Search Results (250)

Contact-surface construction affects pressure distribution, physiological response, and perceived comfort in body-contact furniture. This study compared five contact interfaces for classroom nap chairs: rigid polypropylene (PP), a thermoplastic polyurethane (TPU)-surfaced PP laminate, woven mesh, closed-cell ethylene-vinyl acetate (EVA) foam, and flexible polyurethane (PU) foam. Twenty-six participants, including 13 females and 13 males, were tested in a 95° study posture and a 135° nap posture at the head–neck, waist–back, and hip–thigh regions. Four participant-level pressure indicators were direction-corrected and combined using an equal-weight geometric mean. The pressure index was integrated with electrodermal activity (EDA) at the participant level and subsequently combined across postures with weak subjective calibration. Under the 95° posture, EVA foam ranked highest at the hip–thigh region, while PU foam ranked highest at the waist–back and head–neck regions. Under the 135° posture, woven mesh ranked highest at the hip–thigh and head–neck regions, while PU foam remained highest at the waist–back region. Final integrated suitability differed significantly among materials in all three body regions (Friedman χ² (4) = 90.246–96.769, all p < 0.001). M4 had the highest mean in the head–neck region (0.648), but did not differ significantly from M5 (0.634; Holm-adjusted p = 0.075). M5 had the highest mean in the waist–back region (0.821), and M3 in the hip–thigh region (0.679); both were significantly higher than the corresponding second-ranked interfaces (Holm-adjusted p < 0.001). Exploratory stiffness models indicated peak locations near 130 kPa for the head–neck region and 140 kPa for the hip–thigh region, whereas the waist–back response was highest at the lower measured boundary of 70 kPa. These findings support region-specific interface design rather than a uniform contact surface for the entire chair. Full article

Titanium dioxide (TiO₂) photocatalysis is a promising sustainable solution for water decontamination; however, the industrial application of TiO₂ is hindered by its wide band gap and high handling and recovery costs. This work proposes to overcome these issues by developing a composite coating of nanopowder TiO₂ and reduced graphene oxide (rGO) applied onto commercial polyurethane (PU) foams by means of a simple, low-energy dip-coating process designed to enhance pollutant adsorption and photocatalytic activity. The rGO-TiO₂ coating was optimized by exploring different surface pre-treatments of the PU foams, the deposition of rGO-TiO₂ multilayers, and the variation in the rGO-TiO₂ mass ratio (1:3, 1:4, and 1:5). The prepared materials were characterized by optical microscopy, SEM-EDX, DSC, and thermogravimetry, while the stability of the coating was preliminarily evaluated through ultrasonic tests. The water decontamination capability of the coated foams was investigated by adsorption and UV-Vis photodegradation tests using a 3 mg/L aqueous solution of Rhodamine B (RhB) as a model contaminant. The results demonstrated that the rGO-TiO₂ 1:3-coated samples achieved complete RhB photodegradation within 90 min, with a pseudo-first-order kinetic constant of 0.0446 1/min. Moreover, pre-treating the foam with a 3 M NaOH solution improved coating adhesion onto the PU substrate while maintaining comparable decontamination efficiency. Full article

Polyurethane (PU) foams are widely used in footwear midsoles because their cellular structure, density, impact-attenuation capability, and mechanical durability can be tailored through formulation design. In this study, polyester-based PU foams were prepared at different isocyanate indices while keeping the main formulation components constant, and their structure-property relationships were evaluated under midsole-relevant conditions. The samples were characterized by density, tensile and compression testing, standard abrasion wear testing, water absorption, temperature-dependent flexural resistance, Fourier transform infrared (FTIR), scanning electron microscope (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis/derivative thermogravimetry (TGA/DTG), and dry/wet tribometry. FTIR results confirmed the formation of urethane/urea-related linkages and the absence of detectable residual isocyanate groups, whereas DSC indicated broad heat-flow events typical of segmented PU systems, including high-temperature events that should be interpreted together with TGA. TGA/DTG analysis showed similar initial degradation behavior for all formulations; however, the 138-index sample exhibited the highest t_90% value, indicating improved high-temperature mass retention. Tribometric tests revealed an environment-dependent coefficient of friction (COF) response: the 138-index sample exhibited the lowest steady-state COF under dry sliding (μ_ss = 0.211), whereas the 113-index sample showed the lowest COF value under wet sliding conditions (μ_ss = 0.176). Overall, among the three stable formulations investigated, the 113-index formulation exhibited the most balanced multi-property performance. These results suggest that, within the tested formulation range, midsole-relevant PU foam performance is associated with a balance of formulation characteristics rather than simply with increasing the isocyanate index. Full article

