Polyurethane Fibers Research Articles

Multifunctional stretchable strain sensor based on polydopamine/ reduced graphene oxide/ electrospun thermoplastic polyurethane fibrous mats for human motion detection and environment monitoring

Various sensors have been developed to monitor the changes in physical quantities to meet the growing demand for wearable electronics. While it is still a huge challenge to design a multifunctional flexible sensor with both high strain responsivity and good breathability. In this work, through electrospinning, ultrasonication and in-situ polymerization of dopamine, we prepared a multifunctional strain sensor. We decorated polydopamine (PDA) onto the surface of reduced graphene oxide (RGO)/thermoplastic polyurethane (TPU) fibers. Here, PDA containing hydrophilic groups (-OH, –NH2) was used to improve the hydrophilic breathability of the membrane and prevent the RGO falling off from TPU fibrous mat. The PDA/RGO/TPU (PRT) fibrous strain sensor exhibits excellent comprehensive performance of excellent stretchability, good durability (stretching/releasing test of 9000 cycles under 50% strain), high sensitivity (gauge factor (GF) 23.2 within 60% strain, 185 towards 60%–100% strain), and fast response time (100 m s). Specially, owing to the introduction of PDA, the water vapor volatilization rate of our PRT strain sensor (38%) is almost the same as the blank control group (39%), indicating that our fibrous sensor has excellent breathability. In order to monitor various movements of human body parts (finger, wrist, elbow, and leg bending), our sensors were attached to volunteers' joints to monitor resistance changes in real time. In addition, our PRT fibrous mat also has excellent sensitive performances towards organic gases and humidity, showing its multifunctional ability for detecting various environment stimuli.

An integrated sustainable and profitable approach of energy efficiency in heritage buildings

Abstract The aim of Sustainable Development Goal 7 is to ensure access to affordable, reliable, sustainable and modern energy for all. Increased energy efficiency is particularly important in the construction industry because urban agglomerations currently consume up to 80% of global energy, 40% of which is attributable to buildings. In countries like Italy however, where historical buildings constitute a significant part of the building patrimony, improving energy efficiency is not always straightforward as interventions must take into account the historical materials used as well as the context of the construction. Therefore, the aim of this research was to establish a methodology that would identify the most effective means of achieving energy efficiency taking into account the historical aspects of a building and its cultural context. The methodology proposed and described in this paper involves: preliminary analyses to identify the elements of value and the level of transformability of facades; the selection of different insulating materials; dynamic simulations of building behaviour; analyses of intervention costs in relation to each type of insulation and finally the preparation of a multi-criteria matrix to identify the most effective method of improving energy efficiency of a historical wall with differing degrees of transformability. Each insulating material was analysed in relation to heating and cooling requirements and material cost impact. The methodology was applied to a case study in the Province of L’Aquila, Italy. In the paper a multicriteria framework, for the improvements in the thermal efficiency of a building, it is presented. Specifically the attention is focused on heating requirements, cooling requirements and cost impact. The results indicate that, with respect to historical building, it is possible to adopt strategies finalyzed to improve the energy efficiency of these buidings, contributing in this way, also toward the SDG7. Specifically, the best performance for a wall with a high level of transformability can be obtained using calcium silicate, extruded polystyrene, kenaf and hemp, whilst, in the case of a wall with a low level of transformability, the best materials are calcium silicate, polyurethane and linen fiber. Finally, in the case in which external constraints prevent the application of a thick coat and internally there is limited space, the use of calcium silicate was found to be the best energy efficient measure.

Electrospun PCL-based polyurethane/HA microfibers as drug carrier of dexamethasone with enhanced biodegradability and shape memory performances

