Polyurethane Fibers Research Articles

Electro-induced tensile deformation of over-braiding composite tube with carbon fiber reinforced shape memory polyurethane filament

2D shape memory composite tubes, which has excellent flexibility and high durability, have been widely used in intelligent material design. Here we report fabrication of an over-braiding pure shape memory polyurethane (SMPU) and continuous carbon fiber reinforced SMPU (CCF/SMPU) braided tubes with different braided layers (L1, L2, L3). The dynamic thermomechanical behaviors, tensile properties, shape memory behaviors and tensile recovery forces had been investigated. Tensile shape recovery force was recorded to find effects of recovery temperature, applied voltage on the shape memory behaviors. We found that the tensile load, shape recovery ratio and recovery force increase with the braided layers increased. The maximum shape recovery ratio could be reached to 98.8% and shape recovery force of over-braiding CCF/SMPU composite tube was up to 14.825 N. The infilling of carbon fibers could improve the tensile strength and shape memory behaviors simultaneously. Such an effect could be benefit to explore applications of braided composite structures both with high strength and deformation recovery capacity.

Compressive Properties of Polyurethane Fiber Mattress Filling Material

There is an inevitable trend toward exploring new, environmentally friendly fibers that can be used as raw material for mattresses with moderate hardness and air-permeable characteristics. Ethylene-propylene side by side (ES), high-shrinkage fibers, and thermoplastic polyester elastomer (TPEE) chips were introduced into polyethylene glycol terephthalate (PET)/polybutylene terephthalate (PBT) chip by melt blending to modify PET/PBT fiber. The modified PET/PBT (hereinafter referred to as PLON) is more suitable for mattress filling material than PET/PBT. To explore the compressive properties of PLON cushion made of PLON fiber and expand the scope of the PLON cushion’s application, a layered hardness test, hardness classification test and variance analysis were used to comprehensively evaluate the surface hardness, core hardness, bottom hardness and hardness classification of the mattress made of PLON cushion. The conclusions are: (1) The materials of the support layer have a significant effect on the hardness grade S. The hardness of the mattress with PLON as the support layer is between the spring and the coir; (2) when PLON is used as the material of the support layer, it possesses higher supporting force than coir and the characteristics of light weight and high resilience, which coir does not have; it is also softer than a spring mattress. As cushion material, it provides higher support for mattresses than foam. Practical applications, densities and structure were clarified through the above research, with implications for broader applications for PLON blocks in mattress products.

Biocompatible liquid metal coated stretchable electrospinning film for strain sensors monitoring system

Liquid metals (LMs) are potential inorganic materials which could be applied in flexible and deformable electronics owing to their fluidity, low viscosity, high metallic conductivity, and low toxicity. However, recently reported sensing devices based on LMs required complex processes with high cost. Herein, a flexible three-dimensional (3D) conductive network was prepared by coating LM droplets onto an electrospun thermoplastic polyurethane (TPU) fiber film. The LM is suspended between the TPU fibers and self-coalesces into a vertically buckled and laterally mesh-like structure, which provides good biocompatibility, conductivity, and stretchability simultaneously. The LM-TPU composite-film-based flexible device demonstrates a multitude of desired features, such as a widely workable stretching range (0%–200%), sufficient sensitivity under stretching strain (gauge factor (GF) of 0.2 at 200% strain), and outstanding stability and durability (9000 cycles). In vitro biocompatibility experiments show that the LM-TPU composite film directly attached to the skin has excellent biocompatibility. Such strain sensor-based integrated monitoring systems could monitor human body motions in real time, such as muscle movement and joint motion, revealing application prospects in healthcare and human-machine interfacing.

A Novel Finding of Tribological and Mechanical Linking to Micro‐Convex Texture on Hydrophilic Composites Surface under Water‐Lubricating Conditions

Inside Cover: In article number 2100844 by Zhiwei Guo and co-workers, a hydrophilic composite consisting of thermoplastic polyurethane (TPU) and polyvinyl alcohol (PVA) fibers is designed, which can spontaneously produce many micron-level micro-convex textures on the surface when immersed in water for a period of time. The hydrodynamic lubrication effect and cavitation effect caused by these micro-convex textures endow the composite with excellent tribological properties, and the micro-convex textures will not disappear completely with the friction process.

