Search Results (3,827)

Thermosetting polyurethane (PU) has recently been introduced as an asphalt modifier to improve the mechanical strength and durability of pavements. However, the permanent crosslinked network of thermosetting PU makes the material difficult to repair once damage accumulates. In contrast, self-healing asphalt technologies rely on either extrinsic healing agents or intrinsic dynamic bonds to restore stiffness and delay cracking. Dynamic disulfide bonds are a promising class of reversible covalent bonds that can rearrange at moderate temperatures and have been widely used to build self-healing polyurethane networks. This study investigates a disulfide-crosslinked polyurethane-modified asphalt binder (DP10) and compares its fatigue and healing performance with base asphalt (BA), thermosetting PU-modified asphalt (P10), and styrene–butadiene–styrene (SBS)-modified asphalts (S3 and S10). A dynamic shear rheometer (DSR) was used to conduct time sweep fatigue tests, linear amplitude sweep (LAS) tests, and fatigue–healing–fatigue protocols. Fourier transform infrared spectroscopy (FTIR) was employed to confirm the formation of polyurethane and disulfide structures. Results show that DP10 significantly increases fatigue life at small to medium strain levels compared with BA and P10 and performs competitively with SBS-modified binders. More importantly, DP10 exhibits a much higher healing index than P10 and maintains strong healing capability over repeated fatigue–healing cycles, approaching the intrinsic healing level of base asphalt. These findings demonstrate that incorporating dynamic disulfide bonds into thermosetting PU networks provides a practical route to binders that combine high strength with recoverability, which is attractive for long-life, self-healing pavement design. Full article

In this study Laminated Veneer Lumber (LVL)—widely used in structural wood applications—was manufactured from seven poplar veneers bonded with polyurethane (PU) adhesive and reinforced with either one sheet of glass fiber or carbon fiber fabrics. In order to determine the effects of the fiber fabrics incorporated into the structure of the produced LVLs on their thermal and acoustic insulation performance in structural applications, the thermal conductivity coefficient (λ), thermal transmittance (U), sound absorption coefficient (α), and sound transmission loss (dB) values were determined. The experimental results indicated that the thermal conductivity coefficient of the glass fiber-reinforced LVL was lower than that of both the control group and the carbon fiber-reinforced LVL. The thermal transmittance coefficient, an important indicator of thermal insulation performance in buildings, followed a similar trend. Regarding the sound absorption coefficients, the fiber fabric-reinforced LVL samples demonstrated lower coefficients compared to the control group. For sound transmission loss, no significant differences were observed among the groups, and the sound transmission loss was found to increase with frequency. Results indicate that glass fiber-reinforced LVL composites can be used as replacement of other wood-based insulating materials in green buildings which exhibit worse sound insulation or thermal insulation and which are significantly more affected by changes in relative humidity of surrounding air. Full article

To prepare a modified asphalt with excellent road performance, thermoplastic polyurethane/graphene oxide (TPU/GO) incorporating dynamic disulfide bonds was developed as an additive and the synergistic effect of TPU and GO on asphalt was evaluated. Modified asphalts with different TPU/GO contents (2%, 4%, 6%, 8%) were prepared and TPU-modified asphalts were also prepared as control groups. The compatibility between TPU/GO and asphalt was evaluated by fluorescence microscopy (FM) and the dispersion of GO in TPU and asphalt was observed by emission scanning electron microscope (SEM). The road performance of modified asphalts was also assessed in this study. The FM results show that TPU/GO has good compatibility with asphalt, and the SEM results reveal that GO can be uniformly dispersed in TPU matrix, so that GO can also be evenly dispersed in asphalt and avoid the problem of GO aggregation in asphalt. The results also demonstrate that TPU/GO-modified asphalt comprehensively utilizes the respective advantages of TPU and GO. TPU/GO-modified asphalt has excellent low-temperature performance compared with base asphalt. The 5 °C ductility of 8%TPU/GO-modified asphalt is 440% higher than that of base asphalt and the BBR test also showed that the stress relaxation capacity of TPU/GO-modified asphalt is also significantly stronger than that of base asphalt. Moreover, the introduction of GO in asphalt can improve the creep recovery rate and complex modulus compared with TPU-modified asphalt, indicating better high-temperature rutting resistance. Comprehensive performance evaluation indicates that 8% TPU/GO-modified asphalt is the optimal dosage for engineering applications, balancing high-temperature rutting resistance, storage stability, anti-aging performance, and low-temperature behavior. Full article