Shape memory polymers (SMP) with better biodegradability and better stability have great potential applications in biomedical fields, such as the drug carriers or the tissue engineering scaffolds. In this study, poly(e-caprolactone)(PCL)-based polyurethane(PU) microfibers were fabricated with the containing of hydroxyapatite(HA) to enhance the biodegradability and to exhibit excellent shape memory performance. The composition, the morphology, the thermal stability, and the mechanical properties of the microfibers were characterized and detected using Fourier transform infrared spectroscopy (FTIR), 1H nuclear magnetic resonance (1HNMR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC). and dynamic mechanical analysis (DMA), etc. And dexamethasone was selected as drug model to investigate the delivery and release behaviors of the carrier of the microfibers. It was revealed that HA enhanced the degradation rate of the shape memory polyurethane (SMPU) fibers, and the fibers could guarantee a sustained long time drug release. The detection on the shape memory performance found that, with the different addition amounts of HA, the composite microfibers of (SMPU) and HA exhibited the different shape memory transition temperature (Ttrans) values. And with the addition of 3 wt% of HA, the excellent shape recovery ratios of Rr (> 97%) and the shortest recovery time of ~ 6 s could be obtained. With further increase of the amounts of HA, the recovery force and the recovery time were reduced and prolonged, respectively. The obtained results proved that the biodegradable SMPU/HA composite microfibers have more valuable application prospects in biomedical fields.

INVESTIGATION OF FLUID STRUCTURE INTERACTION (FSI) EFFECT ON A FRP (FIBER REINFORCED POLYMER) POLE USING ANSYS

This paper presents a simulation study on a fiber-reinforced polymer (FRP) light pole that is being used in Yanbu Industrial City, Saudi Arabia. The light poles in this area are subjected to cyclic wind load blowing from the Red Sea. It is of great interest to re-investigate the strength and integrity of the structure for future improvement. A three-dimensional numerical simulation has been performed to analyze the effect of wind velocity over the FRP pole. The pole is conical in shape, having a circular hollow cross-section in both the ends and tapered uniformly. The pole considered for simulation is having a height of 6 meters and have conicity of 18 mm/m. The FRP pole is a combination of unsaturated polyester, vinyl ester, epoxy, phenolic, polyurethane, and glass fibers, which are reinforced by the centrifugal process. The computational fluid dynamics (CFD) simulation results are validated with the mathematical calculation. The adopted method is fluid-structure interaction (FSI) with SST k-ω (shear stress transport) turbulence model, which is used to simulate the wind velocity over the FRP pole using ANSYS Fluent. The velocity of air considered for simulation ranges from 10 to 50 m/sec. The study provided a good correlation between mathematical calculation and the CFD simulation for each air velocity. The study revealed maximum deflection and equivalent stress occurred at the top and bottom end, which are 217 mm and 85 MPa respectively. The exact region of crack is also predicted for different wind velocity. This method can also be adopted for any FRP poles available.

Molecular weight switchable polyurethanes enable melt processing

Preparing polymers with both high molecular weight and good processability is a continuing challenge. Herein, we report the development of molecular weight switchable polyurethane (MWSPU) containing dynamic oxime-carbamate bonds. The molecular weight of this MWSPU decreased when heated to 130 °C and recovered upon cooling as the result of the breaking and reformation of thermally reversible oxime-carbamate bonds. The viscosity also decreased as temperature increased, which enabled high-performance polyurethane fibres to be prepared by melt processing. This is the first study to prepare polyurethane fibres by melt spinning below the degradation temperature.

Light‐Liquid Selective Filters: Light‐Liquid Selective Filter‐Mounted Nanowire‐Networked Polyurethane Fiber for an Ultraviolet Sensor (Adv. Mater. Interfaces 19/2019)

The SnO2 nanowire-networked polyurethane fiber covered with a (1H,1H,2H,2H-heptadecafluorodec-1-yl) phosphonic acid-coated Al2O3 nanoparticles can stably detect ultraviolet intensity even when exposed to liquids. More details can be found in article number 1901015 by Taekyung Lim, Sanghyun Ju, and co-workers.

Optimum insulation thicknesses and energy conservation of building thermal insulation materials in Chinese zone of humid subtropical climate

