Elastic Polyurethane Research Articles

Bio-based Polyurethane Based on a Dynamic Covalent Network with Damage Tolerance for Controlled Release of Fertilizers

Bio-based polyurethanes are promising for the controlled release of nutrients and fertilizers, but their toughness and plasticity need to be improved. We developed a smooth, dense, elastic, and indestructible bio-based polyurethane (BPU) coating with a nutrient controlled release ∼150% superior, a tensile strength ∼300% higher, and a toughness ∼1200% higher than those for the original BPU coating. Through a one-step reaction of soybean oil polyols (accounting for more than 60%), isocyanate, and benzil dioxime, the dynamic covalent network based on oxime-carbamate replaces part of irreversible covalent cross-linking. The dynamic fracture-bonding reaction in the modified coating BPU can effectively promote the hydrogen bond recombination and oxime-carbamate chain migration in the coating process, which avoids the structural defects caused by coating tear and fertilizer collision. This work provides a simple and versatile strategy for building controlled-release fertilizer coatings.

Experimental study on the interface shear performance of elastic polyurethane concrete–steel plate

The delamination and sliding failure of steel bridge deck pavements occur frequently due to insufficient shear resistance between their interface. Adopting an elastic polyurethane concrete (EPUC) bridge deck pavements can solve this problem. In this study, an interface shear experiment was conducted to investigate the interface shear performance of the EPUC–steel plate, in which 108 EPUC–steel plate composite specimens were divided into 36 groups. The emphasis of the research was to establish the interface failure mode, the shear stress–shear deformation curves characteristics and the constitutive model. Then, the impacts of temperature, loading rate and hygrothermal aging factors on the interface shear strength were determined. Test results showed that the interface failure mode was in the form of adhesion failure at the low-temperature section (−20 °C, −10 °C, 0 °C and 10 °C), mixed failure at 25 °C and 45 °C, and cohesive failure at 70 °C. The interface failure mode was changed from mixed failure to cohesive failure after hygrothermal aging. The shear stress–shear deformation curves at the low-temperature section, 25 °C and after hygrothermal aging exerted a two-stage development law, which could be described by an exponential function. Meanwhile, the curves at the high-temperature section (45 °C, 70 °C) exerted a three-stage development law, which can be described by the Popovics model. The interface shear strength decreased with the increase in temperature, whereas the interface shear strength remained at a high level at the high temperature. At the low-temperature section, the interface shear strength increased with the rise in shear rate, depicting a linear relationship. In the normal and high-temperature sections, the interface shear strength firstly increased and then decreased with the rise in the shear rate, depicting a quadratic parabolic relationship. The interface shear strength decreased with the increase in aging. Within the same age, the higher the temperature, the greater decrease in interface shear strength.The research results can provide experimental and theoretical support for the popularization and application of EPUC bridge deck paving materials.

Treating Waste with Waste: Facile Preparation of Elastic Thermoplastic Polyurethane Monolith for Efficient Oil/Water Separation

Abstract An auspicious thermoplastic polyurethane (TPU) monolith has been prepared by a facile and cost-effective method of thermally induced phase separation (TIPS). With superb porous structure, excellent hydrophobicity/oleophilicity, and superior elasticity, the obtained TPU monolith exhibits an outstanding adsorption capacity, high oil/water separation efficiency, and good recycling performance, achieving the goal of treating waste with waste.

The impact of stain removal and bleaching on the adhesion strength of water-based varnish layers in oak

The aim of this study is to determine the performance of water-based varnish adhesion on the process of stain removal, bleaching and impregnation applied to wood surfaces. In order to accomplish this objective, the selected sessile oak (Quercus petreae Mill.) wood samples were firstly contaminated with grease and PVAc glue, after they were cleaned. Then, the wood samples were bleached by using oxalic acid (C2H2O4) and hydrogen peroxide (H2O2). Secondly, preprocessed specimens impregnated with imersol aqua (IA) and wood protective chemicals (WP) and together both these chemicals (IA+WP). Finally, adhesion strength performance of the wood samples were tested after they covered by single component primary resin (SCPR), double component polyurethane modified with acrylic (DCAP) and double component elastic polyurethane (DCEP). The adhesion resistance of varnish layers is determined according to ASTM 4541 principles. As a result, the oil stain removal and the protective chemical applications decreased the adhesion strength on the wood surface of water-based varnish layers. Contrary, the glue stain removal and the C2H2O4 and H2O2 bleaching increased the adhesion strength. Also, it was determined that DCEP applications have the highest value in oak wood samples.

