Materials Science Forum Vol. 1023

Abstract: The study of composites made from residual organic materials and polymeric resins, has a great projection due to the use of new raw materials and the good physical, mechanical and aesthetic characteristics these materials present in the construction industry. The manufacturing processes of these composites include the necessary pressure application to generate an efficiently compact material, where matrix and reinforcement bonding are efficient. This study defines how the compaction force influences the flexural strength of composites made from polyester resin as polymer matrix, and rice husk as reinforcement material. This is achieved by testing different series of specimens, made by applying different compaction forces in a cold process, to analyse the relationship between compaction and flexural strength. Specimens are made varying only the compaction force, from 2, 5, 8, 11, 14, and 17 tons. The results show that, when the compaction force increases, the flexural strength in the composites also increases, however, there is a pressure range where the flexural strength values are very close, conditioning the use of pressure in relation to the decrease in the specimen section.

Abstract: Cost-efficient 3D-printing can create a lot of new opportunities in engineering as it enables rapid prototyping of models and functional parts. In the present study, Polylactic acid (PLA) cubic specimens with different types of infill patterns (IPs), rectilinear, grid and cuboid, were additively manufactured by Fused Filament Fabrication 3D-printing. The PLA cubes are fabricated with one perimeter and different IPs density (10, 20, and 30%). Subsequently, the compressive strengths of the PLA materials were measured in two loading directions, i.e., the layers building direction is parallel (PD) to the loading axis and perpendicular (ND) to the loading direction. An optical microscope was used to examine the deformed IPs in both loading directions. The compressive flow stress curves of the PLA cubes infilled with rectilinear and grid patterns exhibited strong fluctuations with lower compressive strengths in the loading direction along ND. The PLA with 30% grid IP revealed a superior strength of ~12 kN in the loading direction along PD. On the contrary, the same material exhibited a worst compressive strength 3 kN along ND.

Abstract: The demand for wound management treatment especially advanced and active wound care products is huge. In this study, the scaffolds were prepared from gellan gum (GG) incorporated ball clay (BC) at different concentrations to investigate their swelling properties, water vapor transmission rates (WVTR), mechanical characteristic and thermal behavior. There are three different concentrations of BC were added into the GG scaffolds which were 5% w/w (GG/BC5), 10% w/w (GG/BC10) and 15% w/w (GG/BC15). Swelling ratio of GG scaffolds were increased upon addition of ball clay, while WVTR values of all scaffolds were decreased in the range of 1081–1164 g m⁻² d⁻¹. The mechanical performance results show that the GG/BC10 has the highest compressive stress at break (26 ± 5 MPa) and compressive strain at break (110 ± 21%). For thermal behavior, it shows that the thermal stability of GG scaffolds had improved after the addition of ball clay attributed to the interaction between GG and ball clay. The results show that the GG/BC scaffolds could be a potential candidate to be used as an active wound care product.

Abstract: Glass fiber reinforced plastics (GFRP) are composite materials with high strength and flame retardancy, and the disposal process is expensive to cause illegal dumping. Therefore, new recycling technology of waste GFRP are desired. In this study, recycling of waste GFRP using pyrolysis with sodium hydroxide (NaOH) under an inert atmosphere was attempted by gasification of resin and conversion of glass fiber into soluble sodium silicate. The pyrolysis behavior of GFRP, the characteristics of the obtained residue, the composition and the yield of generated gas, and the silica extraction into the solution were investigated. As a result, the gasification of the resin and the conversion of the glass fiber into soluble sodium silicate were promoted by pyrolysis with NaOH. It was confirmed that the gas yield, especially flammable gases (H₂ and CH₄), and the silica extraction increased and the residual ratio decreased as the increase of the heating temperature, NaOH addition and heating time.

Abstract: Zeolites A and X, well-known as practical materials, were successfully synthesized with high cation exchange capacity (CEC) using two industrial wastes, waste crushed stone powder and aluminum dross, by alkali fusion treatment. Waste stone powder and aluminum dross are industrial wastes, and effective utilization of these wastes has been highly expected. Since the main components of the two wastes are Si, Al and O, those wastes can be used as starting materials for synthesis of zeolites. In this study, these industrial wastes were converted into crystalline zeolite-X and –A using alkali fusion. The stone powder, dross and the mixture of these wastes were transformed into a soluble phase via alkali fusion, and then agitated in distilled water at room temperature to give an intermediate gel-like solid, followed by synthesis at 80 °C to give the final product. The zeolites were successfully synthesized via the alkali fusion process, and selective synthesis of zeolites A and X was achieved by controlling the mixing ratio of aluminium dross to stone powder.