Rigid polyurethane foams (RPUFs) are widely used as lightweight thermal insulation materials. Their properties can be improved by incorporating inorganic fillers. However, the effect of filler particle size has not been sufficiently investigated. This study examines the influence of aluminosilicate microsphere diameter (80, 150, 300, and 500 μm) on the properties of RPUFs. Foams containing 10 wt.% microspheres (M) were prepared by the free-rise method. Their cellular structure, apparent density, mechanical, acoustic, thermal, and thermomechanical properties were evaluated. The addition of microspheres reduced the average cell diameter from 184 ± 29 μm for PU_0 to 147–174 μm, depending on microsphere size, and increased the apparent density from 31.3 to approximately 37 kg·m⁻³. The compressive strength decreased from 186 ± 6 kPa for PU_0 to 159 ± 2 kPa for PU_500M, whereas the tensile strength increased from 257 ± 14 kPa for PU_0 to 323 ± 14 kPa for PU_500M. The highest average sound absorption coefficient (0.14) was obtained for PU_300M, representing a 75% improvement over PU_0 (0.08). The composites also showed improved thermal stability and storage modulus. Among the investigated composites, PU_300M exhibited the most balanced combination of mechanical and acoustic properties. Full article

Rigid polyurethane foams are used in impact-attenuation systems due to their tunable cellular structure and energy dissipation capacity. However, expanded polystyrene (EPS), commonly used for impact protection, presents limitations related to impact attenuation performance and limited design flexibility. This study evaluates the impact performance of rigid polyurethane foams modified with diethanolamine and assesses formulation efficiency using Data Envelopment Analysis (DEA). Rigid PU foam formulations containing 0–3 wt% DEOA were synthesized and characterized by impact testing, apparent density measurements, Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy, and Thermogravimetric Analysis/Derivative Thermogravimetry. DEA was applied to correlate diethanolamine content with impact absorption efficiency. Excessive crosslinking and reduced energy dissipation were observed above 2 wt%, while concentrations below 0.5 wt% resulted in poorly structured foams. The formulation containing 1 wt% DEOA was identified as the most efficient among the investigated formulations, exhibiting the best overall performance, reducing transmitted peak acceleration by 13.8% compared with neat PU foam, while exhibiting an approximately 48% increase in apparent density, more complete consumption of NCO groups, a more uniform cellular structure, and only modest changes in thermal degradation behavior. These findings indicate that the improved impact performance is associated with the combined effects of increased apparent density, modified cellular morphology, and changes in the polyurethane network promoted by DEOA, underscore the promise of diethanolamine-modified rigid polyurethane (PU) foams for protective applications. Full article

Rigid polyurethane foam was evaluated as a filler material for a tubular railway vehicle energy absorber. Cubic samples cut from a cylindrical PU foam sample with a density of 175 kg/m³ were tested under quasi-static uniaxial compression to determine the material’s compressive response and provide input data for finite element modelling. The experimental results showed a non-linear stress–strain response typical of cellular foams, while samples from the central region of the cylinder exhibited a lower stress response than those from the outer region. An Ogden foam material model was calibrated in Ansys using compression data obtained by experimental tests and then applied to numerical models of three absorber configurations: an empty steel tube, a fully foam-filled steel tube, and a foam-filled tube with an additional concentric steel core. The simulations compared the force–stroke response and absorbed energy of each configuration under quasi-static axial loading through a conical bushing. Over a 60 mm stroke, compared to the empty tube, the fully foam-filled tube absorbed an additional 16% energy and the concentric-core configuration absorbed an additional 9.5%. These results indicate that rigid PU foam filling can improve the quasi-static energy absorption capacity of tubular railway collision absorbers. Full article

