Papers by Author: Jaafar Sahari

Abstract: Optimization of molding parameter on the flexural strength of carbon black/graphite/epoxy (CB/G/EP) nanocomposites using Taguchi method was studied. Three molding parameters was chosen in this study which are molding temperature, molding pressure and molding time. Experimental trials were carried out based orthogonal array design using those three parameters. The results were analyses using the signal to noise (S/N) and analysis ofvariance (ANOVA). Flexural strength of the CB/G/EP nanocomposites increases from 56.23 MPa to 65.11 MPa usingoptimize parameter obtained from the analysis method. These results shown that the Taguchi method is successfully to get optimum parameters of molding parameters to produce CB/G/EP nanocomposites.

Abstract: Optimization of the moulding parameters on the carbon black/graphite/epoxy (CB/G/EP) composite for bipolar plate application using the Taguchi method was carrying out. Moulding parameters of the compression moulding process such as moulding temperature, moulding pressure and moulding time were measured. Analysis of variance (ANOVA) shows that, the most significant moulding parameter is moulding time with percentage contribution of 59.98%.The confirmation experiment using additive model shows that, the electrical conductivity of CB/G/EP composites was 168.50 S/cm. The electrical conductivity of CB/G/EP composite was improved 65.72 % compare with the initial trial. The results show that Taguchi method is an effective approach to obtain the optimal moulding parameters of the CB/G/EP composites.

Abstract: Co/Pd bi metallic catalyst supported on MgO has been prepared by sol gel method, at different calcination temperatures of 250 and 550 C. They were introduced in to the reactor for 5 hrs of reaction. The CNTs were collected. The obtained CNTs were characterized by XRD and SEM and the yield was observed. It has been concluded that the catalyst calcined at higher temperature will lead to higher yield and more uniform and smaller diameter CNTs.

Abstract: Polymer composite has attracted many researchers from various field of application due to its unique features and properties including light weight, low cost, ease to process and shaping and corrosion resistant [1-3]. Fillers is typically added to enhance the chemical and physical properties of polymers [4, 5]. One of the properties is the electrical conductivity. Carbon based filler such as graphite (G), carbon black (CB), carbon fibers (CF) and carbon nanotubes (CNT) has been extensively used to improve electrical properties of polymer composite [6-8]. Electrical properties of the composite can be explained from percolation theory which means electrical percolation in mixtures of electrically conducting and non-conducting materials [9]. The concentration of conducting phase must above the critical value called percolation threshold, in order for the material become electrically conductive [10].

Abstract: This study investigates the effect of carbon nanotubes (CNTs) as conductive fillers and epoxy resin as matrix on the electrical conductivity and hardness property. The different CNTs weight percentage (0 ~ 10 wt.%) were added into the epoxy resin. The dispersion of CNTs in epoxy resin was conducted by high speed mixer through mechanical shearing mechanism. The mixture of CNTs/epoxy was poured into the mold and compression molding was conducted for fabrication of CNTs/epoxy nanocomposites. The electrical conductivity and hardness of CNTs/epoxy nanocomposites by several of CNTs loading concentration were measured by the four point probe and dynamic ultra micro hardness tester. Agglomeration of CNTs in epoxy matrix was observed on fractured surface by scanning electron microscopic. Non conductive epoxy polymer becomes conductor as addition of CNTs. Electrical conductivity of CNTs/epoxy nanocomposites were increased with increasing of CNTs loading concentration. Hardness property of CNTs/epoxy nanocomposites ware reached the highest value at 5 wt.%, and then it was decreased.

Abstract: Electrical properties of carbon nanotubes-based epoxy nanocomposites for high electrical conductive plate were investigated. Dispersion and incorporation mechanism between two conductive fillers with different sizes (CNTs and Graphite) in the polymer matrix are the key factors in the fabrication of high electrical conductivity plate. Different variation of carbon nanotubes (CNTs) (1~10 wt %) and Graphite (G) (60 ~ 69 wt %) loading concentration were added into the epoxy resin. Dispersion of CNTs and G in epoxy resin were conducted by the internal mixer with a Haake torque rheometer. The mixture of G/CNTs/EP was poured into the steel mold, and G/CNTs/EP nanocomposites had been fabricated through compression molding. The electrical conductivity of nanocomposites in terms of variation of G and CNTs concentration were measured by the four point probe for in a plane electrical conductivity. The results revealed that addition of G/CNTs and increasing curing temperature are effective ways to produce high electrical conductive nanocomposites. The highest electrical conductivity was reached on 104.7 S/cm by addition 7.5 wt% of CNTs. Dispersion quality of G and CNTs in the epoxy matrix was observed on the fractured surface by scanning electron microscopic.

