Polyurethane Films Research Articles

Complete recycling and valorization of waste cotton-spandex blended fabrics into value-added UV-blocking cellulose/graphene films and transparent polyurethane film

Complete recycling and valorization of waste cotton-spandex blended fabrics into value-added UV-blocking cellulose/graphene films and transparent polyurethane film

Efficacy of a Topical Nitric Oxide-Releasing Gel on Polymicrobial Wound Infections.

Wounds are colonized frequently by heterogeneous microflora. Pseudomonas aeruginosa (PA) and Staphylococcus aureus (SA) are two of the most isolated bacterial species from wounds, and both typically form highly organized biofilms. Nitric oxide (NO) is a short-lived, diatomic, lipophilic gas with antimicrobial activity. Recently, NO and its derivatives have been shown to exhibit broad-spectrum antimicrobial activity against bacteria, viruses, and parasites. P. aeruginosa strain ATCC 27312 or military isolate PA09-010 were combined with methicillin-resistant S. aureus strain MRSA USA300 to demonstrate the ability of NO to reduce polymicrobial infections in a porcine wound infection model. Deep partial-thickness wounds (10 mm × 7 mm × 0.5 mm) were made on four animals using a specialized electrokeratome. Wounds were inoculated with MRSA USA300 combined with PA09-010 in three animals and MRSA USA300 combined with PA27312 in one animal, then wounds were covered with polyurethane film dressings. After 48 hours, three wounds were recovered for baseline enumeration. The remaining wounds were randomly assigned to treatment groups and treated once daily. The NO topical gels tested were combinations of two phases, ointment phases with various concentrations (2-20%) combined with hydrogels with fast or slow release kinetics. A 4-day study with microbiological recovery was conducted on day 4. A separate 7-day study was also conducted, with microbial burden assessed on day 7. The largest efficacy against MRSA USA300 was observed for the NO formulation with 2% concentration and fast release kinetics. This treatment reduced the MRSA USA300 bacterial count by more than 99.97% and 99.95% from baseline in wounds co-infected with PA09-010 and PA 27312, respectively, at day 7. Treatments showed a minimal efficacy against PA27312 and PA09-010 strains in both assessment times. MRSA USA300 was reduced to a lesser extent when it was combined with PA27312 as compared to PA09-010. These studies demonstrate that NO-releasing topical formulations effectively reduce the MRSA burden in established biofilms composed of multiple microorganisms. Minimal efficacy against PA was observed. It has been demonstrated that MRSA bioburden is significantly reduced when inoculated together with P. aeruginosa. A better understanding of mechanisms of host-bacteria interactions, in single or mixed species biofilms, may lead to the development of novel therapeutic approaches. Overall, NO offers a promising alternative treatment against MRSA in polymicrobial infections.

A Self-Healing Transparent Waterborne Polyurethane Film with High Strength and Toughness Based on Cation-π Interactions.

Giving waterborne polyurethane (WPU) coatings self-healing properties not only maintains the coating's environmentally friendly characteristics but also extends the material's service life and enables sustainable development. Therefore, self-healing WPUs have received an increasing amount of attention from researchers. However, it is a serious challenge to overcome the original shortcomings of WPU coatings, such as poor strength, low hardness, and weak adhesion, as well as the introduction of self-healing properties resulting in further degradation of strength-mechanical properties and heat resistance. Here, we provide a design strategy to introduce a noncovalent physical cross-linking network based on cation-π interactions into the WPU molecular structure to prepare a series of self-healing transparent WPU coatings with high strength. The coating exhibited a very high tensile strength (66.11 ± 3.28 MPa) and excellent flexibility (0.5 mm), with a scratch repair efficiency of up to 98.2% for 12 h of repair at 60 °C. In addition, the coating also has good optical properties and has broad application prospects in the fields of transparent protective coatings and adhesives.

Biocompatible Carbon Dots/Polyurethane Composites as Potential Agents for Combating Bacterial Biofilms: N-Doped Carbon Quantum Dots/Polyurethane and Gamma Ray-Modified Graphene Quantum Dots/Polyurethane Composites.

