Mariatti Jaafar

Preparation and Characterization of Ethylene Vinyl Acetate (EVA)/Natural Rubber (SMR L)/Organoclay Nanocomposites: Effect of Blending Sequences and Organoclay Loading

Ethylene vinyl acetate (EVA)/natural rubber (SMR L)/organoclay thermoplastic elastomer nanocomposites were melt compounded in an internal mixer, Haake Rheometer, at 120°C and 50 rpm rotor speed. In this paper, we demonstrate the effect of different blending sequences and organoclay loading from 2 to 10 phr (parts per hundred resins) on the tensile properties, morphology, thermal degradation, flammability, and water absorption behavior of EVA/SMR L/organoclay nanocomposites. EVA/SMR L/organoclay TPE nanocomposites were prepared by three different blending sequences, and each exhibited different tensile properties. Results indicated that the presence of organoclay increases the tensile properties, resistance toward thermal degradation, resistance to water permeation, and flame retardancy for all the nanocomposites prepared via different blending sequences. However, the optimum results for all the properties studied were achieved when EVA was blended with organoclay first and SMR L was incorporated later into the blend. The optimum organoclay loading was achieved at 2 phr. Results from scanning electron microscopy (SEM) and X-ray diffraction (XRD) studies showed that at 2 phr organoclay loading, nanostructures of individual silicate layers were achieved, whereas at 8 phr organoclay loading, agglomeration was observed. Flammability of the nanocomposites decreased when the organoclay loading increased.

Mechanical Properties Evaluation of Woven Coir and Kevlar Reinforced Epoxy Composites

The utilization of coconut fibers as reinforcement in polymer composites has been increase significantly due to their low cost and high specification of mechanical properties. Whereas kevlar fibers has widely used as the core material in flexible body armors due to its great mechanical properties, such as high strength, light weight, good chemical resistance and thermal stability. The research work is concerned with the evaluation of high speed impact and flexural test of hybrid textile reinforced epoxy composites. Samples were prepared from coir yarn, kevlar yarn, interlaced of coir and kevlar yarn with different warp/weft orientation and pure epoxy as control specimen. The woven samples were produced using handloom and the composites specimens were prepared using hand lay-up technique. From the results obtained, it was found that woven kevlar composites samples displayed the highest impact properties while it exhibits the lowest flexural properties. Results also showed that the composite plate for woven coir yarn (warp) and kevlar yarn (weft) has the flexural strength and impact strength of 17 MPa and 67 kJ/m², which presented as the nearest properties to woven Kevlar composite respectively. These results indicate that coir as a natural fiber can be used as a potential reinforcing material for high impact resistance such as body armors in order to reduce the usage of synthetic materials whilst utilizing the natural resources.

Optimization of Conductive Thin Film Epoxy Composites Properties Using Desirability Optimization Methodology

Multiwalled carbon nanotubes (MWCNTs)/epoxy thin film nanocomposites were prepared using spin coating technique. The effects of process parameters such as sonication duration (5–35 min) and filler loadings (1-2 vol%) were studied using the design of experiment (DOE). Full factorial design was used to create the design matrix for the two factors with three-level experimentation, resulting in a total of 9 runs () of experimentation. Response surface methodology (RSM) combined with E.C. Harrington’s desirability function called desirability optimization methodology (DOM) was used to optimize the multiple properties (tensile strength, elastic modulus, elongation at break, thermal conductivity, and electrical conductivity) of MWCNTs/epoxy thin film composites. Based on response surface analysis, quadratic model was developed. Analysis of variance (ANOVA), -squared (-Sq), and normal plot of residuals were applied to determine the accuracy of the models. The range of lower and upper limits was determined in an overlaid contour plot. Desirability function was used to optimize the multiple responses of MWCNTs/epoxy thin film composites. A global solution of 12.88 min sonication and 1.67 vol% filler loadings was obtained to have maximum desired responses with composite desirability of 1.