Coating of silver nanoparticles on polyurethane film surface by green chemistry approach and investigation of antibacterial activity against S. epidermidis

Silver nanoparticles with potential antibacterial properties are included in biomaterials for the production of medical devices, which are used for diagnoses or treatment purposes. The aim of the current study was coating the polyurethane (PU) films with silver nanoparticles (AgNPs) due to their antibacterial efficacy. PU films were first modified by chitosan (CH), treated with AgNO3 to let CH chelate with silver ions, and then treated with vitamin-C (vit C) or glucose (Glu) to reduce the adsorbed ions to atomic silver to form AgNPs. The surfaces of the films were examined by ATR-FTIR, XPS, XRD, and SEM. Chemical bond formation between CH and Ag ions and AgNPs were determined by ATR-FTIR. Meanwhile, XPS and SEM analyses proved the presence of reduced metallic silver and nanoparticles on the film surfaces, respectively. According to the SEM analyses, a homogeneous distribution of AgNPs, with sizes 99–214 nm and 37–54 nm, on the film surfaces were obtained depending on Glu or vit C reduction, respectively. The films presented excellent antibacterial performance against Gram positive Staphylococcus epidermidis ( S. epidermidis). These results suggested that the mentioned green technology can be easily applied to obtain AgNP coated polymeric surfaces with very high antibacterial efficacy. Although there are some studies dealing with AgNP formation on PU sponges or fibers, to the best of our knowledge, this is the first study showing AgNP formation on the CH conjugated PU films.

Elastomer–Alginate Interface for High‐Power and High‐Energy Zn Metal Anodes

AbstractSpontaneous corrosion and uncontrolled dendrite accumulation of Zn rapidly degrades zinc–metal battery performance. Artificial interfaces have been widely fabricated on Zn metal anodes, yet most interfaces are detrimental to ion transfer and adapt poorly to spatial changes during Zn plating/stripping. Herein, a hybrid interface, consisting of a thermoplastic polyurethane (TPU) fiber matrix and Zn‐alginate (ZA) filler, is designed, which serves as a physical barrier between anode and electrolyte to inhibit side reactions. Encouragingly, ZA regulates Zn2+ transport and endows uniform Zn deposition by inducing plating/stripping underneath the hybrid interface. At the same time, the TPU frame acts as a super‐elastic constraint to further suppress rampant dendrite evolution and accommodate a large amount of deposited Zn. Consequently, the interface‐protected Zn anode delivers high cycling stability (1200 h at 5 mA cm–2/5 mA h cm–2; 500 h at 10 mA cm–2/10 mA h cm–2), realizing an exceptional cumulative capacity of over 6000 mA h cm–2. This enhancement is well maintained in the full cell when coupled with a vanadium‐based cathode. The unique matrix‐filler architecture and mechanistic insights unraveled in this study are expected to provide a general principle in designing functional interfaces for metal anodes.

Preparation and Dielectric Sensitivity of Polyurethane Composite Fiber Membrane Filled with BaTiO3.

Polyurethane dielectric elastomer (PUDE) is considered a potential underwater flexible actuator material due to its excellent designability and environmental tolerance at the molecular level. Currently, the application of the polyurethane elastomer as an actuating material is constrained by such problems as the conflict between various properties such as dielectric properties and modulus and the low level of dielectric sensitivity. This is a common challenge facing polyurethane dielectric research related to the uneven distribution of dielectric fillers in the matrix. Besides, another challenge for the academic circles is the easy agglomeration of micro and nanofillers. Given the above-mentioned background of the application and technical problems, the coaxial electrospinning technology is proposed in this paper. The polyurethane fiber network is constructed with the preferred hydrolysis resistant polyether-Diphenylmethane diisocyanate (MDI) thermoplastic polyurethane elastomer as the matrix material. Dispersed by ultrasound, the micro nano dielectric filler is integrated into polyurethane fiber through the coaxial dual-channel design. Additionally, directional constraint molding is conducted to improve the agglomeration of small-scale particles induced by the loss of mechanical energy in traditional blending. After characterization, the distribution of BaTiO3 particles in the fiber bundle is relatively uniform. Compared to the polyurethane dielectric composites prepared by traditional blending (BaTiO3-Dielectric Elastomer, BaTiO3-DE), the dielectric sensitivity factor of the polyurethane composite fiber membrane (BaTiO3-Dielectric Elastomer Membrane, BaTiO3-DEM) is enhanced by over 25%; the electrostrictive strain of BaTiO3-DEM is boosted by least 10%.