Background: Pathogen bacteria appear and survive on various surfaces made of steel or glass. The existence of these bacteria in different forms causes significant problems in healthcare facilities and society. Therefore, the surface engineering of highly potent antimicrobial coatings is highly important in the 21st century, a period that began with a series of epidemics. Methods: In this study, we prepared two types of photodynamic polyurethane-based composite films encapsulated by N-doped carbon quantum dots and graphene quantum dots irradiated by gamma rays at a dose of 50 kGy, respectively. Further, we investigated their structural, optical, antibacterial, antibiofouling and biocompatibility properties. Results: Nanoelectrical and nanomechanical microscopy measurements revealed deviations in the structure of these quantum dots and polyurethane films. The Young's modulus of elasticity of the carbon and graphene quantum dots was several times lower than that for single-walled carbon nanotubes (SWCNTs) with chirality (6,5). The electrical properties of the carbon and graphene quantum dots were quite similar to those of the SWCNTs (6,5). The polyurethane films with carbon quantum dots were much more elastic and smoother than the films with graphene quantum dots. Antibacterial tests indicated excellent antibacterial activities of these films against a wide range of tested bacteria, whereas the antibiofouling activities of both composite films showed the best results against the Staphylococcus aureus and Escherichia coli biofilms. Biocompatibility studies showed that neither composite film exhibited any cytotoxicity or hemolysis. Conclusions: Obtained results indicate that these composite films could be used as antibacterial surfaces in the healthcare facilities.

The efficacy of a nitric oxide-releasing formulation on nares isolated Methicillin-Resistant Staphylococcus aureus in porcine wound infection model.

The colonization of Staphylococcus aureus (SA) acquired in nosocomial infections may develop acute and chronic infections such as Methicillin-Resistant Staphylococcus aureus (MRSA) in the nose. As a commensal microorganism with the ability to form a biofilm, SA can dwell on the skin, nostrils, throat, perineum, and axillae of healthy humans. Nitric oxide (NO) is an unstable gas with various molecular functions and has antimicrobial properties which are converted into many potential treatments. Methicillin-Resistant Staphylococcus aureus MRSA BAA1686 isolated from nasal infection was used in a porcine wound infection model. Deep partial-thickness wounds (10mm x 7mm x 0.5mm) were made on three animals using a specialized electrokeratome. All wounds were inoculated and then covered with polyurethane film dressings for biofilm formation. After 48 hours, three wounds were recovered from each animal for baseline enumeration. The remaining wounds were randomly assigned to six treatment groups and treated once daily. The treatment groups are as follows: NO topical ointments concentrations of 0.3, 0.9 and 1.8%, Vehicle Ointment, Mupirocin 2%, and Untreated Control. Microbiological recoveries were conducted on day 4 and day 7. The greatest efficacy observed from the NO formulations against MRSA BAA1686 was the 1.8% concentration. This agent was able to reduce more than 99% of bacterial counts when compared to Baseline, Vehicle Ointment, and Untreated Control wounds on both assessment days. Mupirocin 2% was the overall best treatment against MRSA BAA1686 on both assessment days, with a significant reduction (p ≤ 0.05) of 4.70 ± 0.13 Log CFU/mL from day 4 to day 7. Overall, the positive control Mupirocin 2% was the most effective in eliminating MRSA BAA1686 throughout the study. This experiment demonstrated a downward trend from the highest concentration of NO topical ointment formulations to the lowest concentrations on both assessment days (0.3% - 1.8%). Out of all NO topical ointments, the highest concentration (1.8%) was the most effective with the potential to be an alternative treatment against a MRSA nasal strain biofilm.

In vitro biostability testing of stent cover materials

Abstract Cast polyurethane films made of an aliphatic polycarbonate-based thermoplastic polyurethane (Carbothane PC) and poly(ether urethane) (Pellethane) were manufactured and their biostability under a static strain rate was investigated in vitroin comparison to unloaded samples. The PU films were stretched to an elongation of 300% and exposed to hydrogen peroxide/cobalt chloride (H2O2/CoCl2) solution for specific periods of time (up to 63 days). Unstrained PU samples were treated in the same way for comparison. The samples were observed for surface degradation via scanning electron microscopy and the bulk erosion by measuring the weight difference. The surface roughness greatly increased in strained Pellethane with scanning electron microscopy (SEM) evidence of deep cracks and holes or ragged and stretched fractures perpendicular to the direction of stress. Carbothane showed a lower degradation compared with Pellethane under mechanical constraint.

