Search Results (9,062)

Paulownia wood, as a fast-growing natural material, exhibits inherently low axial compressive strength. To improve the axial structural performance of Paulownia wood, wood-cored glass fiber-reinforced polymer (GFRP) sandwich Paulownia wood columns were developed in this study. Nevertheless, the behavior of such columns remained largely unexplored—particularly under elevated temperatures and upon subsequent cooling. Consequently, an experimental program was conducted to characterize the influences of GFRP wrapping layers, steel hoop end confinement, high temperature, post-cooling strength recovery, and chamfer radius on the axial compressive performance of the columns. End crushing occurred in the absence of steel hoops, whereas mid-height fracture dominated when end confinement was provided. As the temperature rose from room temperature to 100 °C and 200 °C, the load-bearing capacity of the columns decreased by 38.26% and 54.05%, respectively, due to the softening of the GFRP composites. After cooling back to room temperature, the post-high-temperature specimens recovered approximately 95% of their original capacity, confirming that no significant thermal decomposition had been initiated. The load-bearing capacity also increased significantly with the number of GFRP layers, as the additional thickness provided both higher axial load capacity and enhanced lateral confinement of the wood core. Relative to a 4.76 mm chamfer, a 9.52 mm radius increased axial capacity by 14.07% by mitigating stress concentration. A theoretical model accounting for lateral confinement was successfully developed to predict the axial load-bearing capacity of the wood-cored GFRP sandwich columns. Full article

This work presents a comprehensive study on the synthesis and application of Al₂O₃ fibers derived from an ammonium aluminum carbonate hydroxide (AACH) precursor. Through a hydrothermal route, the influence of critical synthesis parameters, including aluminum nitrate and urea concentrations, reaction temperature and time, and stirring conditions, on fiber morphology and aspect ratio was systematically investigated. The as-synthesized AACH fibers were subsequently converted into thermodynamically stable α-alumina fibers via controlled annealing. These high-aspect ratio alumina fibers were incorporated into polydimethylsiloxane (PDMS) to produce electrically insulating, thermally conductive composites. The thermal performance of fiber-filled composites was benchmarked against that of particle-filled counterparts, with the former exhibiting significantly enhanced thermal conductivity. Furthermore, the dielectrophoretic alignment of alumina fibers led to an additional increase in thermal conductivity, underlining the importance of high-aspect ratio fillers. This study uniquely combines the controlled synthesis of alumina fibers with their incorporation and alignment in a polymer matrix, presenting a novel and effective approach for engineering anisotropic, thermally conductive, and electrically insulating composite materials. Dielectrophoretic alignment of α-Al₂O₃ fibers synthesized through optimized hydrothermal conditions and incorporated into PDMS composites deliver over 95 % higher thermal conductivity than spherical fillers. Full article

The delamination of building facades creates a critical demand for inorganic adhesive mortars with high long-term adhesion. Geopolymer (GP) represents an eco-friendly alternative to Portland cement (PC). However, the effect of polymer additives, commonly used in cement-based adhesive mortars, on GP mortar remains insufficiently studied. This study examines the effects of hydroxypropyl methylcellulose (HPMC) and vinyl acetate-ethylene (VAE) polymer on the workability, mechanical properties, durability, and microstructure of GP mortar. Results show that an optimal HPMC content (0.4 wt%) improves the fluidity, compressive strength, and adhesive strength of GP mortar, approximately 6%, 16%, and 20%, respectively. These enhancements are attributed to the incorporation of uniformly distributed microbubbles in the mortar matrix. Beyond this optimal content, however, HPMC impairs flowability and adhesion due to its thickening effect. In contrast, VAE addition significantly enhanced adhesive strength by approximately 28%, albeit at the cost of a 17% reduction in compressive strength, resulting from the retardation of the alkali activation process. This gain in adhesion is associated with the formation of a continuous polymer film that establishes both physical interlocking and chemical bonding with the GP matrix. Furthermore, HPMC improved the durability of the GP mortar, while VAE did not contribute to this aspect. These insights offer valuable guidance for designing high-performance GP-based adhesive mortars suitable for building applications. Full article

SPCEs are crucial for electrochemical sensing because of their portability, low cost, disposability, and ease of mass production. This study details their manufacture, surface modifications, electrochemical characterization, and use in chemical and biosensing. SPCEs integrate working, reference, and counter electrodes on PVC or polyester substrates for compact sensor design. Surface modifications, such as plasma treatment (O₂, Ar), nanomaterial addition (AuNPs, GO, CNTs), polymer coatings, and MIPs, enhance performance. These changes improve sensitivity, selectivity, stability, and electron transport. Electrochemical methods such as CV, DPV, SWV, and EIS detect analytes, including biomolecules (glucose, dopamine, and pathogens) and heavy metals (Pb²⁺, As³⁺). Their applications include healthcare diagnostics, environmental monitoring, and food safety. Modified SPCEs enable rapid on-site analysis and offer strong potential to transform our understanding of the physical world. Full article

