Key Engineering Materials Vol. 841

Abstract: The Philippines is expected to have an increase in consumption of waste plastic laminates known as sachets, composed of polyethylene (PE) and polyethylene terephthalate (PET) and used in various food and non-food consumer goods. The increase in demand of these sachets has led the country to become one of the top ocean polluters worldwide. Chemical recycling- specifically selective dissolution and reprecipitation- is seen as one viable option for the recovery of these polymers. In this study, the absorption and dissolution kinetics of D-limonene, a potential candidate solvent, in the two-layer (2LL) and three-layer (3LL) laminates were modelled and analyzed for the design of separation equipment to recovery PE. The absorption of limonene for both laminates was observed to initially follow Fickian diffusion, but plateaus when the dissolution rate becomes comparable with the solvent diffusion rate. The dissolution of the 3LL almost closely follows Fickian behavior, while 2LL initially follows Fickian behavior. Deviations from Fickian dissolution may be attributed to the difference in swelling behavior between the non-uniform solvent-polymer diffusion layer and the glassy polymer layer.

Abstract: Oil palm trunk is lignocellulose biomass and agricultural residual waste that has not been utilized to its maximum potential. The feasibility of paper production from oil palm trunk (OPT) was studied for one alternative application. OPT was treated with 8% (w/v) alkaline solution (NaOH), subsequently with a different concentration of H₂O₂ solution (2, 4, 6 and 8% w/v). The results showed that the brown color of OPP was converted to a pale yellow color after bleaching with H₂O₂ while hemicellulose and lignin were also removed. Arrowroot flour was used as a binder for mold oil palm paper. The optimum condition for oil palm paper production was 15% (w/v) NaOH for 60 min then 6 % (v/v) H₂O₂ for 30 min. The obtained OPP paper showed a density of 183.53 ± 1.86 g/cm³, a water absorption of 0.0904 ± 0.0010 mL/cm², a tensile index of 2.60 ± 0.07 Nm/g and a burst index of 1.22 ± 0.04 kPa m²/g. All value properties of the obtained OPP paper showed that the OPP value was lower than that of available commercial Kraft paper (KI125 and KT125). Meanwhile, this OPP paper process could continuously improve to be a container formation.

Abstract: Electrospinning is an important method for preparing nanofibers, which are highly promising for applications in a wide range of fields such as purification/filtration, photoelectric devices, battery separators, catalysis and tissue engineering. These applications often use composite materials and have specific requirements for mechanical properties. Therefore, how to get nanofibers films with ideal mechanical properties by changing the composite mode is an important process problem for the given two or more materials. Based on the far-field electrospinning, this study selected polyacrylonitrile (PAN) and thermoplastic polyurethane (TPU) to explore the differences of three composite methods: mixed spinning, multi-nozzle simultaneous spinning and superposition spinning. Three kinds of analysis can be seen in this study, which include morphology features, thickness measurement and mechanical properties of samples. Multi-nozzle simultaneous spinning has very limited changes. Mixed spinning and superposition spinning are beneficial to the improvement of nanofibers films morphology and mechanical properties. Among them, the composite films through superposition spinning are thinner.

Abstract: The electrospinning/spray technique is a promising approach to fabricate composite films for many applications in flexible electronic devices. In this study, an elastic film with remarkable conductivity is synthesized by electrospinning TPU (thermoplastic polyurethanes) fibers and electrospraying graphene nanosheets into the single collector. This technique allows the graphene nanosheets to adhere uniformly to a carbon textile matrix for promoting its conductivity. But the graphene is possible to be oxidized into graphene oxide during electrospray, which is attributed to the high-voltage field, the rapid evaporation of the solvent and the full exposure to air. And the spinning fibers have the potential to induce the behavior as well. The instability of graphene during the process can make an impact on the overall conductivity and uniformity of composite films. So, we set up a series of experiments on the study of oxidization behavior of graphene and its influence on the performance of composite films. With different parameters, some samples are synthesized to conduct Raman spectroscopy analysis as well as take the measurements of overall conductivity through a 4-point probe electrical conductivity device. The oxidization behavior of graphene during the electrospinning/spray process can be well characterized by the results from the Raman spectrums. And the results of electrical conductivity measurements can provide powerful evidence to ensure the great conductivity of composite films via electrospinning/spray process.