Investigation of Wettability, Thermal Stability, and Solar Behavior of Composite Films Based on Thermoplastic Polyurethane and Barium Titanate Nanoparticles.

Herein, composite films were produced by incorporating different amounts (1, 3, 5, and 7%) of barium titanate nanoparticles into the thermoplastic polyurethane matrix using a solution casting method. This study examined the impact of the presence and concentration of a barium titanate additive on morphologic properties, mechanical performance, thermal stability, solar behavior, and wettability of produced film samples. The films were characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, thermal gravimetric analysis, scanning electron microscope, ultraviolet-visible near-infrared spectrophotometer, water contact angle, and tensile strength measurements. In the present study, the mass loss of samples containing 7% barium titanate was 24% lower than that of the pure polyurethane reference. The increase of barium titanate rate added to polyurethane enhanced the solar reflectance property of the films, including the near-infrared region. As a prominent result, the transmittance value decreased significantly compared to the reference in the ultraviolet region, and it dropped to 3% for the highest additive concentration. The contact angle values of polyurethane films increased by 11-40% depending on the barium titanate addition ratio. The nano additive also positively affected the mechanical performance of the reference polyurethane film by slightly increasing the tensile strength values.

Highly breathable and stretchable strain sensors based on porous films for human motion and gas detection

With the rapid development of flexible wearable sensors in the fields of medical detection and environmental monitoring, it is urgent to develop multifunctional sensors with high sensitivity, fast response, wide sensing range, excellent comfort and multi-stimulus response. In this paper, a porous thermoplastic polyurethane (TPU) film with high stretchability and breathability was prepared by facial liquid phase separation, and a flexible wearable sensor was developed through vapor deposition of polypyrrole (PPy) within the porous TPU film matrix. The fabricated sensor can detect pressure, strain and gas, has a wide pressure detection range (up to 98 kPa), fast response speed (100 ms), sensitivity of up to 0.33 kPa−1 and working stability. Furthermore, it has an extremely high tensile strength of 790 % and can operate in the 0–400 % stretch range with a maximum sensitivity of 238.2. Importantly, the flexible porous TPU/PPy multifunctional sensor has excellent breathability and the capability to monitor NH3 gas, and the gas detection limit can reach 10 ppm. This work provides a new route for achieving high-performance and wearing comfortable strain sensors with broad application prospects in human activity detection and NH3 gas monitoring devices.