Fibers and Textiles for Personal Protective Equipment: Review of Recent Progress and Perspectives on Future Developments

This article reviews recent developments in fibers and textiles for Personal Protective Equipment (PPE) applications. Fibers are grouped into six categories: highly extensible elastomeric fibers, cellulose-based fibers, commodity synthetic fibers, high strength inorganic materials, and high performance polymer fibers. New developments with highly extensible elastomeric fibers include polyester-based elastic fibers and shape memory polyurethane. In the case of cellulose-based fibers, environmentally friendly processes and nanotechnology-enabling treatments are developed for natural fibers where attempts are made to transfer interesting attributes of the feedstock to regenerated cellulose fibers. Commodity synthetic fibers comprise polyolefins, polyester, and polyamide; they have seen recent developments in terms of surface functionalization and the formation of structures at the nanoscale. In terms of high strength inorganic materials, basalt fibers and carbonaceous materials have found increased use in PPE. Boron is also generating considerable interest for fibers and coatings. Research on high-performance polymer fibers includes further improving their short- and long-term performance, moving to the nanoscale for new functionalities, and exploring their recyclability. An additional section describes a series of special textile structures relevant to PPE involving 3D textile structures, auxetic textile structures, shear thickening fabrics, nanoporous structures, phase change materials, and some specially designed textile-based composite structures for improved protection against mechanical hazards. The article ends with some perspectives on promising avenues for further developments.

Stress concentration-relocating interposer in electronic textile packaging using thermoplastic elastic polyurethane film with via holes for bearing textile stretch

Electronic textile (e-textile) devices require mechanically reliable packaging that can bear up to 30% stretch induced by textile crimp stretch, because the boundary between the rigid electronic components and the soft fabric circuit in the e-textile is prone to rupture due to mismatch of their mechanical properties. Here, we describe a thin stress-concentration-relocating interposer that can sustain a textile stretch of up to 36%, which is greater than the 16% stretch of conventional packaging. The stress-concentration-relocating interposer consists of thin soft thermoplastic polyurethane film with soft via holes and is inserted between the electronic components and fabric circuit in order to move the area of stress concentration from the wiring area of the fabric circuit to the film. A finite element method (FEM) simulation showed that when the fabric is stretched by 30%, the boundary between the electrical components and the insulation layer is subjected to 90% strain and 2.5 MPa stress, whereas, at 30% strain, the boundary between the devices and the wiring is subjected to only 1.5 MPa stress, indicating that the concentration of stress in the wiring is reduced. Furthermore, it is shown that an optimal interposer structure that can bear a 30% stretch needs insulating polyurethane film in excess of 100 μm thick. Our thin soft interposer structure will enable LEDs and MEMS sensors to withstand stretching in several types of fabric.

High strength and anti‐freezing piezoresistive pressure sensor based on a composite gel

AbstractPiezoresistive sensors constructed by functionalized elastic gel have received broad research by virtue of the visible advantages, such as low‐cost, stability of signal collection, and excellent compress strain. Herein, a new method about improved in situ polymerization of pyrrole monomer coated on polyurethane (PU) sponge was developed, which endowed the sponge with high and homogeneous conductivity. Then, a conductive polypyrrole@polyurethane‐polyacrylamide (PPy@PU‐PAM) composite gel was constructed by filling the PPy@PU sponges with PAM gel. The composite gel showed favorable compression performance attributed to the excellent elasticity of the PAM gel and porosity of the elastic PU sponge. The obtained elastomer exhibited excellent compressibility (869 kPa). Moreover, the addition of glycerin endowed the elastomer with excellent frost resistance and compression resilience at −20°C, which could greatly broaden the application in extreme environments. The piezoresistive sensor established by the composite elastomer can withstand and sense high pressure both at 25 and −20°C. Therefore, the pressure sensor shows potential applications in various fields, such as, health‐care monitoring system, motion signal collection, and robotic control.