Implementing thermal insulation on the building has been acknowledged as a highly effective way to achieve cost-effective energy conservation. For implementing thermal insulation, a key problem is the proper selection of wall insulation in terms of material types and optimum thicknesses because it is challenged to balance energy-saving effects and economic benefits. To address this problem, we investigated the new aerogel super-insulation material for building-energy-conservation application in this paper. Specifically, we took a typical office building of humid subtropical climate as a model, established a whole-life-cycle-assessment model to exploit the optimum economic thickness, and further evaluated the energy-saving rate, economic benefits, the greenhouse-gas emissions, etc. Besides, we compared the super-insulated aerogel with four commonly-used insulation materials, i.e., expanded polystyrene, extruded polystyrene, foamed polyurethane, and glass fibers. Experimental results showed that aerogel had the minimum optimum thickness of 3.7 mm. When aerogel was implemented with the optimum thickness, the annual cooling and the heating load for the hollow shale brick building were reduced by 7.5% and 18.2%, respectively. Additionally, compared with the other materials, aerogel achieved a faster reduction for greenhouse-gas emissions as the thickness increased. The aerogel insulation could lead to lower carbon emissions, e.g., CO2 (8.169 kg/(m2yr)) emissions with LPG fuel, and thus would be more preferable for environmental protection. The building energy simulations employed can be further strengthened in the future by considering the effect of urban microclimates and actual internal heat gains in offices.

Electrospun polyurethane fibrous membranes of mimicked extracellular matrix for periodontal ligament: Molecular behavior, mechanical properties, morphology, and osseointegration.

Based on mimicking of the extracellular matrix structure and function, electrospun polyurethane fibers are proposed as osseointegration implant membranes for the periodontal ligament. Polyurethane in different solution ratios of N, N-dimethylformamide:tetrahydrofuran of 100:0 (PU100), 70:30 (PU70), and 50:50 (PU50) was prepared before fabrication into fibers by electrospinning. The viscosities of the solutions were measured. The molecular behaviors of the electrospun polyurethane fibers were characterized by Fourier transform infrared spectroscopy and dynamic mechanical thermal analysis. The morphologies were observed by scanning electron microscopy. Tensile testing was used to evaluate the mechanical performance. Biological performance was tested by osteoblast culturing. The cells were evaluated for cell morphology, viability, proliferation, and alkaline phosphatase activity. The results demonstrated that PU100 showed low molecular interaction and entanglement, formation of irregular various fibers, flexible mechanical behavior, and unique biological characteristics of cell adhesion, migration, proliferation, and alkaline phosphatase activity. The results indicated that the structure of PU100 was similar to natural extracellular matrix. Finally, it could be deduced that the PU100 has promise as a fibrous membrane for the periodontal ligament.

Light‐Liquid Selective Filter‐Mounted Nanowire‐Networked Polyurethane Fiber for an Ultraviolet Sensor

AbstractFiber‐sensor‐based real‐time monitoring of the degree of exposure of the human body to ultraviolet (UV) rays is one of the technologies in the field of smart healthcare‐based wearable devices. With the development of wearable UV sensors, it is essential to build technologies with stable durability and excellent sensing capabilities for continuous movement and with water, sweat, and external contaminants. In this study, a fiber sensor is investigated that can stably detect UV intensity even when exposed to liquids such as water. The device consists of SnO2 nanowires, which are sensitive to UV intensity, arranged on a polyurethane (PU) fiber in a random network pattern, with the aim to minimize the amount of current change caused by various tensile and compressive stresses encountered by the wearable sensor. To prevent the distortion of the measured current that may occur in the semiconductor sensing channel as a result of external water exposure, a (1H,1H,2H,2H‐heptadecafluorodec‐1‐yl) phosphonic acid (HDF‐PA)‐coated Al2O3 nanoparticles (NPs) with a UV transmittance of 77% are coated on the networked SnO2 nanowire channel. The SnO2 nanowire‐networked PU fiber covered with the HDF‐PA coated Al2O3 NPs is confirmed to be sensitive only to UV, without reacting to external water under various bending conditions.

Layer-by-layer electrospun membranes of polyurethane/silk fibroin based on mimicking of oral soft tissue for guided bone regeneration

Guided bone regeneration is an effective method that can enhance bone volume at a defect site of the mandible before material implantation. Layer-by-layer electrospun membranes of polyurethane/silk fibroin (SF) were fabricated to mimic oral soft tissue. The electrospun polyurethane fibers were initially fabricated into a membrane. Next, the polyurethane layer was covered with electrospun SF fibers at different thicknesses. Then, the SF layer was covered with electrospun polyurethane fibers. Afterward, the morphologies of the membranes were observed and analyzed by scanning electron microscopy. The physical properties of the membranes were evaluated from the contact angle and mechanical properties. The biological performances were evaluated by observing cell adhesion, viability and proliferation, alkaline phosphatase activity, and calcium content. The results demonstrated that the membrane with a thin SF core showed better physical properties and mechanical performance than the thicker SF cores. Finally, the results deduced that the membrane with a thin SF core was promising for guided bone regeneration.

