Search Results (891)

This study critically addresses the challenge of selecting optimal insulation materials for contemporary, energy-efficient building envelopes, a decision with profound environmental, structural, and occupational health consequences. The paper responds to the growing demand for sustainable, resilient solutions by comparing wool, a bio-based, regenerative material, and expanded polystyrene (EPS), a synthetic polymer widely implemented in the construction industry, and advanced laboratory testing (thermal conductivity, moisture buffering, freeze–thaw resistance) is discussed in a comprehensive synthesis of the recent literature. Also, field evaluations from European retrofits and pilot projects (UK, Denmark, Finland, Iceland, Norway, Sweden, Germany and France) further contextualize performance outcomes, and life cycle impacts are considered. Recent results reveal that wool insulation achieves a moisture buffering value (MBV) between 1.8 and 2.7 (g/m²) % RH, minimal vapor resistance (mvr = 1–2), and preserves functional and structural integrity through more than 100 freeze–thaw cycles, leading to significant stabilization of the interior microclimate and enhanced durability. In contrast, EPS delivers lower thermal conductivity (0.032–0.037 (W/mK), critical for reducing heating/cooling demand, but exhibits limited vapor permeability (lvp = 60–150 MN·s/(g·m)), increased risk of condensation and mold, and reduced compressive strength (<22% after 30 cycles), especially when ventilation details are inadequate. Hybrid envelope systems leveraging both EPS and wool are demonstrated to optimize energy efficiency (up to 23% seasonal savings) and reduce interior humidity fluctuations, while lifecycle and recycling assessments show wool panels to be markedly superior in carbon footprint reduction and circularity. The stratification of insulation layers incorporating wool for vapor and moisture control, and EPS for pure thermal resistance is emerging as best practice in sustainable retrofit and new-build projects. Recommendations highlight the necessity for rigorous laboratory validation, international standards alignment, and integrated material design for robust hygrothermal comfort and environmental performance. The review also covers wool- and EPS-based hybrid composites, showing how natural fibers can improve key mechanical properties without compromising thermal insulation performance or environmental benefits. Full article

Frozen sand molds are the key material in digital frozen sand mold green casting technology, and their mechanical properties directly affect casting quality. Currently, these molds are primarily prepared by mechanical stirring, mixing, and compaction, which tend to cause imbalanced moisture adsorption and localized wet–dry differences, ultimately impairing the performance and quality of the castings. In this study, an ultrasonic vibration-assisted platform was established to prepare chromite sand frozen sand molds. By introducing ultrasonic vibration into the preparation process, a superior “sand grain–ice crystal” microstructure was constructed, leading to significantly enhanced mechanical properties. The tensile and compressive strengths were increased by approximately 10%, and the optimal process window for achieving the best mechanical performance of chromite sand was obtained. Full article

The reprocessing of wood–plastic composites (WPCs) significantly affects their structural integrity and thermal behavior. Despite this, the effect of reprocessing on PVC-based WPCs has not been extensively investigated, and the mechanism is not well understood. This study evaluated the effect of reprocessing on the properties of a PVC-based WPC. Small pieces of extruded WPC boards (2–4 mesh) were first milled to a granulation of 50 mesh, and then the material was reprocessed by compression molding, with part of the samples reinforced with glass- and carbon-fiber fabric. The physical and mechanical properties of the reprocessed material were analyzed, and the chemical and thermal characteristics of the reprocessed WPC were compared with the virgin WPC. The results of the mechanical and physical property tests showed that the reprocessed WPC had satisfactory properties compared with the virgin WPC. Samples reinforced with carbon-fiber fabric showed a statistically significant increase in tensile and flexural strength in comparison with unreinforced reprocessed WPC samples. Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) showed that partial dehydrochlorination, thermal degradation and a decrease in thermal stability occurred. Overall, the results of this study show that although chemical degradation and a decrease in thermal stability were present in the reprocessed WPC, it retained satisfactory mechanical and physical properties that could be improved by reinforcing it with carbon-fiber fabric. Full article