The construction industry faces intensifying pressure to mitigate its environmental impact, particularly concerning the reliance on non-biodegradable materials and hazardous formaldehyde-based adhesives. Although bio-based alternatives are emerging, many still depend on virgin feedstocks, and the valorization rates for abundant waste streams like used cooking oil remain critically low. To bridge this gap, this study developed a sustainable, formaldehyde-free Modified Reused Palm Oil-Polyurethane (MRPO-PU) adhesive specifically for binding sugarcane bagasse particleboards. The synthesis process involved filtering used palm oil and subjecting it to epoxidation and hydroxylation reactions to yield a functional bio-polyol, the chemical structure of which was validated via Fourier Transform Infrared Spectroscopy (FTIR). This bio-polyol was subsequently mixed with polymeric diphenylmethane diisocyanate (pMDI) and combined with alkali-treated bagasse at varying adhesive ratios ranging from 15 to 85 wt%. Physical and mechanical evaluations demonstrated a robust positive correlation between adhesive content and composite integrity. Specifically, increasing the adhesive loading enhanced density up to 444 kg/m³ and minimized thickness swelling to 5.1%, while flexural and compressive strengths significantly improved. The data suggests an optimal efficiency range between 45 and 55 wt%. Ultimately, this research validates a dual-waste valorization strategy, offering a scalable circular economy model that transforms agricultural residues and spent oils into high-performance, eco-friendly construction materials. Full article

Reactive structural adhesives—epoxies, polyurethanes, and acrylics—are essential in high-performance applications, yet their development remains complex due to multiscale adhesion mechanisms, combinatorial formulation spaces, and stringent performance requirements. Traditional trial-and-error approaches are time- and resource-intensive. Machine learning (ML) provides a powerful framework to accelerate adhesive design by capturing nonlinear relationships between formulation, processing, and performance, while enabling predictive modeling, optimization, and experiment prioritization. This review presents a process-oriented guide for ML-assisted adhesive development, covering component selection, feature engineering, initial dataset design, model choice, and iterative workflows integrating classical design-of-experiments, active learning, and Bayesian optimization. Emphasis is placed on interpreting ML outputs through the lens of polymer chemistry, reaction kinetics, and fracture mechanics to extract mechanistic insights and guide rational formulation design. Key challenges—including small, noisy datasets, multi-component interactions, and multi-objective trade-offs—are discussed, along with emerging directions such as collaborative databases, automated knowledge extraction, and hybrid ML–chemistry approaches to further enhance structural adhesive development. The review underscores the potential of integrating ML into adhesive R&D to reduce experimental burden, improve formulation efficiency, and enable data-driven exploration of complex chemistries. Full article

This study employs a mono-caprylate waterborne polyurethane microencapsulation technique to construct a core–shell phase-change microcapsule system with a structured composite core material. By integrating a silica network with phase change materials (ethyl palmitate/paraffin), a stable core material is formed. The silica not only acts as a physical framework to prevent leakage but also regulates the phase change temperature and latent heat through molecular interactions at its surface active sites. The shell layer polyurethane, derived from a fatty acid monoglyceride prepolymer, exhibits a structure highly similar to that of the core material, ensuring efficient and complete encapsulation, while the aqueous system aligns with green manufacturing requirements. The system successfully achieves two types of performance-tunable microcapsules: the silica–ethyl palmitate type exhibits a broad phase change temperature range near room temperature, while the silica–paraffin type demonstrates high latent heat of phase change in the medium-temperature range. This diversity in performance broadens the material’s application scenarios. Its broad temperature range characteristic is particularly suitable for building energy efficiency and electronic thermal management fields, effectively mitigating temperature fluctuations and reducing energy consumption, demonstrating significant application value and innovative potential. Full article

