Porous Polyurethane Foam Research Articles

Layered oxyiodide CdBiO2I: An efficient visible light responsive and scalable photocatalyst

Developing high-performance visible-light driven photocatalyst (λ≥420 nm) makes significance for the efficient utilization of solar energy. Mass production and easy recycling are equally important for the practical application of powdery photocatalyst. However, it is challenging to meet the above requirements at the same time. In this work, we develop an efficient visible-light responsive layered oxyiodide CdBiO2I nanosheets prepared by a facile direct precipitation method at ambient atmosphere, and demonstrate its upgradable features well fitting potential application. CdBiO2I has a layered crystal structure consisting of [CdBiO2]+ layer and I– single layer, differing from that of BiOI composed of [BiO2]2+ layer and I- double layers. It displays an absorption edge of 520 nm in visible region, with a band gap of 2.52 eV. CdBiO2I has a large intrinsic effective mass difference of hole/electron, exceeding BiOI by 8-fold, which results in much higher charge separation efficiency and production of more reactive species (superoxide radicals and holes). The degradation efficiency of CdBiO2I nanosheets for tetracycline hydrochloride reaches 84% under the visible light irradiation within 1 h, in which the degradation rate is 10 times that of BiOI. In addition, mass production (12 g catalyst at one time) and immobilization onto porous polyurethane foam of CdBiO2I powder are also demonstrated, which indicates the scalable properties and easy recovery of the catalyst, highlighting the advantages of the current preparation method and prefiguring its potential in practical applications. This work may enlighten future research on the exploitation of solar-driven catalyst with high efficiency and strong practical applicability.

Multifunctional and high‐stability RGO/PANI wrapped polyurethane foam for flexible piezoresistive sensor applications

AbstractDue to its excellent durability and steady mechanical qualities, three‐dimensional porous polyurethane foam (PUF) presents a wide range of possibilities for flexible piezoresistive sensors. Its extreme flammability, poor electrical conductivity, and susceptibility to outside factors present serious difficulties, though. In this study, a waterborne polyurethane‐coated flexible PUF sensor that incorporates reduced graphene oxide (RGO) and polyaniline (PANI) through a methodical, step‐by‐step dip‐coating methodology is successfully developed. The final product has a water contact angle of 133°, which improves its ability to adapt to a variety of environmental circumstances. Flexible graphene sheets are incorporated to improve heat resistance and flame retardancy, and PANI and RGO provide strong bonding to the PUF framework, ensuring outstanding structural stability even after 1500 cycles. The flexible foam sensor shows promise for use in flexible piezoresistive sensors and electronic skin due to its remarkable strain monitoring range of up to 70%, quick response time of 0.39 s in sensitivity experiments, and adaptability to different physical activities like walking and gesturing.

Sandwich-Structured Mxene/Waste Polyurethane Foam Composites For Highly Efficient Electromagnetic Interference, Infrared Shielding and Joule Heating.

Electromagnetic interference (EMI) shielding and infrared (IR) stealth materials have attracted increasing attention owing to the rapid development of modern communication and military surveillance technologies. However, to realize excellent EMI shielding and IR stealth performance simultaneously remains a great challenge. Herein, a facile strategy is demonstrated to prepare high-efficiency EMI shielding and IR stealth materials of sandwich-structured MXene-based thin foam composites (M-W-M) via filtration and hot-pressing. In this composite, the conductive Ti3C2Tx MXene/cellulose nanofiber (MXene/CNF) film serves as the outer layer, which reflects electromagnetic waves and reduces the IR emissivity. Meanwhile, the middle layer is composed of a porous waste polyurethane foam (WPUF), which not only improves thermal insulation capacity but also extends electromagnetic wave propagation paths. Owing to the unique sandwich structure of "film-foam-film", the M-W-M composite exhibits a high EMI shielding effectiveness of 83.37dB, and in the meantime extremely low emissivity (22.17%) in the wavelength range of 7-14µm and thermal conductivity (0.19W m-1 K-1), giving rise to impressive IR stealth performance at various surrounding temperatures. Remarkably, the M-W-M composite also shows excellent Joule heating properties, capable of maintaining the IR stealth function during Joule heating.