The current need for thermal insulation building materials has led to the development of new materials and technologies, which are necessary to reduce carbon emissions. Lignocellulose materials are promising options for thermal insulation materials in construction, offering appropriate mechanical and environmental properties. While recent reviews focus primarily on material properties, a critical gap remains in the technical analysis of processing parameters and the comparative evaluation of alternative fabrication methods. This study provides a semi-systematic overview of manufacturing processes for lignocellulose-based thermal insulation, highlighting key production methods at the development stage: the most common hot pressing and compression molding, as well as less used hot drying, air-laid, wet-laid, needle-punching, and biological fabrication (mycelium-based). The results show that there is no single ideal method due to a fundamental trade-off: hot pressing provides superior mechanical strength, mycelium and needle-punching provide optimal thermal insulation, while room-temperature drying and blow-molding methods are the most environmentally friendly due to their minimal energy consumption. The key factors determining material performance are the material density, size, and type of raw material, which are strictly regulated by processing parameters. Full article

Cementitious materials are naturally brittle, which makes them prone to cracking. This study effectively employs autogenous healing techniques using microcapsules to solve this issue. The goals were twofold: first, to microencapsulate isophorone diisocyanate (IPDI) as a catalyst-free healing agent; and second, to evaluate how these microcapsules improve the healing abilities of cementitious materials. Polyurethane (PU) prepolymer with an NCO content of 19.8% was successfully created. Using interfacial polymerization, smooth, spherical microcapsules of IPDI with an average diameter of 38 to 62 micrometers were produced. The elastic modulus of the microcapsules ranged from 0.23 to 0.18 GPa, while their hardness varied between 5.29 and 4.15 MPa. Over six months, the microcapsules showed a weight loss of 9.72% to 12.47%, depending on their size, under ambient conditions. Specimens containing 3% of fabricated microcapsules demonstrated the ability to seal cracks less than 100 µm wide by up to 70%. Specimens that incorporated 3% of their cement weight in IPDI microcapsules achieved an impressive 74% recovery rate in compressive strength. In contrast, control mortars without microcapsules showed a recovery rate of less than 50%. Analysis using Energy Dispersive Spectroscopy (EDS) revealed a significant presence of carbon in areas where the microcapsules had ruptured and the cracks had healed. This confirms the effectiveness of the healing process, consistent with established self-healing theories. The water tightness recovery trace showed a recovery rate of up to 61%. Additionally, the specimens containing microcapsules exhibited higher initial compressive strength than the control specimens. However, this also indicates that some microcapsules may have ruptured unintentionally during preparation and molding. Therefore, further research on the mechanical properties of microcapsules, especially their stiffness in cementitious composites, is necessary. Full article

Harmless treatment significantly raises the alumina content of secondary aluminum dross (SAD), laying the foundation for the preparation of MgAl₂O₄ (MA) refractory bricks from SAD by doping MgO. Relevant research on different molding methods, as well as the effects of binder types and dosages on the physical properties (such as compressive strength, thermal conductivity, and thermal shock resistance) of sintered bricks, remains inadequate. In this study, 15 wt% MgO was first added to make the Al₂O₃/MgO mass ratio of SAD close to the theoretical value of 2.53 for MA formation, and the SAD-MgO premix was used as raw material. The influence of molding methods and binders on the properties of sintered bricks was investigated. The results indicate that dry pressing outperforms casting in physical performance. When calcium lignosulfonate (CL) was used as the binder for dry pressing, the average compressive strength reached a maximum of 102.12 MPa, the corresponding thermal conductivity was 2.24 W/(m·K), and the sample withstood 11 thermal shock cycles. Binder dosage experiments showed that the optimal CL addition was 5 wt%, and the recommended upper limit was 10 wt%. This work provides a new perspective for the high-value utilization of SAD in the preparation of spinel refractory bricks. Full article

