Post on 25-Sep-2019
ON VIBRATION CHARACTERISATION,
MECHANICAL AND PHYSICAL PROPERTIES
EFFECTS OF ULTRA VIOLET IRRADIATION ON WASTE BIOPOLYMER BASED
SHAIQAH BINTI MOHD RUS
A thesis submitted in
fulfillment of the requirement for the award of the
Degree of Master of Mechanical and Manufacturing Engineering
Faculty of Mechanical and Manufacturing Engineering
UniversitiTun Hussein Onn Malaysia
viii
ABSTRACT
Disposal of waste cooking oils becomes a problem in the developed countries
because the limited options to dispose them and usually people will pour waste
cooking oil down to the drain or sewers which contribute to clog and unpleasant
odour. Thus, in this research, vegetable waste palm oil is used as a raw material in
order to create foam and further processed into granulate form which is powder that
are compressed using hot compression moulding technique. The fabricated samples
produced after hot compress were represented as waste bio-polymer (WB) and later
on, these WB were irradiated with ultra violet-irradiation (UV-irradiated) and the
samples become UV-irradiated WB. WB and UV-irradiated WB samples with three
different thickness/laminated structure with minimum thickness of 5.4 mm, three
layer thicknesses of 10.8 mm and four layer thicknesses of 16.2 mm. These samples
were examined by means of vibration transmissibility test and other physical tests.
Vibration transmissibility test was operated at 1 mm and 1.5 mm for displacement
transmissibility, 0.1 g and 0.15 g for acceleration transmissibility base excitation
whereas the physical and mechanical properties were studied through compression
test, differential scanning calorimeter (DSC) and density test. The morphological
studies were observed using scanning electron microscope (SEM). UV-irradiation
does not give influence towards WB in terms of damping ratio since it gives the most
excellent vibration damping of 0.707. WB sample looks like needle, sharp, fibrous,
coarse structure which can be seen at 0, 250 and 500 hour UV-irradiation WB but
when the time exposure of UV is increasing, the surface morphology of the sample
becomes blunter and the texture is much flatter. However, the overall structure has
no major difference from 0 hour to 1000 hour UV-irradiation indicates that this UV-
irradiated WB has high photo-stability. From the density test, the results indicated
that WB (0 hour UV) is denser than UV-irradiated WB (1000 hour UV) which is
1025.73 kg/m3 and 914.87 kg/m
3 respectively. The result of glass transition, Tg
values for WB and UV-irradiated WB were decreased from 48.66˚C to 48.31˚C as
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the time of exposure of UV increases. As a conclusion, this WB and UV-irradiated
WB are useful as a new material product which has been recycled to become bio-
polymer generated from waste cooking oil; this product have good quality to survive
in robust environmental condition in terms of UV radiation.
x
ABSTRAK
Pelupusan sisa minyak masak membawa masalah terutamanya di negara membangun
kerana pilihan untuk melupuskan sisa minyak masak adalah terhad dan kebiasaannya
orang awam membuang sisa minyak masak ke dalam longkang dan pembetung
membawa kepada masalah sumbat dan bau. Oleh itu dalam kajian ini, sisa minyak
masak sayur telah digunakan sebagai bahan mentah untuk menghasilkan busa
seterusnya diproses menjadi butiran (serbuk) dan dimampatkan menggunakan mesin
penekanan panas. Sampel fabrikasi ini dinamakan sebagai bio-polimer sisa (WB)
yang kemudiannya diradiasikan dengan sinaran ultraviolet (UV) menjadikannya
ultraviolet-radiaso bio-polimer sisa (UV-irradiated WB). WB dan “UV-irradiasi
WB” sampel mempunyai tiga ketebalan/lapisan berbeza iaitu ketebalan lapisan
minimum 5.4 mm, tiga lapisan ketebalan 10.8 mm dan empat lapisan ketebalan 16.2
mm. Sampel-sampel ini telah diuji dengan menggunakan ujian getaran
kebolehantaran dan ujian-ujian fizikal yang lain. Ujian getaran kebolehantaran telah
dijana pada 1 mm, 1.5 mm, 0.1 g dan 0.15 g pada pengujaan asasnya manakala sifat
mekanikal telah diperiksa melalui ujian mampatan, Kalorimetri Imbasan Kebezaan
(DSC) dan juga ujian ketumpatan. Struktur morfologi telah diperhati dengan
menggunakan Mikroskop Imbasan Elektron (SEM). Sinaran UV tidak mendatangkan
kesan terhadap WB dalam nisbah redaman kerana ia memberikan nisbah redaman
getaran yang paling baik iaitu keduanya pada 0.707. Sampel WB kelihatan tajam,
berstruktur kasar pada 0, 250 dan 500 jam UV-irradiasi tetapi apabila masa
pendedahan UV meningkat, permukaan morfologi sampel menjadi tumpul dan lebih
mendatar. Bagaimanapun, keseluruhan struktur permukaan tidak mempunyai
perbezaan major daripada 0 jam UV kepada 1000 jam UV menunjukkan UV-
irradiasi mempunyai stability-foto yang tinggi. Hasil kajian menunjukkan bahawa
WB (0 jam UV) lebih tumpat daripada UV-irradiated WB (1000 jam UV) yang
masing-masing bernilai 1025.73 kg/m3 dan 914.87 kg/m
3. Keputusan nilai suhu
transisi gelas, Tg untuk WB dan UV-irradiated WB semakin menurun daripada
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48.66˚C kepada 48.31˚C apabila meningkatnya tempoh masa pendedahan UV
terhadap WB. Kesimpulannya, WB ini dan UV radiasi WB adalah berguna sebagai
bahan produk baru yang telah dikitar semula untuk menjadi bio-polimer yang
dihasilkan daripada sisa minyak masak; produk ini mempunyai kualiti yang baik
untuk bertahan dalam keadaan alam sekitar yang lasak dari segi radiasi UV.
