Polyurethane Membrane Research Articles

Preparation of degradable castor oil-based waterborne polyurethane with tannic acid as crosslinking agent and its application on leather surface coating

In recent years, the types and quantities of polyurethane products have increased day by day. However, traditional petroleum-based water-based polyurethanes not only have the problem of difficult waste disposal, but also accelerate the depletion of petroleum materials. Herein, an eco-friendly polymer was successfully prepared by introducing tannic acid (TA) into castor oil-based waterborne polyurethane (WPU). The effects of the incorporation of TA, a bio-based material, on the particle size of the resulting polyurethane (PU) dispersion, and the thermal performance, mechanical properties, and hydrophobicity of PU membranes were systematically investigated. Finally, ATR-FTIR and SEM of cured films after degradation were measured to characterize the degradation ability of the membranes. It was found that the tensile strength of the samples is improved from 12.67 to 19.57 MPa with the TA content increasing from 0 to 1.5%, nevertheless their elongation at break declines from 306.51 to 237.12%. A noteworthy increase in the glass transition temperature (Tg) was exhibited by using DSC and DMA for the resulting PU films with increasing the TA content. Besides, the improvement in the water absorption of the blend films decreases from 14.5 to 10.2% according to the advantage of TA increasing the degree of cross-linking of the system. After 120 days of degradation, it can be seen that the urethane bond and the aliphatic ester bond played a vital role in the degradation process through the infrared of the degraded films. At the same time, the introduction of TA improves the degradation performance of WPU films. What is more, the application of WPU dispersions containing tannins on the leather surface shows excellent comprehensive performance, which means that WPU dispersions have potential applications as leather finishing agents. This work takes advantage of two kinds of bio-based materials, the mass of bio-based materials accounts for 57% of the total mass, which not only shortens the utilization of petroleum resources, but also effectively resolved the problem that poor quality of castor oil-based WPU and traditional waste is difficult to degrade, improving the commercial value of castor oil-based PU.

Stencil Printing of Liquid Metal upon Electrospun Nanofibers Enables High-Performance Flexible Electronics.

Flexible electronics as an emerging technology has demonstrated potential for applications in various fields. With the advent of the Internet of Things era, countless flexible electronic systems need to be developed and deployed. However, materials and fabrication technologies are the key factors restricting the development and commercialization of flexible electronics. Here we report a simple, fast, and green flexible electronics preparation technology. The stencil printing method is adopted to pattern liquid metal on the thermoplastic polyurethane membrane prepared by electrospinning. Besides, with layer-by-layer assembly, flexible circuits, resistors, capacitors, inductors, and their composite devices can be prepared parametrically. Furthermore, these devices have good stretchability, air permeability, and stability, while they are multilayered and reconfigurable. As proof, this strategy is used to fabricate flexible displays, flexible sensors, and flexible filters. Finally, flexible electronic devices are also recycled and reconfigured.

Optimization of a New Integrated Separation Process for Azeotropes Based on Genetic Programming

AbstractA solution strategy of a distillation‐membrane separation process based on genetic programming algorithm (GP) is proposed. It can automatically match diverse membrane materials according to different azeotropic systems and generate various integrated processes. For the membrane, which is still in the experimental research stage, a theoretical prediction method of membrane cost is recommended. Taking the benzene‐cyclohexane system as an example, a GO‐AgNPs/PI membrane and polyurethane membrane were matched, respectively, and the optimal integrated processes can be obtained. The GP strategy provides a strong guidance for the comprehensive design and optimization of distillation‐membrane separation by using various new membranes.