Carbon fiber-reinforced polymer (CFRP) composites are in urgent demand in the aerospace, new energy vehicle, and wind power sectors owing to their superior specific strength, specific modulus, and lightweight potential. However, molding defects, such as voids, dry spots, and delamination, arising from their anisotropy and weak interlaminar bonding, severely constrain their service performance. Advanced molding technologies represent the key to overcoming this bottleneck. This paper systematically reviews typical advanced molding technologies in the field of CFRP composites, including resin transfer molding (RTM) and vacuum-assisted resin transfer molding (VARTM) in liquid composite molding, autoclave molding and compression molding (CM) in prepreg molding, and automated fiber placement (AFP) and material extrusion (ME) in automated molding. From an integrated perspective of “technological evolution–process characteristics–defect mechanisms–optimization strategies,” this review summarizes the technical principles, development trajectories, and core advantages of each process, analyzes the formation mechanisms of typical defects, including voids, dry spots, delamination, wrinkles, warpage, and melt instability, and summarizes multidimensional optimization advances in process parameter regulation, numerical simulation, resin modification, equipment upgrading, path planning, and thermal management. Furthermore, the differences and complementarities among these processes in terms of molding precision, efficiency, cost, and applicable scope are compared. Finally, future development directions, including digital twins, green low-carbon manufacturing, ultra-large integrated structures, multi-process integration, standardized defect characterization, and low-cost collaborative design, are discussed. This paper aims to provide systematic theoretical references and technical support for the optimization and upgrading, process integration, and industrial application of advanced CFRP molding technologies. Full article

Recycled polypropylene (rPP) biocomposites represent a convergent strategy for plastic waste valorization and agro-industrial residue reutilization. This study quantifies tensile, flexural, and compressive performance (ASTM D638, D790, D695) of rPP biocomposites incorporating raw corn stover (Zea mays), banana pseudostem (Musa spp.), and barley residue (Hordeum vulgare) fibers at 10, 20, and 30 wt%, processed by single-screw extrusion and compression molding without compatibilizer. Two-way ANOVA with Tukey HSD post hoc analysis (α = 0.05) evaluated effects of fiber type and concentration. Tensile strength declined monotonically across all systems, from 24.9 MPa (neat rPP) to 7.9 MPa at 30 wt% banana fiber. Corn fiber exhibited exceptional tensile concentration stability (only −11% across the full range) and the best flexural retention at 10 wt% (36.6 MPa, 79% of neat rPP). A performance plateau was identified at 20 wt% under both tensile and flexural loading, beyond which further addition produced no significant reduction. Under compression, fiber type exerted its largest statistical effect (F = 81.231), all three systems were mutually distinguishable, and no plateau was observed. These results establish a loading-mode-resolved mechanical baseline for uncompatibilized rPP biocomposites, with corn fiber at 10–20 wt% as the most versatile formulation across all loading modes. Full article

Short carbon fiber-reinforced thermoplastic composites (SCFRTPCs) are widely employed in energy, aerospace and competitive sports due to their high specific strength/stiffness and design freedom. The Large Format Additive Manufacturing (LFAM) process, as an advanced technology for fabricating thermoplastic composite components, enables the rapid production of complex large-scale composite components and prototypes. Nevertheless, achieving satisfactory mechanical load-bearing performance remains a key challenge. To overcome this limitation, a methodology was developed for manufacturing short carbon fiber/Nylon 6 (SCF/PA6) composite components with programmable load-bearing performance via large-format additive manufacturing–compression molding (LFAM-CM). This process innovatively synergizes material stiffness enhancement with component deposition path planning, utilizing the high-orientation and low-porosity tape-shaped beads produced by LFAM to fabricate components. The experimental results demonstrate a peak load capacity of 549N, representing 33%, 231%, and 144% enhancements versus randomly oriented fiber, high-porosity, and non-path-planned components, respectively. Simultaneous meso- and macro-scale bearing performance analysis demonstrated the cross-scale synergistic enhancement effect of this process on component load-bearing capacity. Finally, a systematic analysis of energy dissipation, stiffness, and damage tolerance revealed the underlying mechanisms for enhanced load-bearing performance. This work establishes an expanded design paradigm where multivariate coupling replaces linear structure–property relationships, providing practical frameworks for the development of next-generation functionally graded components with tailored mechanical–electrical–thermal multifunctionality. Full article