xii
CONTENTS
TITLE i
DECLARATION v
DEDICATION vi
ACKNOWLEDGEMENT vii
ABSTRACT viii
ABSTRAK x
CONTENTS xii
LIST OF TABLES xvi
LIST OF FIGURES xvii
LIST OF SYMBOLS xxi
LIST OF ABBREVIATIONS xxii
CHAPTER 1 INTRODUCTION 1
1.1 General introduction 1
1.2 Problem statement 3
1.3 Hypothesis of research 4
1.4 Objectives of research 5
1.5 Scope of research 5
1.6 Significant of research 6
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CHAPTER 2 LITERATURE REVIEW 7
2.1 Introduction 7
2.2 Polymer 8
2.2.1 Polymer synthesis 12
2.2.2 Polymer from renewable resources 13
2.2.3 Composites from oil-based polymers 15
2.3 Bio-polymer 16
2.4 Green technology 17
2.4.1 Recycling of bio-polymer foam 18
2.5 Environmental impact 19
2.6 Foam generation 20
2.6.1 Formation of foam 21
2.6.2 Production of foam 22
2.7 Modification of polymer using fillers 23
2.7.1 Composite foam and its properties 24
2.8 UV-irradiation on biopolymer 31
2.9 Vibration and its characteristics 32
2.9.1 Vibration classification 34
2.9.2 Vibration transmissibility measurement 34
2.10 Damping and its characteristic 40
2.10.1 Damping mechanism 41
2.10.2 Controlling damping 42
2.10.3 Data acquisition technique and constitutive
of WB model 43
2.10.4 Damping measurement system 45
2.11 Amorphous and glass transition, Tg 48
2.11.1 DSC materials and its properties 51
2.12 Summary 54
xiv
CHAPTER 3 METHODOLOGY 55
3.1 Introduction 55
3.2 Methodology chart 55
3.3 Fabrication of WB 58
3.4 Hot compression technique 60
3.5 UV weatherometer 61
3.6 Physical and mechanical tests 62
3.6.1 Morphology study 63
3.6.2 Density test 63
3.6.3 Compression test 64
3.6.4 Vibration transmissibility test 65
3.6.5 Determination of friction losses 69
3.6.6 Natural frequency of system deformation 71
3.6.7 Differential Scanning Calorimeter (DSC) 72
3.7 Summary 73
CHAPTER 4 RESULTS AND DISCUSSION 74
4.1 Introduction 74
4.2 UV-irradiated WB morphology 75
4.3 Density of UV-irradiated WB 76
4.4 Static stiffness (K), compression strain
and stiffness analysis on UV-irradiated
WB in transmissibility system 78
4.5 Calculated value of natural frequency
of WB and UV-irradiated WB 81
4.6 Frictional losses (fixture losses) in WB
and UV-irradiated WB system 82
4.7 Vibration transmissibility results for
laminated structure of WB and
UV-irradiated WB system 85
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4.8 Damping characteristic of WB and
UV-irradiated WB fabricated 95
4.9 Summary to the vibration results and
discussion 97
4.10 Conclusion to the glass transition
temperature results and discussion 99
CHAPTER 5 CONCLUSION AND RECOMMENDATION 101
5.1 Conclusion 101
5.2 Future recommendation 103
REFERENCES 104
APPENDICES 116
xvi
LIST OF TABLES
Table 2.1 Data of peak transmissibility and resonance frequency
varied with resin technologies, density and hardness
(Koshute et al., 2001) 37
Table 4.1 Average compressive strain of UV-irradiated WB its
physical properties 80
Table 4.2 The damping ratio value of friction losses in force
vibration test 84
Table 4.3 (a) Data of resonance peak varied with fabricated WB
(0 Hour UV) and UV-irradiated WB (1000 Hour UV),
its base excitation and percentage of changes, ∆ 92
Table 4.3 (b) Data of resonance frequency varied with fabricated
WB (0 Hour UV) and UV-irradiated WB (1000 Hour UV),
its base excitation and percentage of changes, ∆ 94
Table 4.3 (c) Data of attenuation frequency varied with fabricated
WB (0 Hour UV) and UV-irradiated WB (1000 Hour UV),
its base excitation and percentage of changes, ∆ 95
Table 4.4 Damping ratio of WB (0 Hour UV) and UV-irradiated WB
(1000 Hour UV) by data measured from displacement and
acceleration transmissibility test and its percentage of
changes, ∆ 97
Table 4.5 Tg value for WB (0 hour UV) and UV-irradiated WB
(250, 500,750 and 1000 hour UV) 99
xvii
LIST OF FIGURES
Figure 2.1 Polymers with linear and nonlinear chain architectures
(Robyr, 2001) 9
Figure 2.2 Polymer compliance as a function of temperature
(Robyr, 2001) 10
Figure 2.3 Global PU production year 2012,
(utech-polyurethane.com, 2014) 11
Figure 2.4 Split of polyurethanes market by end-use application
(Biesman, 2002) 12
Figure 2.5 Particle structure of waste bio-polymer foam
(Najibah, 2014) 19
Figure 2.6 Gelation Reaction or PU Cross Linking Reaction
(Kaushiva, 1999) 21
Figure 2.7 Effects of calcium carbonate of different particle sizes
and compositions on the Tensile Strength of Flexible
PU Foam (Latinwo et al., 2010) 25
Figure 2.8 Effects of calcium carbonate of different particle sizes
and composition on the Elongation-at-break of Flexible
PU Foam (Latinwo et al., 2010) 25
Figure 2.9 (a) density, (b) elongation and (c) tensile strength of foam
with concentration of CaCO3 (Usman et al., 2012) 26
Figure 2.10 Loss factor (tan δ) of unfilled and nano-filled PU rigid
foam (Nikje and Tehrani, 2010) 27
Figure 2.11 Compressive stress-strain curve for foam samples.
Loading direction is parallel to the foam rise direction
(Alonso et al., 2006) 28
Figure 2.12 Variation of the carbon black volume fraction in the foamed
xviii
NRs as a function of foaming temperature and filler content
(Lee and Choi, 2007) 30
Figure 2.13 Vibration curve for normal (Polyol A) and high resilience
foam (Polyol B) (Broos et al., 2000) 36
Figure 2.14 Typical occupied vertical vibration transmissibility output
(Kolich et al., 2005) 38
Figure 2.15 Mass-spring damper system was modeled as UV-irradiated
WB system 38
Figure 2.16 Foam model loaded with mass (Wang and Low, 2005) 43
Figure 2.17 Schematic of SDOF foam-block system (Joshi et al., 2010) 46
Figure 2.18 Fixture applied for dynamic response testing
(White et al., 2000) 47
Figure 2.19 Frequency response of SDOF system for mass of 2.5 kg and
different base accelerations levels (a) 0.01 g, (b) 0.1 g, and
(c) 0.2 g (Joshi et al., 2010) 48
Figure 2.20 No long-range or short-range order for amorphous structure
(Chelikowsky, 2001) 49
Figure 2.21 Schematic diagram of a power-compensated DSC (Marsh,
2001) 52
Figure 2.22 The DSC curves of PU/EP IPNs with different MMT
contents (Qingming et al., 2006) 53
Figure 3.1 Research Flow Chart 57
Figure 3.2 The Schematic Diagram of UV-irradiated WB Production
Route using Hot Compression Moulding at 90 °C and 26
tonnes 59
Figure 3.3 Wabash Genesis Hyraulic Hot Press moulding machine
schematic drawing of hot compression moulding and its
components (Drobny, 2007) 61
Figure 3.4 UV equipment (a) UV weatherometer (b) UV lamps 62
Figure 3.5 The (a) SEM machine and (b) Auto Fined Coater 63
Figure 3.6 Mettler Toledo Weighing for density test of WB samples 64
Figure 3.7 T-Jaw 3600 Vertical Band Saw machine 65
Figure 3.8 (a) The UTM machine of compression test (b) WB samples
inserted in the UTM machine 65
xix
Figure 3.9 Set-up of vibration transmissibility test 66
Figure 3.10 Schematic diagram of WB test system: (1) load,
(2) sliding top plate, (3) WB, (4) base plate and (5) shaker 67
Figure 3.11 The setup of WB or UV-irradiated WB system in
vibration transmissibility 67
Figure 3.12 Mass spring damper with dry friction 70