This work provides a comparison of two commercial carbon fiber reinforced plastic (CFRP) materials: HexPly^® M18 1/G939 and RTM6/G939. Differences due to the additional thermoplastic in one CFRP are investigated for the two otherwise nearly identical, aromatic epoxy-based composites with respect to thermal degradation. The scenario chosen for testing is based on real incidents of repeated overheating by hot gases between roughly 200 and 320 °C, leading to moderate thermal damage. A special test setup is designed to continuously and alternately load CFRP with hot air in a rapid change. Post-mortem analysis is performed by mass loss, ultrasonic, and mechanical testing. Polymer degradation is analyzed by infrared spectroscopy. Even if the temperature-resistant thermoplastic polyetherimide (PEI) in the M18-1 matrix is enriched between the plies and a compensation of thermal strain during rapid temperature changes is expected, only a weak improvement is observed for residual strength in the presence of PEI, for continuous as well as alternating thermal loading. Thermally induced delaminations are even more pronounced in M18-1/G939. Deep insight is gained into degradation after repeated overheating of CFRP within the chosen scenario. Multivariate data analyses based on infrared spectroscopy allow for the determination of thermal history and residual strength, valuable for failure analysis. Full article

Poly(3-hydroxybutyrate), P3HB, is a biodegradable polymer produced and stored by different bacterial strains, including Ralstonia eutropha H16. P3HB was used to prepare biocompatible composites modified by nanocellulose. This study aimed to assess selected thermal, mechanical, and biological properties of the obtained nanobiocomposites. Thermal properties, as determined by differential scanning calorimetry measurements, were established. The crystallinity of nanocomposites and polymeric matrix was investigated using DSC analyses. The morphology of the nanocomposites was evaluated using scanning electron microscopy. The Food and Drug Administration and the European Medicines Agency confirmed the immunosafety of the tested nanocomposites and noted they had either no or very low levels of endotoxin contamination. Some mechanical properties of the investigated materials were also measured and are presented here. It was estimated that the addition of 1% by mass of nanocrystalline cellulose to P3HB causes the greatest improvement in the plasticization of the material, characterised by the best processing and utility properties. The processing window of nanobiocomposites was extended by approximately 25 °C in reference to the unfilled poly(3-hydroxybutyrate). Mechanical and thermal tests revealed that the most desirable properties oscillate around the addition of 0.5% and 1% nanocrystalline cellulose by mass in the nanobiocomposites. Biological studies on implant applications have shown that the addition of only 0.5% nanofiller to a nanobiocomposite can be of key importance. Full article

The immiscibility of most polymers leads to poor interfacial adhesion in blends, a critical challenge that often limits the mechanical performance of polymer composites. This research introduces shape-forming elements (SFEs), a novel class of coextrusion dies designed to create additional geometric complexity and control over interfacial architecture. Specifically inspired by Julia Set and T-Square fractals, SFEs were simulated, prototyped, and found to be effective in coextrusion of different-colored polymer clays. The SFEs were employed to coextrude architected composites consisting of a liquid crystalline polymer (Vectra A950) and a cycloaliphatic polyamide (Trogamid CX7323). Mechanical testing revealed a strong positive correlation between the draw ratio and both the tensile modulus (adjusted R² = 0.94) and tensile stress at break (adjusted R² = 0.84). However, experimental cross-sections significantly differed from simulation results. These discrepancies were attributed to interfacial instabilities caused by material incompatibility between the two polymers and potential moisture-induced defects. This finding highlights critical challenges that arise during practical processing, emphasizing the importance of addressing polymer compatibility and moisture management to realize the full potential of SFEs in designing advanced polymer composites with targeted properties. Full article