(Invited) Application of Liquid Metals in Battery Technology

Stretchable devices have many potential applications, including wearable electronics, robotics, and health monitoring. These mechanically adaptable devices and sensors can seamlessly integrate with electronics on curved or soft surfaces. Given that liquids are more deformable than solids, sensors and actuators utilizing liquids encased in soft templates as sensing elements are particularly suited for these applications. Such devices, leveraging ultra-flexible conductive materials, are referred to as stretchable electronics.Liquid metals (LMs) have emerged as one of a leading material in this field. In recent years, interest in liquid metals has surged, notably in flexible and soft electronics. When considering liquid metals, mercury often comes to mind due to its fluid state at room temperature. However, its high toxicity precludes its use in wearable technology. Instead, gallium-based liquid metals are preferred due to their safety in such applications.Gallium alone melts at about 30°C, but an alloy of 75% gallium and 25% indium lowers the melting point to 15°C. Adding 10% tin further reduces it to -19°C. These gallium-based liquid metals, which form low-viscosity eutectic alloys, have extremely low melting points and high biocompatibility. In addition, they rapidly form a thin oxide layer on their surface, which complicates patterning on substrates. To address this, metal nanoparticles like nickel can be blended using ultrasonic probing to create a malleable paste.These materials are still under research to explore additional functionalities. Liquid metals are particularly promising for self-healing materials and advanced wiring technologies for sensors and smart devices in stretchable electronics. More recently, their application in battery technologies in addition to sensors and wiring has been proposed. With ongoing advancements in flexible and stretchable electronics, the flexibility of lithium-ion batteries, essential for powering these devices, is also under investigation. This presentation discusses research on flexible battery electrodes using liquid metal and on materials for stretchable battery packages.In our first study, liquid metal served as a battery electrode, integrating the reaction and current collecting layers into a single process, thus simplifying manufacturing. However, this integration results in lower conductivity compared to traditional two-layer electrodes. By employing materials such as Li4Ti5O12 (LTO) or Li2TiS3 (LTS) with liquid metal, we developed a high-conductivity, printable liquid metal electrode ink that combines both functions.In a second application, liquid metal was used as an package for stretchable batteries. Recent studies on batteries have primarily focused on enhancing their stability and lifespan, with less attention to packaging. Conventionally, aluminum laminate film is used to prevent moisture and gas permeation in highly deformable batteries. Our study introduced a novel approach using a layer-by-layer technique to apply a thin liquid metal coating on a gold-coated thermoplastic polyurethane film, resulting in a stretchable packaging film with excellent gas barrier properties. This innovation not only enhances the battery's operational stability but also allows it to function reliably in atmospheric condition.The applications for liquid metals are extensive and hold promise for further exploration in various fields.

High modulus and strength polyurethane film synthesized from lignin-based polyol with various lignin contents and NCO/OH molar ratios

This study explored the synthesis of lignin-polyol (LP) by liquefaction of Kraft lignin in polyethylene glycol and glycerol. LP23 (23 wt% lignin) and LP41 (41 wt% lignin) were obtained with remarkable liquefaction yields of 97.43 % and 93.75 %, respectively. LP-based polyurethane film (LP-PUF) was then fabricated by reacting LP23 and LP41 with hexamethylene diisocyanate. Mechanical properties and hydrophobicity of LP-PUF were optimized by varying NCO/OH molar ratios. LP23-PUF1.9 with NCO/OH of 1.9 showed excellent tensile strength of 34.28 MPa and Young's modulus of 233.27 MPa, while LP41-PUF2.0 with NCO/OH of 2.0 exhibited good tensile strength of 26.03 MPa and Young's modulus of 260.66 MPa. LP23-PUF2.0 displayed high hydrophobicity as indicated by the water contact angle of 96.8° and low surface free energy of 15.68 mN/m. Glass transition temperature (Tg) of LP-PUF varied depending on lignin content and NCO/OH molar ratio. Specifically, the increase of KL content from 23 % to 42 % induced big rise of Tg by 8 °C. The NCO/OH induced change of Tg was relatively weak, as indicated by the small increase of −2.71 °C of LP41-PU1.4 to −1.81 °C of LP41-PUF2.0. The results of this work offer insights for lignin utilization as structural component of high modulus and high strength polyurethane film.

Biodegradation of commercial polyester polyurethane by a soil-borne bacterium Bacillus velezensis MB01B: Efficiency, degradation pathway, and in-situ remediation in landfill soil

Polyurethane (PU), a widely used and durable plastic, persists in the environment, resulting in significant waste management challenges. Therefore, developing eco-friendly degradation technologies, such as screening for efficient biodegrading microorganism strains, is urgently needed to address this issue. Bacillus velezensis MB01B, an efficient polyester PU-degrading bacterium, was isolated from landfill soil and demonstrated the ability to degrade 91.4% of 0.75% Impranil DLN within 24 h under the optimal conditions (30.5 °C and initial pH 6.5). To assess the degradation capability of MB01B, three PU substrates of increasing complexity—Impranil DLN film, polyester thermoplastic polyurethane (TPU) film, and commercial PU desk mat—were tested; after 30 days, weight losses of 24.8%, 18.3%, and 5.4% were observed, respectively. In addition, SEM images showed significant morphological changes on the surface of these PU materials after treatment with MB01B. FTIR analysis of Impranil DLN films following degradation showed reductions in key functional groups (ester and urethane); and the identification of neopentyl glycol and 1,6-hexanediol as degradation intermediates suggested MB01B possesses the capability to hydrolyze ester and urethane bonds. Concurrently, genome sequencing combined with RT-qPCR identified several enzymes, including urethanases and esterases/lipases, involved in PU degradation. Based on these results, the pathway for MB01B to degrade Impranil DLN was inferred. Finally, MB01B was successfully formulated into a solid microbial inoculum with favorable storage properties and used for in-situ degradation of the commercial PU materials (Impranil DLN films, TPU films and PU desk mats) in landfill soil, underscoring its potential for the in-situ biological treatment of PU plastic wastes.