Figure 3.13 The (a) acceleration and (b) displacement responses
(as a function of time) of mass spring damper of free
vibration test 71
Figure 4.1 Morphology surface at 1000x magnification (a) 0 Hour UV
(b) 250 Hour UV (c) 500 Hour UV (d) 750 Hour UV
(e) 1000 Hour UV, with the red circle indicated voids areas 76
Figure 4.2 WB prepared for density test; (a) WB (brighter) and
(b) UV-irradiated WB (darker) 77
Figure 4.3 Density of WB and UV-irradiated WB 78
Figure 4.4 Average of compressive stress-stroke strain curves of WB
and UV-irradiated WB 79
Figure 4.5 The static stiffness (K) of UV-irradiated WB and WB when
loaded with a total mass of 462.42 g 79
Figure 4.6 Natural frequency of WB and UV-irradiated WB as a
function of WB and UV-irradiated WB inserted to the system 82
Figure 4.7 Free vibration data for displacement response 83
Figure 4.8 Displacement transmissibility from base to moveable top
plate at 1 mm of UV-irradiated WB structure (a) four
thicknesses (b) three thicknesses (c) for minimum thickness
of laminated structure 86
Figure 4.9 Displacement transmissibility from base to moveable top plate
at 1.5 mm of UV-irradiated WB structure (a) four thicknesses
(b) three thicknesses (c) minimum thickness of laminated
structure 88
Figure 4.10 Acceleration transmissibility from base to moveable top
plate at 0.1 g of UV-irradiated WB structure (a) four
thicknesses (b) three thicknesses (c) minimum thickness
of laminated structure 89
xx
Figure 4.11 Acceleration transmissibility from base to moveable top
plate at 0.15 g of UV-irradiated WB structure (a) four
thicknesses (b) three thicknesses (c) minimum thickness
of laminated structure 91
Figure 4.12 The DSC curves of WB (0 min UV) and UV-irradiated WB
(250 hour UV, 500 hour UV, 750 hour UV and 1000 hour UV) 98
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LIST OF SYMBOLS
Tan δ - damping factor
ζ - stress
ε - strain
ρ, D - Density
k, K1 .K2, Kc - Stiffness
k3, k5 - Nonlinear stiffness
x, z - Displacement in uniaxial compression
t - time
Cc - Damping coefficient or damping constant
ξ - Damping ratio
A - Contact area
W, M, m - Total mass or total riding mass
ωn - Natural frequency
ω - Forced frequency
ωb - Base frequency
r - Frequency ratio
Kx, Ky, Kz - Stiffness in x, y, or z axis
S - Structural Coefficient
V - Volume
Tr - Transmissibility
NCO - Reactive isocyanate group (-N=C=O)
R - Reactive group from isocyanate
R‟ - Reactive group from polyol
n - Integer (1,2,3…)
Y1, Y2, Y3, Y4 - Displacement amplitude
β - Logarithmic decrement
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LIST OF ABBREVIATIONS
Al - Aluminium
ASTM - American Society for Testing and Materials
C - Carbon
Ca - Calcium
CaCO3 - Calcium Carbonate or Calcite
Cl - Chlorine
CO2 - Carbon Dioxide
Cu - Copper
Comp. - Compression
DSC - Differential Scanning Calorimetry
Fe - Iron
H - Hydrogen
H2O - Water
IIR - Infinite Impulse Response
K - Potassium
MDI - Methylene Diphenyl Diisocyanate
Mg - Magnesium
N - Nitrogen
NaOH - Sodium Hydroxide
NH2 - Amine
O - Oxygen
OH - Hydroxide
PET - Polyethylene Terephthalate
PP - Polypropylene
PU - Polyurethane
RSTD - Resonance Search, Track and Dwell
xxiii
rpm - Revolutions per minute
SDOF - Single Degree of Freedom
SEM - Scanning Electron Microscopy
Si - Silicon
TDI - Toluene Diisocyanate
Ti - Titanium
UTHM - Universiti Tun Hussein Onn Malaysia
UTM - Universal Testing Machine
UV - Ultra Violet
VCS - Vibration Control System
WB - Waste biopolymer
WB1 - One laminated structure of WB
WB2 - Two laminated structure of WB
WB3 - Three laminated structure of WB
wt. - weight
Zn - Zinc
1
CHAPTER 1
INTRODUCTION
1.1 General introduction
Choosing an appropriate and good material is among important factors in producing
a quality design. Material technology increases the capacity and functionality of a
material gives options to designers and innovators to select the best materials for
their inventions. Over the years, polymer composite revolves the characteristics of a
material. These improved materials properties that have been widespread used in
various engineering fields such as in automotive. Recyclable materials can also be
reused in the production of a polymer composite. Using these materials is a good step
in addressing pollution problems involving discard items.
Cooking oil of plant, animal or synthetics fat origin is normally used in
frying, baking and other types of food preparation and flavouring that do not involve
heat such as in salad dressings. It comes totally in liquid form even though some oils
contain saturated fat such as coconut oil, palm oil and palm kernel oil. Proper
disposal of waste cooking oil is an important waste management thus, bio-based
materials produced from this waste have received particular attention to be invented.
According to Sharma and Kundu (2008), for the polyurethane industry, vegetable
oils are becoming extremely important for the preparation of polyols because it
functions as renewable resources.
2
The Polyols from natural oils such as soybean and palm oils (Figure 1.1) are
progressively being viewed by industries as a practicable alternative to hydrocarbon
based feedstock. These oils are renewable, low cost as well as environmental
friendly. Vegetable oil-based polyurethane is used as binders and agricultural films
as reported by the United Soybean Board (Sharma and Kundu, 2008). In this
research, the monomer from waste vegetable oil is used as the bio-polymer foam to
produce waste biopolymer solid (Ghani et al., 2013). Then, the influence of UV
irradiation on the characteristics of this waste biopolymer solid is studied.
Currently, waste cooking oil has proven to be a problematic material (Food
Standards Agency, 2004). People usually pour waste cooking oil into the kitchen
drainage or sewer because they unaware about this waste can be recycled. In point of
fact, waste cooking oil can produce biopolymer foam composites based product and
its physical and mechanical properties of the material formed can be improved.
Consequently, this can reduce the environmental pollution and becomes an
alternative to petroleum based products. Polymer from renewable resources has
improvised over the years resulting in widespread acceptance and use in various
fields. This makes it as an important engineering material because of its distinct
properties compared with other materials.
Recyclable materials such as waste cooking oil, paper powder, and iron
powder can be reused in the production of a polymer for the application of vibration
or damping. This is also a good step in addressing pollution problems involving
discard items. It is founded that one of the major productions from urethane material
flexible polyurethane (PU) foam (Zhang, 2008) and it is widely used as cushioning
material in applications of transportation and packaging. Properties of flexible PU
foam can be improved to fulfill desired application by using suitable choice of raw
materials, additive and manufacturing technology.
