9211 ± 0.83
10.4289 ± 1.11
Elongation at
break (%)
7.5046 ± 0.21
4.9914 ± 0.37
4.1846 ± 0.74
42
0
1
2
3
4
5
6
7
20 30 40 50 60
Percent of Rice Husk Contents, (%)
Tea
r St
reng
th, (
N/m
m)
Figure 4.5: Effect of rice husk loading on the tear strength for recycled RHPE
composite injection grade.
4.3.2 Tensile Test
4.3.2.1 Young Modulus
As expected, the modulus, which indicates materials stiffness, increases
steadily with addition of rice husk contents in the composites, but it slightly dropped
when 50% filled the fibers as shown in Figure 4.6. Because of the greater stiffness of
rice husk than that HDPE, this brings about the improvements in specimen Young’s
modulus that determine stiffness of the specimen (Prachayawarankorn and
Yaembunying, 2005). In other words, rice husk itself has a higher Young’s modulus
compared with HDPE. This reflects the increase of brittleness of the materials
(Hattotuwa et al., 2002).
43
In general, mechanical behavior of a polymer is a function of its
microstructure or morphology (Prachayawarankorn and Yaembunying, 2005).
Fibrous or fiber filler work by having a given stress transferred through the polymer
matrix medium to the dispersed fiber themselves, which have greater strength
stability properties than the polymer medium itself. This is the reason how the filler
increase the modulus of polymer (Azman Hassan). However, for the decreasing
modulus when added with 50% of rice husk is due to the immiscibility between rice
husk and HDPE phase, and tendency to agglomerate within themselves, causing
voids or weak point inside the specimens. Thus, it contributes to weak interfacial
adhesion with polymer matrix (Herrera-Franco et al., 1997).
On the other hand, seem the material used were recycled composite, may be
the Young’s modulus of this recycled composite are slightly decrease upon the
recycling process. This due to the reduction of particles sizes of rice husk fibers upon
recycling then gives effect on the fiber aspect ratio. Nevertheless, although the fibers
have a low aspect ratio, they are able to impart a significant improvement in stiffness
by hindering the movement of HDPE molecules (Abu Bakar et al., 2005).
Based on the research, that had done by Peterson et al. 2002, the maximum
tensile modulus of composite film for thermoforming property analysis is 3.5 GPa.
Therefore, the tensile modulus obtained for the recycled RHPE composites from this
study were satisfied the requirement of the composite film for thermoforming
process. This shows that the recycled RHPE composite were suitable to be used as
thermoform packaging product.
44
0
0.5
1
1.5
2
2.5
3
20 30 40 50 60
Percent of Rice Husk Content, (%)
Youn
g's
Mod
ulus
, (G
Pa)
Figure 4.6: Effect of rice husk loading on the Young’s modulus for recycled RHPE
composite injection grade.
4.3.2.2 Tensile Strength
In the recycled RHPE composites injection grade, the incorporation
between rice husk and HDPE was found to gradually decrease in tensile strength
with additional rice husk content as shown in Figure 4.7. According to Ismail and
Azahari, 2002, this happened due to the immiscibility between rice husk and high-
density polyethylene phases, causing voids or weak points inside the specimens.
Then it is also revealed that no reinforcement be obtained by the addition of filler,
and possible agglomeration, which weaken the stress transfer from matrix to filler.
45
The agglomeration of the fibers may be due to the relatively weak interaction
between fibers and matrix, compared to the strong fiber-fiber interaction caused by
hydrogen bonding. Therefore, fibers have tendency to agglomerate among
themselves into fiber bundles, which consequently lower the area of contact with the
matrix. These fibers tend to cling together in bundles and to resist dispersion as the
fiber content increase (Abu Bakar et al., 2005)
In addition, in accordance with Abu Bakar et al., 2005, the weakened fiber-
matrix interface become potential sites for crack growth because of the inability of
fibers to support the stress transfer to the polymer matrix. Voids in the matrix may
als become site for cracking initiation. So, without having time to strain enough,
these composite were already tended to rupture. La Mantia and Morreale , 2006,
have found that, the decrease of tensile strength is related to the increase of fragility
or brittleness of the samples. This also highlighted by the decrease of elongation at
break. The fact that rigidity, which is quantified by Young’s modulus of the samples,
filled with rice husk is slightly higher.