Piezoresistive fibers with record high sensitivity via the synergic optimization of porous microstructure and elastic modulus

Although different kinds of microengineering have been developed in piezoresistive fibers recently, it is still challenging to achieve a high-pressure sensitivity in these fibers. This is because these microstructures can only geometrically increase the conducting paths under pressure. In this work, via the theoretical calculation and practical experiments, we firstly demonstrated that not only the conducting paths but also the fibers’ elastic moduli of compression exhibit key roles in improving the sensitivities in fibers. Typically, by adjusting the kinetic diffusion coefficient between the spinning dope and the coagulation solution in wet-spinning, various structured (solid, hollow, porous, and hollow-porous) thermoplastic polyurethane (TPU) fibers with variable elastic moduli of compression were developed in this work. As a result, the piezoresistive fiber with a uniform and through porous structure (porous in both the core and the surface) exhibited the highest sensitivity of 0.67 kPa−1 due to its synergic improvement in conducting paths and contact area (with a low elastic modulus of compression of 6.98 kPa) under pressure. To the best of our knowledge, it is the recorded highest sensitivity in the piezoresistive fibers. Beyond the pressure sensing, we also proved the as-prepared porous fibers with an ultra-high stretchability of 2110%, a high performance in strain sensing, and a good candidate in humidity and gas sensing. At last, we successfully applied the piezoresistive fibers in our daily life for wearable sensing, demonstrating its high potential in practical application.

Comparing Percolation and Alignment of Cellulose Nanocrystals for the Reinforcement of Polyurethane Nanocomposites.

The reinforcement of polymer nanocomposites can be achieved through alignment or percolation of cellulose nanocrystals (CNCs). Here, we compare the efficacy of these reinforcement mechanisms in thermoplastic polyurethane (PU) elastomer nanocomposites containing thermally stable cotton CNCs. CNC alignment was achieved by melt spinning nanocomposite fibers, while a percolating CNC network was generated by solvent casting nanocomposite films with CNC contents up to 20 wt %. While in films both the CNCs and the PU matrix were entirely isotropic at all concentrations as confirmed by wide-angle X-ray scattering and birefringence analysis, the CNCs in the fibers exhibited a preferential orientation, which improved with increasing CNC concentration. Increasing the CNC concentration in the fibers reduces, however, the alignment of the PU chains, resulting in an entirely isotropic PU matrix at high CNC contents. The mechanical properties of films and fibers were evaluated using stress-strain measurements. Nanocomposite fibers with low CNC content exhibited superior stiffness, extensibility, and strength compared to the films, while the films displayed superior mechanical properties at high CNC concentrations. These findings are rationalized using common semiempirical models describing the reinforcing effects of CNC alignment in fibers (Halpin-Tsai) and CNC percolation in films (percolation model). The formation of a percolating CNC network leads to a stronger reinforcement than CNC alignment, as the reinforcing effect of the latter is limited by the comparably low aspect ratio of CNCs extracted from cotton. As a consequence, above the percolation threshold for cotton CNCs, isotropic nanocomposite PU films show a higher stiffness than aligned nanocomposite PU fibers.

The effect of fibre morphology on packing phenomena and bed properties in coalescers

In this study, fibre morphology of waste materials and its effect on packing phenomena and bed properties were investigated. Nine waste materials were used in bed coalescers. By scanning electron microscopy, it was determined that surfaces of all fibres were smooth, while cross-section differed from circular, rectangular to irregular. The fibres with circular cross-sections had diameters in the range of 12?0.8 to 40?4 ?m, while the fibres of polypropylene bags and sponges appeared as strips with the widths of 452?11 and 1001?14 ?m, respectively. It was also noticed that polyurethane fibres were connected forming a sponge-like structure, while polyethylene terephthalate fibres were interconnected at some points. In this work, experimental dependence of bed porosity on bed permeability was established for all investigated materials, which allows forming a fibre bed with desired permeability. The exception was the bed formed of fibres of polypropylene bags, which had the largest dimensions and yielded a different porosity-permeability dependence.

