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

ix

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

xi

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

xiii

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

xv

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

xxi

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

xxii

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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