Efficient removal of Cd(II) and methyl orange from aqueous solution using 3D porous polyurethane foams incorporated with polyethyleneimine and sodium carboxymethyl cellulose

The heavy metals and organic substances has deterioration of the ecosystem, resulting in serious environmental pollutions, thus urgent solutions need to be developed in treating these waste water problems. Functional compounds modified 3D polyurethane foams, with high surface to volume ratio has paid much attentions due to their high efficiency of absorption capability. In this study, polyethyleneimine (PEI) was used to incorporated into polyurethane foam (PUF) loaded with sodium carboxymethylcellulose (SCMC), resulting in a cross-linked, 3D interconnective porous polyurethane foam (PCPUF). The results of adsorption experiments demonstrated that PCPUF exhibited a strong adsorption capacity for both MO and Cd2+, with corresponding maximum adsorption capacity of 415.198 mg/g (at 328 K, pH 7) and 166.48 mg/g (at 343 K, pH 7), respectively. Furthermore, the results of cyclic adsorption experiments showed that the removal rates of MO and Cd2+ after five cycles are 90 % and 85 %, respectively, indicating that PCPUF has a good recyclability. Therefore, 3D porous polyurethane foams show promise as an effective adsorbent for removing metal ions and organic substances.

Poly(ionic liquid) Grafted MXene via Si-ATRP and its Polyurethane Composite Foam: Mechanical, Flame Retardant and Sensing Properties

Compared with other types of sensors, capacitive flexible pressure sensors (CFPS), with low sensitivity, are more susceptible to environmental changes. It is still a considerable challenge to achieve high sensitivity, excellent mechanical properties and long-time structural stability simultaneously. Targeting the aforementioned issues, herein, Ti3C2 (MXene) with high dielectric constant was firstly chemically modified with a poly(ionic liquid) (PIL) via surface-initiated ATRP, and then combined with a porous polyurethane foam (PUF) 3D network structure via a one-step blending foaming method. Thanks to the organic-inorganic hybrid network based on the PU/MXene porous structures and the uniformly distributed micro-capacitor structure provided by MXene@PIL, the mechanical properties, structural stability, flame retardancy and dielectric properties of the composite foam were all significantly enhanced. When the content of MXene@PIL was 10%, the sensitivity of CFPS based on this dielectric were 17.1, 5.2, and 2.5/KPa in the pressure ranges of 0-1 KPa, 1-12 KPa and 12-100 KPa, respectively. In addition, the sensor showed the response and recovery times of 88 and 82 ms under a low pressure of 355 Pa. The light, flexible sensor prepared in this work is expected to be used in wearable devices to monitor physiological signals, and it should also be a good candidate for the next generation of man-machine interface characterization devices.

High output power moist-electric generator based on synergistic nanoarchitectonics for effective ion regulation

Moisture is ubiquitous in nature and life processes and contains huge amounts of energy. Moist-electric generation is an emerging energy technology that collects energy from the environment and converts it into electrical energy through the interaction of moisture with materials. However, the low power density of moist electric generators (MEG) hinders their further application, and improving the performance of MEG devices remains a challenge. Herein, we propose a synergistic nanoarchitectonics strategy to fabricate MEG by optimizing the paths of the ion generation, transmission and interception processes to obtain excellent power output performance. Highly hydrophilic poly (4-styrensulfonic acid) nano film was used to cover the surface of the porous polyurethane foam framework to form PU@PSS active composite with abundant movable ions, which also aided in water diffusion and provided evaporation channels. Gridded aluminum and PEDOT:PSS nano layer were used as the top electrode and interception layer because of their metallic activities and hydrogen ion adsorption capacities, respectively. Due to its effective water circulation and ion regulation properties, the MEG worked in an all-weather environment and converted energy from air moisture into high-power electrical energy. In addition, the MEG converted ambient heat energy to increase the efficiency of ion transport, thereby increasing the output power. A single MEG spontaneously produced a maximum open-circuit voltage of 1.25 V·cm−2 and a short-circuit current of 150 μA·cm−2 in a heated condition, and provided an ultra-high output power of 1.875 W·m−2 which is an order of magnitude higher than the output power provided by similar MEG devices. Thus, the strategy adopted achieved an ultra-high power output of moist-electric generation, which will inspire the development of next-generation MEG.