Reinforcement of electrospun polyurethane fibers with resorcinol–formaldehyde resin

AbstractThis work reports a simple method to improve the properties of electrospun nanofibers. The procedure involves developing nanofibers using electrospinning followed by liquid infiltration to reinforce the fibers. Coating of polyurethane nanofibers (PUN) with resorcinol–formaldehyde (RF) significantly improves the properties of PUN. Furthermore, the morphology of fiber interface and the properties of RF coated fibers indicate that RF resin reinforces the interface between the fibers. The method leads to improvement in mechanical properties of PUN. An improvement of about 94% and 281% in mechanical properties like tensile strength and modulus, respectively, compared to neat PUN fibers is achieved by coating with 20% wt/vol of RF solution.

A Catalytic and Interfacing PEDOT:PSS/CuPc Polymerized on Cloth Fiber to Electro‐Metalize Stretchable Copper Conductive Pattern

AbstractCopper conductive pattern should provide dependent flexibility on coated cloth‐fiber to support the signal transmission or current carrier for stretchable and reliable electronics. The design of copper phthalocyanine (CuPc) introduced in poly(3,4‐ethylenedioxythiophene) and polystyrene sulfonate acid (PEDOT:PSS) polymer network promotes the realization of copper electro‐metallization from its inner active dots, leading to a structure of PEDOT:PSS/CuPc‐rooted copper coating. The bridge‐layer of elastic PEDOT:PSS/CuPc interfacing and catalyzing the copper layer with excellent ductility and antioxidation, is developed to sustain the required stretchability for electronics on regular cloth polyurethane fiber. Experimental results demonstrate that this design achieves a perfect 80% conductivity of bulk copper, an ignored resistance changes after bending test, tensile test, 10 days’ natural oxidation, and 10 times’ machine‐washing, respectively. Accordingly, a breakthrough is made to supply the compatible integrity of copper line on cloth fiber for wearable electronics.

Dynamic response of polyurethane foam and fiber orthogonal corrugated sandwich structure subjected to low-velocity impact

Two kinds of foam/fiber sandwich structures were prepared by using Vacuum Assisted Resin Transfer Molding (VARTM) process, on which the low-velocity impact tests were carried out. The force response, specific energy absorption and failure mode of the two sandwich structures under different impact energies, hammer shapes and impact positions were studied. From the force response and energy absorption curves, it can be seen that the corrugated sandwich structure outperformed the flat sandwich structure in terms of low-velocity impact resistance, and showed the best impact resistance when the impact was applied at the corrugated trough position. According to the observation of the impact profile of sandwich structure, the main failure modes of the sandwich structures include foam cracking, fiber breaking, fiber delamination, and debonding between fiber and foam.

Artificial blood vessel biofuel cell for self-powered blood glucose monitoring

Biofuel cell (BFC) is a kind of bio-cell based on biological enzymes. The enzyme as a catalyst can interconvert renewable and sustainable energy into each other more rapidly, such as the biochemical energy in glucose and ethanol into electrical energy. In this work, artificial blood vessel and fuel cell are based on polyaniline/thermoplastic polyurethane (PANI/TPU) fiber membrane with an average fiber diameter of 1300 nm, a film thickness of 167 μm, and a permeability of 18.4 mm s−1. The PANI/TPU fiber membrane was prepared by electrospinning and followed in situ polymerization. The membrane has good flexibility and mechanical properties, and can be stretched up to 200%. The advantages of good hydrophilicity, biocompatibility and high porosity make it possible to efficiently load glucose oxidase and laccase. The prepared BFC can stably output a voltage of 50 mV in simulated blood, and the output electrical signal changes significantly with the change of glucose concentration, which may be used in implantable devices or blood glucose monitoring.