Present research is focused on the preparation and characterization of bio-based polymer blends intended for sustainable food-packaging applications, starting from poly(butylene 2,5-furanoate) (PBF), characterized by very good barrier performance but quite high mechanical rigidity. In order to further improve gas permeability and increase its ductility, binary blends were prepared, combining PBF with varying amounts of poly(pentamethylene furanoate) (PPeF), another furan-based polyester with outstanding mechanical flexibility and gas barrier properties. The resulting materials were processed into compression-molded films and investigated through molecular, morphological, structural, thermal, and mechanical analyses. Blending turned out to be the winning tool in order to keep the high thermal stability of the reference homopolymers, increasing, at the same time, mechanical ductility and further lowering the permeability to oxygen and carbon dioxide compared to those measured for neat PBF. All these results were achieved without the use of any compatibilizer. Lastly, in order to test the end of life of these materials, composting studies were carried out, revealing a higher degree of weight loss for the blends compared with PBF homopolymer. Full article

The incorporation of cellulosic-based fillers as reinforcements into biocomposites represents a promising strategy to enhance the performance of sustainable packaging materials. In this study, poly(lactic acid)/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PLA/PHBV) films reinforced with 1 and 3 wt% of cellulose microfibers (CM) derived from yam, potato, and cassava hulls were developed through melt extrusion followed by compression molding. The physicochemical, mechanical, optical, microstructural, thermal, and molecular properties of the films were evaluated. Results showed that both the CM source and concentration significantly influenced the biocomposites performance. Cassava-derived CM at 3 wt% provided the best barrier properties, while increasing CM content, regardless of the source, generally reduced solubility, increased moisture content, enhanced stiffness, and decreased elongation at break, although excessive loading negatively affected structural homogeneity. CM incorporation also reduced film gloss and transparency, particularly in yam-based composites. Thermal analysis indicated a multi-step degradation process with only minor variations in thermal stability, and no major chemical modifications of the biocomposites were detected. Overall, cassava-derived CM produced the most balanced performance, highlighting the importance of filler source and loading in tailoring PLA/PHBV biocomposite functional properties. Full article

The increasing demand for porous stainless-steel materials produced by selective laser melting (L-PBF) for biomedical implants, filtration systems, heat exchangers, and energy devices has created an urgent need to improve their mechanical performance. Optimizing process parameters and microstructural properties is therefore critical for enhancing the overall functionality and reliability of L-PBF porous stainless-steel structures. This paper studies the effect of an aging heat treatment on the mechanical properties of L-PBF specimens, manufactured with stainless steel Uddeholm Corrax powders. The porosity was selected to be about 3%, based on manufacturer’s experience on the production injection mold inserts, with the ability to drain air. To reach this porosity, a set of manufacturing variables were selected, quantified in terms of VED (Volumetric Energy Density) of 59.01 J/mm³. The analysis of the mechanical behavior was focused on the compressive and flexural strength, dynamic Young’s modulus and the energy dissipation during earlier fatigue loading cycles. This study concluded that the heat treatment produces a negligible effect on dynamic Young’s modulus and increases the bending strength by about 25% and the compressive plateau strength by about 17%. Both specimens’ batches exhibit similar fatigue strain accumulation for cyclic compressive tests. Full article