Integrated solar evaporator based on photothermal Cu-CuOx/NC with heat-insulated polyurethane foam enabling highly efficient salt-tolerant desalination and water purification

Renewable solar energy meeting photothermal materials provides a promising approach for freshwater production via interfacial steam generation. The design and manufacture of high-performance evaporators are still highly anticipated for practical applications. Herein, the robust and durable solar evaporator is proposed and fabricated by integration of photothermal Cu-CuOx/NC (CNC) and three-dimensional porous structure heat-insulated polyurethane (PU) foam with polyvinyl alcohol (PVA)/sodium alginate (SA) modifications. The designed PVA-SA-CNC/PU simultaneously possesses fast water transmission, broadband light trapping, satisfactory mechanical robustness and effective heat confinement. When applied as a solar evaporator, the PVA-SA-CNC/PU exhibits a high evaporation rate of 1.99 kg m−2 h−1 and operates stably within ten consecutive cycles under one-sun illumination, which can also handle salt tolerant desalination of seawater and saline water to sustainably produce freshwater. In addition, the functional versatility of the fabricated evaporator is explored to purify various wastewater. This study establishes a highly efficient integrated evaporator with multitasking water purification towards the solution of water shortage.

Thermal heat transfer and energy modeling through incorporation of phase change materials (PCMs) into polyurethane foam

Decreasing HVAC energy consumption through insulation effectiveness enables low energy use, low carbon emissions, and high thermal comfort in sustainable buildings. PCMs for energy storage are an innovative option, but in buildings, their high thermal conductivity is a concern.The PCM latent heat of fusion and thereby it’s transition temperature has been a key parameter in PCM selection but little is known of the effect of PCM on building energy contributions arising from increasing thermal conductivity (k), density (ρ), and specific heat capacity (Cp). To resolve this, in this paper, two PCMs with transition temperature above and below the outdoor temperature incorporated in highly porous flexible polyurethane foam were evaluated using a one-dimensional (1D) foam core panel built in COMSOL Multiphysics®. The simulations were run using the summer season in a humid subtropical climate zone with an outdoor temperature of 35 °C. It was found that apart from the latent heat of fusion, the combined effects of high ρ and Cp could mitigate the increased k of PU-PCM composites to improve the insulation performance. Building energy modeling using EnergyPlus with the foam core incorporated into a structural insulated panel (SIP), revealed that the use of PCMs regardless of the transition temperature could reduce annual electricity consumption by 15–20%, with a significant amount of energy savings arising from the cooling load in summer.