In addition, it is known that waste recycling is an interesting system in order
to achieve an efficient integrated way of handling municipal solid waste. Therefore,
the intention of the research is to produce solid waste bio-polymer from recycling
polymer material based on waste bio-polymer granulate foam to measure damping
characteristics with different thickness which are minimum thickness is 5.4 mm,
three layer thicknesses is 10.8 mm and four layer thicknesses is 16.2 mm, before and
after UV radiation. In this study hot compression method used to produce waste bio-
3
polymer (WB) to focus on mechanical properties of the materials such as vibration
test due to the less research pointed on the mechanical properties on polymer
composites (Gibson, 2000). By using waste cooking oil monomer, bio-polymer foam
was produced and the solid waste bio-polymer (WB) was fabricated by using hot
compression technique from granular particles of bio-polymer foam (Ghani et al.,
2013). After that the solid WB irradiated with UV radiation and the characteristics of
the composite investigated and analyzed in details.
This composite expectantly provide superior damping to absorb vibration,
better mechanical strength, longer service time (measured by UV weatherometer at
prolonged harsh environmental exposure) and cheaper cost. This research would like
to produce waste biopolymer from lowest grade of the green-monomer and natural
fibers which later on irradiated with UV to ensure the robustness of the solid waste
biopolymer formed. Also to ensure the material produced is suitable to use in many
application especially in automotive such as door pockets, covers and instrument
panel in automotive industries.
1.2 Problem statement
The problem of vibration absorbing material in an automotive field or packaging
which is based on petroleum derivative product that cannot be easily degraded
needed some new material that can be used to replace or as alternative to the existing
products. Material from renewable resources substitutes these non-degradable
products and the use of renewable resources in the preparation of various industrial
materials has been strengthened because of the environmental concerns. As a
consequence, the difficult part is to generate new idea and formulae either in
packaging or automotive or building production application.
Among promising area to generate new idea and formula to use biopolymer
foam composites is in automotive application. As far as people concern, the existing
product of automotive internal components such as car dashboard, door panel and
engine casing are produced by using natural fiber and petroleum-based. The usage of
excessive petroleum and chemical based substance pollutes the environment (Dao et
al., 2011). In the meantime, for this research, waste cooking oil monomer is used by
adding cross linker as bio-polymer foam to substitute the existing commercialized
4
substances. The cost effective recycling route for thermosetting polymers is still
unavailable, that may restrict manufacturer‟s choice of materials to optimize the
functional performance of components (Hulme and Googhead, 2003).
Referring to the Polyurethane Foam Association (1991) it is well known that
flexible PU foam scrap is an easy product to recycle and nowadays generating
revenue for many end-users. It has made great steps in technology and end-use
applications to address waste problem since it is suitable to increase the application
of the secondary raw materials. Polyurethane Foam Association (1991) mentioned
that, the economic and environmental value will be protected as well as it can be
used to produce revenue, offset raw material cost and lessen solid waste disposal
problems by recovering and reusing scrap foam. For that reason, the crumbling
technology reveals new ways for the recycling of PU foams and composites. Also it
can be performed by using conventional crushing (Valclavik et al., 2012). In order to
provide a particle size shape, a knife grinder can be used for PU foam.
1.3 Hypothesis of research
The hypotheses of the research are:
i. To prove that the thickness of UV-irradiated waste biopolymer (WB)
influences the vibration and damping characteristic
ii. The UV-irradiated WB has the potential to increase the dissipation of energy
through absorption of vibration for comfortableness of any suitable
application such as, bumper car, door panel or dashboard and also suitable for
safety of packaging purposes.
iii. To ensure that the WB product is robust towards harsh condition in term of
UV radiation.
iv. The application of green polymer material has become important since the
enforcement applied by many institutions and private sectors especially in the
European supermarket chains that banned the use of non-degradable
materials. They create a new policy such as “going green” and sell a wide
range of natural and environment-friendly products.
5
1.4 Objectives of research
The objectives of this research are:
i. To develop solid waste biopolymer (WB) by hot compression technique.
ii. To measure the vibration characteristic and damping of UV-irradiated
WB based on vibration transmissibility test.
iii. To calculate and compare the physical and mechanical properties of UV-
irradiated WB before and after UV irradiation.
iv. To evaluate the physical properties based on SEM, density and DSC
before and after UV- irradiation on solid WB composites.
1.5 Scope of research
i. Literature review on the fundamental process of bio-polymer foam
from vegetable waste cooking oil monomer and fabrication of solid
waste bio-polymer (WB) and the influence of UV radiation on bio-
polymer produced.
ii. Then, the solid WB irradiated through UV weatherometer machine.
iii. The damping characteristics of UV-irradiated WB by using vibration
transmissibility test according to ASTM standard conducted with
different composition ratio or thickness of the samples (minimum
thicknes or three layer thicknesses or four layer thicknesses).
iv. The physical and mechanical properties of UV-irradiated WB were
examined through density and compression test. Meanwhile, the
morphological characteristics of the samples were analyzed by SEM.
The physical properties of the samples also determined based on DSC
before and after UV- irradiation on solid WB composites.
6
1.6 Significant of research
The significances of the research study included:
i. This research intended in improving or adds composite for the applications in
absorbing vibration especially on the inside of automotive and packaging
industry and the robustness of this solid WB towards harsh condition in terms
of UV radiation. This research will determine whether this is able to increase
the polymer mechanical properties of solid WB that serves as a vibration
absorber even after exposure towards UV radiation.
ii. The solid WB was prepared for the application on the car dashboard or door
panel focusing in increasing the comfortableness for driver and passengers.
The emotional disturbance to driver and passengers due to environmental
effect are decreased since the vibration is dissipated by solid WB before
being transmitted to the driver and passengers.
iii. Since solid WB can absorb vibration and vibration is a critical factor during
transport, it can also be used in the packaging, thus eliminating the possibility
for the object to damage. Solid WB on the other hand keeps it protection even
after strong impacts.
iv. This hot compression is an alternative recycling method for solid waste bio-
polymer generated from recyclable of renewable resources.
v. The production cost of the vehicle components will be reduced when waste
oil is used as the raw material for the production of WB.
7
CHAPTER 2
LITERATURE REVIEW
2.1 Introduction
For present-day especially in Malaysia, possibilities for disposing of used cooking oil
and grease are imperfect since people usually pour waste cooking oil into the kitchen
drainage because they unaware that this waste can be recycled. In the fast food
business alone, a single branch which serves fried food such as fried chicken, French
fries and burgers can produce as much as 15 litres of used cooking oil per day.
Considering that there are hundreds of these outlets in Malaysia, the total amount
generated can reach to several thousand litres per day. Properties of degraded used
cooking oil after it gets into sewage system are conductive to corrosion of metal and
it also affects installations in waste water treatment plants. Thus, it increases the cost
of treating effluent or pollutes waterways (Szmigielski et al., 2008).
