Key Engineering Materials Vol. 908

Abstract: The awareness on sustainability of the environment among the researchers leads to the exploration of natural fiber composite materials. Hybridization of synthetic fiber and natural fiber is one of the potential strategies to enhance the mechanical properties as well as the degradability of such composite materials. However, less information concerning the optimization of tribological properties of this hybrid composite is available in literature. The aim of this study is to propose a statistical model to predict and optimize wear and coefficient of friction of kenaf/carbon reinforced epoxy composite. The value of parameters; load and sliding velocity ranges from 10 to 30 N and 20.9 to 52.3 m/s, respectively, are used to assess wear and coefficient of friction (COF) of different stacking sequences using the Analysis of Variance (ANOVA). The tribological test was conducted using a pin-on-disc tribometer. Multifactorial design analysis was employed to optimize the test control variables. It was found that, the optimized factors that affects the coefficient of friction and wear is at load 30 N and sliding velocity of 52.36 m/s. The proposed statistical models for wear and COF have 99.5% and 97.6% reliability, respectively. The generated equation models are bounded within the wear test control factors and ranges. The outcome from this study will be very useful for main parameter prediction for an optimized wear and COF.

Abstract: This study is to determine the effect of graphite as reinforcement material on natural resources carbon foam on the mechanical and physical properties. Sucrose is used as carbon precursor and graphite with various concentration from 0 wt% to 0.3 wt% was added into the carbon foam. Carbon foam was prepared by using template method followed by pre curing and carbonization process. Pre curing process was take place at 250°C and carbonization process was carried out at 900°C under inert atmosphere. The morphology, porosity, density and compressive strength were characterised in this experiment. Through Scanning Electron Microscope (SEM), graphite can be seen clearly embedded into the ‘window’ and fill the void space. Porosity of carbon foam decrease when the concentration of graphite increase and the density of carbon foam increase when the concentration of graphite increase. Carbon foam with 0.3 wt% graphite added shows the highest compressive strength (1.84 N/mm²) compared with carbon foam without graphite added (0.95 N/mm²). The properties of carbon foam are significantly influenced by the addition of graphite loading.

Abstract: Shape memory polyurethane (SMPU) is a very versatile material that has a broad array of applications. The selection of soft segments and hard segments play critical roles in determining the structure-property behaviors of SMPU. This research was conducted to evaluate the role of distinct types of diisocyanate on the final properties of polyurethane (PU). Palm kernel oil polyol (PKO) based PU were produced by using two-step bulk polymerization method with variations of diisocyanates. Isophorone diisocyanate (IPDI), 4,4-methylenebis (cyclohexyl isocyanate) (HMDI) and hexamethylene diisocyanate (HDI) were used in the preparation of PU and the soft segment crystallinity, thermal and shape memory properties of the PU were evaluated. Based on the analyses, it was found that different types of diisocyanate and combination of diisocyanates had huge impact on the properties of the synthesized PU. The Fourier transformation infrared (FTIR) analysis revealed that IPDI based PU achieved the highest hydrogen bonding index value which promoted the phase separation. This is in accordance with differential scanning calorimetric (DSC) and x-ray diffraction (XRD) analysis which showed that IPDI based PU exhibited crystalline soft phase, hence resulted in an excellent shape fixity behavior. On the other hand, HDI and HMDI based polyurethane prepared showed absence of crystalline soft phase based on the DSC thermogram and XRD diffractogram. These results suggest the phase mixing phenomenon between soft and hard segments which contributed to low shape memory behavior of the resulting polyurethane.

Abstract: This study reports the effect of plasticizers namely isopropanol, polyethylene glycol, maltitol and spermidine on the properties of the sodium alginate composite membrane. The concentration of each potential plasticizer was set at minimum to execute performance. Properties of sodium alginate were studied through characterization studies - Field Emission Scanning Electron Microscope (FESEM) to observe on the morphology structure. The membrane performance is also seen through water uptake and swelling ratio tests. Isopropanol produced better plasticizer with the lowest water uptake of 575.53% and less hydrophilic compared to spermidine (1268.46%), polyethylene glycol (1014.30%) and maltitol (595.82%). Further study may require copolymerization to support polyol for ensuring structure firmness. This study proven the plasticizers could enhance membrane’s flexibility in DMFC and becoming a promising choice of additives for better alginate-based membrane establishment.

Abstract: The purpose of this research is to study the mechanical and morphology of sugarcane bagasse (SGB) reinforced unsaturated polyester resin (UPR) composites by utilizing a different percentage of fibre contents and different chemical treatments on fibres. Sugarcane bagasse reinforced unsaturated polyester resin composites have been prepared using the compression molding technique. To enhance better adhesion between fibre and matrix, the SGB was chemically treated with alkaline (NaOH) solution and silane solution for 2 hours. The characterization of mechanical properties such as tensile and flexural strength, and tensile and flexural modulus of SGB-UPR composites were studied and compared. The incorporation of the alkaline + silane treatment of SGB resulted in better tensile and flexural properties of composites than untreated or alkaline-only treated SGB composites. Overall, it can be seen that the 5 % of fibre treated with NaOH + silane treatment showed the best results for tensile and flexural properties. Surfaces of cracked composites were observed using SEM and treated SGB showed better interfacial adhesion with matrix rather than the untreated SGB. Chemical treatment plays an important in enhancing the interfacial adhesion of fibre and matrix in composites.