115 Laboratory Performances of the CIP 10 Personal Aerosol Sampler for the Collection of Submicron Particles

Abstract The CIP 10 is a personal aerosol sampler designed to sample conventional dust or specific occupational inorganic or organic substances such as crystalline silica, isocyanates or mycotoxins. It is widespread used, especially in France. Within the CIP10, the rotating cup contains a porous polyurethane foam devoted to the collection of airborne particles and rotates inside its housing at a speed close to 6700 rpm to induce a 7 or 10 L/min sampling airflow, depending on the particle-size selector. Despite several published works regarding its physical performances, no experimental data exist regarding the sampling efficiency for submicron particles. This study aimed to measure the collection efficiency of the CIP 10 for different types of foam (60 or 75 ppi, functionalized or not) and for the three selectors (inhalable, thoracic, respirable). Polydisperse particles with aerodynamic diameters between 20 nm and 10 µm were produced using various generators and different materials (DEHS, glass beads) in a specific test rig. For a given diameter, the collection efficiency was calculated by comparing the number concentrations measured alternatively upstream and downstream of the rotating cup, using APS (TSI 3321) or SMPS (Grimm DMA Vienna Type, CPC 5.403) spectrometers. While collection efficiency was 100% for particles > 3 µm, it progressively decreased to around 50 % and even below 10 % for aerodynamic diameters of 800 mm and 150 nm, respectively. Collection efficiency was unaffected by the type of foam or sampler flow rate used. Bias maps and consequences on workers aerosol exposure assessment will be discussed.

Lightweight and thermal insulation fabric-based composite foam for high-performance electromagnetic interference shielding

With the rapid development of electronic devices, electromagnetic interference (EMI) has posed serious threats to human health. Therefore, wearable materials with high EMI shielding performance are urgently required for protecting people from electromagnetic radiation. Herein, electroless plating and compression molding methods were utilized to fabricate sandwich structured composite foam. Aramid-carbon blend fabrics with Co–Ni coatings were selected as the surfaces, and the porous polyurethane (PU) foam doped with diverse content of carbon nanotubes (CNTs) served as the core lightweight layer. With the CNTs doping content of 3 wt%, a 3D conductive network is precisely constructed in the core foam with a tested 13.82 GPa tensile strength. Through a “reflection-absorption-reflection” triple-loss mechanism, the resulting composite foam possesses a favorable average EMI shielding effectiveness (SE) of 73.9 dB in the X band (8–12 GHz), which was far more than the requirement of 30 dB for common commercial EMI SE. In addition, the porous structure exhibits excellent thermal insulation properties within a wide range of temperature (0–150 °C) while presenting a low thermal conductivity of 0.0695 W/(m·K). Finally, the prepared composites were applied to the simulation scene of electromagnetic protection to explore its reliability and practicability as a wearable electromagnetic wave proof material. With the good combination of mechanical properties, thermal properties and excellent electromagnetic shielding properties, the prepared composites have a great application prospect in electromagnetic protective materials.

A study on modified fabric‐contained melamine/bentonite polyurethane foam: Pb2+ adsorption and mechanical properties

AbstractIn this study, a porous composite foam with excellent adsorption property toward Pb2+ was obtained by combining modified polyester (PET) fabric with polyurethane (PU) foam and using melamine and bentonite as modifiers. The effects of bentonite content on the adsorption and mechanical property of the modified fabric were studied. Based on the position of the modified PET fabric in porous PU foam, the P‐PU and PU‐P‐PU composite foams are prepared, and the effects of the fabric‐foam interface structure on the mechanical properties and adsorption properties were investigated. Effects of different experimental conditions such as pH value, contact time and initial dye concentration on adsorption capacity were investigated, and kinetic and isotherm of adsorption were used to analyze the adsorption mechanism of Pb2+ by foam. It was found that the porous composite foam have outstanding mechanical property and high adsorption efficiency. The adsorption was well‐described by pseudo‐second‐order kinetic and Langmuir isotherm models. Thus, the porous composite foam has great promise in removing heavy metal ions from water.

Biomimetic three-layer hierarchical scaffolds for efficient water management and cell recruitment

Taking inspiration from the structures of roots, stems and leaves of trees in nature, a biomimetic three-layered scaffold was designed for efficient water management and cell recruitment. Using polycaprolactone (PCL) and polyacrylonitrile (PAN) as raw materials, radially oriented nanofiber films and multistage adjustable nanofiber films were prepared through electrospinning technology as the base skin-friendly layer (roots) and middle unidirectional moisture conductive material (stems), the porous polyurethane foam was integrated as the outer moisturizing layer (leaves). Among which, radially oriented nanofiber films could promote the directional migration of fibroblasts and induce cell morphological changes. For the spatially hierarchically nanofiber films, the unidirectional transport of liquid was effectively realized. While the porous polyurethane foam membrane could absorb 9 times its weight in biofluid and retain moisture for up to 10 h. As a result, the biomimetic three-layered scaffolds with different structures can promote wound epithelization and drain biofluid while avoiding wound inflammation caused by excessive biofluid, which is expected to be applied in the field of skin wounds.