Gamma radiation for sterilization of textile based materials for personal protective equipment

In a pandemic context, personal protective equipment (PPE) as protective clothing is essential to ensure the safety of health professionals, caregivers and patients. Although most of the PPE is disposable, it can be effectively and safely reused once sterilized and washed, as long as they keep an adequate performance. The reuse of PPE also brings unquestionable benefits both in economic and environmental terms. This work aims to evaluate the possibility of using gamma irradiation to sterilize textile materials, with different compositions, intended to be used in the production of PPE. It was determined the number of cycles of sterilization followed by washing + drying that each material was able to withstand, while keeping adequate properties. Changes in morphology, colour, wettability, liquid permeability, and mechanical resistance of the materials were evaluated after different number of cycles and related with modifications in their chemical structure and eventual physical degradation. It was found that two materials, a Jersey knitted fabric 50% cotton/50% polyester and a Twill woven fabric 100% polyester, both coated with a 100% polyurethane membrane (samples A2 and A6, respectively) were able to withstand at least 20 cycles without suffering significant morphological or structural modifications. More, sterilization tests proved that even after that number of cycles, the materials can be efficiently sterilized by gamma irradiation. These results will allow more time to refill supply stocks, in case of an exceptional event such as a pandemic outbreak.

Metal-phenolic networks modified polyurethane as periosteum for bone regeneration

Treatment of bone defects still poses a great challenge in orthopedic clinics, and the vital role of periosteum in such processes has attracted widespread attention. However, studies focusing on the oxidative stress micro-environment with an artificial periosteum at the site of defect have been scarce. The intrinsic anti-oxidative properties and therapeutic potential for bone defects of metal-phenolic networks (MPNs) have provided a potential solution to this. Herein, we have developed a protocatechualdehyde + zinc ion (PCA+ZnⅡ) MPN coating on a thermoplastic polyurethane membrane with a one-pot method to fabricate a new-type of periosteum with meritorious biocompatibility and abilities of modulating oxidative stress condition and promoting osteogenesis and mineralization for better bone regeneration, which has shown to be a promising strategy for constructing artificial periosteum with various MPNs.

MoS2@ZIF-8 doped waterborne polyurethane membranes with water vapor permeable, lubricating, and antibacterial properties

In this research, a multi-functional waterborne polyurethane (WPU) membrane was developed through the in-situ synthesis of molybdenum disulfide/zeolitic imidazolate framework-8 (MoS2@ZIF-8) nanoparticles and then the introduction of these nanoparticles into a waterborne polyurethane emulsion. The photocatalysis of MoS2@ZIF-8 nanoparticles were improved due to the rapid transfer of photo-inspired electrons from MoS2 to ZIF-8, resulting in higher yields of reactive oxygen species (ROS) to kill bacteria. Hence, inactivating 93% and 99.3% of E. coli and S. aureus after 60 min, respectively. Moreover, the inactivation using the MoS2@ZIF-8 nanoparticles was dramatically superior to the pure MoS2 and ZIF-8. Additionally, compared with a pure WPU membrane, the mechanical properties of the composite membranes increased significantly, where the maximum tensile strength and elongation at break reached 51 MPa and 237%, respectively. Meanwhile, the introduction of the MoS2@ZIF-8 nanoparticles into the WPU membrane at a concentration of 0.5% improved the water vapor permeability to as high as 215.55 g/(m2·24 h) and enhanced the tribological properties with an ultralow friction coefficient (0.05). Therefore, the MoS2@ZIF-8/WPU composite membranes show promise as multifunctional coating materials due to their high water vapor permeability, good lubricating performance, and photo-responsive disinfection properties.

Synthesis of Polyurethane Membranes Derived from Red Seaweed Biomass for Ammonia Filtration

The development of membrane technology is rapidly increasing due to its numerous advantages, including its ease of use, chemical resistant properties, reduced energy consumption, and limited need for chemical additives. Polyurethane membranes (PUM) are a particular type of membrane filter, synthesized using natural organic materials containing hydroxy (-OH) groups, which can be used for water filtration, e.g., ammonia removal. Red seaweed (Rhodophyta) has specific molecules which could be used for PUM. This study aimed to ascertain PUM synthesis from red seaweed biomass (PUM-RSB) by using toluene diisocyanate via the phase inversion method. Red seaweed biomass with a particle size of 777.3 nm was used as starting material containing abundant hydroxy groups visible in the FTIR spectrum. The PUM-RSB produced was elastic, dry, and sturdy. Thermal analysis of the membrane showed that the initial high degradation temperature was 290.71 °C, while the residue from the thermogravimetric analysis (TGA) analysis was 4.88%. The PUM-RSB section indicates the presence of cavities on the inside. The mechanical properties of the PUM-RSB have a stress value of 53.43 MPa and a nominal strain of 2.85%. In order to optimize the PUM-RSB synthesis, a Box–Behnken design of Response Surface Methodology was conducted and showed the value of RSB 0.176 g, TDI 3.000 g, and glycerin 0.200 g, resulting from the theoretical and experimental rejection factor, i.e., 31.3% and 23.9%, respectively.