Abstract: Coconut shell (CS) reinforced unsaturated polyester (UPE) composites have been prepared by using hand lay-up and compression molding techniques. To improve fiber matrix adhesion, the CS (30 wt%) was chemically treated by two chemical treatments which are alkaline (NaOH) and alkaline-silane with concentration NaOH (6%) and silane (2%). To enhance the performance of CS-UPE composites, graphene nanoplatelets (GNP) was also added as a nano filler. Scanning electron microscopy (SEM) was used to investigate the morphology of the composite samples. Mechanical properties such as tensile and flexural tests of untreated and chemical treated CS-UPE composites was also studied and compared. Overall, the use of alkalized treated CS-UPE composites showed the best mechanical (strength and modulus). Therefore, alkaline treated CS was selected to be re-prepared with graphene as nano filler in UPE composites at 0.5, 1.0 and 1.5 wt% filler loading, respectively. The presence of GNP in CS-UPE composites have demonstrated a significant enhancement in modulus properties but at the expense of tensile strength. The use of 1.0 wt% of GNP seems more optimize loading since the increment of GNP has reduced the tensile strength, which might be due to the agglomeration issue.

Abstract: Generally, only a few especially acrylic monomers have photoabsorption characteristics to allow for effective stereolithography (STL) to take place. Biomaterial product from palm oil, Acrylated Palm Olein (APO), is seen as an ideal alternative to petroleum-based polymers due the diminishing petrochemical supply and abundant of the natural polymer in the market. In this study, APO as a biopolymer is introduced to synthetic polymers Polyethylene Glycol Dimethylacrylate (PEGDMA) and Polyethylene Glycol Diacrylate (PEGDA), separately. All three polymers offer photoabsorption characteristics that enable them to be the resins for ultraviolet (UV) 3D printing. The crosslinking of both copolymers is optimized by comparing two different UV radiation techniques; UV cured machine and UV STL 3D printer. The degree of crosslinking for both APO-co-PEGDMA and APO-co-PEGDA through gel fraction analysis are studied and compared with their prepolymer resins. As predicted, the maximum degree of crosslinking of APO-co-PEGDMA and APO-co-PEGDA samples are achieved from the fabrication of samples by 3D printing and recorded at 67.50% and 59.50% respectively, comparing to the samples cured by UV cure machine, which recorded maximum crosslinking percentage at only 21.31%. Further analysis is done using swelling test to study water absorption capacities of copolymers and results shows that APO-co-PEGDMA able to retain water at maximum of 42.47% and APO-co-PEGDA at 52.02% from the 3D printed samples, and recorded lowest readings at 22.82% and 25.56% respectively. UV cured samples are recorded to have lowest readings at 3.89% for APO-co-PEGDMA, and 4.23% for APO-co-PEGDA. Fourier Transform Infrared (FTIR) Spectroscopy confirmed the successful crosslinked of the copolymers. Analysis of FTIR shows that there are presence of new peaks and shifting of peaks, indicating that APO is crosslinked with PEGDMA backbone as well as PEGDA backbone. These also suggest that both polymers are suitable to be incorporated with APO as new photopolymer resins, fabricated using UV radiation crosslinking, with PEGDMA shown a slightly better result. All results are agreeable with FTIR results.

Abstract: This paper studied the alternative method for determination of percentage of grafted content in the grafted low density polyethylene (LDPE) film with black seed oil (BSO). BSO was grafted onto LDPE by pre-irradiation grafting method and the grafted samples were evaluated using FTIR qualitative and quantitative analysis. The grafting yield was calculated quantitatively from absorbance peak of two difference peak (1464cm^-1 and 1746cm^-1). Control LDPE film shows no absorbance peak at wavenumber of 1746cm^-1 while, a peak appears for grafted film at the same wavenumber. Therefore, it is possible to consider the peak area in this wavenumber as the grafting extension of BSO in LDPE film. Meanwhile, concerning the infrared (IR) fingerprint of LDPE film, consistent peak characteristic bands of LDPE are also present for all grafted sample at 1464cm^-1. Thus, the grafting yield is computed by using these peaks. Then, further confirmation grafting of BSO onto LDPE film was supported by the XPS spectroscopy. The atomic composition of C decreased 13% after LDPE film was grafted with BSO. While, the O content increases from values of 6.9% to 19.2% after grafting reaction. The increment percentage of O1s after grafting reaction mainly caused by the incorporation of oxygen content of a new polar functional groups of BSO on the surface of LDPE films. These results are in good agreement with FTIR analysis.

Abstract: This paper discuss the use of Box Behnken design (BBD) to optimize parameters used in conducting experiment for radiation induced grafting (RIG) experiment of graft cinnamaldehyde (antimicrobial agent) to polyvinyl alcohol/sago starch (PVA/SS) film in order to develop antimicrobial film for food packaging. BBD is having the maximum efficiency with objective to have maximum value of grafting yield (GY). This experiment involving three parameters which is absorbed dose (kGy), temperature (°C), and reaction time (min), all in three levels. The proposed BBD requires 15 runs of experiment for data acquisition and modeling the response surface. Three regression models were developed, and their adequacies were verified to predict the output values at nearly all conditions. This work resulted in identifying the optimized set parameters values for RIG experiment, which is absorbed dose at 102.67 kGy, reaction time at 51.67 minutes and reaction temperature 44.68°C in order to achieve maximum value of grafting yield at 20.79%. Afterwards, the models were validated by performing actual experiments, taking three sets of random input values. The output parameters (actual value) measured through experiments are in good consistency with the predicted values, where the actual value of GY is 18.7% as compared to predicted value of GY of 20.79%. The deviation value 2.09% prove success of developed model in predicting grafting yield in RIG using limited number of experiments.