From this study, this recycled composite has shown the suitability to be
thermoformed into packaging product. This packaging product usually is made up
from plastic film. Based one research, written by Antonio and Macros, 2003, the
maximum tensile strength for plastic film based recycled composite is 25 MPa.
Therefore, when this value is compared with tensile strength of the recycled RHPE
composite, it shows that the suitability of recycled RHPE composite to be used as
thermoform packaging product.
46
4
6
8
10
12
14
16
18
20 30 40 50 60
Percent of Rice Husk Contents, (%)
Ten
sile
Str
engt
h, (M
Pa)
Figure 4.7: Effect of rice husk loading on the tensile strength for recycled RHPE
composite injection grade.
4.3.2.3 Elongation at Break
Other properties can be discussed in tensile properties is elongation at break
of the composites. This elongation at break were measured the elongation at the
moment of rupture of the test specimens. As we can see in Figure 4.8, the elongation
at break of the composites is gradually decreased correspond to the increased in rice
husk loading. Same reason as tensile strength property, that is due to the
immiscibility between rice husk and HDPE phases, resulting voids or weak point,
inside the specimens (Prachayawarankorn and Yaembunying, 2005).
47
Besides, the decline in elongation at break may be due to the reduction of
extensible matrix in the composites with increasing filler content. Moreover, the
filler particles have created the resistance for the matrix molecules to deform upon
the elongation of the specimens (Ismail and Azahari, 2002). This occurrence has
been proven during the testing of the composite’s melt flow behavior. Referred back
to Figure 4.4, as the filler filled composites increase, the melt flow was decreased
which is due to the interruption of rice husk particle in the molten polymer. This is
also reported by Ismail and Jaffri, in 1999 that the decreasing of elongation at break
with addition of more filler to the polymer matrix. With increasing in filler loading,
the stiffness and brittleness of the composite increase gradually with associated
decrease in the elongation at break.
Theoretically, the stress whitening occurs almost immediately on elongation
of composites containing high filler concentration, or the filler consist of large
particles. In both cases, the matrix is restricted in its ability to stretch between
particles or around larger particles and debonding of the particles causes cavitation
that appears as stress whitening. Smaller particles at the low concentration are free to
move with the matrix, and correspondingly, the matrix is free to stretch around them.
However, very weak interfacial bonding causes almost intermediate separation of the
matrix from the particles, and cavitations begin at low elongation (Harry and John).
Meanwhile, according to Malpas and Kemphorn, 1986, the limitation value of
elongation at break of filled HDPE for thermoform properties is 22 ± 2 %. From this
study, the recycled composites have shown the suitability to be thermoformed into
packaging product as the result obtained were not exceed the maximum value. Then,
these recycled RHPE composites have the ability to be reprocessed into the
thermoform grade product.
48
0
1
2
3
4
5
6
7
8
9
10
30 40 50
Percentage of rice husk content, (%)
Elo
ngat
ion
at b
reak
, (%
)
Figure 4.8: Effect of rice husk loading on the elongation at break for recycled RHPE
composite injection grade.
4.4 Thermoforming Process
From the material characterizations and mechanical testing above, recycled
RHPE composite with 40% rice husk contents was considered as the suitability and
optimal formulation of recycled RHPE composite injection grade for thermoforming
process. Therefore, to prove this concern, the sample of sheet from two-roll milling
was used in compression moulding process (also known as hot press) to produce a
thin film composite. The film was then thermoformed at 123 °C based on the
predetermined temperature of recycled RHPE composite filled with 40 % of rice
husk. The duration of this process was within 10 minutes under 2 bar. The product
developed as in Figure 4.9.
49
Figure 4.9: Product from thermoforming process
CHAPTER 5
CONCLUSIONS AND RECOMMENDATIONS
5.1 Conclusions
Recycled RHPE composite injection grade contained different percentages of
rice husk have been studied on the capability to be processed using thermoforming
technique. The result in this present study showed that a useful recycled composite
injection grade with good properties could be successfully recompounded into a
thermoforming grade. Several conclusions can be made from this study regarding to
the effect of fiber contents to the mechanical properties which are tear and tensile
properties.
The incorporation of the rice husk into HDPE matrix has resulted in the
improvement in the tensile modulus or Young’s modulus, but it caused decrement in
tensile strength and elongation at break, with additional of rice husk contents. This is
due to the greater stiffness of rice husk than that HDPE, that result in the
improvements in specimen Young’s modulus thus determine stiffness of the
specimen.