Stretchable Conductive Fibers of Ultrahigh Tensile Strain and Stable Conductance Enabled by a Worm-Shaped Graphene Microlayer.

Stretchable electrical conductors have demonstrated promising potentials in a wide range of wearable electronic devices, but the conductivity of most reported stretchable conductive fibers will be changed if be stretched or strained. Stable conductance is essential for wearable and stretchable devices, to ensure the performance is stable. Inspired by the peristaltic behavior of arthropods, we designed a graphene coating similar to the caterpillar structure on the polyurethane (PU) fiber surface, enabled by coating the worm-shaped graphene microlayer onto polyurethane filaments. Such worm-shaped filaments can be stretched up to 1010% with a wide reversible electroresponse range (0 < ε < 815%), long-term durability (>4000 stretching/releasing cycles), good initial conductivity (σ0 = 124 S m-1), and high quality factor (Q = 11.26). Remarkably, the worm-shaped filaments show distinctive strain-insensitive behavior (ΔR/R0 < 0.1) up to 220% strain. Furthermore, the filaments as electrical circuits of light emitting diodes (LEDs) to track signals from robust human joint movements are also demonstrated for practical application. Such worm-shaped filaments with distinctive strain-insensitive behavior provide a direct pathway for stretchy electronics.

Ultra‐Stretchable Porous Fiber‐Shaped Strain Sensor with Exponential Response in Full Sensing Range and Excellent Anti‐Interference Ability toward Buckling, Torsion, Temperature, and Humidity

AbstractAs a crucial element for wearable devices, high‐performance strain sensors have been spotlighted as an ideal strategy to develop machine‐human interfaces and healthcare systems. It still remains a huge challenge to construct flexible strain sensors with equational response in a broad range. Herein, highly stretchable multi‐walled carbon nanotubes (MWCNTs)–decorated thermoplastic polyurethane (TPU) fibers with a porous microstructure are produced through a scalable and facile strategy by wet‐spinning and ultra‐sonication. The fiber is composed of pure TPU fibers with MWCNTs decorated on the surface. The porous fiber is then assembled as a strain sensor. Interestingly, the effective MWCNTs distribution on the TPU fiber enables exponential sensing over the whole strain range. The sensor possesses a high gauge factor (GF, 102 at 300% strain), very large workable sensing range (300% strain), excellent durability (10 000 cycles), light weight (0.85 g cm−3), and fast response (200 ms). The as‐prepared strain sensor exhibits excellent insensitive properties toward buckling, torsion, temperature, and humidity stimuli. Based on the high sensing performance, the fiber‐shaped strain sensor detects human movements precisely by directly attaching to skin or embedding in garments, demonstrating huge potential in human–machine interfaces, health monitoring application, etc.

Effect of side methyl from mixed diamine chain extenders on microphase separation and morphology of polyurethane fiber

Polyurethane fiber (PUF) can be used as self-adaptive material in the field of nuclear physics and its properties depended on the molecular structure. To explore the effect of side methyl on its degree of microphase separation (DPS) and morphology for PUF, ethanediamine and 1,2-propylene diamine with different molar ratio were used as mixed diamine chain extenders (MDCEs) to fabricate PUF. The effect of side methyl content on the H-bond, crystallinity, DPS and mechanical performance were investigated with FTIR, XRD, AFM, SAXS, universal tensile machine (UTM) and DMA, respectively. The results of FTIR and XRD revealed that the hydrogen bonds (H-bonds) and crystallinity increased with the decrease of side methyl content on account of the reduction effect of steric hindrance. Furthermore, due to the stronger H-bonds and higher crystallinity in hard segment domain (HD), the DPS of PUF was enhanced with the increasing molar ratio of MDCEs in the aspect of the ordered structure in soft segment domain and the enlarged HD. Therefore, PUF showed more excellent mechanical performances with the improved DPS. The elongation at break extended from 482% to 557%. Static stress relaxation rate V increased while static stress relaxation ratio R decreased. Furthermore, Tg,s of soft segment moved to the low temperature direction. These results demonstrated how the microstructure-to-properties of PUF could be influenced by side methyl from MDCEs.