Soft polyurethane foams are commonly found in furniture, mattresses, shoes and soundproofing applications. These crosslinked foams are hard to recycle. This paper describes our approach of introducing chemical breakage points based on amino acid phosphoramidates (APtA) in the PUs’ backbones. The APtA monomers are combined with PEG, PPG and pTHF-chains to achieve different monomer structures. We demonstrate the hydrolysis of these APtA monomers at neutral pH 7 and the mass loss of the foams. It is shown that after 70 days, more than 50% of the p-THF-APtA monomer and 35% of the PPG-APtA monomer have degraded. However, a contrary trend was observed for the foams, with only 2.5% mass loss for the p-THF-APtA foam, but 26% mass loss for the PPG-APtA foam. The foams were also characterized using compression measurements, revealing a stiffer appearance of the p-THF-APtA foam compared to the foams based on PEG and PPG. SEM images were taken before and after the degradation of the foams to show the difference in morphology. Full article

Suberinic acids (SA) derived from birch outer bark are renewable feedstocks for bio-based polyols suitable for rigid polyurethane (PU) foams. Three SA fractions were prepared under different depolymerization conditions: acidification at pH 1 (SA1), pH 5 (SA2), and FeCl₃-assisted treatment (SA3), and their chemical composition was analysed by GC–MS, Py–GC/MS, and GPC–RID. Polyols derived from tall oil fatty acids (TOFA) or epoxidized TOFA with trimethylolpropane were used as the sole polyol components in foam formulations. The SA fractions differed in molecular weight distribution, affecting polyol processability. All foams exhibited similar limiting oxygen index (19–20) and cone calorimetry results, showing no statistically significant differences in flammability. This indicates that variations in depolymerization conditions, including polyphenolic content and removal of higher-molecular-weight fractions during FeCl₃ treatment, do not dominate fire performance under the studied conditions. SA3-based polyols showed the lowest viscosity and produced foams with optimal mechanical and thermal properties, while SA1 offered higher yield with comparable performance. These results demonstrate the feasibility of converting SA fractions into functional polyols for rigid PU foams and highlight the FeCl₃-treated SA3 fraction and SA1 as the most promising candidates for further development. Full article

This study evaluates the performance of foamed geopolymer concrete (FGC) incorporating rigid polyurethane (PU) waste as a partial sand replacement and aluminum powder (AP, 1%) as a foaming agent. The mixtures were based on metakaolin, fly ash, and silica fume. Fresh and hardened properties were assessed, including workability, setting time, density, compressive strength, flexural strength, splitting tensile strength, elastic modulus, water absorption, porosity, gas permeability, and chloride ion penetration. Microstructural characteristics were examined using scanning electron microscopy (SEM). The results show that moderate PU incorporation significantly enhances mechanical performance. The optimal mixture (PU30) achieved a compressive strength of 47.25 MPa at 180 days, representing a 15.6% increase compared to the control. Flexural and splitting tensile strengths improved by 19.9% and 16.7%, respectively, while the elastic modulus increased by 33.8% to 0.95 GPa. These improvements are attributed to enhanced particle packing and more efficient stress transfer within the matrix. In contrast, higher PU contents (>30%) reduced mechanical performance due to increased total porosity and weakened interfacial bonding. Durability-related properties indicated that mixtures PU20–PU30 exhibited reduced permeability and optimized pore structure, characterized by lower pore connectivity. SEM observations confirmed a denser matrix with uniformly distributed pores at optimal PU levels. Additionally, the integration of Random Forest regression with GLCM-based texture analysis demonstrated strong capability in predicting mechanical properties from SEM images. Overall, the combined use of PU waste and AP enables the production of lightweight, structurally efficient, and sustainable FGC with improved mechanical and durability performance. Full article