Mechanical properties of multi-walled carbon nanotube (MWCNT)/polymethyl methacrylite (PMMA) nanocomposite prepared via the coagulation method

Multi-walled carbon nanotube (MWCNT) is well known as one of the best candidates for reinforcing the next generation of high performance nanocomposites due to its excellent mechanical properties. In this study, MWCNTs were dispersed in polymethyl methacrylite (PMMA) matrix to enhance its mechanical strength. MWCNT/PMMA were prepared by simple coagulation method and then hot-pressed to create nanocomposite film consists of rich nanotubes. Samples were prepared in respect to various high filler loading (1%, 3%, 5%, 7% and 10% wt.). Standard ASTM D790 flexural test was used to evaluate the mechanical properties of the composites. The morphology and surface fracture were observed via scanning electron microscope. The properties of the composites where found to be better than the neat PMMA. Flexural strength & flexural modulus of MWCNT/PMMA nanocomposite showed an improvement up to 24.1% and 107.7% compared to the neat PMMA, respectively. These studies therefore demonstrate that MWCNT/PMMA prepared by coagulat...

β-cyclodextrin as a Partial Replacement of Phosphorus Flame Retardant for Poly(Lactic Acid)/Poly(Methyl Methacrylate): A More Environmental Friendly Flame-Retarded Blends

ABSTRACT β-Cyclodextrin was used together with isopropylated triaryl phosphate ester flame retardant to improve the flame resistance of poly(lactic acid)/poly(methyl methacrylate). Poly(lactic acid)/poly(methyl methacrylate)/flame-retardant blend (with and without β-cyclodextrin) was evaluated using limiting oxygen index, Underwriters Laboratories-94 vertical burning test, scanning electron microscopy, and thermogravimetric analysis (in O2 and N2). The addition of β-cyclodextrin was able to reduce the amount of flame retardant required for poly(lactic acid)/poly(methyl methacrylate) blends to achieve self-extinguishing properties. The poly(lactic acid)/poly(methyl methacrylate)20/flame-retardant/β-cyclodextrin blends achieved Underwriters Laboratories-94, V-0, and limiting oxygen index value of 29.3%. A compact and wide coverage of char layer was formed on the burning surface of poly(lactic acid)/poly(methyl methacrylate)20/flame-retardant/β-cyclodextrin blends. GRAPHICAL ABSTRACT

Synthesis of TiO2 Nanotube Arrays in NaOH Added Ethylene Glycol Electrolyte and the Effect of Annealing Temperature on the Nanotube Arrays to their Photocurrent Performance

The present study employs NaOH as an oxygen source in fluorinated ethylene glycol (EG) electrolyte for the formation of titanium dioxide nanotube arrays (TiO2 NTs) by anodic process. The nanotube formed were 125 nm in diameter with length of ~ 7 µm after 30 min of anodization. They were then annealed to study the effect of annealing temperature on the photocurrent generated by the TiO2 NTs. It is found that TiO2 NTs annealed at 400 °C has the highest photocurrent (0.716 mA cm-2 at 0.5 V vs Ag/AgCl). This is attributed to the crystallinity (mostly anatase) of the TiO2 NTs as well as the nanotubular structure which retains at this temperature but not at higher temperature.

Effects of different processing techniques on multi-walled carbon nanotubes/silicone rubber nanocomposite on tensile strength properties

In this work, two different processing techniques were approached to identify the properties of the multi-walled carbon nanotubes (MWCNT) reinforced polydimethylsiloxane (PDMS). The MWCNT was dispersed in the polymer by using the ultrasonic and twin screw extruder mixer. The final composite showed different manner of dispersed tubes in the silicone rubber matrix. High shear twin screw extruder tends to fragment the tubes during processing compound, which can be observed by scanning electron microscope (SEM). Tensile strength of the extrusion MWCNT/PDMS nanocomposites was found to be higher compared to ultrasonic MWCNT/PDMS nanocomposites.