Highly sensitive and stretchable fiber strain sensors empowered by synergetic conductive network of silver nanoparticles and carbon nanotubes

Nowadays the demand for flexible strain sensors is booming for human-centered wearable applications, yet it is still challenging to achieve a high sensitivity at large stretchability of human motions (∼100%). Herein, carbon nanotubes (CNTs) and silver nanoparticles (AgNPs) layers were consecutively deposited on stretchable polyurethane (PU) fiber by ultrasonication and polydopamine (PD) assisted chemical deposition, to achieve a fiber sensor with both high sensitivity and stretchability. Specially, the crack mechanism dominated AgNPs offer low initial resistance and generation of abundant cracks under strain, while slippage mechanism dominated CNTs guarantee the integrity of conductive path at large strain. The as-prepared PU/CNTs/PD/AgNPs sensor achieves far better sensing performance than the conventional PU/CNTs sensor, in terms of high sensitivity (gauge factor of up to 1004.5), wide workable stretching range (150%), good stability (3000 cycles @ 150%) and fast response (53 ms) and recovery (80 ms). Moreover, the PU fiber substrate also endows the strain sensor with characteristics of light-weight, small-size, and good postprocessing capability to be easily integrated into textiles by weaving, greatly facilitating the preparation of sensing textiles for wearable human motion detections. This work not only provides an efficient way to achieve trade-off between high sensitivity and large stretchability of strain sensors, but also presents huge potentials of wearable and comfortable sensing textiles for personal health monitoring.

First-in-Human Segmental Esophageal Reconstruction Using a Bioengineered Mesenchymal Stromal Cell–Seeded Implant

IntroductionResection and reconstruction of the esophagus remains fraught with morbidity and mortality. Recently, data from a porcine reconstruction model revealed that segmental esophageal reconstruction using an autologous mesenchymal stromal cell-seeded polyurethane graft (Cellspan esophageal implant [CEI]) can facilitate esophageal regrowth and regeneration. To this end, a patient requiring a full circumferential esophageal segmental reconstruction after a complex multiorgan tumor resection was approved for an investigational treatment under the Food and Drug Administration Expanded Access Use (Investigational New Drug 17402). MethodsAutologous adipose-derived mesenchymal stromal cells (Ad-MSCs) were isolated from the Emergency Investigational New Drug patient approximately 4 weeks before surgery from an adipose tissue biopsy specimen. The Ad-MSCs were grown and expanded under current Good Manufacturing Practice manufacturing conditions. The cells were then seeded onto a polyurethane fiber mesh scaffold (Cellspan scaffold) and cultured in a custom bioreactor to manufacture the final CEI graft. The cell-seeded scaffold was then shipped to the surgical site for surgical implantation. After removal of a tumor mass and a full circumferential 4 cm segment of the esophagus that was invaded by the tumor, the CEI was implanted by suturing the tubular CEI graft to both ends of the remaining native esophagus using end-to-end anastomosis. ResultsIn this case report, we found that a clinical-grade, tissue-engineered esophageal graft can be used for segmental esophageal reconstruction in a human patient. This report reveals that the graft supports regeneration of the esophageal conduit. Histologic analysis of the tissue postmortem, 7.5 months after the implantation procedure, revealed complete luminal epithelialization and partial esophageal tissue regeneration. ConclusionsAutologous Ad-MSC seeded onto a tubular CEI tissue-engineered graft stimulates tissue regeneration following implantation after a full circumferential esophageal resection.

A highly stretchable and breathable polyurethane fibrous membrane sensor for human motion monitoring and voice signal recognition

Flexible wearable electronic devices are important in modern medical equipment and health detection, but the preparation of a flexible sensor with a high elasticity and breathability remains challenging. We prepared a flexible stretchable fibrous sensor by using a simple manufacturing process. The sensor had a high sensitivity, good stability, wide pressure test range, high tensile resistance, and antioxygenic property and was breathable. The sensor was used to monitor voice signals, by establishing a voice database model and constructing a voice signal processor to recognize the voice signal, which can be applied for speech recognition and rehabilitation training for those with damaged vocal cords. Based on centrifugal electrospinning technology, the polyurethane (PU) fibrous membrane was used as a sensor substrate, and multi-walled carbon nanotubes (MWCNTs) were loaded on the PU fibrous membrane by a cross tensile loading method. Scanning electron microscopy images showed that the MWCNTs and PU fibers formed a dense conductive network. The excellent conductivity provided the MWCNTs/PU stretchable fibrous membrane sensor with a low resistance of ∼800 Ω, a high elongation at break of 272 %, wide response test ranges from 0 % to 203 %, a sensitivity of up to 4177 at a strain of 190 %, and response and recovery times of 94.34 and 94.36 ms, respectively. The sensor had a mechanical durability (multicycle test of 10,000 cycles) and an excellent water vapor transmission rate (WVTR). This excellent performance ensures that the sensor can be used as a wearable device to monitor motion of various parts of the human body.