Biocompatibility studies of polyurethane electrospun membranes based on arginine as chain extender

Electrospun polymers are an example of multi-functional biomaterials that improve the material-cellular interaction and aimed at enhancing wound healing. The main objective of this work is to fabricate electrospun polyurethane membranes using arginine as chain extender (PUUR) in order to test the fibroblasts affinity and adhesion on the material and the polymer toxicity. Polyurethane membranes were prepared in two steps: (i) the polyurethane synthesis, and ii) the electrospinning process. The membranes were characterized by scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy, gel permeation chromatography, and differential scanning calorimetry techniques. The evaluation of PUUR as a scaffolding biomaterial for growing and developing of cells on the material was realized by LIVE/DEAD staining. The results show that the fluorescent surface area of human fibroblasts (hFB), was greater in control dense membranes made from Tecoflex than in electrospun and dense PUUR. From SEM analysis, the electrospun membranes show relatively uniform attachment of cells with a well-spread shape, while Tecoflex dense membranes show a non-proliferating round shape, which is attributed to the fiber’s structure in electrospun membranes. The cell morphology and the cell attachment assay results reveal the well spreading of hFB cells on the surface of electrospun PUUR membranes which indicates a good response related to cell adhesion.

Application of graphene structure/polyurethane membrane in pervaporative desulfurization

AbstractPervaporation (PV) desulphurization based on membrane technology has a great perspective for sulfur removal from transportation fuels. Herein, a unique two‐dimensional structure material–graphene egg yolk‐shell nanostructure (GYSNs) with high‐specific surface area and high dispersibility was prepared. In addition, the resultant GYSNs was incorporated into polyurethane (PU) matrix to fabricate mixed matrix membranes (MMMs). The MMMs were adopted to permselectively pervaporate thiophene with a thiophene/n‐octane solution as the model gasoline system and presented an elevated overall desulfurization performance as compared to the pristine PU membrane. Effects of GYSNs loading and operational variables including feed sulfur concentration, feed temperature, and operating time on the desulfurization performance were discussed. It was found that the MMMs with 0.8 wt% GYSNs loading had a permeation flux of 1411 g·m−2·h−1 and an enrichment factor of 4.32 at 303 K for PV desulfurization of a 1312 ppm thiophene/n‐octane mixture. Noteworthy was that the as‐fabricated MMMs displayed long‐term operation stability. This is a positive step forward for practical applications of MMMs in gasoline desulfurization.

Highly Efficient Self-Repairing Slippery Liquid-Infused Surface with Promising Anti-Icing and Anti-Fouling Performance.

Smart slippery liquid-infused porous surfaces (SLIPSs) have aroused remarkable attention owing to tremendous application foreground in biomedical instruments and industry. However, challenges still remain in fabricating durable SLIPSs. In this work, a fast and highly efficient self-repairing slippery surface (SPU-60M) was fabricated based on a polyurethane membrane and silicone oil. By introducing a great quantity of reversible disulfide bonds into the polymer backbone and hydrogen bonds in the polymer interchain, this SLIPS material could be quickly repaired in 15 min with 97.8% healing efficiency. Moreover, the self-healing efficiency could be maintained at 42.75% after the 10th cutting-healing cycle. Notably, SPU-60M showed excellent self-repairing ability not only in an ambient environment but also in an underwater environment and at ultralow temperatures. Besides, the icing delay time (DT) of SPU-60M could be prolonged to 1182 s at -15 °C, and the ice adhesion strength was only 10.33 kPa at -30 °C. In addition, SPU-60M had excellent anti-fouling performance with BSA adsorption of 2.41 μg/cm2 and Escherichia coli CFU counts of 41 × 104. These findings provide a facile way to design highly efficient self-repairing SLIPSs with multifunctionality.