Certainly, this waste cooking oil should not be simply poured down into the
drain. This waste cooking oil becomes fats, oil and grease which clog the sanitary
sewer system, causing increase in repair and maintenance cost. Different grade of
waste cooking oil will be modified into different grade of green-monomer and green-
polymer for variety of reasons: biodegradable, improved processing and mechanical
properties (hardness and tensile: influence by cross-link density) and tear resistance.
Thus, manipulation of waste cooking oil can be wisely used as monomer feeds stocks
for polymer application.
8
2.2 Polymer
Polymers are substances consisting of large molecules also known as
macromolecules which the molecules are built up of many subunits called monomers
which are linked together, usually by covalent bonds (Robyr, 2001). Also, polymer is
hydrocarbon based material elements comprise of carbon, hydrogen and oxygen.
Furthermore it is a material that contains a lot of parts or smaller units; chemically
bound to each other. Principally, there are only two really fundamental
characteristics of polymers which are their chemical structure and their molar mass
distribution pattern that determine the cohesive forces, the packing density (and
potential crystallinity) and the molecular mobility with phase transition (Krevelen
and Nijenhuis, 2009).
In a polymer, the number of subunits is generally larger than 100. Robyr,
(2001) also mentioned that assemblies of less than 100 subunits of monomers are
often referred to as oligomers. In living organisms, polymers make up many of the
materials, as for example cellulose, lignin, proteins, and nucleic acids which are the
latter two have highly specific roles in life. Synthetic polymers are man-made
materials, and these polymers have a great industrial importance because they offer
an attractive compromise between ease of processability and final mechanical and
thermal properties.
Polymers without configurationally regularity are called atactic while
configurationally regular polymers can form crystalline structures; whereas atactic
polymers are almost always amorphous as shown in Figure 2.1. The nonlinear
polymers can have branched chains and short chains of oligomers can be grafted to
the main chain while the chains may form a star-like structure. The chains can be
cross-linked and form a network and most properties of linear polymers are
controlled by two different factors which are (Robyr, 2001):
i. Chemical constitution of the monomers: determines the interaction strength
between the chains, the interactions of the polymer with host molecules or
with interfaces. The monomer structure also determines the possible local
confirmations of the polymer chain.
ii. The molecular weight. It determines the slow-mode dynamics and the
viscosity of polymers in solutions and in the melt. These properties are of
utmost importance in polymer rheology and condition their processability.
9
The mechanical properties, solubility and miscibility of different polymers
also depend on their molecular weights.
Figure 2.1 Polymers with linear and nonlinear chain architectures (Robyr, 2001).
In the geometrical arrangements of the atoms in a polymer chain two
categories can be discerned which are arrangements fixed by the chemical bonding,
known as configurations (the configuration of a chain cannot be altered unless
chemical bonds are broken or reformed) and arrangements arising from rotation
about single bonds known as conformations (Krevelen and Nijenhuis, 2009). The
researchers also mentioned that simple molecules may occur in three states, the solid,
the liquid and the gaseous state while polymers cannot be evaporated since they
decompose before boiling.
In addition, the usual states of polymers are the glassy, the rubbery and the
semi-crystalline state all of which are thermodynamically metastable (Krevelen and
Nijenhuis, 2009). The mechanical behavior of a polymer as a function of temperature
is summarized in Figure 2.2. The compliance is about 10-9
Nm-2
in the glassy state
and increases to about 10-5
Nm-2
after the glass-rubber transition and the width of the
rubber plateau depends on the density of entanglement (Robyr, 2001). The researcher
also stated that for chains below the critical molecular weight at the entanglement
limit, Mc, the plateau disappears and the polymer directly enters the terminal flow
region and it is important to note that even in this region polymers still behave as
viscoelastic liquids. This is in contrast toward low-molecular-weight compounds
above their melting point.
Linear Branched Grafted Star Network
10
Figure 2.2: Polymer compliance as a function of temperature (Robyr, 2001)
Robyr, (2001) stated that most polymers show qualitatively similar behavior
under compression or shear but on the other hand under the application of tensile
stress, two different deformation processes after the yield point are known. Ductile
polymers elongate in an irreversible process similar to flow, whereas brittle systems
whiten due the deformation of microvoids (Robyr, 2001). The researcher also stated
that in glassy polymers, the chain entanglements could act as temporary cross-linking
points. One of the most important polymers that contribute to the large global
production is polyurethane. The applications of polyurethane are around the people
playing a vital role in many industries which are from furniture to footwear,
construction to cars. Polyurethane appears in an amazing variety of forms, making it
the most flexible of any family of plastic materials.
As shown in Figure 2.3, the global polyurethane productions are split in to
seven types of polyurethane form which are adhesives, binders, coatings, elastomers,
flexible foam, rigid foam and sealants. From Figure 2.3, it can be seen that, the
percentage of production of flexible foam still the largest between the types of
polyurethane form and in this research, the WB foam produced were in the category
of flexible foam of PU.
11
Figure 2.3: Global PU production year 2012, (utech-polyurethane.com, 2014)
Since each sector requires its own approach, the polyurethanes market can
also be described in terms of end-use applications, which is particular use in defining
market strategies (Biesman, 2002). Based on Figure 2.4, the largest percentage of
polyurethanes market by end-use application lies in furniture category which is 29%
and second largest of percentage were construction and automotive. For that reason,
the WB produced were intended to apply in furniture and automotive since these
categories were in high demand globally.
5% 2%
19%
22% 28%
22%
2%
Adhesives
Binders
Coatings
Elastomers
Flexible Foam
Rigid Foam
Sealants
12
Figure 2.4: Split of polyurethanes market by end-use application (Biesman, 2002)
2.2.1 Polymer synthesis
The foundations of the polyurethanes industry were laid in the late 1930s with the
discovery by Otto Bayer of the chemistry of the polyaddition reaction between
diisocyanate and diols to form polyurethane even though the reaction between
isocyanate and hydroxyl compound was at first known in the 19th
century (Randall
and Lee, 2002). The successful preparation of polymers is achieved only if the
macromolecules are stable and polymers are often prepared in solution where
entropy destabilizes large molecular assemblies (Robyr, 2001).
For that reason, monomers have to be strongly bonded together and also, reaction
kinetics favourable to polymeric materials must be fast, so that high-molecular-
weight materials can be produced in a reasonable time. The polymerization reaction
must also be fast, so that high-molecular-weight materials can be produced in a
reasonable time as well, the polymerization reaction must also be fast compared to
side reactions that often hinder or preclude the formation of the desired product
(Robyr, 2001).
Polymerization reactions are generally divided into two main categories
according to the mechanism of chain growth (Jenkins et al., 1996) which are:
11%
5%
18%
29%
4%
18%
15%
Total market: 9.3 million tonnes
Thermal insulation
Other
Automotive
Furniture
Footwear
Construction
Coatings
13
i. Chain polymerization: chain growth proceeds exclusively by reaction
between a monomer denoted as M in Equation 1 and the reactive site on the
polymer chain denoted as with regeneration of the reactive site at the end
of each growth step and possible production of a side-product L as refer to
Equation 2.1
ii. Does not involve a chain reaction and is divided into two groups:
polyaddition and polycondensation. In both reactions the growth of a polymer
chains proceeds by reactions between molecules of all degrees of
polymerization. In polycondensations a low-molecular-weight product L is
eliminated, while polyadditions occur without elimination as in Equation 2.2.
