RESULTS AND DISCUSSIONS CONCLUSION AND RECOMMENDATIONS

vi 3.9.2 Accelerometer Free Vibration Test - Logarithmic Decrement Method 86 3.9.3 Measurements of Vibration Damping Properties 88

4. RESULTS AND DISCUSSIONS

90 4.1 Stage 1: Production of the Optimum Formulation of NREPDM Blends 90 4.1.1 Modelling Summary 91 4.1.2 Interaction between Variables for Cure Characteristics of the Blends 92 4.1.3 Interaction between Variables for Tensile Properties of the Blends 96 4.1.4 Experimental Analysis on NREPDM blends 100 4.1.4.1 Swelling Behavior 100 4.1.4.2 Differential Scanning Calorimetry DSC Analysis 101 4.1.4.3 Scanning Electron Microscopy SEM Analysis 103 4.2 Stage 2: Facile Method for Surface Treatment of GNPs-Chitosan 105 4.2.1 Selection of Dispersant through Experimental Study 105 4.2.2 FTIR Analysis of Noncovalent Functionalization of GNPs by Chitosan 110 4.2.3 Proposed Reaction Mechanism 113 4.3 Stage 3: Characterization studies on NREPDM filled graphene composites 114 4.3.1 Curing Characteristics 114 4.3.2 Tensile Strength Ts 118 4.3.3 Modulus at 100 M 100 and 300 M 300 Elongation 120 4.3.4 Elongation at break E b 122 4.3.5 Swelling Measurement 124 4.3.6 Structural Analysis 126 4.3.6.1 Fourier Transform Infrared Spectroscopy FTIR Analysis 126 4.3.6.2 X-Ray Diffraction XRD Analysis 129 4.3.7 Scanning Electron Microscopy SEM Analysis 134 4.4 Stage 4: Determination of Vibrational Damping Properties 137 4.4.1 Determination and Selection of Samples using Response Surface Methodology 137 4.4.2 Vibration Test Free Vibration Mode- Logarithmic Decrement Method 137 4.4.3 Dynamic Mechanical DMA Analysis 142 4.4.4 Transmission Electron Microscopy TEM 146