Removal of Hydrogen Sulfide from Swine-Waste Biogas on a Pilot Scale Using Immobilized Paracoccus versutus CM1.

Hydrogen sulfide (H2S) is a toxic and corrosive component that commonly occurs in biogas. In this study, H2S removal from swine-waste biogas using sulfur-oxidizing Paracoccus versutus CM1 immobilized in porous glass (PG) and polyurethane foam (PUF) biofilters was investigated. Bacterial compositions in the biofilters were also determined using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). The biofilters were first tested on a laboratory scale under three space velocities (SV): 20, 30, and 40 h-1. Within 24 h, at an SV of 20 h-1, PG and PUF biofilters immobilized with P. versutus CM1 removed 99.5% and 99.7% of H2S, respectively, corresponding to the elimination capacities (EC) of 83.5 and 86.2 gm-3 h-1. On a pilot scale, with the horizontal PG-P. versutus CM1 biofilter operated at an SV of 30 h-1, a removal efficiency of 99.7% and a maximum EC of 113.7 gm-3 h-1 were achieved. No reduction in methane content in the outlet biogas was observed under these conditions. The PCR-DGGE analysis revealed that Paracoccus, Acidithiobacillus, and Thiomonas were the predominant bacterial genera in the biofilters, which might play important roles in H2S removal. This PG-P. versutus CM1 biofiltration system is highly efficient for H2S removal from swine-waste biogas.

Construction of soft polyurethane cushioning composites based on integral fabric air layer: Reaching new levels in compression and cushioning behaviors

AbstractIn order to prepare a cushioning composite with good resilience and compressibility, the 3D fabric was perforated into a hexagonal honeycomb, high elasticity porous polyurethane foam was used as substrate, and the air layer structure was encapsulated with the packaging film. By changing the hexagonal side length and wall thickness of the honeycomb structure, the integral fabric air layer polyurethane buffer composite was prepared. The properties of the structure were studied, and its compressive capacity under different compressive strains was analyzed. The results show that the mechanical properties of polyurethane foam were improved after adding the integral fabric air layer structure. When the composite HPU‐R1L2 (polyurethane cushioning composites with 1 cm side length and 2 cm wall thickness of hexagonal honeycomb) was compressed to 75%, its compressive capacity was 8.24 times that of PU (Polyurethane foam with 2.5% bentonite). The prepared composite HPU‐R1L1 (Polyurethane cushioning composites with 1 cm side length and 1 cm wall thickness of hexagonal honeycomb) absorbed 96.7% of the energy in the dynamic impact test, indicating that the composite cushioning performance was stronger than that of polyurethane foam. The HPU composites based on the synergistic reinforcement strategy of polyurethane foam and monolithic fabric air‐layer structures are an excellent candidate in the field of commodity packaging and personal protection.

Lightweight Porous Polyurethane Foam Integrated with Graphene Oxide for Flexible and High-Concentration Hydrogen Sensing.

