Polymers最新文献

The casting-curing process is a common technology for manufacturing the Nitrate Ester Plasticized Polyether (NEPE) propellants. The curing process involves a coupled thermal-chemical reaction of the adhesive systems of propellant, which influences the curing stage. Using GID 16 software, a propellant grain curing simulation model was conducted. This study employs a model-fitting method based on non-isothermal DSC experiments to analyze the curing reaction kinetics of propellants. Two methods, Kissinger and Ozawa, were used to determine the activation energy of the curing reaction. The reaction activation energy obtained by the Ozawa method was chosen as the simulation parameter Ea = 59.378 based on the fitting coefficients. The simulation comprehensively onsidered flow, temperature, and curing reaction parameters, achieving multi-field coupling of thermal and curing degree fields during the curing process. The macroscopic temperature variations of the pillars were monitored using thermocouples. The experimental results show that the final curing temperature is stable at about 48.2 °C. At about 21,000 s, the overall temperature of the grain converges. The experimental results were compared with the simulation results, revealing minor discrepancies. Experimental and simulation methods were used to verify the changing law of the temperature field inside the propellant grain. Furthermore, these results have significance for improving the casting-curing industrial process of the composite solid propellant.

Waste recycling is critical for the development of smart cities. Local authorities are responsible for the disposal of waste plastics, but the extent of material recycling is insufficient, and much of the waste generated is incinerated. This conflicts with the trend of decarbonisation. Of particular note are the effects of the COVID-19 pandemic, during and after which large quantities of waste plastics, such as plastic containers and packaging, were generated. In order to develop a sustainable smart city, we need an effective scheme where we can separate materials before they are taken to the local authorities and recyclers. In other words, if material identification can be performed at the place of disposal, the burden on recyclers can be reduced, and a smart city can be created. In this study, we developed and demonstrated smart material identification equipment for waste plastic materials made of PET, PS, PP, and PE using GaP THz and sub-THz wavelengths. As basic information, we used a GaP terahertz spectrometer to sweep frequencies from 0.5 THz to 7 THz and measure the spectrum, and the transmittance rate was measured using the sub-THz device. The sub-THz device used a specific frequency below 0.14 THz. This is a smaller, more carriable, and less expensive semiconductor electronic device than the GaP. Moreover, the sub-terahertz device used in the development of this equipment is compact, harmless to the human body, and can be used in public environments. As a result, smart equipment was developed and tested in places such as supermarkets, office entrances, and canteens. The identification of materials can facilitate material recycling. In this study, we found that measuring devices designed to identify the PET and PS components of transparent containers and packaging plastics, and the PP and PE components of PET bottle caps, could effectively identify molecular weights, demonstrating new possibilities for waste management and recycling systems in smart cities. With the ability to collect and analyse data, these devices can be powerful tools for pre-sorting.

In order to investigate the effects of surface combined body (SCB) type and geosynthetic type on the low-temperature cracking resistance of reinforced asphalt mixtures, low-temperature bending damage tests were conducted on both unreinforced and reinforced double-layer beam specimens, respectively. At the same time, the load-deflection curve during loading was corrected using the linear fitting difference method to determine the mid-span deflection. Then, the low-temperature cracking resistance of the reinforced asphalt mixtures was comparatively analyzed by calculating the maximum flexural tensile strain (ɛ_B). Finally, the extent to which the geosynthetic type and the SCB type affect the low-temperature cracking resistance of the reinforced asphalt mixtures was investigated by means of a two-way analysis of variance (ANOVA). The results showed that the greater the tensile strength of the geosynthetics, the greater the mid-span deflection and ɛ_B of the reinforced double-layer beam specimens. The order is carbon fibre geogrid (CCF) > glass/carbon fibre composite qualified geogrid (GCF) > fibreglass-polyester paving mat (FPM) > unreinforced (UN). In the case of reinforcement, the ɛ_B of the AC-13/AC-20 combination is lower than that of the AC-20/AC-25 combination, with a significant difference, especially in the case of geogrid reinforcement. Analysis by a two-way ANOVA shows that the order of influence on ɛ_B ranks as geosynthetic type > SCB type. This study provides a scientific basis for the rational selection of carbon fibre geogrid-reinforced asphalt pavement structures.