Microporous Spongy Scaffolds Based on Biodegradable Elastic Polyurethanes for the Migration and Growth of Host Cells

Microporous Spongy Scaffolds Based on Biodegradable Elastic Polyurethanes for the Migration and Growth of Host Cells

Highly stretchable, durable, and breathable thermoelectric fabrics for human body energy harvesting and sensing

AbstractStretchable thermoelectrics have recently attracted widespread attention in the field of self‐powered wearable electronics due to their unique capability of harvesting body heat. However, it remains challenging to develop thermoelectric materials with excellent stretchability, durable thermoelectric properties, wearable comfort, and multifunctional sensing properties simultaneously. Herein, an advanced preparation strategy combining electrospinning and spraying technology is proposed to prepare carbon nanotube (CNT)/polyvinyl pyrrolidone (PVP)/polyurethane (PU) composite thermoelectric fabrics that have high air permeability and stretchability (~250%) close to those of pure PU nanofiber fabrics. Furthermore, PVP can not only improve the dispersion of CNTs but also act as interfacial binders between the CNT and the elastic PU skeleton. Consequently, both the electrical conductivity and the Seebeck coefficient remain unchanged even after bending 1000 times. In addition, self‐powered sensors for the mutual conversion of finger temperature and language and detection of the movement of joints to optimize an athlete's movement state were successfully fabricated. This study paves the way for stretchable thermoelectric fabrics with fascinating applications in smart wearable fields such as power generation, health monitoring, and human–computer interaction.

Carbon deposition and argon post-treatment of polyurethane surface: Structural-mechanical and fracture properties

Modification of polymeric surface by plasma ions has perspectives in creating flexible functional materials; their deformation behavior is one of the most important properties, as poor fracture resistance cancels all advantages. Carbon ions were deposited on the surface of elastic polyurethane with subsequent argon treatment. Created carbon-containing nanolayer has increased wettability and nonuniform local mechanical properties. Uniaxial extension to strains >100% induces discontinuous microcracks of carbon-modified surfaces but their propagation is constrained by inhomogeneities of the modified layer. Argon post-treatment improves wettability further but makes local mechanical properties uniform that decreases the fracture resistance. Multi-cycle uniaxial loading to 50% doesn't damage the surface but forms in the modified layer weakened domains – precursors of failure; this improves crack resistance at strains >100% a mesh of disordered microcracks appears preventing propagation of long cracks.

Facile preparation of super lightweight and highly elastic thermoplastic polyurethane bead blend foam with microporous segregated network structure for good interfacial adhesion

The foamability of three different grades of TPU beads was studied, and two of them were selected to fabricate super lightweight and highly elastic TPU blend foams. Four different types of TPU combination blend foams with a microporous segregated network structure (MSNS) were prepared by solution-compression molding in combination with supercritical fluid (SCF) foaming. The results showed that the interface was well combined, and a bimodal cell structure was produced; the continuous phase constituted a MSNS. All TPU blend foams exhibited good springback performance, among which, TPUb70/TPUc70 blend foam had lowest hysteresis loss (3.8%) and lowest stress loss (2.6%). Thermal conductivity results showed they all have good thermal insulation, and the lowest thermal conductivity was 0.037 W/(m·K) for TPUb70/TPUc70 foam. This study offers a simple and cost-effective approach preparing high-performance foams with cushion, sound and shock absorption, and heat preservation for use in electronics, home appliances, sports, etc.