Since molecules of all degrees of polymerization can react with each other,
the average molecular weight grows facter with a higher degree of conversion
2.2.2 Polymer from renewable resources
Nowadays, the increase in environmental consciousness among consumers and
governments, make the polymer industry now facing not only with manufacturing
and marketing concerns but with ecological and legislative issues as well. The
development towards environmental protection and regulation is headed for a
“cradle-to-grave” approach, in which the manufacturer is increasingly responsible for
the handling of raw materials used in production and the finish products, eventual
disposal (Swain et al., 2004). Bio-polymers from renewable resources have gained
much attention in current year. As a consequence the recent research and
development efforts have led to new products based natural resources. Certain of
these are biodegradable polymers like PLA (polylactic acid), cellulose esters,
polyhydoxyalkanoates and starch polymers (Benjamin and Jorg, 2008). Nearly all
polymer material is produced based on crude oil as feedstock.
Polymers from renewable resources have attracted an increasing amount of
attention over the last two decades; predominantly due to two major reasons: 1)
{ } (2.1)
{ } (2.2)
14
environmental concerns and 2) realization that our petroleum resources are finite (Yu
et al., 2006). Composites made of natural fibres and biopolymers are completely
biodegradable and are called “green composites” due to their environmentally
valuable properties. As a result of increasing environmental awareness the use of
traditional composites made of glass, aramid or carbon fiber reinforced plastics have
recently been discussed critically (Benjamin and Jorg, 2008). Mohanty et al., (1999)
defined that when a bio-degradable material (neat polymer, blended product or
composite) is gained totally from renewable resources can call it a green polymeric
material.
Renewable resources of polymeric materials deal an answer to maintaining
sustainable development of economically and ecologically smart technology. The
inventions in the development of materials from bio-polymers, the preservation of
fossil-based raw materials, complete biological degradability, the reduction of the
volume garbage and compost ability in the natural cycle, protection of the climate
through the reduction of the carbon dioxides released, along with the application
possibilities of agricultural resources for the production of bio/green materials are
some of the reasons why such materials have attached the public interest (Mohanty et
al., 1999).
Long et al., (2006) also point out that one of the most promising polymers in
this concern is PLA, since it is made from agricultural products and is readily
biodegradable. Through controlled depolymerisation of lactic acid, lactide can be
prepared which in turn can be founded by the fermentation of corn, sugar cane, and
sugar bead. The glass transition temperature of PLA (Tg) ranges from 50 °C to 80 °C
while the melting temperature (Tm) ranges from 130 °C to 180 °C. In addition, PLA
can be processed by thermoforming and film forming, blow moulding, injection
moulding and sheet extrusion. Bacterially synthesized PHAs invite much
consideration because they can be produced from a variety of renewable resources,
and are truly bio-degradable and highly bio-compatible thermoplastics materials
(Long et al., 2006). For that reason, PHAs are predictable to contribute to the
formation of an environmentally sustainable society as above 90 different types of
PHAs existing of various monomers have been reported and the number is
increasing.
High crosslink solid green-polymer prepared for a wide range application
such as for composite or foam product. Also, bio-polymer can be used as foams for
15
seating, textile lamination, acoustic barriers, energy absorbers and car component
such as bumper. In addition, it is usually used as adhesives to join different materials
in the footwear and automotive. The green monomer preparations begin with the
catalyst preparation to create the epoxies from the unsaturated fatty compounds, and
the second reaction is the acid-catalyst ring opening of the epoxies to form polyols or
green monomer (Andrew et al., 2003). The effect of fillers for the mechanical
properties of all solid polymers will be defined, particularly metal oxide such as
titanium dioxide powder and natural fiber (Rus, 2009).
2.2.3 Composites from oil-based polymers
Polymers composites are used in a wide range of application areas, for example
aerospace, military, construction, electrical and electronics, medicine, marine,
transportation and so on (Guner et al., 2006). It is well-known that composites
involve of two or more materials forming separate phase. Above and beyond, in
polymer industry, vegetable oils which represent a major potential source of
chemicals have been utilized as an alternative feedstock for monomers (Suresh et al.,
2007). Oil-based bio-polymers have many advantages compared to polymers
formulated from petroleum-based monomers. Guner et al., (2006) mentioned that
they are bio-degradable and in many cases, cheaper than petroleum polymers.
Agreeing to the earlier researches Long et al., (2006), in general polymers from
renewable resources (PFRR) can be classified into three groups which are firstly
natural polymers such as starch, protein and cellulose, secondly synthetic polymers
from natural monomers, such as polylactic acid (PLA), and thirdly polymers from
microbial fermentation, such as polyhydroxybutyrate (PHB).
With an annual production capacity worldwide of nearly 12 million tons
(2007), PU are a major consumer plastic material (Behrendt and Naber, 2009).
Founded by Sulong and Rus (2010), PU foams made from palm oil were synthesized
and metal oxide powder was doped as filler to become renewable polymer composite
and the structure of the renewable polymer composite was investigated using SEM
with different percentage of filler. Generally, PU are generally produced from one or
more polyhydroxyl compounds and one or more di- or polyisocyanates (Behrendt
and Naber, 2009). PU resin prepared from castor oil was used to obtain graphite
16
composite as an electrode material. Guner et al., (2006) stated that the 60 %
(graphite, w/w) composite showed good mechanical and appropriated electric
resistance, easy preparation and surface renovation. For other oils such as soybean
oil and rapeseed oil-based polyols have been used to produce PU foams as well.
Canola-PU foam gave better compressive properties than Soybean-PU foam but less
than Castor-PU foam based on Suresh et al., (2007). The differences in performance
were originated to be related to the differences in the number and position of OH-
groups and dangling chains in the starting materials and to the differences in cellular
structure.
For other investigator industrial, materials from soybean oil-based resin and
natural fibers designed for using as the roof, floors or walls of a house or low-rise
commercial buildings. Intended for preparing soybean oil-based resin, first, soybean
oil was epoxidized and vinylated by styrene or acrylic acid (Guner et al., 2006).
Other researcher produced polyurethanes with soybean oil-based polyol or
petrochemical based polyol, and after that prepared glass-reinforced composites from
them. Based on experiment, the mechanical properties discovered that properties of
the soybean oil based composites were as good as with those based on petrochemical
polyol and besides, thermal, oxidation, and hydrolytic stability of soybean oil-based
composite were superior to those of the latter. Suhreta et al., (2005) stated that all
results point out that polyurethane matrix based on soybean oil is a preferable
alternative to the petrochemical polyurethanes in glass-reinforced composites.
