Search Results (3,616)

The quality and durability of adhesive joints in wood flooring are determined by both the type of adhesive and the parameters of the bonding process. This study examines the effects of pressing time and seasoning time on the bending strength of adhesive joints in the middle layer of floorboards manufactured using innovative block-bonding technology. Experimental trials were conducted with two adhesive systems—polyvinyl acetate (PVAC) and polyurethane (PUR)—using a full factorial design and statistical evaluation of joint strength in terms of pressing time and seasoning time. For PVAC, an overall tendency toward increased strength with extended pressing time was observed; however, the strongest effects were associated with interactions between pressing and seasoning times, with the most favorable results obtained for short pressing (5 min) combined with extended seasoning (5 h). In the case of PUR, the relationships were non-linear, and the only statistically significant factor was the interaction between pressing and seasoning times, confirming the necessity of joint optimization. The findings demonstrate that simple one-factor analyses are insufficient to explain adhesive performance, as non-linear and interaction effects are critical in defining joint strength. The results provide new insights for optimizing bonding processes in floorboard production, supporting improvements in material efficiency and mechanical reliability of wood flooring. Full article

Rail transport is widely regarded as a sustainable and environmentally friendly option for long-distance freight and passenger movement during its operation phase. However, its construction and maintenance phases often result in substantial environmental impacts, which must be addressed to improve the overall sustainability of railways. This study aims to identify solutions that improve the performance of railway tracks, reduce maintenance requirements, and minimize environmental impact. With this objective, the potential of artificial inclusions and innovative composite materials in enhancing the sustainability of railway tracks is investigated through a comprehensive methodology, combining experimental, analytical and numerical approaches. A novel composite material, comprising soil, scrap tire aggregates and an adhesive, demonstrated strong potential as a sustainable base layer for ballastless railway tracks, exhibiting minimal strain accumulation (0.29–0.98%) under 50,000 load cycles and adequate damping. Incorporation of cellular artificial inclusions in the substructure layers of ballasted tracks reduced cumulative settlement by up to 33% and slowed track geometry deterioration. Use of planar artificial inclusions beneath a pile-supported railway embankment enhanced the load transfer efficiency and curtailed settlement, while also lowering environmental impact by reducing concrete usage. The findings of this study highlight strong potential of these approaches in improving track performance and the overall sustainability of railways. Full article

Backround: The agr (accessory gene regulator) quorum sensing (QS) system of Staphylococcus aureus participates significantly in its virulence and biofilm formation—either through its activation or suppression. The aim of this study was to investigate the impact of photoactive nanomaterials that have been functionalized with erythrosine B (EryB) on the modulation of this agr QS system on three methicillin-resistant S. aureus (MRSA). Methods: The functionality of the agr system was determined by the CAMP test and by quantitative PCR (qPCR) to analyze the expression of the hld gene, which is located within the RNAIII and encodes δ-hemolysin. The biofilm was evaluated by crystal violet assay and fluorescence microscopy. The anti-biofilm activity was determined by calculating the colony-forming units. The relative expression of the hld gene, determined by qPCR. Results: Using the CAMP test, S66 and S68 strains were found to be agr-positive, and strain S73 was agr-negative. The relative expression of the hld gene increased only in the agr-positive strains (600- and 1000-fold). In these strains, the biofilm was less compact compared to the dense biofilm formed by the agr-negative strain. The anti-biofilm effectiveness on the nanocomposite with EryB after irradiation reduced the growth of biofilm cells by 100- to 1000-fold compared to the biofilm on polyurethane alone. The qPCR results showed a significant decrease in the relative expression of the hld gene in the agr-positive strains after irradiation compared to the non-irradiated samples. Conclusions: These results suggest that photoactive nanocomposites with EryB can significantly reduce biofilm formed by MRSA strains, regardless of the functionality of the agr QS system. Full article

Polyurethane (PU), owing to its superior physicochemical properties, is considered an ideal modifier for asphalt. To improve the mechanical performance and service durability of asphalt pavements, PU-modified asphalts with varying dosages were prepared and evaluated through laboratory experiments and molecular dynamics simulations. Rheological, thermodynamic, and mechanical tests, as well as asphalt–aggregate adhesion energy calculations, were conducted to elucidate the modification mechanism, aging resistance, and interfacial behavior. The results showed that PU incorporation significantly enhanced rutting resistance at high temperatures, flexibility at low temperatures, and overall load-bearing capacity. Under ultraviolet and long-term aging, PU-modified asphalts exhibited notably lower performance degradation than base asphalt. At the molecular level, PU absorbed light fractions and formed a cross-linked network, reducing the free volume fraction and strengthening resistance to deformation. Moreover, PU substantially improved asphalt–aggregate adhesion energy, thereby reinforcing interfacial bonding. These findings provide theoretical insights and practical guidance for the optimal design and engineering application of PU-modified asphalt. Full article