This work presents a signal processing and reconstruction system developed for a flexible optical pressure 2D mapping sensor. The sensor consists of a two-dimensional grid of polyurethane optical fibers (PU-OFs) embedded in polydimethylsiloxane (PDMS), which acts as the input device for acquiring light intensity changes caused by external surface-applied pressure. In this study, we propose a system to process these signals through an inverse model based on the Moore–Penrose pseudoinverse for spatial localization, along with a point-specific pressure estimation model to infer the magnitude of the applied force, which is then used to generate quantitative pressure maps. Experimental results show the system’s overall performance, robustness, and repeatability across multiple pressure levels and locations. In most cases, localization errors remain below 5 mm, while pressure estimation errors are around 5 mmHg when the pressure is correctly localized. Performance metrics, such as recall, specificity, and precision, support the system’s ability to detect, localize, and reconstruct pressure events with consistent reliability. These results establish the viability of the proposed methodology for potential integration into low-cost and flexible optical fiber-based 2D pressure monitoring systems for biomedical applications. Full article

Polymer-based insulation materials are widely used to enhance the energy efficiency of buildings; however, their growing application raises concerns related to resource use and end-of-life management. Rigid polyurethane (PUR) foams are key core materials in structural insulated panels due to their favorable thermal and mechanical performance, yet their life cycle environmental impacts—particularly at end-of-life—remain insufficiently quantified. In this study, a cradle-to-grave life cycle assessment (LCA) of PUR-based insulation used in structural insulated panel systems is conducted in accordance with ISO 14040/44 and EN 15804 standards. The assessment is performed using Sphera LCA software (version: GaBi 10.5) and the CML 2016 impact assessment method. Formulation-level variations in rigid PUR foams, including changes in methylene diphenyl diisocyanate content and pentane blowing agent ratio, are explicitly incorporated to evaluate their influence on key environmental impact categories. The results indicate that increasing pentane content leads to higher global warming potential, while this effect may be mitigated or intensified by concurrent changes in diisocyanate content and foam density in fully formulated systems. Three end-of-life scenarios—landfilling, incineration with energy recovery, and mechanical recycling—are analyzed. The findings provide material-level, decision-relevant insights that support environmentally informed formulation strategies and contribute to the development of more circular polymer-based insulation solutions for the built environment. Full article

Polyurethanes are widely used polymeric materials; their crosslinked structure and compositional diversity significantly hinder effective end-of-life management. The review emphasizes polyurethane recycling technologies, with chemical aspects discussed only insofar as they directly affect recyclability. The influence of polyol and isocyanate structure on phase separation, network architecture and thermal stability is discussed in the context of degradation and depolymerization mechanisms. Mechanical, chemical, thermochemical and emerging biological recycling routes are compared, with emphasis on their respective advantages, limitations and technological maturity. Mechanical recycling remains the most accessible option on an industrial scale but typically leads to reduced mechanical and thermal-insulation performance. Chemical recycling—particularly glycolysis, hydrolysis and aminolysis—enables partial recovery of polyols suitable for reuse in new polyurethane formulations, albeit at the cost of higher energy demand and increased process complexity. The environmental impact of polyurethane recycling is considered in terms of energy consumption, greenhouse-gas emissions, waste-reduction potential and alignment with circular-economy principles. Emerging biological and hybrid recycling strategies are highlighted as promising low-temperature alternatives with potential environmental benefits, despite their current low technological readiness. Key structural and technological barriers to efficient polyurethane recycling are identified, and future research directions toward improved sustainability and resource efficiency are outlined. Full article