Electrospun Fibrous Membrane Containing a Cyclodextrin Covalent Organic Framework with Antibacterial Properties for Accelerating Wound Healing.

Skin wounds are usually accompanied by bacterial infections and inflammations, leading to delayed wound healing, which remain a great challenge in clinical treatment. Therefore, it is of great significance to develop wound dressings that inhibit bacterial infections to accelerate wound healing. Herein, we reported the fabrication of inclusion complex (a β-cyclodextrin covalent organic framework loaded with enrofloxacin and flunixin meglumine)-incorporated electrospun thermoplastic polyurethane fibers (named ENR-FM-COF-TPU) via electrospinning. The obtained ENR-FM-COF-TPU fibrous membrane exhibited excellent physicochemical and biological properties such as uniform and stable morphology, proper hydrophobicity, good water uptake capacity, and admirable biocompatibility, which showed perfect behavior as a wound dressing. In addition, the ENR-FM-COF-TPU membrane achieved a sustained drug release of enrofloxacin and flunixin meglumine and displayed powerful antibacterial activity against Staphylococcus aureus and Escherichia coli with 99% inhibitory efficiency for 50 h. More importantly, the wound healing therapy effect was investigated using a full-thickness skin defect model of mice. It suggested that the ENR-FM-COF-TPU membrane could significantly accelerate and enhance wound healing through downregulating inflammatory cytokines (IL-1β and TNF-α) and increasing the expression of growth factors (VEGF and EGF). Due to its excellent properties, the ENR-FM-COF-TPU membrane may have promising potential in wound healing applications.

Preparation and Performance Evaluation of Antibacterial Melt-Spun Polyurethane Fiber Loaded with Berberine Hydrochloride.

(1) Background: Bacterial infections have long threatened global public safety; hence, it is significant to continuously develop antibacterial fibers that are closely related to people’s daily lives. Berberine hydrochloride is a natural antibacterial agent that has application prospects in the preparation of antibacterial fibers. (2) Methods: This study firstly verified the antibacterial properties of berberine hydrochloride and its possible antibacterial mechanism. Thereafter, berberine hydrochloride was introduced into the self-made melt-spun polyurethane fiber through optimized coating technology. The performance of coating modified polyurethane fiber has been systematically evaluated, including its antibacterial properties, mechanical properties, and surface wettability. (3) Results: Results show that the antibacterial polyurethane fiber with desirable comprehensive properties is expected to be used in the biomedical fields. (4) Conclusions: The research also provides a reference for the development and application of other natural antibacterial ingredients in fiber fields.

A novel interpenetrating segregated functional filler network structure for ultra-high electrical conductivity and efficient EMI shielding in CPCs containing carbon nanotubes

Inspired by the hierarchically dendritic structure of plant root and its extraordinary ability of grabbing soil, polyurethane (PU) fibers with such bio-mimic structure were fabricated by non-solvent induced precipitation under turbulent force to grab multi-walled carbon nanotubes (CNTs) in this work, forming interpenetrating segregated network (IPSN) with CNTs coated on hierarchically dendritic polyurethane (PU) fibers (HDPUFs) and filled into voids between entangled HDPUFs. Prepared CNT/PU composites illustrate an ultrahigh maximum CNT loading of 80 wt% with good flexibility, while only 10% could be achieved for common segregated structure. Meanwhile, a low percolation threshold of 0.25 wt% and a maximum conductivity of 25 S/cm is achieved. Benefiting from significantly reduced insulating polymer coating on CNTs, the electrical conductivity of CNT/HDPUF composites at low CNT loading (≤7 wt%) is orders of magnitude higher than that of CNT/PU composites containing randomly dispersed CNTs with similar filler content. Simultaneously, the specific electromagnetic interference (EMI) shielding efficiency (SE) of CNT/HDPUF composite reaches up to 10526.1 dB cm2/g thanks to their high electrical conductivity and low density, which has been rarely reported previously for CNT-based composites. This work provides a simple and low-cost method to fabricate thin, lightweight, and flexible composite with high filler content, high electrical conductivity and outstanding electromagnetic shielding performance.