Abstract: The electrospun nanofiber/graphene composites is a promising candidate in the field of flexible strain sensors due to the synergic effect of graphene and the nanofibers. It is an effective way to synthesize a uniform graphene-embedded film by simultaneously electrospinning nanofibers and electrospraying graphene nanosheets. In this paper, we prepare two specimens of different materials to study the interaction between graphene nanosheets and nanofibers under the same process parameters, such as thermoplastic urethane (TPU), polyacrylonitrile (PAN). Then, morphology and mechanical properties are used to characterize the interaction. The mechanical test was conducted by the tensile tester, and the surface morphology of electrospun nanofibrous films was observed through a microscope. By comparing these results, the properties of the graphene nanosheets embedded to different nanofibers are explored. This study provides a good way to select an appropriate nanofiber matrix for the application in flexible strain sensors.

Abstract: In recent years, the growing interest in the development of 3D printing has focused more specifically on the utilization of eco-friendly, biodegradable and recycled materials. This paper presents the effect of the addition of cellulose filler on the tensile properties of filaments used in 3D printing. Cellulose-filled thermoplastic composite filaments were extruded from virgin polylactic acid (PLA), recycled acrylonitrile butadiene styrene (ABS), polystyrene (PS), and polyvinylchloride (PVC), and the effect of cellulose filler on the tensile properties of composite filaments was measured. The results revealed that the tensile properties of recycled thermoplastic filaments weakened remarkably whereas the tensile properties of the filament made of virgin PLA slightly improved. However, despite the differences in the results, it was found that cellulose-filled thermoplastic composite filaments can be produced as feedstock used in 3D printing.

Abstract: Babbitt alloys are the most commonly used bearing materials for low speed diesel engines due to their excellent attributes. An understanding of microstructures in these alloys is important, especially quantifying microstructure in 3D. In this study, we used serial sectioning technique to reconstruct 3D microstructure of tin-based Babbitt lining of bimetallic bearing made by centrifugal casting based on medical software Mimics. The morphologies and volume fraction of hard phase particles and α-Sn matrix were obtained. The volume fraction of the reconstructed microstructures was verified by the area fraction of the metallographic sections, which proved a higher reliability of 3D reconstruction. The results of 3D microstructural characterization and analysis will enable a comprehensive understanding the structure–property relationships of these materials.

Abstract: Ternary compound Ti₄ZrSi₃ was prepared by arc melting using a non-consumable tungsten electrode under argon atmosphere, then annealed at 1023K for 30 days, the X-ray powder diffraction data of Ti₄ZrSi₃ was collected on a Rigaku SmartLab X-ray powder diffractometer. The powder patterns of the compound were indexed and structure refinement by using Rietveld method indicate that the Ti₄ZrSi₃ compound crystallizes in the hexagonal structure, space group P6/mcm (No.193) with Mn₅Si₃ structure type, a=b=7.5759(3) Ǻ, c=5.2162(2) Ǻ, V=259.28Ǻ³, Z=2, ρ_x=4.779g cm^-3, the Smith–Snyder FOM F₃₀=148.7(0.0064, 46) and the intensity ratio RIR=1.37. The Rietveld refinement results were R_p = 0.0836, R_wp= 0.1092.

Abstract: In this study cellulose fibrils were successfully prepared from oil palm leaf stalk fibers by treated with water. The oil palm leaf stalk fibers were treated with water at 80 °C for 8 hours and bleached with 10% NaOCl at room temperature for 2 hours. The treated fibers showed a light-yellow color and had % yield around 76.50 wt.%. The fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) indicated the removal of lignin and hemicellulose. The FT-IR peaked around 1725 cm^-1, that indicated that the peak of lignin and hemicellulose disappeared when the oil palm fibers were treated with water. Moreover, the scanning electron microscope (SEM) micrograph showed a grooved surface due to the removal of lignin and hemicellulose from the outer surface of the oil palm fibers.

Abstract: Foamed bitumen improves the properties of base layer, increasing the number of equivalent axles allowed, as result of this is a durable pavement. To achieve this, base layer’s design must count with an amount of filler, to increase the stony aggregate fraction. This research consists with two different types of filler, lime and cement, 1% in dosage respect to the stony aggregate weight. Has been discovered now, that the RAP (reclaimed asphalt pavement) aggregate in addition to mitigate environmental problems, has a significant impact value on the mechanic resistance of the mix.