Advances in Materials Science and Engineering

Using synthetic polymers in the production of superabsorbent polymers offers significant advantages such as low cost, extended service life, and a high water absorption rate. However, concerns about the environmental impact and potential adverse effects on plant growth arise from the degradation products of these polymers after disposal. In addition, handling these polymers can cause rashes, irritations, and even toxic shock syndrome. To overcome these issues, researchers are exploring the synthesis of superabsorbent polymers from natural sources. Cottonseed protein is identified as a potential natural polymer for the synthesis of natural superabsorbent polymers. Notably, there is no existing research on hydrogel synthesis using cottonseed protein and 2-acrylamido-2-methylpropanesulfonic acid (AMPS). This study addresses this gap by focusing on modifying cottonseed protein (CSP) through graft copolymerization, utilizing the partially neutralized form of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) in a water-based solution. N,N-methylene bisacrylamide serves as the crosslinking agent, while potassium persulfate (PPS) and sodium bisulfite (SBS) function as redox initiators. The optimization of hydrogel synthesis conditions was achieved using Design Expert-11 software, adjusting the AMPS to CSP ratio. The research reveals that the hydrogel reaches its maximum swelling capacity (195.7 g/g) with 0.03 g of MBA, 0.01 g of PPS, 0.01 g of SBS, and a 1wt% AMPS to CSP ratio. Swelling properties were assessed under diverse pH conditions, and the study delved into swelling kinetics (both pseudo-first-order model and pseudo-second-order model) and performance under different loads. Grafting evidence was validated through FTIR analysis. The maximum water uptake was obtained when there was no load, and the pH value was around neutral (7). In conclusion, the results indicate that the developed hydrogel holds a promise for applications in water retention, reducing water loss, and serving as an environment-friendly, biocompatible superabsorbent polymer so we can use such hydrogel in biomedical applications.

To address the shortage of the aggregate used in a hot mix asphalt (HMA) pavement in Guangxi, properties such as the aggregate crushing, polished stone, and Los Angeles abrasion values of a type of hard sandstone aggregate used in HMA were tested after various conditioning treatments. The hard sandstone aggregate met the technical requirements for aggregate in HMA. In addition, the influence of the Marshall compaction on the hard sandstone aggregate-combined grading was tested. The combined grading curve changed a little, and the aggregate satisfied the corresponding technical requirements. Therefore, according to the abovementioned results, the hard sandstone aggregate can be used as a coarse aggregate in HMA.

Carbonation resistance ability is one of the most important durability-related proprieties of cement-based materials. Through the carbonation depth experiment, isothermal conduction calorimetry, XRD, BET, and water vapor sorption, the effect of calcium nitrite (Ca(NO₃)₂) on the carbonation properties of cement-based materials is obtained. The result indicates that the addition of Ca(NO₃)₂ improves the carbonation resistance property of cement-based materials if the hydration of cement pastes and microstructure is modified earlier without affecting the late hydration process. In addition, the refined pores and higher tortuosity cut down the channels, thereby impeding the ingress of carbon dioxide gas into cementitious materials, as confirmed by BET and water vapor sorption. The Ca(NO₃)₂ exhibits high performance in improving the carbonation resistance and extending the life of strengthened concrete.