Bioadhesive First-Aid Patch with Rapid Hemostasis and High Toughness Designed for Sutureless Sealing of Acute Bleeding Wounds.

The global military and civilian sectors express widespread concern over the significant hemorrhage associated with various acute wounds. Such bleedings lead to numerous casualties in military confrontations, traffic accidents, and surgical injuries. Consequently, the rapid control of the bleedings, particularly for extensive and pressurized wounds, is crucial in first-aid situations. In this work, a double-layered bioadhesive patch that combines a superabsorbent adhesive hydrogel with a highly tough antibacterial polyurethane film, which is called as Bio-Patch, is proposed. The Bio-Patch demonstrates superior mechanical strength and forms robust bioadhesion to acute bleeding wounds. Furthermore, the Bio-Patch enables protecting against external Gram-negative and Gram-positive bacteria. Thanks to the double-layered structures having synergistic functions of stable barrier and robust adhesion, the Bio-Patch provides optimal wound sealing (burst strength exceeding 310mmHg) both in vitro and in vivo. It also demonstrates superior hemostatic effects (less than 30 s) in vivo. This offers promising opportunities for rapid control of extensive and pressurized hemorrhage in first-aid clinical scenarios.

MXene-coated polystyrene microparticles for amorphous photonic crystal coating with enhanced color saturation, flame retardancy, and electromagnetic interference shielding

To enhance the color saturation of the amorphous photonic crystal (APC) coating composed of polystyrene (PS) microparticles, MXene nanosheets were deposited on the surface of the PS microparticles through strong electrostatic attraction. Three distinct colored APC coatings were achieved using Mayer rod-coating methods, employing PS microparticles of varying sizes. The intrinsic black nature of MXenes results in these coatings exhibiting high brightness of structural colors under ambient lighting conditions. Additionally, the three distinct colored APC coatings demonstrate high color saturation and low angular dependence. The thermal stability and flame retardancy of PS and PS@MXene microparticles with different MXene content were investigated. PS@MXene microparticles (three different diameters) containing 5 wt% MXene exhibited char residues of 11.0, 8.7, and 6.7 wt% at 700 °C during decomposition, whereas pure PS microparticles showed a char residue of <1.7 wt%. The peak heat release rate and total heat release of the PS@MXene microparticles were lower than those of pure PS, as characterized by a microscale combustion calorimeter. Furthermore, crack-free APC coatings on a black polyurethane substrate were successfully prepared using the Mayer rod-coating method, assisted by polyacrylic acid and ethylene glycol. The APC coatings containing PS@MXene microparticles with 5 wt% MXene, deposited on the surface of the polyurethane film, demonstrated shielding performances of approximately 20 dB. This work presents a straightforward and environmentally friendly method for constructing multifunctional APC coatings.