Highly Sensitive and Stretchable Polyurethane Fiber Strain Sensors with Embedded Silver Nanowires.

Flexible strain sensors have attracted a great amount of attention for promising applications in next-generation artificially intelligent devices. However, it is difficult for conventional planar strain sensors to meet the requirements of miniature size and light weight for flexible electronics. Herein, a highly sensitive and stretchable fiber strain sensor with a millimeter diameter was innovatively fabricated by the capillary tube method to integrate silver nanowires (AgNWs) in polyurethane (PU) fibers. Scanning electron microscopy results demonstrate that AgNWs were embedded into the surface layer of PU fibers and formed completely conductive networks. The unique AgNW networks endow the PU/AgNW fibers with superior electrical conductivity of 3.1 S/cm, high elongation at break of 265%, wide response range of 43%, high gauge factor of 87.6 up to 22% strain, fast response time of 49 ms, and excellent reliability and stability. Such satisfactory stretchability and sensitivity is attributed to the combination of the highly stretchable PU matrix and the embedded architecture of the AgNW conductive network. Moreover, PU/AgNW fibers can be employed as wearable devices to detect various human motions and to drive light-emitting diodes at a lower voltage (2.7 V).

QUV Accelerated Aging Effects on the Structure and Properties of Polyether Polyurethane Fibers

This paper presents an experimental study about the effects of UV irradiation on polyether polyurethane (PU) fibers investigated by FTIR, SAXS and AFM, and the multiple mechanism is finally proposed.The results show that, at low UV irradiation (0.6W/m2, 0.9W/m2), the mechanism responsible for UV degradation of polyether PU fibers could be described as a primary reaction causing the break up of chemical bonds and forming the new quinone structure, along with a secondary reaction to explain hydrogen peroxide formed in the presence of UV irradiation, water and oxygen environment which promotes QUV aging by providing loose structure of polyether PU fibers. Moreover, the micro phase separation is promoted for a parallel reaction occurred to produce new polyether PUs and more compact micro domains by the residual isocyanate in pre-polymerization stage and alcohols formed under QUV aging. Under higher UV irradiation (1.2W/m2, 1.5W/m2), in addition to the primary reaction, a tertiary reaction showing the re-polymerization occurred under accumulation of aging products (carboxylic acids and alcohols) is also considered as the mechanism, while the secondary reaction would be inhibited for the peak assigned to H2O2 is not observed. Also, this decreases micro phase separation of polyether PU fibers for the primary reaction is dominant.

Study on microstructure and mechanical properties of polydiacetylene composite biosensors

ABSTRACT10,12‐Pentacosadiynoic acid (PCDA) monomers were mixed with polyurethane (PU) or poly(ethylene oxide) (PEO) and the mixtures were electrospun to obtain composite nanofibers that were then photopolymerized via ultraviolet radiation, resulting polydiacetylene (PDA) in the nanofibers. The PDA demonstrated color‐changing properties in the presence of Escherichia coli, which exhibited potential for developing flexible colorimetric biosensors for medical textiles. Phase separation was found in the PEO–PDA fibers, resulting in amorphous PEO accumulation at the fiber surface. In contrast, the PU–PDA fibers demonstrated a homogeneous microstructure throughout the fibers. Tensile test results suggested a molecular orientation in the PU–PDA fibers that significantly improved the mechanical properties of the fibers. The presence of PDA in the matrix polymer reduced the overall strength and breaking elongation of both composite nanofibers in comparison to 100% PEO and PU fibers. A single PU–PDA fiber showed significantly higher stiffness and modulus than a single PEO–PDA fiber. Force–distance curve analysis suggested that the PU–PDA fibers exhibited an elastic deformation. In a comparison, the PEO–PDA fibers were brittle and showed low modulus. The results of structural and mechanical properties suggest that the PU–PDA nanofibers are a promising composite for developing nonadherent, durable, and flexible colorimetric biosensors used in medical textiles. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47877.