5. CONCLUSION AND RECOMMENDATIONS

148 5.1 Conclusion 148 5.3 Recommendations for Future Work 152 REFERENCES 154 vii LIST OF TABLES TABLE TITLE PAGE 2.1 2.2 2.3 2.4 2.5 2.6 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 Typical property ranges of EPDM Applications for EPDM Impact of filler parameters on the properties of filled rubber material Properties of GNPs and CNTs Level of sulphur and the ratio of accelerator to sulphur List of published studies on polymer using RSM Properties of NR SMR 20 Properties of EPDM Properties of ENR-50 Properties of sulphur system Properties of accelerator Properties of 6PPD anti-oxidant agent Classification of raw material General properties of graphene nanoplatelets KNG-150 General properties of chitosan General properties different types of solvents Levels of variables 2 4 Factorial design matrix used for the screening factors Experimental matrix and the output response table Typical formulations Compounding formulation used in NREPDM filled with unfunctionalized and functionalized GNPs Factors and the constraints on the responses for the selection of the worst, middle and best samples 18 19 26 31 44 51 54 55 56 57 58 59 60 61 62 63 74 75 76 77 83 85 viii 4.1 4.2 4.3 4.4 4.5 4.6 Regression equations for different responses Comparisons of experimental and predicted tensile strength values of NREPDM blends DSC results obtained for neat rubbers with their blends The observation of the 2 hour of sonication time FTIR spectra evaluation for non-covalent treatment of GNPs Log decrement values and damping ratios of GNPs filled NREPDM nanocomposites 93 99 102 106 110 141 ix LIST OF FIGURES TABLE TITLE PAGE 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10 2.11 2.12 2.13 2.14 2.15 2.16 2.17 2.18 2.19 2.20 2.21 2.22 Schematic of elastomeric networks under tensile deformation Chemical formula of natural rubber Ozone cracking on side wall of tire Various applications of NR Chemical structure of ethylene-propylene diene rubber EPDM Interface between miscible and immiscible of polymer blends General schematic of epoxidation on NR latex Payne effect of filled rubber Stress softening of filled rubber also known as Mullins Effect Layered graphite tightly bonded in hexagonal rings Schematic illustration of GNP production Mechanism of ultrasonication Chemical modification of graphene Schematic of grafting-to and grafting-from approaches Schematic representation of non-covalent functionalization of GO through surfactants, polyelectrolytes, polymers and DNA Solvent casting methods for the preparation of GNPs-polymer The mechanism of FGS incorporation into polymer for melt blend technique Reaction of sulphur vulcanization Different crosslink structures:a monosulfidic, b disulfidic, c polysulfidic, when x = 3-6, d pendant sulphide, e cyclic monosulphide, f cyclic disulphide Rheometer curve Elements of a vibratory system Summary of RSM analysis flow 13 14 16 16 17 22 23 27 27 28 29 32 34 35 37 39 41 42 43 45 47 49 x 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 3.20 3.21 3.22 3.23 3.24 3.25 3.26 4.1 Flowchart of the overall experiment Masticated NR Masticated EPDM Masticated ENR-50 a Stearic scid b Zinc oxide and c Sulphur a Perkacit MBTS b Perkacit TMTD 6PPD anti-oxidant agent Commercialize graphene nanoplatelets KNG-150 Chitosan a Dumbbell die cutter b Dumbbell-shaped samples size for BS 6747 Universal testing machine Toyoseiki Strograph Photograph of swelling measurements of NREPDM filled GNPs samples a Fourier transform infrared FTIR-6100 JASCO b thin film of sample for ATR-FTIR Schematic illustration of an X-ray diffraction setup Schematic illustration of diffraction according to Bragg’s law Panalytical XPert PRO diffractometer machine Differential scanning calorimetric DSC Transmission electron microscopy TEM Haake rheomix OS internal mixer machine NREPDM blends product from internal mixer The compounding sample placed in the mold a GT 7014 - A hot press machine and b Example of vulcanized sample a Ultra-sonication setup b Sonicator dispersing GNPs Logarithmic decrement method free vibration of a damped single degree of freedom system Shape and dimensions of test specimen for the measurement of the vibration damping properties Test set-ups for free vibration test Response surface plot showing variation in a scorch time ts 2 ; b cure time t 90 ; c maximum torque M H and 53 54 55 56 57 58 59 61 62 65 66 67 69 69 70 71 72 73 78 78 79 80 81 87 88 89 xi 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10 4.11 4.12 4.13 4.14 4.15 4.16 d torque difference M H – M L Response surface plot showing variation in a tensile strength Ts; b modulus at 100 elongation M 100 , c modulus at 300 elongation M 300 and d elongation at break E B The swelling percentage and crosslink density of the NREPDM blends DSC thermograms of neat rubbers with R0, R15 and R10 SEM micrographs showing tensile fracture surface of NREPDM blends at 7030 blend