Thermally conductive, mechanically robust alumina-incorporated polyurethane films prepared by ultraviolet light curing

Abstract The development of heat dissipating composite materials for electronic systems can be expedited using alumina particles as modifiable polymer-matrix fillers. However, these composites are difficult to synthesize given the tradeoffs between thermal conductivity, insulating characteristics, and conduciveness to processing. To that end, the present study is focused on synthesizing environmentally friendly polyurethane films that could be cured by ultraviolet light within minutes, without requiring high-temperature heat treatment. Through the optimization of alumina modification, hybridization of thermally conductive fillers, filler content, and stirring time on the thermal conductivity of the polyurethane composites, this study improves the process for sustainability, low-cost, and convenient preparation. The experimental results confirmed that the use of surface modification and hybrid fillers is effective for enhancing the thermal conductivity, with the value of the polyurethane integrated with 50 wt% Al2O3 and 5 wt% Al2O3–poly (catechol/polyamine) being 76.40 wt% higher than that of pure PU (0.44 W/mK). Additionally, the use of hybrid fillers resulted in superior mechanical and thermal properties (such as tensile strain, tensile strength, thermal expansion coefficient, and temperature resistance) compared with those of pure PU and films incorporated with only a single filler.

Synthesis and Application of Dendritic Waterborne Polyurethane with Long Alkyl Chains and Silicone Chains as a Fluorine-Free Water Repellent

With environmental and health issues being raised, researchers have shifted their study from fluorinated to fluorine-free waterproof agents. However, most of the reported fluorine-free water repellents exhibit a significant drawback in their poor stability and durability of water repellency. In addition, the use of higher concentrations in these repellents results in the fabric becoming stiff, which negatively impacts the hand of the treated fabrics. To address these issues, dendrimer-like waterborne polyurethane prepolymers were initially synthesized using isophorone diisocyanate, polytetrahydrofuran, N-methyldiethanolamine, and trimethylolpropane as the primary materials. In this synthesis, sorbitan tristearate served as the dendrimer-like blocking agent, while single-ended bis-hydroxypropyl silicone oil was employed as functional monomers to enhance the hand and water repellency of the prepolymers. Then, dendrimer-like waterborne polyurethane was finished on the cotton fabric using a pad–dry–cure procedure. The test results showed that the water contact angle of dendrimer-like waterborne polyurethane film increased from 104.28° to 107.00° with the content of single-ended bis-hydroxypropyl silicone oil increasing, and the water contact angle of dendrimer-like waterborne polyurethane-finished fabrics reached 148.6° alone with a standard spray test rating of 90–95. In addition, the water contact angle of dendrimer-like waterborne polyurethane-finished fabrics was still greater than 140° even after five standard washes. The single-ended bis-hydroxypropyl silicone oil addition facilitated similar hand to the original fabric in dendrimer-like waterborne polyurethane-finished fabrics with high concentrations, surpassing market water repellents. This work is of great significance for improving the stability and durability of water repellency, and the hand of waterborne polyurethane fluorine-free water repellents in the textile industry.

Caffeic Acid Based Polyurethane Membrane Modified Screen-Printed Electrodes and Their Application for the Simultaneous Determination of Melatonin and Serotonin

Caffeic acid (CA) based polyurethane (PU) films were synthesized and characterized for the simultaneous determination of melatonin (MT) and serotonin (5-HT). The CA based PUs were synthesized using a polyol mixture of 4,4’-diisocyanodiphenylmethane (MPI), polyethylene glycol-200 (PEG), and CA. The PEG–CA monomer units in the polyol were varied in molar ratios of 99:1, 97:3, 95:5, and 90:10. The synthesized PUs were characterized by FTIR spectroscopy and thermal analysis. These CA based PU films were coated onto screen-printed carbon electrodes (SPCEs) with varying thicknesses and used for the simultaneous determination of MT and 5-HT. Electrochemical responses of MT and 5-HT were evaluated using differential pulse voltammetry. The limit of detection and correlation coefficient for MT were 280 µM and 0.9797, respectively, while for 5-HT, the detection was 150 µM with a correlation coefficient of 0.9690. The precision, expressed as the relative standard deviation was 2.633% for MT and 4.668% for 5-HT. These findings suggest that CA based PU-modified electrodes hold potential in medical and biomedical applications.