A sandwich structure composite wound dressing with firmly anchored silver nanoparticles for severe burn wound healing in a porcine model.

Wounds may remain open for a few weeks in severe burns, which provide an entry point for pathogens and microorganisms invading. Thus, wound dressings with long-term antimicrobial activity are crucial for severe burn wound healing. Here, a sandwich structure composite wound dressing anchored with silver nanoparticles (AgNPs) was developed for severe burn wound healing. AgNPs were in situ synthesized on the fibers of chitosan nonwoven fabric (CSNWF) as the interlayer of wound dressing for sustained release of silver ion. The firmly anchored AgNPs could prevent its entry into the body, thereby eliminating the toxicity of nanomaterials. The outer layer was a polyurethane membrane, which has a nanoporous structure that could maintain free transmission of water vapor. Chitosan/collagen sponge was selected as the inner layer because of its excellent biocompatibility and biodegradability. The presence of AgNPs in the CSNWF was fully characterized, and the high antibacterial activity of CSNWF/AgNPs was confirmed by against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. The superior wound healing effect on deep dermal burns of presented composite wound dressing was demonstrated in a porcine model. Our finding suggested that the prepared AgNPs doped sandwich structure composite wound dressing has great potential application in severe wound care.

β-Cyclodextrin functionalized polyurethane nano fibrous membranes for drug delivery

The present study gives an investigation on the physico-chemical property changes occurred for the β-cyclodextrin (CD) functionalized polyurethane (PU) fibrous membranes. Modified PU membranes exhibited lower fiber diameter which can positively promote activity of the membranes in biomedical applications. Functionalized membranes also showed higher hydrophilicity and thermal stability. Incorporation of CD could also provide higher vapour transmission rate, hemocompatibility and cell viability for PU membranes. 15 wt% CD incorporated PU membrane (PU/15CD) exhibited better physico-chemical properties and were used for drug loading studies. To provide better biological performance, PU/15CD membranes were further functionalized with nanochitosan (NC). An antibacterial drug gentamicin sulphate was used for providing antibacterial activity to the system. The gentamicin releasing ability and antibacterial activity of the drug loaded PU/15CD-5NC membranes were investigated. The modified membranes exhibited better drug releasing potency than PU membrane. Hence, the fabricated antibacterial fibrous membranes can be suggested for drug delivery applications.

Monitoring of Lactate in Interstitial Fluid, Saliva and Sweat by Electrochemical Biosensor: The Uncertainties of Biological Interpretation

Lactate electrochemical biosensors were fabricated using Pediococcus sp lactate oxidase (E.C. 1.1.3.2), an external polyurethane membrane laminate diffusion barrier and an internal ionomeric polymer barrier (sulphonated polyether ether sulphone polyether sulphone, SPEES PES). In a needle embodiment, a Pt wire working electrode was retained within stainless steel tubing serving as pseudoreference. The construct gave linearity to at least 25 mM lactate with 0.17 nA/mM lactate sensitivity. A low permeability inner membrane was also unexpectedly able to increase linearity. Responses were oxygen dependent at pO2 < 70 mmHg, irrespective of the inclusion of an external diffusion barrier membrane. Subcutaneous tissue was monitored in Sprague Dawley rats, and saliva and sweat during exercise in human subjects. The tissue sensors registered no response to intravenous Na lactate, indicating a blood-tissue lactate barrier. Salivary lactate allowed tracking of blood lactate during exercise, but lactate levels were substantially lower than those in blood (0–3.5 mM vs. 1.6–12.1 mM), with variable degrees of lactate partitioning from blood, evident both between subjects and at different exercise time points. Sweat lactate during exercise measured up to 23 mM but showed highly inconsistent change as exercise progressed. We conclude that neither tissue interstitial fluid nor sweat are usable as surrogates for blood lactate, and that major reappraisal of lactate sensor use is indicated for any extravascular monitoring strategy for lactate.