This study investigates the structure–property–performance (SPP) relationships of two thermoplastic polyurethanes (TPUs), FILAFLEX FOAMY 70A and SMARTFIL^® FLEX 98A, manufactured by fused filament fabrication (FFF). Disc specimens were produced with varying gyroid infill densities (10–100%) and Archimedean surface textures, and their tribological and surface characteristics were analyzed through Ball-on-Disc tests, profilometry, and optical microscopy. SMARTFIL^® FLEX 98A exhibited a sharp reduction in the coefficient of friction (μ) with increasing infill, from 1.174 at 10% to 0.371 at 100%, linked to improved structural stability at higher densities. In contrast, FILAFLEX FOAMY 70A maintained a stable but generally higher coefficient of friction (0.585–0.729) across densities, reflecting its foamed microstructure and bulk yielding behavior. Surface analysis revealed significantly higher roughness in SMARTFIL^® FLEX 98A, while FILAFLEX FOAMY 70A showed consistent roughness across infill levels. Both TPUs resisted inducing abrasive wear on the steel counterpart, but their stress-accommodation mechanisms diverged. These findings highlight distinct application profiles: SMARTFIL^® FLEX 98A for energy-absorbing, deformable components, and FILAFLEX FOAMY 70A for applications requiring stable surface finish and low adhesive wear. The results advance the design of functionally graded TPU materials through the controlled tuning of infill and surface features. Full article

The acoustic, thermal, and mechanical performances of sawdust-reinforced polyurethane (PU) foam are investigated for different thicknesses and varying mesh sizes. Acoustic properties are explored using a combination of impedance tube testing and mathematical modeling with the Johnson–Champoux–Allard–Lafarge (JCAL) model, a simplified JCAL model and a model of non-uniform cylindrical pores with a log-normal radius distribution (NUPSD). Thermal Insulation and mechanical properties are determined by measuring the effective thermal conductivity (K_eff) and by tensile strength tests, respectively. Compared with pure PU foam, the presence of sawdust matches noise reduction coefficients (NRC) and increases sound absorption averages (SAA) by nearly 10%. Increasing thickness and width of backing air gap have the usual effects of improving low- and mid-frequency absorption and shifting resonance peaks toward lower frequencies. As well as superior acoustic performance, samples with Mesh 16 sawdust reinforcement provide both useful insulation (K_eff = 0.044 W/mK) and tensile strength (~0.06 MPa), confirming their multifunctionality. Although the JCAL model provides reasonable fits to the sound absorption data, some of the fitted parameter values are unphysical. Predictions of the NUPSD model are relatively poor but improve with sample thickness and after fiber addition. Full article

The increasing demand for sustainable construction materials has driven interest in utilizing waste biomass within polymer composites. Rigid polyurethane foams, widely valued for thermal insulation, exhibit a significant flammability issue. This study investigates the impact of incorporating various waste biomass materials, including brewers’ spent grain, coffee grounds, and soybean husk and their combustion ashes on the selected properties of rigid polyurethane foams. The primary objective is to assess the potential of these eco-friendly additives as replacements for traditional raw materials, aiming to enhance fire resistance and thermal stability and thereby promoting circular economy principles in the construction sector. Composite foam samples were fabricated using a mixing and casting technique, incorporating 5% wt. of fillers into the polymer matrix. Thermal stability and flammability were evaluated using cone calorimetry and thermogravimetric analysis. The findings indicated that while biomass inclusion did not significantly improve char formation, the addition of ash substantially increased char yield, a critical factor in fire suppression. Although biomass and ash may influence flammability, they do not inherently bolster the intrinsic thermal stability of the polyurethane matrix itself. Full article

Many transportation structures collapse or sustain severe damage as a result of natural disasters such as earthquakes, floods, wars, and similar attacks. These collapsed or severely damaged structures must be rebuilt and returned to service as quickly as possible. Water is used in the mix for cement-bound concrete roads. It is known that drought problems are emerging due to climate change and that water resources are rapidly depleting. Significant amounts of water are used in concrete production, further depleting water resources. In order to contribute to the elimination of these two problems, the usability of polyurethane resin binder in road pavement construction was investigated. Polyurethane resin binder road pavement is a new type of pavement that does not contain cement or bitumen as binders and does not contain water in its mixture. This new type of road pavement can be opened to traffic within 5–15 min. After determining the aggregate and binder mixture ratios, four different curing methods were applied to the created samples. After the curing, the samples were subjected to compression test, flexural test, Bohme abrasion test, freeze–thaw test, bond strength by pull-off test, ultrasonic pulse velocity (UPV) test, SEM-EDX analysis, XRD analysis, and FT-IR analysis. The new type of road pavement created within the scope of this study exhibited a compression strength of 41.22 MPa, a flexural strength of 25.32 MPa, a Bohme abrasion value of 0.99 cm³/50 cm², a freeze–thaw test mass loss per unit area of 0.77 kg/m², and an average bond strength by pull-off value of 4.63 MPa. It was observed that these values ensured the road pavement specification limits. Full article