51
However, the immiscibility between rice husk and high-density polyethylene
phases, causing voids or weak points inside the specimens result in the decreased in
tensile strength and elongation at break. It is also observed that no reinforcement is
obtained by the addition of filler, only possible agglomeration, which weaken the
stress transfer from matrix to filler. This effect also related to the increase in fragility
or brittleness of the samples. , The filler particles have created the resistance for the
matrix molecules to deform upon the elongation of the specimens, which has been
proven with the composite’s melt flow behavior i.e. MFI test.
The same situation also occurred on tearing properties. The tear strength was
decreased with the increases the percentage of rice husk filled in the composites. The
decreased in tear strength of the composite due to the inability of the filler to support
stresses transferred from polymer matrix. This has been attributed to the incapability
of rice husk fibers to dissipate stress through the shear yield prior to fracture, and
they hindered the local chain motions of the HDPE molecules that enable the matrix
shear yield. If the fiber-matrix interfacial strength is too low, poor stress will then
occurs and a weak composite were resulted. Then, it decreases the ability of
composite to resist the stress during slit propagation.
The overall results from this study shows that the mechanical properties of
recycled RHPE composites injection grade were strongly affected by the rice husk
contents thus effect the interfacial adhesion between fibers-matrix phases. However,
the best formulation that can be thermoformed based on the optimum value of
modulus and strength of the composites are gave by the recycled RHPE composites
contained 40% rice husk.
52
From the result obtained, there is several factors influence the suitability of
this recycled RHPE composite to be thermoformed. This can be found from the
analysis of FTIR, DSC and also MFI. The rice husk contents was not undergo
degradation and thermal degradation during the injection moulding process, as well
as not formed thermoset composite product. Besides, MFI value of recycled RHPE
composite also found fall within the range of MFI value for the standard
thermoform grade that is between 2-10 g/10 min. Moreover, it also found that, the
mechanical properties of this recycled RHPE composite were fulfilling the
requirements of thermoform material grade. This shows the suitability of recycled
RHPE composite can be reprocessed or recompounded into thermoforming grade
compound/product.
5.2 Recommendations
There are a few approaches, which may be used to improve the weakness in this
research study. The suggestions are:
1. Recycled RHPE composite has to use a coupling agent to get better in
mechanical properties. This formulation will be achieved in good dispersion
and wetting of the fibers in the matrix, then giving rise to a strong interfacial
adhesion.
2. Further study on thermoforming process that need to be carried out on the
determination of the optimum operating condition which are forming
temperature, air forming pressure and heating time onto the thermoformed
recycled RHPE composites injection grade.
53
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57
APPENDIX
APPENDIX A
PERFORMANCE OF RECYCLED HIGH DENSITY POLYETHYLENE (HDPE)/
RICE HUSK COMPOSITE INJECTION GRADE FOR THERMOFORMING
PROCESS
Fatimah Zaharah, C.M., Wan Aizan, W.A.R.
Polymer Engineering Department,Faculty of Chemical and Natural Resources
Engineering, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor, Malaysia
ABSTRACT All thermoplastic polymers can be remelted and recompounded into a new
grade, but the presence of certain additives, blends, or fillers like glass fibers may limit
the application area of the recyclate. In this present study, it was my aim to investigate
the ability of recycled rice husk-filled-high density polyethylene (RHPE) composite
injection grade to be processed using thermoforming technique. Various recycled RHPE
composite injection grade, that is with composition 30%, 40% and 50% of rice husk were
investigated in this study. These composites were first grinded to a fine form using
laboratory grinder machine before being melt-blended and milled into sheets on a two-
roll mill. Then, test specimens were prepared to study on the mechanical properties that is
tearing test and tensile test. The results showed the tear and tensile strength were reduced
significantly with the percentage increase of rice husk contents. However, the Young
modulus had increased. MFI was found to decrease as compared to the virgin HDPE, but
is within the standard MFI for thermoforming material grade. FTIR spectroscopy and
DSC thermal analysis used to characterize the recycled composite materials. Recycled
RHPE composites containing 40% rice husk exhibit good properties and showed high
capability to be thermoformed.