ratio: a R0 b R15 c R10 at 300X magnifications TEM image of the graphene dispersed with different solvents: a ethanol and b toluene FTIR spectra of chitosan, GNP, GNP functionalized chitosan Noncovalent functionalization of GNPs through amide linkage with the chitosan Effect of unfunctionalized and unfunctionalized GNPs loading on the scorch time ts 2 of NREPDM nanocomposites Effect of unfunctionalized and functionalized GNPs loading on the cure time t 90 of NREPDM nanocomposites Effect of unfunctionalized and functionalized GNPs loading on the maximum torque M H of NREPDM nanocomposites Effect of unfunctionalized and functionalized GNPs loading on the torque difference M H -M L of NREPDM nanocomposites Effect of unfunctionalized and functionalized GNPs loading on the tensile strength Ts of NREPDM nanocomposites Effect of unfunctionalized and functionalized GNPs loading on modulus at 100 elongation M 100 of NREPDM nanocomposites Effect of unfunctionalized and functionalized GNPs loading on modulus at 300 elongation M 300 of NREPDM nanocomposites Effect of unfunctionalized and functionalized GNPs loading on the elongation at break Eb of NREPDM nanocomposites 95 97 100 103 104 109 112 113 115 115 116 117 119 120 121 122 xii 4.17 4.18 4.19 4.20 4.21 4.22 4.23 4.24 4.25 4.26 4.27 4.28 4.29 4.30 Schematics of tensile fractured mechanism of a neat NREPDM; b a NREPDM nanocomposite at lower GNPs loading; and c a NREPDM nanocomposite at a higher GNPs loading overloading Effect of GNPs loading on the swelling behaviour of NREPDM blends filled unfunctionalized and functionalized GNPs ATRIR spectra of vulcanized NREPDM blends and NREPDM filled unfunctionalized GNPs nanocomposites ATRIR spectra of vulcanized NREPDM blends and NREPDM filled functionalized GNPs nanocomposites Raw material characterization: XRD pattern analysis of commercial Graphene Nanoplatelets KNG -150 K NANO XRD patterns of unfunctionalized GNPs filled NREPDM blends XRD patterns of functionalized GNPs filled NREPDM blends SEM micrographs of the tensile fracture surfaces of the vulcanized NREPDM blends of 0 wt GNPs SEM micrographs of the tensile fracture surfaces of the nanocomposites: abc unfunctionalized GNPs filled NREPDM; def functionalized GNPs filled NREPDM at 500x magnification Free decay curves of GNPs filled NREPDM nanocomposites containing a vulcanized NREPDM; b 5wt functionalized GNPs; c 1wt unfunctionalized GNPs; d 5wt unfunctionalized GNPs and e 3wt unfunctionalized GNPs Storage modulus as a function of temperature Loss modulus as a function of temperature Tan delta as a function of temperature TEM micrograph of NREPDM nanocomposites a-b 3 wt of unfunctionalized GNPs R5; c-d 5 wt of functionalized GNPs R2 at different magnification 123 125 127 128 130 131 133 134 136 139 143 144 145 147 xiii LIST OF ABBREVIATIONS ANOVA ASTM BS C CH CNTs COOH CV DSC E B ENR ENR-50 EPDM DMTA e.g ENB et. at. etc i.e FTIR GNPs GO LGM MAH Mc MBTS M H - - - - - - - - - - - - - - - - - - - - - - - - - - - Analysis of variance American standard testing method British standard Carbon Hydrocarbon Carbon nanotubes Carboxylic group Conventional vulcanization Differential scanning calorimetry Elongation at break Epoxidized natural rubber Natural rubber having 50 of epoxidation Ethylene propylene diene monomer Dynamic mechanical thermal analysis Example Ethylidene norbornene and others Et cetera In example Fourier transform infrared spectroscopy Graphene nanoplatelets Graphene oxide Lembaga getah Malaysia Maleic anhydride Molecular weight between crosslink 2,20-dithiobis benzothiazole Maximum torque xiv M L M H -M L M 100 M 300 MWNT NR NVH OH Phr PNCs Qm R2 RD RSM SEM SWNT Tg Ts T 2 T 90 Tm TMTD TEM TOR UTM Vc Vr Vs XRD W W 1 Wt 6PPD - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Minimum torque Torque difference Modulus at 100 elongation Modulus at 300 elongation Multi-walled carbon nanotube Natural rubber Noise, vibration and harshness Hydroxyl group Parts per hundred rubber Polymer nanocomposites Weight increase of the NREPDM blends in toluene Constant of determination Research and development Response surface methodology Scanning electron microscopy Single-walled carbon nanotube Glass transition temperature Tensile strength Scorch time Cure time Melting temperature Tetramethylthiuram disulfide Transmission electron microscopy Trans-polyoctenylene rubber Universal testing machine Crosslink density Volume fraction of the swollen rubber Molar volume of the solvent toluene X-ray diffraction Initial mass of samples before the immersion in toluene Mass of samples after the swelling Weight percent dN-1,3-Dimethylbutyl-N’-phenyl-p phenylenediamine xv LIST OF UNITS o C ms min kg mm μm s nm g Hz - - - - - - - - - - - Celsius Meter per second Percentage Minute Kilogram Millimeter Micrometer Second Nanometer Gram Hertz xvi LIST OF PUBLICATIONS

1. Noraiham Mohamad, Juliana Yaakub, Jeefferie Abd Razak, Mohd Yuhazri Yaakob,