Microcellular thermoplastic polyurethane (TPU) foams with dynamic covalent bonds demonstrating exceptional self-healing capabilities, coupled with precisely controlled micron-scale cellular architectures, present a promising solution for developing advanced materials that simultaneously achieve damage recovery and low density. In this study, a series of self-healable materials (named as PU-S) with high light transmittance possessing two dynamic covalent bonds (oxime bond and disulfide bond) in different ratios were fabricated by the one-pot method, and then the prepared PU-S were foamed utilizing the green and efficient supercritical carbon dioxide (scCO₂) foaming technology. The PU-S foams possess multiple dynamic covalent bonds as well as porous structures, and the effect of the dynamic covalent bonds endows the materials with excellent self-healing properties and recyclability. Owing to the tailored design of dynamic covalent bonding synergies and micron-sized porous structures, PU-S₅ exhibits hydrophobicity (97.5° water contact angle), low temperature flexibility (T_g = −30.1 °C), high light transmission (70.6%), and light weight (density of 0.12 g/cm³) together with high expansion ratio (~10 folds) after scCO₂ foaming. Furthermore, PU-S₅ achieves damage recovery under mild thermal conditions (60 °C). Accordingly, self-healing PU-S based on multiple dynamic covalent bonds will realize a wide range of potential applications in biomedical, new energy automotive, and wearable devices. Full article

Polyurethane-coated fabrics are widely employed as tarpaulin materials. However, due to the long duration and large space requirements of natural exposure tests, studies on fabric degradation remain scarce. To systematically investigate the natural aging patterns and mechanisms of polyurethane-coated fabrics, this study conducted 24-month natural aging tests in three representative regions: Xishuangbanna (tropical monsoon climate), Xiamen (subtropical maritime monsoon climate), and Jinan (temperate monsoon climate). Changes in appearance, mechanical properties, surface morphology, elemental composition, and microstructure were thoroughly analyzed. The results indicated that gloss decreased by over 60%, the color difference exceeded 5.8, and tear strength was reduced by more than 50%. SEM, ATR-FTIR, and XPS analyses revealed that hydrolysis and oxidation occurred in the coating, leading to coating thinning, fiber exposure, and even damage. In Xishuangbanna, high temperature, high humidity, and strong solar radiation are responsible for the most severe degradation of fabrics. High temperature, humidity, and salt fog synergistically accelerated the aging process. In Jinan, significant thermal strain contributed to deterioration, and fabrics exhibited the mildest degradation. This multi-region natural exposure study realistically simulates in-service aging behavior, providing important validation for accelerated laboratory aging methods, product reliability improvement, and service-life modeling. Full article

Spent coffee grounds represent an abundant waste resource with potential for sustainable material applications. This study investigates the use of carbonized spent coffee grounds (CSCG) as fillers in polyurethane (PU) coatings for carbon fiber-reinforced polymer (CFRP) substrates to enhance mechanical durability and anti-icing performance. SCGs were dried, sieved (<100 µm), and oxidatively carbonized in air at 100–300 °C for 60–120 min, then incorporated into PU at 1 or 5 wt.% and applied by spray-coating. A full-factorial design was employed to evaluate the effects of carbonization temperature, particle size, and filler loading. The optimized formulation (300 °C, 100 µm, 5 wt.%) showed the highest water contact angle (103.5°), lowest work of adhesion (55.8 mJ/m²), and improved thermal stability with 60% char yield. Mechanical testing revealed increased tensile modulus with reduced strain, and differential scanning calorimetry indicated an upward shift in glass-transition temperature, suggesting restricted chain mobility. Ice formation at 0 °C was sparse and discontinuous, attributed to lowered polar surface energy, rough surface texture, and porous carbon morphology. These results demonstrate that CSCGs are effective sustainable fillers for PU coatings, offering combined improvements in mechanical, thermal, and anti-icing properties suitable for aerospace, wind power, and other icing-prone applications. Full article