Keywords: Rice husk; HDPE; recycled composite; processing grade; thermoforming
1.0 Introduction
Polymer composites have been subjected to increasing interest, study, and
utilization for some decades. During the last years, however, the increase in
environmental concern has pointed out how it is also necessary to reduce and rationalize
the use of polymeric materials, not only due to their non-biodegradability, but due to their
production requires large amounts of oil, which is notoriously not renewable. All these
issues have induced to look for alternatives. Thus, the interest arises toward polymer
composites filled with natural organic fillers, especially in conjunction with recycled
and/or recyclable polymer matrices. This class of composites (sometimes indicated as
“green composites”) shows other interesting features [5].
Besides, environmental legislation, consumer concern, and waste management
approaches based on concepts like the ‘polluter pays’ are all increasing the pressure on
manufacturers of materials and end-products to consider the environmental impact of
their products at all stages of their life cycle including ultimate disposal, a ‘cradle to
grave’ approach. At this moment, ‘designing for recycling’ or ‘eco-design’ are becoming
a philosophy that is applied to more and more materials and products. Recycling must be
an important part of our daily lives if we are to preserve the natural resources of our
planet.
Although, in theory, all thermoplastic polymers can be remelted and
recompounded into a new grade, the presence of certain additives, blends, or fillers like
glass fibers may limit the application area of the recyclate. Therefore, in this present
study, it was intended to investigate the ability of recycled rice husk-filled-high density
polyethylene composite injection grade to be processed by thermoforming process, which
is produced packaging product.
2.0 Methods
2.1 Materials
The raw materials that were been used in this research are Rice husk- High
Density Polyethylene (RHPE) composites injection grade, where HDPE as a matrix while
rice husk as filler or fiber reinforcement in this composite. There were three compositions
of the composites had been used, 30%, 40% and 50% of rice husk contents.
2.2 Sample preparations
The materials provided, which are the samples of RHPE composites injection
grade were ground using grinder/crusher machine in the polymer laboratory to form find
particles. These find/small particles would make the next processing easy to perform. The
condition of this process was in room temperature. Then, the crushed recycled
composites were mix blended together by means of two roll mills. The compounding of
this composite was set up at 135° C for 7 to 10 minutes excluded 10 minutes of cooling
time. This two toll mills has a function to mix blending the materials in melt state as well
as it would form a sheet as in Figure 3.1. The purpose of this melt blending is to ensure
the materials are well dispersed and to homogenize them. The milled sheets were then
used for the preparation for samples testing, that are tearing and tensile test. The amounts
of these materials to form a sheet were 30 grams.
2.3 Material characterizations
The chemical components of samples pure HDPE injection grade and one of the
compositions of recycled composites were studied by using FTIR spectrometer. Then,
samples were pressed in thin disc to get the thickness of 10-100 µm for FTIR
measurements. The FTIR spectra were recorded on a Spectrum 2000 GX spectrometer
(Perkin-Elmer) using KBr disc technique for 16scans. The resolution was 4cm-1 and the
spectra scanned range was 4000-370 cm-1.
Then, thermal analysis of the materials that is recycled composites was carried out
using Differential Scanning Calorimetry (DSC 7 – Perkin Elmer). The samples were
placed in sealed 10 mg aluminium pans under constant nitrogen flow. DSC was
performed by heating a recycled composite sample of about 5-12mg from 80 to 160°C.
The heating rate was used at 5 °C/min. The objective from this measurement was to study
the melting points of those composites.
Melt flow index was performed according to ASTM D 1238, in melt flow indexer
with the temperature of 190°C. The weight of 2.16kg was applied to a plunger and the
molten material was forced through the die. The extrudate was cut manually referred to
Procedure A at the time of 30sec then it was weighed. Then, melt flow index was
reported as g/10min.
2.4 Material Performance Test
For this section, the performances of materials were studied by doing mechanical
tests, which includes tear and tensile tests. Thus, the optimal composition of recycled
RHPE composite could be determined for producing a good thermoform product. For
tearing test, the specimen was cut to the appropriate shape from a sheet (trousers shape)
to create a tear when the specimen pulled in tension. This testing was carried out
according to BS2782 Method 360 B, Part 3 by using a tensile test machine, which is
Instron Machine Model 5567. The average thickness of the specimen was measured for
ten test specimens. Then the specimen was placed in the grips of the testing machine and
pulled at a rate of 20 mm per minute with 10 N load until rupture. Then the tensile test
was performed by elongate a specimen and measuring the load carried by the specimen.
The sheet produced was cut into tensile test samples. The tensile tests were carried out
according to ASTM D-683 Type V on samples were tested at the constant room
temperature (23 ± 2°C). Load of 100 N at 5mm/min were applied to the specimens. The
tensile property measurements were carried out in a Universal Testing Machine, that is
Instron Machine Model 5567.