Reducing environmental hazards in the elimination of oil spills through the use of sorption materials based on polyurethane foams containing waste from agricultural and polymer industries

The work is devoted to the development of a sorption material based on elastic polyurethane foam (PUF) containing waste from agricultural and polymer industries. The fillers were fruit shells of buckwheat grains, rice, acacia sawdust, fruit shells, rice straw, walnut shells and ground corn cobs, hardwood sawdust, polymeric waste of expanded polystyrene foam. Oil from the Romashkinskoye field (Tatarstan) was used as a pollutant. The optimal mass ratio of the components of the material A of the PPU component: B of the PPU component: filler = 1: 0.6: 0.16-0.72 (depending on the type of filler) has been determined. The best absorbing capacity of ∼ 13 g / g is possessed by a material based on polyurethane foam and rice straw. Sorption material for cleaning aquatic ecosystems has a high absorbing capacity not only for petroleum products (diesel fuel, industrial oil), but also for products of inorganic origin (vacuum oil). The sorption material is selective and has a higher absorption capacity with respect to oil than to water, the coefficient of selectivity of absorption is 0.4 for an exposure time of 120 min. The possibility of utilization of waste sorption material by the method of thermochemical degradation using a destructive agent based on PPU component A was investigated. The resulting destructate is a homogeneous liquid, easily combined with BND 60/90 bitumen with the formation of a homogeneous polymer-bitumen binder.

Impact of fatigue loading on the surface of polyurethane treated in argon and acetylene plasma

Soft plasma-treated polymers have good prospects in the creation of biomedical products. Their application is associated with cyclic mechanical loads. The practical applicability of such coatings is unclear without investigating the effect of deformation on the structure of modified surfaces. Elastic polyurethane (synthetic two-phase polymer) was used in this work. Its surface was preliminarily cleaned from low-molecular fractions by argon plasma and then treated by plasma chemical decomposition of acetylene in argon plasma for 30...120 s. The structural and mechanical inhomogeneities of the obtained carbon-containing nanocoatings depend on the treatment time and were caused by the composition of the initial substrate. Uniaxial fatigue loading leads to the formation of transverse folds on the coatings in the unloaded state (a result of elastic-plastic deformation of the coating); under tension these folds are open and form local nanocracks. One of the variants of plasma modification did not give the formation of cracks; it is associated with the areas with a pronounced stiffness contrast of this coating.

Proizvodnja i ispitivanje elektormagnetnih generatora milimetarske skale za udarne kretnje visokih amplituda

Environment vibrations are an important source of energy, often occurring at very low frequencies, but with large amplitude. The possibility to use the large amplitude of the motions is important to enhance the energy harvester's output power. In this paper, an electromagnetic energy harvester is designed and fabricated to produce electricity from low- frequency high amplitude impact motions using an elastic polyurethane cylinder. This millimeter-scale electromagnetic generator (MS-EMG) includes a movable magnet attached to a free sliding mass, a fixed coil, and a polyurethane holding chamber. Polyurethane is a very stable elastic polymer that provides continuous large-amplitude movement for the magnet and plays an effective role in impact capability. Therefore, the effect of impact excitation and the polyurethane foam was investigated simultaneously. The performance of the device was studied, experimentally, for the environment vibrations in the range of 1 to 10 Hz. The impact motions were applied using a simulator that was fabricated for this work. The fabricated MS-EMG with a volume of 1.07 cm3 and a mass of 8.74 g show the capability of producing a voltage of 44.41 mV and power of 10.48 µW over a 100 Oresistive load, using a 6 Hz frequency impact motion. Finally, an analytical model is used to simulate the device performance which showed a good agreement with the experimental results.

Elastic polyurethane shock absorbers

Elastic polyurethane shock absorbers

Directional Transportation in a Self-Pumping Dressing Based on a Melt Electrospinning Hydrophobic Mesh.