2.3 Bio-polymer
Bio-polymers are polymers that are biodegradable and the raw materials for the
production of these polymers are renewable either based on agricultural plant or
animal products or synthetic. The main types of bio-polymer based are starch, sugar,
cellulose and synthetic materials. Bio-polymers comprise monomeric units that are
covalently bonded to form polymers (Averous and Pollet, 2012). The main category
of bio-polymers consists of three, based on different monomeric units used and the
structure of the bio-polymer formed (i) polynucleotides, which are long polymers,
composed of 13 or more nucleotide monomers, (ii) polypeptides, which are short
17
polymers of amino acids and (iii) polysaccharides, which are often linear bonded
polymeric carbohydrate structures (Chandra and Rustgi, 1998).
Referring to the Proterra International Center (2012), the present and future
developments in biodegradable polymers and renewable raw materials focus on the
scale up production and improvement of product properties. Larger scale production
will increase obtainability and reduce prices. Presently, in order to produce bio-
degradable polymers either renewable or synthetic, raw materials may become a
concern. There are two main strategies may be followed in synthesizing a polymer
which is, one is to build up the polymer structure from a monomer by a process of
chemical polymerization and the alternative one is to take a naturally occurring
polymer and chemically modify it to give it the desired properties. But the
disadvantage of chemical modification is that the biodegradability of the polymer
may be adversely affected. As a result, it is a failure aimed at related search for
cooperation between the desired material properties and bio-degradability.
2.4 Green technology
The applied research of green production technologies is the mainstream of the
current human civilization awareness that benefactor‟s energy conservation and
environmental protection. In order to saving the energy consumption of the existing
products and benefits the society by the development of the new energy for
environmental protection (Yijun and Gengxin, 2011). The main problem should be
pointed and the improvement on the efficiency of the energy conservation and
environmental protection should be made in order to diminish unnecessary energy
waste.
By means of focusing on cost minimization and risk management techniques,
internal today would apply in an operation context (Viet et al., 2011). As an example
firms would focus to decrease environmental burden and associated costs of raw
materials or disposal by integrate their employees concerns in decisions and ensure
proper worker safety and health standard. Effective utilization of land, water, energy
and other natural resources makes business more productive and economical.
If green technology research work can attract massive amount of funds for
development with good progress, this technology can definitely preserve the
18
environment by the practice of the complete green technology. By means of strive to
sustain economic growth without harming the planet or exhausting its resources
while improving the quality of life for current and future generations.
2.4.1 Recycling of bio-polymer foam
It is known that, the studies on WB using granular foam based on waste vegetable
cooking oil for particular application are uncommonly found. However, one of the
inventions from Kansas Polymer Research Center, Pittsburg State University
introduced the production method for rigid PU foam using soybean oil with two
different types of polyol in order to compare the mechanical strength (Guo et al.,
2006). A different invention is from Zhang (2008) that produced flexible PU foam
synthesized from the castor oil.
Polyurethanes (PU) foam wastes from end-of-life vehicles and many other
sources are getting increased attention worldwide as a result of rapidly rising
amounts and increasingly tight legislation on its treatment and disposal (Ron, 2004
and Vaclavik et al., 2012). In addition, around 25000 tonnes PU foam was recycled
by regrinding founded by the researchers. Vaclavik et al., (2012) noted that new
ways for recycling of rigid PU foams and composites by crumbling technology. It
was implemented in this research by using conventional crushing and grinding
methods. A knife grinder is used for flexible and rigid bio-polymer foam and it was
provided a smaller particle size depends on grinder speed (Vaclavik et al., 2012).
On the other hand, the same particle size can appear quite smooth to the
naked eye, but would have a small size, shape and roundness if observed using SEM
as shown in Figure 2.5. In this case, particle size of waste bio-polymer foam had
coarseness surface as observed from SEM. These behavior were affected the
vibration test. Based on previous master student research (Najibah, 2014), flexible
PU foam was better compared to rigid PU foam in vibration and damping
characteristic using the same procedure of WB production because of flexible hot
biopolymer gave more stiffness than rigid hot biopolymer which has more to
hardness and brittle behavior. For that reason, in this research flexible PU foam was
used in the production of WB to determine the effects of UV-irradiation towards
WB.
19
Figure 2.5: Particle structure of waste bio-polymer foam (Najibah, 2014)
2.5 Environmental impact
Governments begin to make laws and regulations to protect the environment because
of the importance of environmental issues around the country and of course for the
sake of the world. The use of six toxic materials in the manufacturing of all
electronic and electrical equipment restricted by the Restriction of Hazardous
Substances (RoHS) of the European Union (Jack et al., 2010). The researchers also
said that it is important for firms to understand how to design and manage green
product since the protection on the environment has appeared as one of the hottest
global. For the time being, consumers are paying more attention as to whether
companies are environmentally friendly since they are willing to purchase eco-
friendly or so called green products even though these product are often more
expensive.
Bio-polymers are sustainable, renewable and carbon neutral, because they are
made from plant materials which can be grown every years for an indefinite period.
For that reason, a sustainable industry can be created by using those bio-polymers.
The feedstock for polymers derived from petrochemicals at the end will be run out
that encourages bio-polymers production for replacing those petrochemicals. In other
way, biopolymers have the potential to lessen carbon emission and reduce carbon
dioxide quantities in the atmosphere since the carbon dioxide released when they
degrade. Then the carbon dioxide that released can be reabsorbed by crops grown to
replace them which is makes them close to carbon neutral.
20
In addition, lots of researches have been conducted to help corporation to
become more environmentally friendly through process re-engineering such as reuse,
remanufacturing, recycling and collaboration.
2.6 Foam generation
The leading commercial applications of polyurethane polymers for millable
elastomers, coatings and adhesives, were established between 1945 and 1947,
followed by flexible foams in 1953 and rigid foams in 1957 (Randall and Lee, 2002).
Foam is an essential engineering material which offers unique benefits in terms of
low cost and weight, stress-free to fabricate and has good energy absorption
properties. Since that time, they have been finding use in an ever-increasing number
of applications and polyurethanes are now all around and playing a vital role in many
industries. Furthermore, foam is used in many applications; acoustic absorption,
impact retardation and mechanical damping (Singh et al., 2003 and Lee and Choi,
2007). Nowadays, most modern automotive seats, static comfort and vibration
isolation are now succeeded through the use of foam alone.
In general, PU foam is made from a formula that contains a host of
components selected to achieve the desired grade of foam which are these
components included polyol, isocynate, water, catalyst, surfactants, cross-linkage
agent, auxiliary blowing agent, and additives such as colorant, flame retardant,
antistatic agent, bacteriostat or UV stabalizer. Between all chemical components,
polyol and isocyanate are the main components used to forms PU linkage.
Kaushiva (1999) stated that the chemical reaction between polyol and
isocyanate is called gelation reaction and another chemical reaction occurred during
foam generation which is called blowing reaction. The reaction demonstrates in
Figure 2.6. Klempner and Sendijarevic (2004) stated that the chemical reaction
between polyol and isocyanate is an exothermic process for which heat of reaction
had been reported approximately 24 kcal/mol of urethane. During the reaction, water
reacts with isocyanate to produce carbon dioxide ( ) which disperses to the
existing gas bubbles in the polyol and so expands the foam and heat would generate
in the mixture which plays a large role on expanding the gas into the liquid to form a
21
desired cellular-structure. It was noted that the internal temperature of foam bun/rise
would build upon the order of 140 °C during the foam generation.