2.5 Product Thermoforming
After getting the optimal formulation of recycled RHPE composite based on the
best mechanical properties performance, this composite then were precede for
thermoforming process. This stage of process was done only to prove the capable of
recycled RHPE composite injection grade could be thermoformed to produce product
through thermoforming process.
3.0 Results and discussion
3.1 Material Characterizations
FTIR spectra of recycled rice husk-filled- HDPE composites injection grade are
presented in Figure 1. The spectrum shows the wave numbers in the region of 2600-3100
cm-1 and 1375-1465 cm-1. These wave numbers illustrating the metil upon saturated
hydrocarbon that is produced from C-H stretching of aliphatic carbon, and CH2 and /or
CH3 deformation respectively which present the chemical group in HDPE molecules.
While, peak position also shows the stretching of aromatic carbon upon C=C at
1529.889 cm-1, 3114.832 cm-1 and 3440.191 cm-1 assigned to O-H stretching of
hemicullose and 1705.638 cm-1, which is assigned to C=O stretching of lignin in rice
husk component (Prachayawarankorn and Yaembunying, 2005).
Even the material used in this study was a recycled composite, but it can retain
the existing of rice husk component in the composite. Therefore, it indicates that the
major chemical structure of rice husk filled in HDPE samples is not affected by
recycling process. It also shows the rice husk contents was not undergo degradation
during the injection moulding process, as well as not formed thermoset composite
product. As a result, this shows the ability of recycled RHPE composite can be
reprocessed or recompounded into other grade compound/product.
Fig. 1. FTIR spectra for pure HDPE and recycled rice husk-filled HDPE
composite
From the DCS analysis, the results are summarized as the melting temperature of
the materials used. The comparison between the vary percentage of rice husk in the
recycled RHPE composite injection grade are illustrated in Figure 2. The melting
temperature of pure HDPE injection grade was found to be 130°C [5]. The incorporation
of 30%, 40%, and 50% of rice husk contents in that composite were reduced the Tm of
pure HDPE to 128°C, 127°C and 125°C respectively. It can be seen that Tm of pure
HDPE was depressed by about 2-5°C by addition of percentage of rice husk contents.
The addition of rice husk in HDPE lowered the Tm of HDPE and shifted to further lower
temperatures when the amount of rice husk contents was increased. However, for the
curve of RH40PE, there is shows two peaks. The second peak occurs may be due to the
presences of impurity during the samples preparation. The impurity might be the pure
HDPE materials that were not mixed well during the process. Therefore, it also gave the
thermal reading upon the DSC analysis at around 130°C.
0
5
10
15
20
0 30 40 50
Percentage of Rice Husk (%)
MFI
Val
ue (g
/10m
in)
Fig. 2. Effect of rice husk loading on
the melting point for recycled RHPE
composite injection grade.
Fig 3. Effect of rice husk loading on the
flow behavior for recycled RHPE
composite injection grade.
Since temperature does not differ much from the pure RHPE therefore recycled
RHPE does not undergo much thermal degradation, thus can be reprocessed for other
usage. The predetermined Tm for the thermoform processed parameter using recycled
RHPE are 128.16 ◦C, 127.16 ◦C and 125.95 ◦C with respect to 30%, 40 %, 50 % rice husk
contents.
Melt flow index values of pure HDPE injection grade and varies compositions of
rice husk contents in recycled RHPE composite injection grade are shown as in Figure 3.
It can be seen that the melt flow index of pure HDPE injection grade gave greater value
than others recycled RHPE composites injection grade. As the rice husk content
increases, the MFI value decreases for all composites. This is an expected event as
addition of fillers or fibers i.e rice husk to the HDPE restricts molecular motion, imposing
extra resistance to flow [1]. While, according to [7] the lower MFI value is due to the
interruption of rice husk particle in the molten polymer to be extrudate from the capillary
rheometer.
The molecular structure of samples composites has an influence on its properties
and processing characteristics. The MFI value gives a rough indication of molecular
weight or chain length. A material with a high melt index has shorter chains and a lower
molecular weight or smaller molecules, and vice versa. This corresponds to the general
deterioration in physical properties such as melt viscosity, heat softening point, tensile
strength at rupture and others, as the MFI increases or decrease. Therefore, the lower MFI
value indicates that greater melt viscosity in the filled samples.