Construction industry remains a major driver of global resource use and waste generation, therefore, identifying sustainable material alternatives is increasingly important. Recycled-textile-based insulation presents a promising pathway to support circular economy principles by diverting post-consumer waste from landfills and reducing reliance on virgin petrochemical materials. This study conducts a cradle-to-gate life cycle assessment (LCA) using SimaPro to compare polyurethane (PU) foam and recycled denim (cotton fiber) insulation. The system boundary includes raw material extraction, transportation, and manufacturing. A functional unit of 1 m² of installed insulation with a thermal resistance of RSI = 1 m²·K/W at the factory gate ensures comparability, with mass-based results reported as secondary metrics. The results indicate that recycled denim exhibits higher embodied carbon per unit mass, despite lower production energy and lower cradle-to-gate impacts per installed area, reinforcing the need for a declared-unit-based comparison tied to thermal performance. Air leakage is evaluated separately as a complementary performance indicator influencing in-service energy behavior showing significantly lower air leakage for PU; but is not included in the cradle-to-gate normalization. However, it could be argued that materials with improved airtightness may enable the use of reduced insulation thickness while still achieving equivalent performance, thereby potentially lowering overall material demand. Nevertheless, recycled denim offers environmental advantages by reducing landfill waste and promoting resource conservation through material reuse. A transient coupled heat–moisture model in COMSOL Multiphysics, using climate data from Arizona and Florida, further reveals that denim absorbs more moisture than polyurethane. This leads to larger heat flux fluctuations, highlighting a trade-off between denim’s sustainability advantages and its reduced hygrothermal durability. Overall, these findings demonstrate the limitations of single-metric comparisons and emphasize the need for performance-based, multi-criteria assessments that integrate functional efficiency with circularity. Future research should incorporate occupant health and comfort to enable a more comprehensive evaluation of insulation sustainability. Full article

The need to reduce polyurethane (PU) foam waste has encouraged the development of sustainable foam formulations based on recycled raw materials and environmentally friendly additives, addressing both waste management and comparable foam properties to those based on fossil resources. In the present investigation, more sustainable water-blown rigid PU foams were investigated using recycled polyol and halogen-free flame retardants (FRs) for fire-resistant insulation applications. Two series of foam formulations were prepared: a first series with virgin polyol and the inclusion of a halogen-free FR additive (6 wt%) and a second series with recycled polyol (10% added respect to the total polyol) and halogen-free FR additives (6 wt%). Two types of FR were used: FR900, specifically identified as 3,9-Dimethyl-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane-3,9-dioxide, in powder form with 24% phosphorus content and reactive polyol based FR140, an oligomeric ethyl ethylene phosphate, in liquid form with 19% phosphorus content. The density, cellular structure, aged thermal conductivity, dimensional and hydrolytic stability, fire properties, and mechanical properties were characterized for novel foamed systems. Rigid foamed materials with very low densities around 50 kg/m³ were obtained. On the one hand, the inclusion of FR900 into the PU formulation containing virgin polyol generated foam with the lowest thermal conductivity (36.10 mW/mK) due to the smaller open cell content (11.7%) and cell size reduction (433 microns). On the other hand, the inclusion of recycled polyol reduced the foam density by 6 kg/m³ (44.1 kg/m³), increased the cell size average (848 microns) and open cell content (15.1%), maintained thermal conductivity (38.73 mW/mK), slightly improved the fire properties, and worsened the mechanical properties in comparison with the PU reference containing only virgin polyol. The results obtained by the foam containing recycled polyol and 6% FR900 are remarkable, presenting an increase in density (50.3 kg/m³) and in open cell content (73%), but a very high reduction in cell size (465 microns) and thus a low value of thermal conductivity of 37.04 mW/mK with respect to the reference material containing recycled polyol. Moreover, this PU foam containing recycled polyol and FR900 offered improved fire resistance (148.2 kW/m² of Maximum Average Rate of Heat Emission (MARHE), 179.1 kW/m² of Maximum Heat Release Rate (HRRmax), and 24.6 MJ/m² of Total Heat Release (THR)) and mechanical properties (6.97 MPa of Young’s modulus and 0.24 MPa of collapsed stress) for the construction sector. The inclusion of FR140 does not improve the properties of the foam system containing recycled polyol, mainly due to the deterioration of the cellular structure (in the open cell content and cell size). Full article