Enhanced water and oxygen barrier performance of flexible polyurethane membranes for biomedical application

In order to improve water and oxygen barrier properties, the surface of two commercial medical grade polyurethane (PU) membranes (Chronoflex® AR-LT and Bionate® II) was modified by a spray deposited film of poly(ethylene-co-vinyl alcohol) (EVOH). The influence of the temperature, the deposited layer thickness and the EVOH ethylene group percentage (27%, 32%, and 44% for EVOH27, EVOH32, and EVOH44, respectively) on the barrier properties of the PU/EVOH multilayered membranes was investigated. The increase of the EVOH layer thickness leads to higher oxygen barrier properties (the highest barrier improvement factor of 412 was obtained). However, in case of the deposited layer thickness higher than 18 μm, microcracks appeared on the treated surface promote a significant loss of the barrier effect. Due to its higher crystallinity degree, EVOH27 provides a higher oxygen barrier effect compared to EVOH32 and EVOH44. On the contrary, an increase of the water barrier properties was observed with the increase of the percentage of ethylene groups. Moreover, the delamination of the EVOH layer was noted after water permeation, especially in case of EVOH44, which is the most hydrophobic layer. Nevertheless, significant decrease of the water and oxygen permeability of the modified PU membranes was achieved, thus showing the benefit of using the EVOH spray deposition for the biomedical application, which requires high performance material with flexible and barrier properties.

Surface Modification of Polyurethane Membrane with Various Hydrophilic Monomers and N-Halamine: Surface Characterization and Antimicrobial Properties Evaluation.

Reducing microbial infections associated with biomedical devices or articles/furniture noted in a hospital or outpatient clinic remains a great challenge to researchers. Due to its stability and low toxicity, the N-halamine compound has been proposed as a potential antimicrobial agent. It can be incorporated into or blended with the FDA-approved biomaterials. Surface grafting or coating of N-halamine was also reported. Nevertheless, the hydrophobic nature associated with its chemical configuration may affect the microbial interactions with the chlorinated N-halamine-containing substrate. In this study, a polymerizable N-halamine compound was synthesized and grafted onto a polyurethane surface via a surface-initiated atom transfer radical polymerization (SI-ATRP) scheme. Further, using the sequential SI-ATRP reaction method, different hydrophilic monomers, namely poly (ethylene glycol) methacrylate (PEGMA), hydroxyethyl methacrylate (HEMA), and [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide (SBMA), were also grafted onto the polyurethane (PU) substrate before the N-halamine grafting reaction to change the surface properties of the N-halamine-modified substrate. It was noted that the chains containing the hydrophilic monomer and the polymerizable N-halamine compound were successfully grafted onto the PU substrate. The degree of chlorination was improved with the introduction of a hydrophilic monomer, except the HEMA. All of these hydrophilic monomer-containing N-halamine-modified PU substrates demonstrated a more than 2 log CFU reduction after microbial incubation. In contrast, the surface modified with N-halamine only exhibited significantly less antimicrobial efficacy instead. This is likely due to the synergistic effects caused by the reduced chlorine content, as well as the reduced surface interactions with the microbes.

Inkjet Printed Textile Force Sensitive Resistors for Wearable and Healthcare Devices.

Pressure sensors for wearable healthcare devices, particularly force sensitive resistors (FSRs) are widely used to monitor physiological signals and human motions. However, current FSRs are not suitable for integration into wearable platforms. This work presents a novel technique for developing textile FSRs (TFSRs) using a combination of inkjet printing of metal-organic decomposition silver inks and heat pressing for facile integration into textiles. The insulating void by a thermoplastic polyurethane (TPU) membrane between the top and bottom textile electrodes creates an architectured piezoresistive structure. The structure functions as a simple logic switch where under a threshold pressure the electrodes make contact to create conductive paths (on-state) and without pressure return to the prior insulated condition (off-state). The TFSR can be controlled by arranging the number of layers and hole diameters of the TPU spacer to specify a wide range of activation pressures from 4.9kPa to 7.1MPa. For a use-case scenario in wearable healthcare technologies, the TFSR connected with a readout circuit and a mobile app shows highly stable signal acquisition from finger movement. According to the on/off state of the TFSR with LED bulbs by different weights, it can be utilized as a textile switch showing tactile feedback.