3.2 Material Performing Test
Table 1 shows the mechanical properties of recycled RHPE composites injection
grade. While, Figure 4 shows effect of rice husk loading on the tear strength for recycled
RHPE composite injection grade. Incorporation of filler into a polymer matrix may
increase or decrease the tear strength of the composites. Referred to Figure 4, the tear
strength was decreased with the increases the percentage of rice husk filled in the
composites. The decreases tear strength of the composite due to the inability of the filler
to support stresses transferred from polymer matrix.
This has been attributed to the incapable of rice husk fibers to dissipate stress
through the shear yield prior to fracture, and they hindered the local chain motions of the
HDPE molecules that enable the matrix shear yield. Since the fiber-matrix, interfacial
strength is too low, poor stress will then occurs and a weak composite were resulted.
Then, it decreases the ability of composite to resist the stress during slit propagation [8].
Table 1: Mechanical properties of recycled RHPE composites injection grade
Samples
RH30PE
RH40PE
RH50PE
Tear strength
(N\mm)
5.5064 ± 0.41
4.6244 ± 0.08
3.8051 ± 0.09
Young’s
modulus (GPa)
1.232 ± 0.98
2.347 ± 0.83
1.842 ± 1.11
Tensile
strength (MPa)
16.258 ± 0.98
13.9211 ± 0.83
10.4289 ± 1.11
Elongation at
break (%)
7.5046 ± 0.21
4.9914 ± 0.37
4.1846 ± 0.74
0
1
2
3
4
5
6
7
20 30 40 50 60
Percent of Rice Husk Contents, (%)
Tea
r St
reng
th, (
N/m
m)
Fig. 4. Effect of rice husk loading on tear strength for recycled
RHPE composite injection grade.
Besides, the modulus, which indicates materials stiffness, increases steadily with
addition of rice husk contents in the composites, but it slightly dropped when 50% filled
the fibers as shown in Figure 5. Because of the greater stiffness of rice husk than that
HDPE, this brings about the improvements in specimen Young’s modulus that determine
stiffness of the specimen [10]. In other words, rice husk itself has a higher Young’s
modulus compared with HDPE. This reflects the increase of brittleness of the materials
[3],
However, for the decreasing modulus when added with 50% of rice husk is due to
the immiscibility between rice husk and HDPE phase, and tendency to agglomerate
within themselves, causing voids or weak point inside the specimens. Thus, it contributes
to weak interfacial adhesion with polymer matrix [4].
Based on the research [9], the maximum tensile modulus of composite film for
thermoforming property analysis is 3.5 GPa. Therefore, the tensile modulus obtained for
the recycled RHPE composites from this study were satisfied the requirement of the
composite film for thermoforming process. This shows that the recycled RHPE
composite were suitable to be used as thermoform packaging product.
0
50000
100000
150000
200000
250000
20 30 40 50 60
Percent of Rice Husk Content, (%)
You
ng's
Mod
ulus
, (M
Pa)
Fig 5. Effect of rice husk loading on the
Young’s modulus for recycled RHPE
composite injection grade.
4
6
8
10
12
14
16
18
20 30 40 50 60
Percent of Rice Husk Contents, (%)
Ten
sile
Str
engt
h, (M
Pa)
Fig. 6. Effect of rice husk loading on the
tensile strength for recycled RHPE
composite injection grade.
In the recycled RHPE composites injection grade, the incorporation between rice
husk and HDPE was found to gradually decrease in tensile strength with additional rice
husk content as shown in Figure 6. According to [3], this happened due to the
immiscibility between rice husk and high-density polyethylene phases, causing voids or
weak points inside the specimens. Then it is also revealed that no reinforcement be
obtained by the addition of filler, and possible agglomeration, which weaken the stress
transfer from matrix to filler.[5], have found that, the decrease of tensile strength is
related to the increase of fragility or brittleness of the samples.
The maximum tensile strength for plastic film based recycled composite is 25
MPa [2]. Therefore, when this value is compared with tensile strength of the recycled
RHPE composite, it shows that the suitability of recycled RHPE composite to be used as
thermoform packaging product.
Other properties can be discussed in tensile properties is elongation at break of the
composites. This properties were measured the elongation at the moment of rupture of the
test specimens. As we can see in Figure7, the elongation at break of the composites are
gradually decrease correspond to the adding up the rice husk loading. Same reason as
tensile strength property, that is due to the immiscibility between rice husk and HDPE
phases, resulting voids or weak point, inside the specimens [10].