Reliable detection of high-concentration hydrogen (H2) leakage in sharp-vibration environments is highly desired such as in the application of space rockets. As hydrogen has to be detected simultaneously in a wide concentration range and at high concentrations (e.g., 100 v/v%) with outstanding linearity in response/concentration, lightweight features, and excellent tolerance against saturation and vibration, it remains challenging. Here, a flexible and high-concentration H2 sensing has been developed through "dipping-drying" a three-dimensional (3D) porous polyurethane (PU) foam integrated with graphene oxide (GO-PU). Multilayered honeycomb-structured graphene oxide appears to be tightly adhered to faveolate PU. Benefiting from the numerous adsorption sites of the "dual honeycomb" structure and abundant surface functional groups of GO, the GO-PU foam exhibits distinguished response and linearity toward 2-100 v/v% H2 and shows excellent lightweight, tailorability, and flexibility. Remarkably, the foam possesses outstanding sensing stability against 0-180° bending and low 0-20% straining, along with outstanding H2 sensing performance even after being pressed by a weight of 200 g, immersed in water, and frozen in a refrigerator at -10.8 °C. Practically, the GO-PU foam has potential for high-concentration H2 leakage detection, and our synthetic strategy may provide a way to avoid adsorbing saturation in other flexible gas sensing.

Unique biofilm structure and mass transfer mechanisms in the foam aerated biofilm reactor (FABR)

ABSTRACT The foam-aerated biofilm reactor (FABR) is a novel biofilm process that can simultaneously remove carbon and nitrogen from wastewater. A porous polyurethane foam sheet forms an interface between wastewater and aerated water, making it a counter-diffusional biofilm process similar to the membrane-aerated biofilm reactor (MABR). However, it is not clear how biofilm develops the foam interior, and how this impacts mass transfer and performance. This research explored biofilm development within the foam sheet and determined whether advective transport within the sheet played a significant role. Foam sheets with 2-, 4.5- and 9-mm thicknesses were explored. Oxygen, nitrate, nitrite and ammonia profiles in the sheet were measured using microsensors, and biofilm imaging studies were carried out using optical coherence tomography (OCT). On the foam’s aerated side, a dense nitrifying biofilm formed. Beyond the aerobic zone, much less biomass was observed, with a high porosity foam-biofilm layer. The higher effective diffusivity within the foam for the 4- and 9-mm sheets suggested advective transport within the foam channel structures. Using an effective diffusivity factor in conventional 1-D biofilm models reproduced the measured substrate concentration profiles within the foam. Four different practical conditions were modelled. The maximum TN removal efficiency was about 70% and a nitrogen removal flux of 1.25 gN.m−2.d−1. We conclude that mass transfer resistance occurred primarily in the dense, nitrifying layer near the aerated side. The rest of the foam sheet was porous, allowing the advective mass transfer.

Flexible Pseudocapacitive Iontronic Tactile Sensor Based on Microsphere‐Decorated Electrode and Microporous Polymer Electrolyte for Ultrasensitive Pressure Detection

AbstractWearable sensor as the initial terminal is in great requirement for people pursuing healthy life. High‐performance tactile sensors are the guarantee of accurate pressure information acquisition. Herein, a flexible iontronic tactile sensor is developed by utilizing a highly conductive poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) thin film decorated with polymethyl methacrylate microspheres as pseudocapacitive electrode and a porous polyurethane foam composited with Na+/Cl−ion‐enriched polyvinyl alcohol gel as polymer electrolyte through a facile method of solution‐casting followed by freeze‐drying. By taking advantages of both high pseudocapacitance and rationally designed microstructures, the developed tactile sensor shows an ultrahigh sensitivity (≈162.90 kPa−1), a broad detection range (≈160 kPa), a low detection limit (≈30 Pa), a fast response time (≈25 ms), and excellent repeatability and durability. Thanks to the ultrahigh sensitivity, the sensor is capable of detecting subtle pressures caused by dynamic micromotions such as touching a sandpaper surface, dropping water droplets, and adding water into a beaker. Application of a smart glove mounted with such sensor unit and array for a fast and accurate Braille recognition is also demonstrated. The proposed facile and efficient strategy of fabricating flexible ultrasensitive tactile sensors will be favorable to various wearable subtle pressure sensing applications.