Head injuries remain one of the major health concerns in contact sports such as boxing. Despite the widespread use of protective gloves and helmets, their biomechanical effectiveness in mitigating head acceleration and reducing brain injury risk remains uncertain. This study aims to biomechanically assess available boxing equipment solutions and identify the brain–skull system’s response to physical forces from a boxing punch. A dedicated experimental setup was developed using mini triaxial accelerometers and a high-speed camera to measure head accelerations in a Primus unbreakable dummy. Tests were performed using gloves of different masses (0 oz, 10 oz, and 16 oz) and three head protection configurations: no helmet, rugby helmet, and boxing helmet. The resultant accelerations were analyzed and compared across test conditions. Peak wrist accelerations ranged from 195.00 to 271.77 m/s², while head accelerations did not exceed biomechanical injury thresholds. The boxing helmet, composed of multilayer polyurethane foam, did not consistently decrease acceleration; in some cases, it produced higher overloads due to increased head mass and moment of inertia. A rugby helmet made of open-cell EVA (ethylene vinyl acetate) foam with lower density exhibited more favorable energy-dissipation characteristics under low-impact conditions. Glove mass also influenced acceleration differently between male and female participants, likely due to variations in punch velocity and force generation. This work is a pilot study using two trained adult volunteers to validate the combined IMU–video measurement framework. The results serve as hypothesis-generating mechanistic observations rather than population-level effect estimates. Protective effectiveness in boxing depends on a complex interaction between material properties, geometry, and user biomechanics. Optimal equipment design should balance energy absorption and mass to minimize both linear and rotational accelerations. Future studies should integrate advanced material modeling and finite element simulations to support the development of adaptive, lightweight protective systems. Full article

The oxidation of flexible polyurethane (PUR) foams significantly impacts product durability, vehicle indoor air quality, and volatile organic compound (VOC) emissions. This study investigates oxidation kinetics and VOC emissions (65–155 °C) from foams with indices between 70 and 115 (molar ratio of NCO to NCO-reactive groups × 100), where a higher index represents greater hard segment (methylene diphenyl diisocyanate) and lower soft segment (polyether polyol) content. Using a flow-through setup with PTFE chambers and Tenax thermodesorption tubes and dinitrophenylhydrazine (DNPH) cartridges, VOCs from initial analyte loading, hydroperoxide degradation, and autoxidation were distinguished, providing robust kinetic data unaffected by diffusion interference. A higher index accelerated soft segment degradation, increasing oxidation rates and VOC emissions. The activation energy of 1,2-propanediol-1-acetate-2-formate increased from 87 kJ/mol in low-index to 108 kJ/mol in high-index formulations. VOC emissions from high-index foams were tripled for acetaldehyde during long-term aging at 65 °C. While most emissions followed Arrhenius behavior, formaldehyde and acrolein deviated above 100 °C, with higher hard-segment content extending their Arrhenius range. These findings link PUR composition to degradation behavior and emissions, enabling formulation improvements. The results advance methods for evaluating raw material contributions and the performance of antioxidants under realistic aging conditions. Full article

To overcome the typical limitations of conventional polyurethanes, including insufficient thermal stability, mechanical strength, and recyclability, this study presents a high-performance and reprocessable poly(urethane–urea) nanocomposite reinforced with Ti₃C₂T_x MXene (MX-AHPU). The formation of strong hydrogen bonds between the urea groups of the polymer and the oxygen-functionalized MXene surface was confirmed by FTIR, XRD, and XPS, which also verified the complete reaction of –NCO groups. MXene incorporation substantially improved thermal stability, as evidenced by TGA showing a higher onset decomposition temperature and increased char residue. DSC analysis indicated a raised glass transition temperature, reflecting restricted chain mobility. The composite demonstrated remarkable mechanical enhancement, with tensile strength increasing by 70% to 26.7 MPa and toughness rising by 28% to 311.8 MJ·m⁻³, while maintaining exceptional elongation (>3600%). Dynamic mechanical analysis revealed a lower activation energy for stress relaxation (26.6 kJ/mol for MX-AHPU, 30.9 kJ/mol for neat AHPU), indicating enhanced molecular mobility and energy dissipation. Importantly, the material exhibited excellent recyclability, retaining most of its mechanical performance after three reprocessing cycles due to the reversible nature of the interfacial hydrogen bonds. This work provides an effective strategy for designing sustainable, high-performance polyurethane–urea composites suitable for demanding applications such as flexible electronics and advanced coatings. Full article