Polylactic Acid Scaffold Fabricated by Combination of Solvent Casting and Salt Leaching Techniques: Influence of β-Tricalcium Phosphate Contents

β-tricalcium phosphate (β-TCP) is a ceramic that commonly been used in bone tissue engineering. This material exhibits low mechanical properties such as low fracture toughness and brittleness. To overcome these problems, polylactic acid (PLA)/ β-TCP scaffolds for bone tissue engineering were prepared by using the combination method of solvent casting and salt leaching. These methods were used to produce three-dimensionally interconnected pores of the scaffold according to different ratio of β-TCP with porogen agent (sodium chloride (NaCl)). It is found that porosity and pore size of the scaffolds were independently controlled by the ratio and the particle size of the added porogen. The increases of pore interconnectivity were observed with increasing of PLA/ β-TCP/ NaCl ratios. Scaffolds with 80-90 wt% of total porogen content displayed acceptable mechanical properties for bone tissue engineering applications. Morphology observed by scanning electron microscopy (SEM) revealed that highly porous three-dimensional scaffold (>80 wt%) with well interconnected porous structure could be achieved by this combination process.

Fabrication of PEDOT:PSS/Graphene Conductive Ink Printed on Flexible Substrate

Nowadays, flexible electronic is an important technology to produce flexible electronic devices due to it offers the attractive features such as possibility of product types and designs, with reducing size and weight, and low cost. Poly (3,4-ethelenedioxythiophene):poly (stylenesulfonate) (PEDOT:PSS) is a conductive polymer which possess high conductivity, high electrochemical, and low redox potential. PEDOT:PSS and PEDOT:PSS/Graphene (GP)/Dimethyl sulfoxide (DMSO) conductive ink ware deposited on Polyethylene terephthalate (PET) flexible substrate using desktop inkjet printer. Conductivity and thickness of conductive pattern at 1, 3, 5, 10, 20 layers were investigated in this study. It is observed that sheet resistivity of the conductive pattern is influenced by number of printed layers. Addition of GP at 20 layers of PEDOT:PSS/GP/DMSO conductive pattern exhibits the lowest sheet resistivity at 44 ohm/sq compared to PEDOT:PSS conductive pattern of 1.81×104 ohm/sq.

Influence of Hydroxyl and Carboxyl Functionalized Multi-Walled Carbon Nanotube and Filler Loading on the Tensile Properties of Epoxy Composites

In this study, three various types of fillers; pristine multi-walled carbon nanotube (MWCNT), hydroxyl functionalized multi-walled carbon nanotube (MWCNT-OH) and carboxyl functionalized multi-walled carbon nanotube (MWCNT-COOH) were used to prepare epoxy (EP) composites via ultrasonication and casting techniques. The effect of pristine MWCNT and functionalized MWCNT (MWCNT-OH and MWCNT-COOH) and fillers loading (0-1.0 vol%) on tensile properties of EP composites were investigated and compared. To identify the effectiveness of functional groups on the EP composites, the MWCNT, MWCNT-OH and MWCNT-COOH were compared through tensile testing. The addition of pristine MWCNT decreased the material’s tensile strength and modulus, while the addition of MWCNT-OH decreased the material’s tensile strength. However, among the EP composites, the 0.4 vol% MWCNT-COOH/EP composite exhibited a 12.80% increase in tensile strength (44 MPa). The tensile modulus of 0.4 vol% MWCNT-OH/EP and MWCNT-COOH/EP composites were found to be significantly higher compared to unfilled epoxy which were approximately 15.60% (2376 MPa) and 18.54% (2436 MPa) respectively. In conclusion, the MWCNT-COOH/EP composite showed slight improvement in both the tensile strength and modulus. The effect of functionalized MWCNT was supported by morphological analysis, which demonstrated an improvement in MWCNT-COOH dispersion with slightly fine agglomerates particles at 0.4 vol%.