3D shape-stable temperature-regulated macro-encapsulated phase change material: KAl(SO4)2·12H2O-C2H2O4·2H2O-CO(NH2)2 eutectic/polyurethane foam as core and carbon modified silicone resin as shell

• The configured KAl(SO 4 ) 2 •12H 2 O-C 2 H 2 O 4 •2H 2 O-Urea eutectic PCM possesses excellent thermal properties. • The enthalpy reduction of PCM@PUF is only 1.70% compared with PCM. • CMS thin-layer with enhanced mechanical properties guarantees the thermal stability of PCM. • PCM@PUF@CMS borrows from the structure of Micro-encapsulated PCM and magnifies it. Micro-encapsulated phase change materials (PCMs) have been confirmed a high-efficiency way to store latent heat, but their poor mechanical properties, expensive and complicated synthesis block their industrial application. Herein, borrowing from this structure and magnifying it, we prepared a novel 3D shape-stable temperature-regulated macro-encapsulated PCMs. The KAl(SO 4 ) 2 ·12H 2 O-C 2 H 2 O 4 ·2H 2 O-CO(NH 2 ) 2 (APSD-OAD-Urea) was configured as PCM to composite with light-weight porous polyurethane foam (PUF) framework, and the enthalpy reduction of PCM@PUF (core) was only 1.70%. Subsequent, carbon modified silicone resin (CMS, shell) was introduced to macro-encapsulate PCM@PUF. The results showed that with the optimized mass ratio of 75%APSD-25%OAD and extra addition of 10% Urea, the obtained PCM had a relatively high enthalpy (194.6 J/g), appropriate phase transition temperature (42.17 °C) and suppressed supercooling (0.504 °C). CMS thin-layer with 2.0 mm thickness increased resistance to deformation, impressions, scratches, and possessed a brilliant sealing effect on PCM@PUF to achieve leak-free and operation steady of PCM. PCM@PUF@CMS with low thermal conductivity from inside out displayed an outstanding thermal insulation performance. Moreover, the fluctuation of the thermodynamic property after 150 thermal cycles is relatively small. All these above enable the application of PCM@PUF@CMS in the thermal energy storage system and provide a novel strategy for the preparation of macro-encapsulated PCMs.

Polyurethane-Nanolignin Composite Foam Coated with Propolis as a Platform for Wound Dressing: Synthesis and Characterization.

This piece of research explores porous nanocomposite polyurethane (PU) foam synthesis, containing nanolignin (NL), coated with natural antimicrobial propolis for wound dressing. PU foam was synthesized using polyethylene glycol, glycerol, NL, and 1, 6-diisocyanato-hexane (NCO/OH ratio: 1.2) and water as blowing agent. The resultant foam was immersed in ethanolic extract of propolis (EEP). PU, NL-PU, and PU-NL/EEP foams were characterized from mechanical, morphological, and chemical perspectives. NL Incorporation into PU increased mechanical strength, while EEP coating showed lower strength than PU-NL/EEP. Morphological investigations confirmed an open-celled structure with a pore diameter of 150–200 μm, a density of nearly 0.2 g/cm3,, and porosity greater than 85%, which led to significantly high water absorption (267% for PU-NL/EEP). The hydrophilic nature of foams, measured by the contact angle, proved to be increased by NL addition and EEP coating. PU and PU-NL did not show important antibacterial features, while EEP coating resulted in a significant antibacterial efficiency. All foams revealed high biocompatibility toward L929 fibroblasts, with the highest cell viability and cell attachment for PU-NL/EEP. In vivo wound healing using Wistar rats’ full-thickness skin wound model confirmed that PU-NL/EEP exhibited an essentially higher wound healing efficacy compared with other foams. Hence, PU-NL/EEP foam could be a promising wound dressing candidate.

The Influence of Microstructure on Sound Absorption of Polyurethane Foams through Numerical Simulation

Front Cover: The structure of isocyanate contains unsaturated bonds and has high activity. It easily reacts with some organic or inorganic substances with active groups. In the preparation of polyurethane foam, a porous polyurethane foam can be generated by reacting isocyanate radicals with the hydroxyl compound in the plant-based polyol. This is reported by Shuming Chen and co-workers, in article number 2000075.