Voltammetric determination of alpha lipoic acid using chitosan-based polyurethane membrane electrode

In this study, chitosan-based polyurethane (PU) membrane modified electrodes were prepared for sensitive, practical and fast measurement of α-lipoic acid (ALA), which is an important biomolecule. PU membranes were synthesized using hexamethylene diisocyanate, chitosan, caffeic acid and polyethylene glycol compounds. Chemical structure, thermal stability and morphological properties of the prepared PU membranes were determined with different instrumental techniques. Surface morphology, wettability and hydrophilicity of synthesized chitosan-based PU membranes were investigated. Gold electrode was modified by these PU membranes with different film thicknesses. The bare and PU membrane coated electrodes were used for deduction of ALA by cyclic voltammetry, differential pulse voltammetry and amperometry techniques. In addition, sensitivity, linearity, repeatability and deduction limit of PU modified electrodes were investigated. Modified electrodes showed wide linear detection range (5–200 µmolL−1), low detection limit (4.931 µmolL-1) and short response time. Results show that polyurethane modified electrodes are good alternative for ALA determination.

Optimization of Polyurethane Membrane Physical Characteristics of Red Seaweed Biomass Using a Box-Behnken Design

The polyurethane membrane is used as a separator either by filtration or adsorption, and this process is significantly affected by its strength and physical condition. We synthesized polyurethane membranes using red seaweed with Gracilaria sp as a hydroxyl source. The Box-Behnken Design of the Response Surface Methodology (RSM) using Software Design Expert Version 10.0.3.0 with three factors (TRL, TDI, and Glycerin). The F-value of 0.42 suggests that the membrane is less fit, while the P-value of 75.10% indicates that the quadratic design model is suitable for data analysis of physical characteristics. The optimal physical characteristics were obtained at a composition of 0.233 g TRL, 2.675 g TDI, and 0.254 g glycerin with a physical point of 6.5 (strong and elastic). Optimal polyurethane membrane has good thermal and mechanical properties at temperatures of Tg 58 °C, Tm 322 °C, and Td 534 °C, as well as stress and nominal strain values of 69.3 MPa and 5.74%. Polyurethane membrane synthesized from red seaweed has good physical properties. The result of this research is the basis for the development of polyurethane membrane applications from red seaweed.

Polyurethane membranes reinforced with calcium carbonate and oyster powder for application in the separation of CH4/CO2 from greenhouse gases

Polyurethane membranes reinforced with calcium carbonate and oyster powder for application in the separation of CH4/CO2 from greenhouse gases

Multifunctional electromagnetic interference shielding films comprised of multilayered thermoplastic polyurethane membrane and silver nanowire

A well-designed multilayered composite film with alternating thermoplastic polyurethane (TPU) nanofiber membranes and silver nanowire (AgNW) layers was fabricated by vacuum-assisted filtration. The continuous AgNW conductive layer and the sandwich structure facilitated electron transmission efficiency and electromagnetic (EM) wave dissipation through multiple reflections and resonance effect, which resulted in a high electromagnetic interference (EMI) shielding effectiveness (SE) of 97.3 dB mainly attributed to the improvement of SEA. In addition, the surface plasmon resonance of AgNWs endowed the multilayered film excellent photo-thermal property that allowed the rapid increase of surface temperature to 78.0 °C within 100 s under 300 mW/cm2 sun irradiation. The multilayered film displayed excellent triboelectric energy generation ability when pressed using structured polydimethylsiloxane (PDMS) film, which generated high output voltage and current of 225 V and 21.3 μA, respectively. This work provides a promising solution for designing multifunctional films for efficient EMI shielding of wearable electronics.