Development and Application of a Test System for Modeling Tunnel Excavation with Transparent Rock Surrogate

Abstract Physical modeling using transparent rock or soil surrogates and optical measurement is an effective way to obtaining the displacement and stresses within test specimens in geotechnical engineering. To apply the prospective modeling method to investigating the mechanism of excavation-induced failure of rock surrounding tunnels, a novel test system is developed for modeling tunnel excavation with transparent rock surrogate. The system includes three parts: one transparent acrylic chamber and its reinforcing units for containing scaled models, a dead-weight loading device consisting of levers and pulleys, and a three-dimension optical stressometer made of polyurethane block and fiber Bragg gratings. The test system is then employed to visualize the excavation of a round tunnel and some favorable results are gained. To some extent, the work in this article improves the physical modeling techniques and provides an effective method for the modeling research in rock tunnel engineering.

Fabrication and characterization of electrospun polyurethane blended with dietary grapes for skin tissue engineering

The tissue-engineered skin has emerged as a plausible alternative approach to the traditional wound dressing owing to its inherent advantages. Further, in tissue engineering applications, fibrous scaffold obtained through textile technologies is widely attractive. The present study focused on the fabrication of electrospun textile polyurethane wound dressing scaffold incorporated with grape extract. The fabricated composites showed smooth as well as reduced fiber (730 ± 127 nm) and pore (873 ± 51 nm) diameter than the control polyurethane (fiber diameter –890 ± 117 and pore diameter –1064 ± 74 nm) as revealed in the scanning electron microscopy. The formation of hydrogen bond in Fourier transform infrared spectroscopy revealed the interaction between the polyurethane and grape. The addition of grape enhanced the wettability behavior (86° ± 2) and the surface roughness (469 nm) of the polyurethane membrane. Thermal gravimetric analysis and mechanical testing revealed the enhancement of thermal and tensile strength with the incorporation of the grape into the polyurethane matrix. The in vitro blood compatibility and cytocompatibility studies revealed enhanced antithrombogenicity behavior and the non-toxic nature to human dermal fibroblast cells for the fabricated composites than the pristine polyurethane. Hence, the addition of grape into the polyurethane matrix had enhanced the physicochemical characteristics and biocompatibility parameters which could promote this candidate as a valid alternative for skin tissue engineering regeneration.

Kurkumin Yüklü Biyo-Bazlı Elektroeğirme Poliüretan Yapılar

Polymeric electrospun fibers present well-design scaffolds for wound healing applications. Here, the fabrication of biobased polyurethane (PU) blend fibers containing curcumin (Cur) was reported. Not only polymer concentration but also curcumin concentration affects the morphology, diameter, and contact angle values of the fibers. Morphological investigations revealed that the diameter and hydrophilicity of the PU fibers increased upon addition of curcumin. Effect of process parameters (applied voltage, flow rate, and tip-to-collector distance) on the average diameter and the hydrophilicity of the PU and PU/Cur fibers were examined. Optimum conditions to obtain uniform and bead-free PU/Cur fibers were determined as 12.5 kV, 1 mL/h, and 17 cm. This study demonstrates that the electrospinning process provides a simple way of obtaining bioactive agent loaded fibrous scaffolds, as well as contributing to a better understanding of the effect of process variables in the fabrication of PU/Cur blend fibers for wound healing applications.

Design of polyurethane fibers: Relation between the spinning technique and the resulting fiber topology

ABSTRACTProperties or characteristics of fibers are affected by their topology. In fact, these topologies are found to have significant impacts in the functionalities of many applications. Hence, in this study, the relations between the spinning techniques and the topology of the resulting fibers are studied with the aim to provide a guideline for future reference where fibers with certain topology can be fabricated to suit specific applications. For this purpose, polyurethane is chosen to be the raw material to fabricate the fibers due to its versatility to be applied in various fields. The surface morphology, structures, and alignments of the fibers are studied. It is found that the polymer solution properties largely influence the mechanisms in the spinning process and can significantly affect the topology of the fibers. For instance, viscous solutions enable the spinning of coiled and smooth fibers, whereas conductive solutions encourage the splaying of the solution jet which results in the spinning of straight fibers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47706.