To tackle the long-standing issue of inadequate corrosion protection in waterborne coatings, this study innovatively incorporates hollow glass microspheres (HGB) into waterborne epoxy zinc-rich primers through physical blending, constructing a dual-layer synergistic anticorrosion system comprising an HGB-modified primer and a zirconium phosphate/urushiol titanium polymer (UTPCZrP)-modified waterborne epoxy topcoat. Optimal performance is achieved with 2 wt% HGB addition: the dual-layer coating retains favorable physicochemical and mechanical properties while enhancing anticorrosion performance by 1–2 orders of magnitude, boasting an impedance of 3.2 × 10⁶ Ω, a corrosion rate as low as 5.71 × 10^–6 mm/year, 99.98% protection efficiency (stable after 25-day immersion), and 720 h salt spray resistance without corrosion diffusion. This method exhibits universality in waterborne polyurethane (WPU) and polyester (WPE) systems, yielding impedance values of 3.57 × 10⁶ Ω and 2.7 × 10⁶ Ω, respectively, with over 90% improved anticorrosion performance and long-term stability. By optimizing components and synergistic system design, this work significantly enhances waterborne coatings’ anticorrosion efficiency, reduces raw material costs, and provides a scalable technical pathway for high-performance, eco-friendly anticorrosion coatings. Full article

With the rapid development of infrared detection methods and military surveillance technologies, flexible and wearable infrared stealth materials (ISM) have attracted increasing attention. Inspired by the layered structure of penguins’ fat–feather–oil, this study prepared a three-layer MXene/waterborne polyurethane (WPU)-foam rubber-phase change microcapsule (PCM)/WPU composite material (M-F-P) via the solution blending and doctor-blading method. The outermost layer of the M-F-P composite is an MXene/WPU conductive film, which features a low infrared emissivity and Joule heating performance to adapt to suddenly cold environments. The porous foam rubber in the middle layer provides excellent thermal insulation performance, which effectively inhibits heat conduction and enhances infrared stealth efficiency. Meanwhile, as a four-directional elastic material, it exhibits deformation recovery capability in both the warp and weft directions as well as the 45° direction. The bottom layer of the PCM/WPU film has a phase change enthalpy of 154.3 J/g and possesses efficient thermal management capability. It achieves dynamic thermal regulation through the cycle of heat absorption at high temperatures and heat release at low temperatures. Full article

Wood, which is flammable, is commonly used as a building material and can be improved using a suitable surface treatment. A promising coating solution is polyurea, featuring properties like flexibility, mechanical resistance, resistance against water, etc., but it is also easily flammable. Expandable graphite (EG) is effective as a flame retardant and environmentally suitable. In this study, we studied the suitability of polyurea improved with EG. Spruce wood samples with dimensions of 50 mm × 40 mm × 10 mm were divided into eight groups, each including five samples. Each group was subjected to two applications of polyurea and EG in various combinations to examine the best combination with the lowest mass loss. The second component of the experiments aimed to examine the effectiveness of EG, which was applied in different weights. During the experiments, samples were thermally loaded in an apparatus for 10 min, where a heat flux of 30 kW·m⁻² was applied to the sample surface and the mass loss was continuously recorded. Lastly, thermal analysis was performed. The best results were observed for the combination of NEOPROOF mixed with 0.3 g of EG covered with NEODUR. The thermal analysis results revealed substantial differences: NEOPROOF, a polyurea, had only one degradation step, while NEODUR, which also contained polyurethanes, decomposed in several steps. Full article