This study explores the possibility of making cardboard and molded egg carton packaging from corn residues and common reed as alternatives to wood-based pulp. Six formulations were made: corn husks (CHs), corn leaves (CLs), corn leaves (35%) plus corn husks (30%) and a corn blend (15%) of wollastonite (CaSiO₃) (CH + CL + W), a corn blend (CH + CL: husks 60%, leaves 40%), mixed corn waste (MCW) and shredded common reed (SR). Optical microscopy was used to evaluate the fiber morphology, including the calculation of the flexibility coefficient, the cell wall rigidity and the Runkel ratio, for raw materials and fiber after alkaline hydrolysis and casting of egg cartons in silicone molds. The grammage, burst strength and index, folding endurance, thickness and moisture content were measured in the cardboard samples, while warping, compressive deformation, moisture and ink absorption were measured in the egg cartons. The flexibility coefficient of the common reed fibers (64.5%) was better than that of the corn fibers (23.6%), and so was the Runkel ratio (0.86 vs. 1.2). In the case of cardboard formulations, the maximum burst strength (462.4 kPa) and the maximum burst index (3.0 kPa·g/m²) values were obtained with the MCW formulation, and the highest folding endurance (42 and 38 double folds) was obtained with the CH and SR formulations, respectively. The addition of wollastonite improved folding endurance to 28 double folds and reduced moisture content to 4.1%, whereas the moisture content was reduced but burst strength decreased to 250.5 kPa. Egg cartons made from corn were found to satisfy all the requirements tested for good packaging, while the reed-based cartons were found to have inadequate ink absorbency time (20 min), making them less printable. Overall, mixed corn residues seem to be the most promising raw materials for sustainable packaging, and wollastonite can be used to adjust the flexibility–strength balance. Full article

Microneedle systems represent a promising minimally invasive approach for transdermal drug delivery; however, their performance strongly depends on the composition and mechanical properties of the polymer matrix. The aim of this study was to select an optimal polymer composition for the fabrication of dissolving microneedle arrays produced by the mold casting method. The study focused on evaluating mechanical strength, dissolution behavior, and penetration efficiency of different polymer systems. Microneedle matrices were fabricated using polyvinylpyrrolidone (PVP K-30), methylcellulose, sodium alginate, and hyaluronic acid at various concentrations, alone and in combination. No active pharmaceutical ingredient (API) was incorporated; the study was performed using blank polymeric systems intended for subsequent drug loading. The microneedles were manufactured using 3D-printed and silicone molds. Their performance was evaluated by in vitro dissolution testing, pH measurement, penetration studies in gelatin gel and Parafilm M models, and mechanical compression testing. Monopolymer systems demonstrated either rapid dissolution with insufficient mechanical strength or improved strength at the expense of prolonged dissolution time. Combined polymer formulations showed superior structural uniformity and balanced performance. In particular, the system containing 5% PVP K-30 and 10% sodium alginate demonstrated the best overall characteristics, achieving high penetration efficiency (up to 96%), uniform dissolution (78%), and appropriate dissolution time (8.5 ± 0.5 min). Addition of hyaluronic acid further improved structural uniformity and handling properties. The results indicate that composite polymer matrices provide an optimal balance between mechanical stability, penetration ability, and dissolution rate. The formulation consisting of 5% PVP K-30 and 10% sodium alginate was identified as the most promising base for further development of drug-loaded dissolving microneedle systems. Full article

Application of polyacrylonitrile-derived carbon fiber (CF) as a thermal insulation material is restricted by inherently high thermal conductivity. Encapsulation of poly(p-phenylene benzobisoxazole) (PBO) on CF was supposed to improve the mechanical and heat resistance of CF, which would be desired to improve mechanical and thermal-insulating performances. In this work, PBO molecules were uniformly coated onto the surface of air plasma-treated CF. Carbonized PBO-encapsulated CF (CF@CPBO) was prepared via thermal treatment at 600–1400 °C. At higher carbonization temperatures, CF@CPBO exhibited a cleaner surface, more radial graphite layers within fibers, enhanced crystallinity of carbon layers (amorphous to 0.337 nm of interplanar spacing), reduced defective/graphitic content (0.959–0.909 of I_D/I_G), decline in surface O content (20.1–9.6 at.%) and improved symmetry of the C-C deconvoluted peak. After weaving them into a net and compression molding, CF@CPBO felts with a random distributed structure (no voids and no fiber bundles) presented improved compression strength (10.5–25.6% of enhancement than unmodified CF) and excellent compression-recovery performance (130.9–110.8 MPa) through 10 cycles. Thermal conductivity values of CF@CPBO felts at 30–1800 °C were 0.13–1.42 W/m/K, which were 42.2–62.6% of unmodified CF. This work proposes an efficient strategy for regulating the high-performance organic fiber structure through heat treatment-induced processes. Full article