A novel piezoelectric material, polyacrylonitrile (PAN) nanofibers, exhibits significant piezoelectric effects when a high content of planar zigzag structures is present. To enhance the contribution of planar zigzag structures to energy conversion while preserving the structure of PAN nanofibers, a novel approach was developed to increase planar zigzag content by incorporating cellulose nanocrystals (CNCs) rather than modifying conventional synthesis conditions. In this study, CNCs were introduced during the electrospinning process of PAN formation, and the increased planar zigzag content was confirmed through X-ray diffraction (XRD), electrical characterization, and Fourier transform infrared spectroscopy (FTIR) analyses. This study, for the first time, demonstrates that CNC addition to PAN enhances the mechanical properties and piezoelectric performance by promoting the formation of zigzag structures, which play a crucial role in the piezoelectric effect. The PAN-CNC composite holds great potential for applications in new piezoelectric devices. With CNC incorporation, the voltage increased by 68.9%, and the current increased by 80% compared to regular PAN. The generated energy is suitable for human applications and can also power commercial devices, making these findings pivotal for the advancement of piezoelectric materials and devices.

As the demand for polymer materials increases, conventional petroleum-based synthetic polymers face several significant challenges, including raw material depletion, environmental issues, and the potential for biotoxicity in biological applications. In response, bio-based polymers derived from natural sources, such as cellulose, alginate, chitosan, and gelatin, have garnered attention due to their advantages of biocompatibility and biodegradability. However, these polymers often suffer from poor physical stability due to the high density of hydrogen bonds and the large structure of pyranose rings. This review explores the potential of incorporating dynamic covalent bonds into biopolymers to overcome these limitations. The chemical structures of biopolymers contain numerous functional groups that can serve as anchoring sites for dynamic bonds, thereby enhancing the mechanical properties and overall stability of the polymer network. The review discusses the performance improvements achievable through dynamic covalent bonds and examines the future potential of this technology to enhance the physical properties of biopolymers and expand their applicability in biological fields.

Different films were synthesized from starch or polysaccharides extracted from distillers dried grains with soluble (DDGS) in combination with different percentages of linear polyethyleneimine (PEI) hydrochloride polymer to assess the mechanical and antimicrobial properties of the resulting composites. Moreover, a simple method for the extraction of the polysaccharide content from DDGS is reported. The materials obtained were characterized by ATR-FTIR, NMR, and XPS spectroscopy, swelling capacity, and by organic elemental analysis. In particular, the stability of the film prepared with only DDGS in copper ion solutions was improved by the incorporation of PEI. ¹³C HRMAS NMR studies evidenced the incorporation of the PEI polymer in the new films. Moreover, the release of PEI molecules from the films was studied by ¹H NMR experiments in D₂O to explain the antimicrobial properties of the PEI-based films against Staphylococcus aureus, with the DDGS-10% PEI films being the most active surface. Furthermore, the incorporation of copper ions into the different films enhanced their antimicrobial activity. Additionally, the starch-10% PEI film exhibited good swelling capacity in deionized water (~1500%), which decreased with the addition of salts (~250%). Instead, the DDGS-10% PEI film showed low swelling capacity in deionized water (~80%), with this capacity increasing with the addition of salts (~250%). The mechanical properties of the films improved considerably when 3% PEI was used.

Cellulose-derived battery separators have emerged as a viable sustainable alternative to conventional synthetic materials like polypropylene and polyethylene. Sourced from renewable and biodegradable materials, cellulose derivatives-such as nanofibers, nanocrystals, cellulose acetate, bacterial cellulose, and regenerated cellulose-exhibit a reduced environmental footprint while enhancing battery safety and performance. One of the key advantages of cellulose is its ability to act as a hybrid separator, using its unique properties to improve the performance and durability of battery systems. These separators can consist of cellulose particles combined with supporting polymers, or even a pure cellulose membrane enhanced by the incorporation of additives. Nevertheless, the manufacturing of cellulose separators encounters obstacles due to the constraints of existing production techniques, including electrospinning, vacuum filtration, and phase inversion. Although these methods are effective, they pose challenges for large-scale industrial application. This review examines the characteristics of cellulose and its derivatives, alongside various processing techniques for fabricating separators and assessing their efficacy in battery applications. Additionally, it will consider the environmental implications and the primary challenges and opportunities associated with the use of cellulose separators in energy storage systems. Ultimately, the review underscores the significance of cellulose-based battery separators as a promising approach that aligns with the increasing demand for sustainable technologies in the energy storage domain.