The precipitation of cellulose and polyacrylonitrile and its copolymer (PAN) solutions is a well-known process that has been extensively described in numerous studies. It is suggested that “soft” precipitants (aqueous solutions of solvent, alcohols) be used in place of “rigid” ones (water) to control the rate at which solutions precipitate. Diffusion processes can also be controlled by lowering the temperature of the interacting system’s constituent parts. The appearance and structure of the resulting fibers (films) are directly correlated with the rate of coagulation. Adding a composite additive to the solution is an unusual method of altering the rate of polymer phase release. The introduced additive should dissolve in a common solvent, which will ensure the competition of precipitation between the polymer phases. It is shown that using optical methods it is possible to trace the evolution of the polymer phase precipitation and the formed morphology. For 12% solutions of cellulose, PAN and mixed systems in N-methylmorpholine-N-oxide (NMMO) the kinetics of the movement of isoconcentration planes was traced and the growth rates of the precipitated polymer zone were estimated. The introduction of PAN additives into cellulose enables the influence of diffusion processes and minimizes the formation of finger-like defects (vacuoles). When the PAN content in the system is 30% or more, the formation of defects in the precipitated solution is significantly suppressed, which is crucial for achieving a uniform morphology. Full article

Background/Objectives: Semi-solid extrusion (SSE) three-dimensional (3D) printing offers a versatile approach for fabricating personalized oral dosage forms. This study aimed to develop and optimize losartan potassium tablets produced via SSE 3D printing, focusing on the effects of polymer composition, tablet geometry, drug loading, and superdisintegrant concentration on printability and performance characteristics. Methods: Formulations containing hydroxypropyl methylcellulose (HPMC) 4500 at various concentrations were evaluated for suitability in an ethanol–water (9:1 v/v) solvent system. The optimized formulation (5% w/w HPMC 4500) was used to print tablets with varying shapes, drug loadings (5–15% w/w; approximately 50–150 mg losartan potassium per tablet), and croscarmellose sodium concentrations (0–3% w/w). Printed tablets were characterized for dimensional accuracy, mass uniformity, disintegration time, and drug release behavior. Drug release kinetics were modeled to elucidate the release mechanism. Results: All SSE-printed tablets exhibited excellent dimensional precision (SD < 0.8 mm) and mass uniformity (SD < 0.12 g). Increasing drug loading enhanced the initial release rate, reaching up to 63% in 45 min for 15% loading. The addition of 1% croscarmellose sodium reduced disintegration time to approximately 25 min. Drug release profiles were best described by the Korsmeyer–Peppas model (R² > 0.96), indicating diffusion-controlled release. Conclusions: SSE 3D printing demonstrated robustness and flexibility in producing losartan potassium tablets with consistent quality, tunable release properties, and strong potential for personalized pharmaceutical manufacturing. Full article

Highly permeable and selective membranes are crucial for energy-efficient gas separation. Two-dimensional (2D) graphitic carbon nitride (g-C₃N₄) has attracted significant attention due to its unique structural characteristics, including ultra-thin thickness, inherent surface porosity, and abundant amine groups. However, the interfacial defects caused by poor compatibility between g-C₃N₄ and polymers deteriorate the separation performance of membrane materials. In this study, amino-functionalized g-C₃N₄ nanosheets (CN@PEI) was prepared by a post-synthesis method, then blended with the polymer Pebax to fabricate Pebax/CN@PEI mixed matrix membranes (MMMs). Compared to g-C₃N₄, MMMs with CN@PEI loading of 20 wt% as nanofiller exhibited a CO₂ permeance of 241 Barrer as well as the CO₂/CH₄ and CO₂/N₂ selectivity of 39.7 and 61.2, respectively, at the feed gas pressure of 2 bar, which approaches the 2008 Robeson upper bound and exceeded the 1991 Robeson upper bound. The Pebax/CN@PEI (20) membrane showed robust stability performance over 70 h continuous gas permeability testing, and no significant decline was observed. SEM characterization revealed a uniform dispersion of CN@PEI throughout the Pebax matrix, demonstrating excellent interfacial compatibility between the components. The increased free volume fraction, enhanced solubility, and higher diffusion coefficient demonstrated that the incorporation of CN@PEI nanosheets introduced more CO₂-philic amino groups and disrupted the chain packing of the Pebax matrix, thereby creating additional diffusion channels and facilitating CO₂ transport. Full article

Y₂O₃ nanoparticles were used in a polyethersulfone (PES) as additives to increase the permeation properties of the polymeric membranes. Membranes were manufactured by diffusion-induced phase inversion in N-methyl-pyrrolidone (NMP) using a different concentration of nanoparticles. Y₂O₃ is used in polymeric membranes to enhance their functional properties, especially in wastewater treatment processes. Incorporating Y₂O₃ nanoparticles into the polymer matrix improves the membrane’s hydrophilicity, permeability, and mechanical strength. Additionally, Y₂O₃ provides better properties and reduces fouling. Recent studies highlight its potential as a modifying agent for advanced composite membranes. This paper investigated challenges in the synthesis of Y₂O₃-enhanced membranes and links synthesis with performance. It was observed that the composite membranes have better permeation properties by adding a small amount of Y₂O₃. For membranes at 21 wt.% PES permeability increase from 107 to 112 L/m²·h/bar. Fouling performance increases by adding nanoparticles, relative flux decreases by 30% for membranes without nanoparticles and by 10% for membranes with nanoparticles, both at a concentration of 25% PES. Rejection increases for membranes at 21%Pes from 21% for membranes without nanoparticles to 39% for membranes with nanoparticles. The influence of Y₂O₃ nanoparticles on the membranes’ performance was determined by filtration experiments to establish the permeability, fouling, retention, and the water flux; by contact angle to establish the surface hydrophilicity; and by SEM to investigate the membranes’ structures. Full article