Comparative Analysis of Aliphatic and Aromatic Isocyanates on Soy-Based Polyurethane Films Modified with Schiff Base Diol

Comparative Analysis of Aliphatic and Aromatic Isocyanates on Soy-Based Polyurethane Films Modified with Schiff Base Diol

Synergistic antibacterial material of cetylpyridinium/Cu2+/sepiolite and its application in thermoplastic polyurethane films

Seeking non-antibiotic solutions against bacterial infections has become a global priority. Therefore, this work employs sepiolite as the carrier to load cetylpyridinium (CP+) and Cu2+, constructing a CP+/Cu2+/sepiolite (PCS) system with excellent antibacterial and application properties. Sepiolite, serving as a micro-container for storing antibacterial agents, enhances their thermal stability and realizes their “burst + sustained” release. Antibacterial agents improve the organic compatibility of sepiolite and provide a synergistic antibacterial effect. With the released antibacterial agents and contact inactivation effect, PCS at 10 mg/L and 75 mg/L achieve 100 % inactivation of Staphylococcus aureus and Escherichia coli within 120 min, respectively. Furthermore, the sepiolite carrier with an intact fibrous structure facilitates the loading-release and antibacterial activity of agents in PCS. The obtained PCS disperses uniformly in thermoplastic polyurethane and binds tightly with it, improving its mechanical properties. Film of ST-10wt%PCS with 10 wt% PCS inactivates 100 % of Staphylococcus aureus and 93.0 % of Escherichia coli in 4 h, while exhibiting superior elongation at break (263 %) and tensile strength (35 MPa) compared to the pure film (242 % and 30 MPa). Thus, it is evident that the resulting PCS holds promise for the direct use or manufacture of functional products to combat bacterial infections.

Robust Self-Healing Adhesives Based on Dynamic Urethane Exchange Reactions.

Thermoset polyurethanes (PUs) have been successfully reprocessed as covalent adaptable networks (CANs) by catalyzing carbamate exchange. Here we extend bond exchange beyond the internal network cross-links to create a dynamic urethane adhesive. Interfacing PU CANs to substrates with nucleophilic functional groups creates adhesives capable of reversible transcarbamoylation with the substrate, which has not been demonstrated previously by CAN adhesives. Two types of thermoset PU films were synthesized, one containing the green carbamate exchange catalyst Zr(tmhd)4 and the other containing no catalyst. Although otherwise identical in chemical and network properties, as indicated by FT-IR spectroscopy and dynamic mechanical thermal analysis (DMTA), the film containing catalyst showed dynamic bond exchange behavior through stress relaxation analysis. When evaluated as an adhesive, the CAN film exhibited self-healing properties and retained its adhesive strength for five cycles, which is attributed to reversible covalent bonding to the glass substrate. This work expands industrially relevant CANs to structural adhesives and demonstrates their potential value in an application that presently employs PUs as single-use materials.

Evaluating a novel portable semiconductor liquid cooling garment for reducing heat stress of healthcare workers in a hot-humid environment

Limited research focused on exploring personal cooling garments (PCGs) that offer excellent portability, along with a substantial, long-lasting, and consistent cooling effect for healthcare workers exposed to extreme heat while combating the COVID-19 pandemic. To address this gap, a novel, energy-efficient, and portable semiconductor liquid cooling garment (SLCG) was introduced, which incorporates a semiconductor-powered cold source and a cooling vest crafted from a semi-transparent thermoplastic polyurethane (TPU) film that offers extensive body coverage. Its practical cooling efficacy was assessed through a human trial involving ten male participants engaging in two protocols under a hot-humid environment (i.e., 30 ± 0.5 °C, RH = 80 ± 5 %). These protocols included both low-intensity (Prot.1) and moderate-intensity (Prot.2) exercises, mimicking the physical demands faced by healthcare workers. SLCG significantly reduced the mean, torso and local skin temperatures during both Prot.1 and Prot.2 (p < 0.05), also with a notable reduction in heart rate and sweat loss during Prot.1 (p < 0.05). Rating of perceived exertion as well as thermal sensations, wetness sensations and comfort sensations in the whole-body and local-body (i.e., head & neck, trunk, arms and legs) were all remarkably improved using SLCG during Prot.1 (p < 0.05). These perceptual sensations in SLCG were only improved in the whole body during the resting stage, and in the trunk region during Prot.2 (p < 0.05). Furthermore, participants felt no significant added weight or movement restrictions with SLCG in either protocol.