Figure 2.6: Gelation Reaction or PU Cross Linking Reaction (Kaushiva, 1999)
Other components in recipe working as per surfactants are essential
components in foam formation with the intention to produce a well open-celled
morphology. They implement to lessen surface tension in PU, emulsifying in
compatible ingredients, promoting bubble nucleation, stabilizing the rising foam, as a
consequence decreasing the deformation effects and the most significant is to
stabilize the cell wall. Through polymerization, surfactant prevents the coalescence
of rapidly growing cells until those cells have achieved sufficient strength to become
self-supporting (Klempner and Sendijarevic, 2004). Without this, cell coalescence
would result in a total foam collapse. The catalyst is generally used in foam
formulation and blow reaction. Above and beyond, it is also for reassuring
completeness of reaction or “cure” in finished foam.
2.6.1 Formation of foam
Generally, most foamed polymers are generated by diffusing a gas all the way
through a fluid polymer phase and stabilizing the resultant foam (Klempner and
Sendijarevic, 2004). The foam is stretched out by increasing the bubble size before
stabilize the system. There are many sources of gases may be involved in foaming
process such as air from environment, gas such as from carbon dioxide, a low boiling
liquid or gas may be produced by a chemical reaction.
The preparation of foams by the dispersion method usually consists of three
steps as followed (Klempner and Sendijarevic, 2004):
Step 1: Bubble formation: The first step in producing foam is formation of gas
bubbles in a liquid system and the bubbles will usually form more easily at
H
Isocynate Alcohol Urethane
H H
Isocyanate Alcohol Urethane
22
the liquid-solid interface
Step 2: Bubble growth: Once a bubble was formed, it may grow by diffusion of gas
from solution in the liquid phase into the bubble
Step 3: Stabilization: There are many aspects that affect the stability of bubble
which are pure liquids without surface tension. Moreover, a surfactant may
be most effective for stabilization if it is design. Last but not least, the
temperature can also affect stability which an increasing the temperature
also increases the reaction rates as well as reduces both viscosity and
surface tension.
2.6.2 Production of foam
Referring to the Sung et al., (2007), flexible PU foam is created by one-shot and free
rise method which is means that the isocyanate, polyol, water and other ingredients
are rapidly and intensively mixed and immediately poured to carry out the foaming.
The method point out that once the process is taking place, the formation of foam is
exothermic until they are complete. Fundamentally, flexible PU foams are made
through two categories of fabrication process which are slabstock foam and moulded
process where slabstock foams are used for cushioning (Polyurethane Foam
Association, 1991) and in furnishing industry such as mattress and carpet backing
whereas moulded foam are mainly used in transportation application such as
automotive seating (Zhang, 2008).
Two basic procedures are used for slabstock foam. Firstly, the chemical mix
is poured onto the moving conveyor, where it is allowed to react and expand and the
conveyor allow the foam to rise into a “bun” or slab anywhere from two to four feet
high. Then, the continuous slab is then cut, put in storage, and allowed to cure for up
to 24 hours. Mentioned by Klempner and Sendijarevic, (2004) the slabstock foam is
executed in an open environment and on the other hand, for moulded foams, is
processes where individual items are produced by pouring foam chemicals into
specially shaped moulds and allowing the foam reaction to take place and it is also
call closed mould process.
23
The researchers also mentioned that usually, for the small or laboratory scale
production, the flexible PU foams can be prepared as a simple hand or cup-foam
mixes to techniques of box-foaming mixes. This technique is also called free rise-
bun. Generally, the methods to make foams in laboratory scale are as follows
(Klempner and Sendijarevic, 2004):
i. the components lists in recipe are weighed manually according to the
proportion need
ii. they are mixed using the mechanical device according to the sequence of
mixture
iii. after a mixing, the mixtures were poured into a cup or mould prepared
iv. the flexible foam is moving out from the mould or cup and leaving for
cured after a short period
2.7 Modification of polymer using fillers
Usually, filler are described as materials that are added to the formulation to reduce
the cost. In general, fillers are solid additives and dissimilar from plastic matrices in
composition and structure which are added to the polymers to increase bulk or
improve the behavior. Fillers practically used as solid additives into the polymer to
examine its physical and mechanical properties of material development (George,
2000). There are a lot of factors e.g. properties of fillers and their fibres aspect ratio
and particulate shape size, as well as filler-matrix interface would affect and govern
the properties of composites material. Air and other gases could be considered as
fillers in cellular polymers in certain condition.
Therefore, it is essential to have some basic knowledge about using fillers in
any research. Agreeing to Lutz and Grossman (2000), each class of the fillers seems
to show specific characteristics that make them exclusively suited for the given
application. Fillers are much stiffer and stronger than the polymer which that one to
increase its modulus and strength.
2.7.1 Composite foam and its properties
24
Flexible PU foams are one of the significant classes plastic used in the manufacture
of such materials as foam mattresses, pillow, furniture, cushioning materials for
automobiles, packing, recreation, shoes and so on (Usman et al., 2012). From the
time when early 50 s, the fabrication of naval vessels, military vehicles, aircraft,
building and offshore structure have been apply from epoxy foams. On the other
hand, the discussion about rubber foam is not extensively covered but foamed
rubbers are globally manufactured and are in service all over the world (Lee and
Choi, 2007).
Mello et al., (2009) carried out post-consumer plastic bottle waste PET
(Polyethylene terephthalate), PET as per reinforcement filler in flexible PU foams.
The intention was to discover alternatives for recycling of polymer packaging;
decrease the cost material and getting better mechanical properties from the new
composite created. A particulate shape in size of < 297 μm were prepared by the
researchers and it is added to PU at a concentration of 1.5 parts by hundred parts of
polyol. They conducted some mechanical test such as tensile resistance, tear
resistance and break strain (%) for testing in mechanical strength and the results
presented by such testing revealed that the mechanical performance of PET foams
exceeded than standard foam for all layers (top, mid top, mid bottom and bottom).
Furthermore, the PET filled is also used to conduct the wear, compression strength
and compression set tests and from the results achieved, a filled foam yield a better
wear which has less mass losses during the wear test, a better compressive strength
which point out that PET particles can efficiently absorb the compression energy and
lower compression set test value.
Referring to the results achieved in Latinwo et al., (2010) study, it was
noticed that filler material improved the hardness characteristics of the flexible
polyurethane foam to compositions up to 35%. Moreover, the researchers found that
the properties such as tensile strength and elongation at break goes down negatively
when particle size of fillers were added as shown in Figure 2.7 and Figure 2.8.
Coarse filler filled composite obtained better tensile strength than fined filler filled
composite among all and it is may cause by fact of less surface area of coarse
particles in disturbing the foam reaction (Latinwo et al., 2010).
104
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