Abstract: Sintering is a key step in the preparation of metal foams. The present work focuses on the sintering effects on the properties of titanium foam prepared using the slurry technique. Sintering affects the density as well as the mechanical properties of the sintered parts. To achieve a high density of the titanium alloy foam, the effects of various parameters including temperature, time profile and composition have to be characterized and optimized. This paper reports the use of the Taguchi method in characterizing and optimizing the sintering process parameters of titanium alloys. The effect of four sintering factors: composition, sintering temperature, heating rate and soaking time to the density has been studied. The titanium slurry was prepared by mixing titanium alloy powder, polyethylene glycol (PEG), methylcellulose and water. Polyurethane (PU) foam was then impregnated into the slurry and dried at room temperature. This was later sintered in a high temperature vacuum furnace. The various factors were assigned to an L9 orthogonal array. From the Analysis of Variance (ANOVA), the sintering temperature was found to give the highest percentage of contribution (34.73) followed by the composition of the titanium alloy powder (26.41) and the heating rate (0.64). The optimum density for the sintered titanium alloy foam was 1.4873±0.918 gcm-1. Confirmatory experiments have produced results that lay within the 90% confidence interval.

Abstract: This investigation gives attention on the rheology characteristics of polymer composites based on graphite and carbon black as fillers for further processing using an injection molding machine. In such a high solid loading system, the particles exhibit a very strong tendency toward agglomeration. This rapidly increases the viscosity of the mixture and decreases moldability. The presence of agglomerates in the mixture in particular may result in defect within the microstructure in the final product, even though it is sometime necessary in electrical conductivity. Composite materials in this study are polypropylene (PP) as matrix, and graphite (G) and carbon black (CB) as fillers, with a varied composition according to the percentage weight (% wt) of CB. Twin screw co-rotating extruder was used for mixing materials in order to achieve the best homogeneity of this compound. The measurement results obtained using capillary rheometer equipment showed that the addition of CB to the mixture of PP/G increase the viscosity of the materials, increase the activation energy and generally reduce the fluidity of composite materials. The value of the mixture viscosity increases with increasing the number of CB, reducing the ability of materials to be formed (moldability). Material viscosity, activation energy, fluidity and moldability shows how suitable the compound material to be processed by using injection molding machine.

Abstract: The objective of this paper is optimization mixing parameters in terms of mixing process of polymer nanocomposites using Taguchi method. Considering the mixing parameters such as rotational speed, mixing temperature and mixing time were performed to reveal the electrical conductivity data. Taguchi method was used by electrical conductivity analyses based on three level factorial designs. Orthogonal arrays of Taguchi, the signal-to-noise (S/N) ratio, and the analysis of variance (ANOVA) were utilized to find the optimal levels and the effect of mixing parameters on electrical conductivity. Confirmation analysis measurements with the optimal levels of mixing parameters were carried out in order to show the optimum electrical conductivity of Taguchi method. The result shows that Taguchi method is effective in solving the quality problem occurred on the mixing parameters of the polymer nanocomposites.

Abstract: This research concerns the effect of compression molding parameters on conducting polymer composite (CPC) properties such as electrical conductivity and flexural strength. In the present work on CPC, focus is given to graphite (G) as filler and polypropylene (PP) was use as the binder. The Taguchi’s L9 orthogonal array has been used as design of experiment (DOE) while the electrical conductivity and flexural strength were assumed to be quality characteristic (responses). The electrical conductivity was measured using four point probes and flexural strength was measured using three point tests according to ASTM D638. Classical analysis of variance (ANOVA) was used to investigate the significant of each compression molding parameters and finally propose the optimum compression molding parameters. But for several responses, the optimum condition for one response is not very likely to the optimum condition for other response.