In this work, the viscoelastic behavior of high-density polyethylene (HDPE) and polypropylene (PP) was studied through stress relaxation experiments conducted at different strain levels. The main objective was to evaluate classical, fractional, and conformable derivatives to analyze molecular mobility, using statistical methods to identify the most accurate representation of the viscoelastic response. Besides the coefficient of determination (R²), the average absolute deviation (AAD) and mean squared error (MSE) were used as evaluation metrics, along with a multivariate analysis of variance (MANOVA) and the response surface methodology (RSM) to optimize the correspondence between experimental data and model predictions. The findings demonstrate that the spring-pot, Fractional Maxwell (FMM), Fractional Voigt-Kelvin (FVKM), and Kohlrausch-Williams-Watts (KWW) models effectively describe stress relaxation under statistical criteria. However, a joint analysis using RSM revealed that the choice of mathematical model significantly influences the outcomes. The FVKM was identified as the most effective for HDPE, while the KWW model best characterized PP. These results highlight the importance of optimization tools in advancing the characterization of polymer viscoelasticity. The ability to select the most accurate models for HDPE and PP under varying conditions can directly improve the performance and durability of products in critical industrial sectors such as packaging, automotive, and medical devices, where long-term mechanical behavior is crucial. By offering a framework adaptable to other materials and modeling approaches, this work provides valuable insights for optimizing polymer processing, improving product design, and enhancing the reliability of polymer-based components in a range of industrial applications.

This paper developed a carbon nanotube (CNT)-coated aramid fiber sensor, which was successfully used to monitor the resin flow front and sense the fluid pressure difference during the (VARI) process. The electrical resistance change of the CNT-coated fiber sensor was compared with that of buckypaper materials. The results show that the electrical resistances of CNT sensors show rapid growth successively along the infusion direction once the flow front reaches the sensor position during resin infusion in the VARI process. The electrical resistance of CNT-coated fiber sensors may increase by as much as 12 times after full impregnation. For the thicker preform, the resistance change ΔR/R₀ of sensors on the top surface is closely related to fluid pressure, and bigger fluid pressure close to the inlet may result in a larger ΔR/R₀. Two competitive factors affecting the electrical resistance of a CNT-coated sensor are revealed: aramid fiber tow swelling due to resin impregnation, and the compaction effect arising from resin pressure on the CNT network. In addition, the sensors on the top surface show a bigger ΔR/R₀ than the bottom ones, and as the preform thickness decreases, these sensors tend to show smaller ΔR/R₀.

The advent of 3D printing has revolutionized the fabrication of microfluidic devices, offering a compelling alternative to traditional soft lithography techniques. This review explores the potential of 3D printing, particularly photopolymerization techniques, fused deposition modeling, and material jetting, in advancing microfluidics. We analyze the advantages of 3D printing in terms of cost efficiency, geometric complexity, and material versatility while addressing key challenges such as material transparency and biocompatibility, which have represented the limiting factors for its widespread adoption. Recent developments in printing technologies and materials are highlighted, underscoring the progress in overcoming these barriers. Finally, we discuss future trends and opportunities, including advancements in printing resolution and speed, the development of new printable materials, process standardization, and the emergence of bioprinting for organ-on-a-chip applications. Sustainability and regulatory frameworks are also considered critical aspects shaping the future of 3D-printed microfluidics. By bridging the gap between traditional and emerging fabrication techniques, this review aims to illuminate the transformative potential of 3D printing in microfluidic device manufacturing.