Abstract: Aflatoxin B1 (AFB1) is one of the mycotoxins with the most dangerous poisons and poses a threat to living things. Several detection methods for Aflatoxin B1 (AFB1) with high sensitivity (LC-MS technique, HPLC, ELISA, etc.) still require lengthy preparation time and are not real-time and portable. Aflatoxin B1 (AFB1) detection is one of the major challenges in the field of food safety because Aflatoxin B1 (AFB1) attacks the food and agricultural products sector. One of the potential sensors that can be used as a base for Aflatoxin B1 (AFB1) detection is the Quartz Crystal Microbalance (QCM) sensor. This study examines the performance of the Quartz Crystal Microbalance (QCM) sensor as one of the Aflatoxin B1 detection techniques through the physical deposition method. The Quartz Crystal Microbalance (QCM) sensor modified uses polyvinyl acetate (PVAc) material as a container to embed a molecular model that will be detected through a molecular imprinting polymer (MIP) process coated on QCM using the electrospinning method. The response results show that the value of the sensor response using the MIP process is more significant than without the MIP process. The sensor characteristics demonstrated by the PVAc/AFB 50 sample have a limit of detection (LOD) value is 0.63 ppb, and a limit of quantitation (LOQ) is 1.91 ppb with a coefficient correlation is 0.97 for testing with a concentration range of 5.0 – 40.0 ppb. Therefore, the MIP process in QCM provides a favorable response for the detection of AFB1 in the future.

Abstract: The objective of this research was to study the optimum condition of esterified oil production from low free fatty acid of mixed crude palm oil (LMCPO) by using a response surface methodology (RSM) with esterification reaction in a batch mode. LMCPO obtained from a vacuum refining process of mixed crude palm oil (MCPO) to extract the partial FFA in oil which was used as a raw materials in a food production. Therefore, remaining FFA of 6.170 wt.% in LMCPO should be reduced to less than 1 wt.% by using esterification when required these oils to use as feedstock for producing biodiesel. After esterification process, FFA in esterified oil was studied to optimize the four independent variables of methanol (5-25 vol.%), sulfuric acid (0.5-4.5 vol.%), reaction time (5-65 min) and speed of stirrer (100-500 rpm). The results showed that the optimal condition of 25 vol.% methanol, 2 vol.% sulfuric acid, 500 rpm speed of stirrer, and 30 min reaction time at 60°C reaction temperature can decreased the FFA level to less than 0.212 wt.%. However, it was found out that the high consumptions of methanol and sulfuric acid required for reducing FFA to lowest value. Thus, the selected condition of 17.4% methanol, 1.6% sulfuric acid, 300 rpm speed of stirrer, and 35 min reaction time was chosen to save the chemical contents because this condition achieved to reduce FFA to acceptable level of 1 wt.%. For the actual experiment, FFA can be decreased to 0.212 wt.%, and 1.028 wt.% respectively. The yields of 96.67 wt.% for crude esterified oil and 94.22 wt.% for pure esterified oil were achieved based on LMCPO under the selected condition.

Abstract: Although small amount of binder in asphalt concrete mixture may commonly range from 3.5 to 5.5% of total mixture as per many international specifications, it has a significant impact on the total cost of pavement construction. Therefore, this paper investigated the effects of five carbon nanotubes contents of 0.05%, 0.1%, 0.15%, 0.2%, 0.25% by asphalt weight as an additive material for binder on performance characteristics of asphalt mixtures. Performance properties of CNTs modified asphalt mixtures were investigated through the Marshall stability (MS) test, indirect tensile (IDT) test, static modulus (SM) test, wheel tracking (WT) test. The results indicated that asphalt mixtures with CNT modified binder can improve both the rutting performance, IDT strength and marshall stability of tested asphalt mixtures significantly at higher percentages of carbon nanotubes. However, the issue that should be considered is the construction cost of asphalt pavement. Based on the asphalt pavement structural analysis and construction cost, it can be concluded that an optimum CNT content of 0.1% by asphalt weight may be used as additive for asphalt binder in asphalt mixtures.

Abstract: In recent years, concrete structures have tended to be taller and larger than before. With that trend, concrete as a material has diversified, and various kinds have been developed to meet differing quality requirements. In particular, the need for high-strength concrete is increasing. In general, high-strength concrete has a low water-binder ratio, so its workability is inferior to general concrete. Including admixtures such as silica fume is one way to remedy this problem. Previous studies have discussed the quality and hardening characteristics achievable using silica fume. Nevertheless, expected increasing demand for high-strength concrete dictates the need to understand not only its properties when fresh, but also to have an accurate picture of its vibration compaction properties on construction sites. In this study, the effect of adding silica fume on the workability of mortar was investigated by evaluating its fresh properties, plastic viscosity, and vibration propagation characteristics. Changes to mortar’s fresh properties due to pressure were also investigated to clarify its behavior in pumping environments. The study confirmed that the addition of silica fume decreases plastic viscosity and increases vibration propagation characteristics, and that increased plastic viscosity due to pressurization can be reduced.

Abstract: The growing demand for finding alternative applications for ceramic products wastes develops their usage as construction materials. The main objective of this paper is to evaluate the feasibility of recycled toilet bowl (RTB) wastes as pozzolanic materials in mortar mixture. The properties of RTB material were examined in terms of chemical composition, particle size distribution (PSD), X-ray diffraction (XRD) analysis, compressive strength, pozzolanic reactivity, sulfate resistance, and alkali-silica reaction according to ASTM C 618 and C 311 test specifications. The results demonstrated that the use of RTB materials as pozzolanic materials positively affects compressive strength development and durability by fully corresponding to all criteria of the ASTM C 618 guideline. Furthermore, chemical composition, PSD, and XRD test results had equivalent values to ASTM class F fly ash analysis.