Besides, the decline in elongation at break may be due to the reduction of
extensible matrix in the composites with increase of filler content. Moreover, the filler
particles have created the resistance for the matrix molecules to deform upon the
elongation of the specimens [3]. This occurrence has been proven during the testing of
the composite’s melt flow behavior. Referred back to Figure 4.3, as the filler filled
composites increase, the melt flow was decreased which is due to the interruption of rice
husk particle in the molten polymer. Thus, increasing in filler loading; the stiffness and
brittleness of the composite increase gradually with associated decrease in the elongation
at break.
0
1
2
3
4
5
6
7
8
9
10
30 40 50
Percentage of rice husk content, (%)
Elo
ngat
ion
at b
reak
, (%
)
Fig 7. Effect of rice husk loading on the elongation at break
for recycled RHPE composite injection grade.
The limitation value of elongation at break of filled HDPE for thermoform
properties is 22 ± 2 % [6] From this study, the recycled composites have shown the
suitability to be thermoformed into packaging product as the result obtained were not
exceed the maximum value. Then, these recycled RHPE composites have the ability to be
reprocessed into the thermoform grade product.
4.0 Conclusion
The incorporation of the rice husk into HDPE matrix has resulted in the
improvement in the tensile modulus or Young’s modulus, but it caused decreases in tear
strength, tensile strength and elongation at break, which additional of rice husk contents.
This due to the greater stiffness of rice husk than that HDPE, then it brings about the
improvements in specimen Young’s modulus that determine stiffness of the specimen.
However, the immiscibility between rice husk and high-density polyethylene phases,
causing voids or weak points inside the specimens causing decreased in tear strength,
tensile strength, and elongation at break However, the best formulation that can be
thermoformed based on the optimum value of modulus and strength of the composites are
gave by the recycled RHPE composites contained 40% rice husk.
From the result obtained, there is several factors influence the suitability of this
recycled RHPE composite to be thermoformed. This can be found from the analysis of
FTIR, DSC and also MFI. The rice husk contents was not undergo degradation and
thermal degradation during the injection moulding process, as well as not formed
thermoset composite product. Besides, MFI value of recycled RHPE composite also
found fall within the range of MFI value for the standard thermoform grade that is
between 2-10 g/10 min. Moreover, it also found that, the mechanical properties of this
recycled RHPE composite were fulfilling the requirements of thermoform material grade.
This shows the suitability of recycled RHPE composite can be reprocessed or
recompounded into thermoforming grade compound/product.
5.0 References
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[2] Antonio, F.A., and Macros, V.D. (2003). A Mechanical Analysis on Recycled
PET/HDPE Composite. Polymer Degradaion and Stabiliy, 80. 373-382.
[3] Hattotuwa, G.B.P., Ismail, H. and Baharin Azahari (2002). Tensile Properties of Rice
Hisk Powder Filled Polypropylene Composite. University of Science
Malaysia: Post Graduate Research Paper
[4]Herrera-Franco, P., Valadez-Gonzalez, A. And Cerventes-Uc, M., (1997).
Developement and Characterization of a HDPE-Sand-Natural Fiber
Composite. Composite Part B, 28B. 331-343.
[5] La Mantia, F.P., and Morreale, M. (2006). Mechanical Properties of Recycled
Polyethylene Ecocomposites Filled With Natural Organic Fillers. Polymer
Engineering And Science, 10. 1131-1139.
[6] Malpas, V.E., and Kemphorn, J.T. (1986). Setting Conditions for Polyolefin
Thermoforming. Plastic Engineering. 53-57.
[7]Naurah Mat Isa, (2005). Injection Moulding Process Parameters and Performance
Analysis of Column En Cap Based on RHPE Composite. Universiti
Teknologi Malaysia: Projek Sarjana Muda.
[8] Nurfatimah Abu Bakar, (2006). Effect of Oil Palm Empty Fruit Bunch Fiber Length
and Content on Mechanical Properties of PVC-U Composite. Universiti
Teknologi Malaysia: Projek Sarjana Muda.
[9]Peterson, S., Jayaraman, K. and Bhattacharyya, D., (2002). Forming Performance
and Biodegradability of Woodfiber-BioPol Composite. Composite: Part A,
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[10] Prachayawarakorn, J. and Yaembunying, N., (2005). Effect of Recycling on
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