This study explores the investigations of bamboo fiber-reinforced polyester composites with chopped glass fiber (CGF) filler, focusing on addressing the challenges of low mechanical properties, limited thermal stability, and high moisture absorption. The two types of composites were fabricated using the hand layup method, that is, long unidirectional 0° bamboo fiber (BF) and randomly oriented short bamboo fiber (BP) reinforced a polyester matrix with chopped glass fiber (CGF) filler. By incorporating CGF filler, significant improvements in mechanical properties were achieved across both types of bamboo fiber, surpassing the limitations of unfilled composites. Notably, the composite formulation consisting of 40% wt. of unidirectional 0° BF and 5% wt. of CGF filler exhibited superior ultimate tensile strength, flexural strength, impact strength, water absorption, and thermal stability. This composite demonstrated remarkable enhancements, with increases of up to 131.22 MPa, 128.76 MPa, 113.3 kJ/m², 1.94% water absorption, and up to 255°C (representing a 10% improvement) in thermal stability compared to the unfilled composite. Statistical analysis revealed quadratic models for the mechanical properties of long unidirectional 0° bamboo fiber composites, while water absorption exhibited a linear two-factor interaction model. For randomly oriented short bamboo fiber, the models for tensile, flexural, and water absorption properties were linear, while the impact energy model showed a quadratic relationship. These statistical models provide valuable insights into predicting the properties of bamboo fiber-reinforced polyester composites. This research underscores the significance of bamboo fiber-reinforced polyester composites in wall partition systems. This study paves the way for improved performance in these areas. The findings highlight the potential of incorporating CGF filler, enabling enhanced mechanical strength, increased thermal stability, and improved resistance to moisture-related issues. The derived statistical models offer valuable guidance for predicting the properties of these composites, facilitating their application and adoption in the construction industry.

The purpose of this study is to synthesize Cu-doped MgO nanoparticles and test the performance of photocatalytic degradation of methyl orange (MO). Mg(NO₃)₂, CuCl_2, NaOH, and fresh Calotropis procera leaf extract were used as precursors. The prepared nanoparticles were characterized by using FT-IR, XRD, SEM, and UV-Vis spectrometer to study the functional group, crystal structure, surface morphology, and absorption edge, respectively. The wide band above 3000 cm⁻¹ from the FT-IR spectrum corresponds to the stretching vibrations of flavonoids and phenolic compounds of Calotropis procera leaf extract. Furthermore, the Mg-O bonding of undoped MgO and Cu-doped MgO NPs is represented by new peaks which appeared at 831 and 835 cm⁻¹, respectively. The crystal size of undoped MgO and Cu-doped MgO nanoparticles is 13.04 nm and 12.08 nm, respectively. The SEM microstructure of pure MgO showed higher agglomeration than the Cu-doped MgO nanoparticles. The degradation efficiency of the Cu-doped MgO NPs was compared with that of the MgO NPs, and the photocatalytic activity of these NPs was evaluated using the photocatalytic degradation rates of MO dye. Cu-doped MgO NPs showed higher degradation efficiency than pure MgO NPs. The insertion of Cu in the MgO structure improved the photocatalytic efficiency of the MgO NPs under optimal conditions. Therefore, Cu-doped MgO exhibits high photocatalytic activity compared with undoped MgO nanoparticles under sunlight irradiation.

This study focuses on the fabrication and analysis of the mechanical behaviour of unidirectional (UD) glass fibre-reinforced polymer (GFRP) facesheet and polyvinyl chloride (PVC) foam core sandwich structures fabricated by a vacuum-assisted resin infusion method (VARIM). These sandwich structures are commonly used in marine and wind turbine blade applications. To date, relatively little knowledge about the functional behaviour of UD GFRP compared to composites reinforced with bidirectional mats is available for day-to-day applications. The effects of the facesheet orientation, facesheet thickness, and core thickness on the mechanical behaviour of the specimens were examined. The UD fibres were oriented in cross-ply (0/90), angle-ply (+45/−45), and quasi-isotropic orientations. Various mechanical properties such as tensile, flexural, flatwise compression, and edgewise compression tests were examined. Characterization of the tensile properties of the facesheet showed that the cross-ply orientation had a higher strength than the angle-ply and quasi-isotropic orientations. The flexural load-carrying capacity of the cross-ply facesheet orientation was superior to the other orientations. The increase in the core thickness changed the flexural failure mode from face yield and core shear to core indentation. Flatwise compression (FWC) was tested to determine the core characteristics of the sandwich structure, and the peak loads of 4.90, 1.81, and 3.90 kN were obtained for 10-, 15-, and 20 mm core thicknesses, respectively. Edgewise compression (EWC) exhibited stable end crushing for thinner facesheet, whereas thicker facesheet showed core crushing and buckling. When the facesheet thickness was increased from 1.5 mm to 3 mm in the EWC, the buckling load increase ranged from 2.53% to 44.83% for core thicknesses 10-, 15-, and 20 mm, respectively.