Benefiting from their outstanding porosity, considerable specific surface area, and natural flexibility, cellulose nanofibers (CNFs)/MOF materials have emerged as competitive candidates for advanced flexible energy storage devices. However, conventional CNFs/MOFs aerogels or films often suffer from poor recoverability under compression, bending, and folding, accompanied by severe plastic deformation that compromises the cycling and structural stability of devices. To address this issue, we report a rationally designed flexible PU/CNFs/ZIF-8/PANI composite foam with an interconnected micro-mesoporous structure. Using polyurethane foam as a soft substrate and CNFs/ZIF-8 as building blocks, the composite was fabricated through a combined strategy of impregnation, in situ ZIF-8 growth, hot-pressing, and in situ aniline polymerization with simultaneous etching of the ZIF-8. The incorporation of carboxylated CNFs enhances the hydrophilicity of the PU skeleton. This, in combination with the hot-pressed framework, establishes an interconnected 3D network, thereby effectively preventing the agglomeration of active materials. Meanwhile, the hierarchical pores derived from the sacrificial ZIF-8 template provide abundant electroactive sites, accelerate ion transport, and facilitate high PANI loading. By virtue of this synergistic architectural effect, the resultant electrode achieves a high specific capacitance of 449 F/g at 0.2 A/g, with 97% capacitance retention after 2000 cycles at 5 A/g. Furthermore, the composite foam demonstrates excellent mechanical flexibility, with a tensile strength of 0.87 MPa and an elongation at break of 230%. This work offers a feasible approach for developing high-performance flexible supercapacitors and provides novel perspectives for the rational design of portable energy storage devices. Full article

Rigid polyurethane foams are often manufactured in sealed molds, so knowledge of the density distribution in the molded blocks is essential. A study was conducted with the aim to estimate density distribution within a rigid polyurethane foam block (average core density of ≈96 kg/m³) manufactured in a rectangular sealed mold. The density of 150 rectangular samples was determined experimentally. Characteristic locations of the foams’ columns in the block were outlined, having similar foaming conditions. Averaged density in the characteristic columns was calculated for each characteristic location. A mathematical model was developed based on density data of characteristic columns, approximated with second- and third-degree polynomials. Density distribution was calculated, and corresponding color charts with density zones and equidensity lines were constructed for six horizontal and two vertical sections of the block. It was found that the common center of the elliptical equidensity lines is located asymmetrically, ≈17 mm above the geometric center of the untrimmed block. Density gradients were calculated in directions parallel and perpendicular to the foams’ rise direction. The developed mathematical model allowed us to estimate density distribution within the rigid polyurethane foam block manufactured in a rectangular sealed mold. Full article

The passive safety performance of trains is important. To ensure passenger safety and avoid vehicle climbing and excessive deformation in a collision, anti-climbing energy absorption devices can be installed at the end of each vehicle. In this study, two new types of anti-climbing energy absorption structures—a five-section frame filled with a PU foam core (FSF-F) and a five-section frame filled with a honeycomb aluminum core (FSF-H)—were prepared. The mechanical properties of the FSF-F and FSF-H structures were compared using a dynamic loading test and a simulation. The results showed that the energy absorption performance of the FSF-H was better than that of the FSF-F. Combined with the actual working conditions of a train, the mechanical properties of FSF-H under an offset load were further studied. The results show that it has good energy absorption performance under an offset impact and can be used as an energy absorption device at the end of the train carriage. Full article

Traditional flexible polyurethane (PU) foams frequently exhibit limited mechanical support and suboptimal moisture–heat regulation, which can compromise the microenvironmental comfort required for high-quality sleep. In this study, natural luffa fibers (LF) were incorporated as a microstructural modifier to simultaneously enhance the mechanical and moisture–heat regulation performance of PU foams. PU/LF composite foams with varying LF loadings were prepared via in situ polymerization, and their foaming kinetics, cellular morphology evolution, and physicochemical characteristics were systematically investigated. The results indicate that LF functions both as a reinforcing skeleton and as a heterogeneous nucleation site, thereby promoting more uniform bubble formation and controlled open-cell development. At an optimal loading of 4 wt%, the composite foam developed a highly interconnected porous architecture, leading to a 7.9% increase in tensile strength and improvements of 19.4% and 22.6% in moisture absorption and moisture dissipation rates, respectively, effectively alleviating the heat–moisture accumulation typically observed in unmodified PU foams. Ergonomic pillow prototypes fabricated from the optimized composite further exhibited enhanced pressure-relief performance, as evidenced by reduced peak cervical pressure and improved uniformity of contact-area distribution in human–pillow pressure mapping, together with an increased SAG factor, indicating improved load-bearing adaptability under physiological sleep postures. Collectively, these findings elucidate the microstructural regulatory role of biomass-derived luffa fibers within porous polymer matrices and provide a robust material basis for developing high-performance, sustainable, and ergonomically optimized sleep products. Full article