Volume 45, Issue 3

With the rapid development of urbanization and transportation, noise pollution has become one of the most severe environmental problems for people. It usually causes various disorders and significantly affects human work efficiency and living standards. In the noise control field, using sound-absorbing materials to reduce noise is a critical way to reduce the harm of noise pollution. As the most widely used sound absorption material, porous materials are lightweight, have a wide absorption frequency range, and have strong sound absorption ability. They have great potential in the field of sound absorption. This paper first summarizes the sound absorption mechanism of porous sound absorption materials and the critical factors affecting the sound absorption of porous materials. Secondly, the latest research status of fiber, foam, and new porous sound absorption materials in recent years is reviewed, and the advantages and disadvantages of different porous sound absorption materials are expounded. Finally, the future development trend of porous sound-absorbing materials is prospected. With the continuous expansion of knowledge in this field, it is expected that porous sound-absorbing materials will continue to improve and find more practical applications in emerging fields in the future.

3D printing polymers and their composites have shown considerable potential in various application fields, yet their limited mechanical properties have hindered widespread use in structural materials. Recently, postprocessing techniques have been proposed as efficient and convenient methods to enhance the mechanical properties of 3D printing structures. This study systematically investigates the effects of thermal annealing and microwave irradiation on the microstructure and mechanical properties of 3D printing carbon fiber reinforced polyamide 12 (CF/PA12). The results clearly demonstrate that thermal annealing significantly outperforms microwave irradiation in improving fiber–matrix interfacial adhesion and crystallization. Specifically, thermal annealing provides necessary time for molecular chain relaxation, effectively releasing internal stresses. Additionally, thermal annealing optimizes the transcrystalline structure at the fiber–matrix interface and the volume fraction of crystalline regions within the matrix. Compared to the pristine samples, the annealed 3D printing specimens exhibited increases of 19.34 % in tensile strength and 27.11 % in flexural strength. This research provides an in-depth insight into enhancing 3D printing CF/PA12 composites through postprocessing techniques and offers a scientific basis for their large-scale application.

This research explored the impact of a novel polymer chain extender with high epoxy functionality on the crystallization properties of polylactic acid (PLA). FT-IR and Raman spectrometer were utilized to characterize the structure of PLA after chain extension. The dosage of the chain extender (HSMG) in PLA was varied to investigate its effect on the crystallization behavior of PLA via differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X-ray diffraction analysis (XRD). The results indicated that incorporating HSMG into PLA significantly altered its crystallization behavior, without significantly changing its crystal structure.

To investigate the influence of AO 2246 and AO 4426 on the damping properties of polyvinyl alcohol/chlorinated polyethylene (PVA/CPE) composites, a series of composites were prepared by adding AO 4426 into PVA/CPE-AO 2246 under the constant mass ratio of hindered phenol in the composites. The dynamic mechanical properties and microstructure of materials were investigated by DMA, DSC, SEM, and FT-IR. The results showed that a new damping peak appeared near 50 °C by adding AO 4426, which indicated phase separation between AO 4426 and the matrix occurred. With the increase of AO 4426, the damping peaks in the low-temperature section were improved. The value of low-lying region between the double damping peaks, when the hindered phenol coexisted was higher than that of the composites containing only AO 4426, which indicated that the damping temperature domain of the composites was effectively broadened. At the melting temperature of AO 4426 microcrystalline and AO 2246 microcrystalline, no obvious peaks were observed simultaneously, indicating that the hindered phenols inhibited the crystallization of each other.

Chitosan-based nanofibers loaded with therapeutic agents are promising for wound treatment but loading hydrophobic compounds remains challenging. To address the limitations of curcumin incorporation in chitosan/polyethylene oxide (CS/PEO) nanofibers, we developed a novel Pluronic-based micelle to encapsulate curcumin, followed by the incorporation of zinc oxide nanoparticles (ZnO-NPs) as an antibacterial agent to improve the performance of the wound dressings’ materials. We successfully fabricated CS/PEO scaffolds via electrospinning, incorporating curcumin-loaded micelles and synthesized ZnO-NPs. Comprehensive morphology characterization was performed using SEM, and the presence of ZnO-NPs and curcumin was verified by EDX and FT-IR spectroscopy. The developed nanofibers showed a slower release profile, with approximately 80 % of curcumin released into the aqueous medium within 24 h and appearing to progress to a steady state by five days. Notably, the nanofiber mats exhibited antibacterial activity against the Gram-positive bacterium Staphylococcus aureus , and supported fibroblast proliferation and attachment, indicating excellent biocompatibility. These findings suggest that the developed nanofiber scaffold, characterized by its controlled drug release, potent antibacterial properties, and biocompatibility, holds promise as an advanced wound dressing material.

With the development of modern industry, the water pollution is getting severer which causes the huge environmental problems. In this work, the novel photocatalytic polyelectrolyte composite hydrogels based on crosslinked poly(2-acrylamido-2-methylpropane sulfonic acid) equipped with graphite carbon nitride (g-C 3 N 4 ) were exploited via a facile preparation route, which exhibited extremely high removal ratio of 95 % and 94.5 % to Rhodamine B and tetracycline, respectively, through the synergistic effect of adsorption and photodegradation. Remarkably, the recyclability was also observed on the as-prepared hydrogels, which enabled to reuse for 15 times with the few attenuations of removal efficiency to contaminants. This study provides the new insights into the photocatalyst composite hydrogel and possesses the profound significance of the treatment of organic pollutants.

An improved vacuum infusion (VI) process, called dynamic pressure molding (DPM), has been proposed to reduce void formation during infusion. In this method, the conventional VARTM process is modified by mounting a rigid chamber on top of the mold. The compaction pressure on the vacuum bag and the infusion pressure are independently and dynamically controlled during infusion to achieve the optimal impregnation for avoiding void formation. To reduce the postinfusion time, the premature sealing of the inlet, the heated air compression, and the two-sided drainage are also used in the DPM. Two different characteristics of the preform are tested at various infusion strategies. A one-dimensional nonisothermal filling model coupled with preform deformation is performed to numerically analyze the complete filling process. Results show that the four-step DPM enables at least 96.53 % of the infusion phase to be within the optimal infusion mode, but its effectiveness in reducing the total filling time depends on the preform characteristics. Several limitations of the DPM are interpreted. For comparison purposes, the typical VI process is also modeled.

This project aims to develop a manufacturing method for a newly designed soft robot gripper in one shot by utilizing a low-viscosity liquid silicone rubber (LSR) lost-core injection molding embedded with a polyvinyl alcohol (PVA) water-soluble core inside. Due to the relatively high viscosity of LSR, higher injection pressures were needed to complete the mold-filling process. This, in turn, resulted in a washout of the PVA lost core. Therefore, this study used a lower viscosity of LSR and pressure to avoid this problem. Ansys structural analysis simulation was used to get the experiment variables and then compare them with the real experiment results. The maximum pressure employed in the simulation of the gripper bending is 30 kPa with 119.38 mm, while the experimental is 112.65 mm total deformation. Finally, the washout of the lost core, the bending restriction problem, and the complicated manufacturing problems in this area were tackled in this study. The design of a finger with a greater angle at the edge and the use of low-viscosity LSR as the primary material in a one-shot lost core LSR injection molding method are extensions from previous studies that are believed to be valuable inventions for academic and practical applications.