Reversible addition–fragmentation chain-transfer (RAFT) polymerization has become an efficient method in the field of polymer synthesis. Recently, the RAFT polymerization technique has been successfully used to prepare functional materials and develop various sensing methods used in different scenarios. The polymerization reaction can be initiated by thermal, electrochemical, photochemical, enzymatic, and mechanical stimulation. More interestingly, RAFT polymerization can be performed in situ by recruiting a large number of signal tags at the solid interface to amplify the signals. In this review, we addressed the latest achievements in the preparation of sensing materials and the design of different sensors based on the RAFT polymerization technique for sensing ions and small molecules and bioimaging of tumor cells and viruses. Then, electrochemical and optical biosensors through the signal amplification of the RAFT polymerization method were summarized. This work could provide inspiration for researchers to prepare fascinating sensing materials and develop novel detection technologies applied in various fields. Full article

This study focuses on a novel lightweight technology for manufacturing variable-axial fiber-reinforced polymer components. In the presented approach, channels following the load flow are implemented in an additively manufactured basic structure and impregnated continuous fiber bundles are pulled through these component-integrated cavities. Improved channel cross-section geometries to enhance the mechanical performance are proposed and evaluated. The hypothesis posits that increasing the surface area of the internal channels significantly reduces shear stresses between the polymer basic structure and the integrated continuous fiber composite. A series of experiments, including analytical, numerical, and microscopic analyses, were conducted to evaluate the mechanical properties of the composites formed, focusing on Young’s modulus and tensile strength. In addition, an important insight into the failure mechanism of the novel fiber composite is provided. The results demonstrate a clear correlation between the channel geometry and mechanical performance, indicating that optimized designs can effectively reduce shear stress, thus improving load-bearing capacities. The findings reveal that while fiber volume content influences the impregnation quality, an optimal balance must be achieved to enhance mechanical properties. This research contributes to the advancement of production technologies for lightweight components through additive manufacturing and the development of new types of composite materials applicable in various engineering fields. Full article

Pleurotus ostreatus is one of the most frequently cultivated mushroom species. It has attracted considerable attention not only because of its short cultivation time, but also because of the wide range of substrates on which it can be cultivated, such as lignocellulosic materials, synthetic polymers and wastewater. The popularity of the oyster mushroom stems not only from its rapid growth and high adaptability, but also from its functional ingredients, which include laccase, proteoglycan and β-glucan. As understanding the molecular biology of Pleurotus ostreatus is crucial for evaluating its commercial and scientific applications, modern molecular tools have been used to search for the genes and proteins involved in the development of this mushroom and production of valuable metabolites. The rapid development of artificial intelligence may make it possible to automate and optimize the entire cultivation process of Pleurotus ostreatus. This report summarizes the cultivation of Pleurotus ostreatus using waste raw materials, the nutritional and medicinal value for applications, transcriptomic and proteomic analyses and the use of artificial intelligence systems. In addition, future perspectives are discussed to make the cultivation of Pleurotus ostreatus environmentally friendly and to ensure an increase in its productivity and quality. Full article

Polymer-based superplasticizers represent an emerging class of additives in cement and concrete production with demonstrated effects on zeta potential, ion exchange, turbidity and rheological behavior during hydration. This study examines the influence of polymer-based grinding aids focusing on the dosage of A2 on the grinding performance of Portland cement. Among the tested additives, A2 exhibited superior dispersing ability and agglomeration-preventing activity, yielding a zeta potential of −8.98 mV. Correspondingly, the release of the ion concentration of Ca²⁺ decreased to 190 mg/L, while SO₄²⁻ increased to 400 mg/L, indicating enhanced ionic interaction at the optimal A2 dosage of 2.5 g. The turbidity tests further revealed that cement samples ground with 2.5 g of A2 remained homogeneously suspended for longer periods compared to other additives. Overall, the analysis of cement surface properties confirmed that polymer-based grinding aids, particularly A2, significantly improve the dispersion stability of cement particles during grinding. Full article