Introduction: Pediatric lower-lip dog bite injuries are challenging due to contamination, tissue loss, and the need to maintain function, appearance, and psychological well-being. This single case describes immediate definitive closure using sharp debridement with adjunct polyhexanide (PHMB), a full-thickness skin graft (FTSG), and a polyurethane (PU) compression foam bolster. Methods: A 10-year-old boy with a severe contaminated lower-lip defect underwent debridement and 0.04% PHMB irrigation. An upper-arm FTSG was inset and compressed with a suture-anchored PU dressing. Topical PHMB gel was used perioperatively and for seven days after bolster removal. Oral antibiotics were given for five days. The patient was discharged eight days after the injury with detailed wound care instructions. Results: Immediate definitive closure was achieved with complete graft survival and no infection, necrosis, unplanned early dressing changes, or reoperations. At 12 months, oral competence, speech, lip mobility, and contour were preserved. However, mild residual esthetic differences remained (dyschromia, shallow border indentation, vellus hairs on the graft). Conclusion: In this single descriptive case, primary closure of a lower-lip injury with the combined intervention was associated with an uncomplicated functional course and manageable esthetic trade-offs at 12 months. These observations are descriptive; comparative studies with standardized functional, esthetic, and psychosocial measures are needed. Full article

Thermoset fibre-reinforced composites are widely used in high-end industries, but a growing demand for more sustainable and recyclable alternatives conveyed the research efforts towards thermoplastics. To expand their usage, new approaches to their manufacture and mechanical performance must be tackled and tailored to each engineering challenge. The present study designed, manufactured and tested advanced multi-layer laminated composites of thermoplastic polypropylene prepreg reinforced with continuous woven fibreglass with interlayer toughening through thermoplastic polyurethane elastomer (TPU) layers manufactured by fused filament fabrication. The manufacturing process was iteratively optimized, resulting in successful adhesion between layers. Three composite configurations were produced: baseline glass fibre polypropylene (GFPP) prepreg and two multi-layer composites, with solid and honeycomb structured TPU layers. Thermal and mechanical analyses were conducted with both the polyurethane elastomer and the manufactured laminates. Tensile testing was conducted on additively manufactured polyurethane elastomer specimens, while laminated composites were tested in three-point bending. The results demonstrated the potential of the developed laminates. TPU multi-layer laminates exhibit higher thermal stability compared to the baseline GFPP prepreg-based composites. The addition of elastomeric layers decreases the flexural modulus but increases the ability to sustain plastic deformation. Multi-layer laminate composites presenting honeycomb TPU layers exhibit improved geometric and mechanical consistency, lower delamination and fibre breakage, and a high elastic recoverability after testing. Full article

Polyurethane foams containing heterocyclic rings are characterized by high thermal resistance, but unfortunately, they are flammable. This work examined the effect of halogen-free flame retardants such as melamine and expanded graphite: EG 096 and EG 290 on the properties of foams with a 1,3-pyrimidine ring. Oligoetherol obtained from 6-aminouracil, ethylene carbonate, and propylene oxide was foamed with polymeric diphenylmethane 4,4′-diisocyanate with the addition of flame retardants. The oxygen index was determined, and flammability tests were conducted on the resulting foams. Their apparent density, water absorption, thermal resistance, thermal conductivity coefficient, and compressive strength were also examined. Both melamine and expanded graphite significantly reduce the flammability of foams. The resulting foams are classified as V-0 flammability class, and their oxygen index is in the range of 24.9–29.5 vol.%. Expanded graphite is a better flame retardant and does not cause deterioration of other foam properties. Full article

(1) Background: This study aimed to determine the optimum parameters for the treatment of Streptococcus mutans biofilm on clear dental aligners. (2) Methods: A 24-h-old S. mutans biofilm was grown on polyurethane (PU) and poly(ethylene terephthalate glycol) (PETG) aligners. These samples were treated with three chlorhexidine digluconate (CHX)-based antiseptic solutions, manual brushing, and a combination of both, with varying exposure times. The number of adhered bacteria was determined in both untreated and treated samples after sonication. Materials were analyzed with atomic force and scanning electron microscopy, and surface free energy (SFE) values were determined using three different models. (3) Results: Our findings indicated that control strategies do not depend on the type of material. PU and PETG surfaces exhibited similar SFE values (41–45 mJ/m²). Differences in surface roughness were insufficient to cause significant changes in S. mutans behavior. The highest efficacy of all three tested antiseptics was established for the exposure time of 1 min, with efficacy deteriorating just after 3 min. (4) Conclusions: The efficacy of CHX against S. mutans early biofilm is material-independent and time-dependent. The optimal exposure time of 1 min should be combined with brushing, with a general recommendation of the antiseptic-first approach. Full article