Self-pumping wound dressings with directional water transport ability have been widely studied for their function of directional extraction of excessive biofluid from wounds while keeping the wound in a moderately humid environment to realize rapid wound healing. However, the existing solutions have not paid close attention to the fabrication of a nonirritating hydrophobic layer facing the wounds, which may cause irritation to wounds and thereby further worsen inflammation. Herein, a flexible and elastic thermoplastic polyurethane (TPU) hydrophobic microfiber mesh (TPU-HMM) produced by melt electrospinning (MES) is reported. The TPU-HMM was compounded to a hydrophilic nanofiber membrane, which was fabricated by blending with polyamide 6 and poly(ethylene glycol) (PA6-PEG) to form a composite self-pumping dressing, for which the breakthrough pressure in a reverse direction was 12.8 times than that in a positive direction and the forward water transmission rate was increased by 700%. It shows good directional water transport ability and is expected to absorb excessive biofluid of the wounds. This solvent-free and easy-process TPU-HMM provides a new strategy for the development of functional self-pumping textiles, and the solvent-free fabrication method for fibers, which eliminates the potential toxicity brought by solvent residues, offers more possibilities for its applications in biomedicine.

The Effects of Plasma Subplantation of Nitrogen Ions on the Structure and Mechanical Properties and Biomedical Surface Properties of Elastic Polyurethane

The Effects of Plasma Subplantation of Nitrogen Ions on the Structure and Mechanical Properties and Biomedical Surface Properties of Elastic Polyurethane

Au‐Nanoparticle‐Array/Aligned‐Ag‐Nanowire‐Based Flexible Dual Plasmonic Substrate for Sensitive Surface‐Enhanced Raman Scattering Detection

AbstractThe fabrication of flexible surface‐enhanced Raman scattering (SERS) substrates for sensitive detection on uneven or irregular surfaces is challenging. In this study, a flexible dual plasmonic SERS (FDPS) substrate rationally constructed using Au nanoparticle (AuNP) arrays/aligned Ag nanowires (AgNWs) and elastic polyurethane (PU) is demonstrated. It exhibits high sensitivity (detection limit of 10−8 m for melamine and 10−10 m for malachite green) and excellent reproducibility. The well‐designed structure of AuNP arrays/aligned AgNWs fabricated using block copolymer self‐assembly and oil–water–air interfacial self‐assembly successfully enhances the electromagnetic field through plasmonic coupling. In addition, the FDPS substrate retains a high SERS sensitivity after exposure to air at room temperature for 30 days because of the high stability of AuNP arrays and antioxidation characteristic of the PU covered on the aligned AgNWs. Even after undergoing stretching, bending, and twisting for 100 cycles, the FDPS substrate maintains a stable SERS activity owing to the introduction of the elastic PU. This study demonstrates a potential application of SERS detection under practical conditions for irregular surfaces and may be helpful in the development of flexible sensors.

Monte Carlo Simulation of Glycerol Poly-alkoxylation: A Novel Application of a Stochastic Algorithm

Propylene oxide (PO) homopolymer and PO/ethylene oxide (EO) copolymers, initiated by the starter glycerol (GLY), are the most popular polyols employed in the production of elastic polyurethanes. Th...

An optical-electrical co-sensing tape for cross-sectional deformation monitoring of shield tunnels

Cross-sectional deformation is a crucial index for evaluating the stability and safety of shield tunnels. Monitoring the cross-sectional deformation has been an important content in assessing the health condition of tunnels. For this reason, an optical-electrical co-sensing tape (OECST) by embedding distributed optical fiber sensor (DOFS) and coaxial cable F-P interferometer sensors (CCFPI) into a high elastic polyurethane tape has been proposed in this paper. It can simultaneously measure the low-strain area of structure with high accuracy by DOFS and large-strain area with relatively lower accuracy by CCFPI. The conceptual and geometric design, fabrication method, and sensing mechanism have been discussed. A laboratory test has also been conducted to validate that the OECST can provide reliable strain measurement. Subsequently, an algorithm has been proposed to measure the cross-sectional deformation of shield tunnels by using OECST strain measurements. The cross-sectional deformation has discontinuous features with large deformation of joints (dislocation, opening, closing, etc.) and small deformation of segments. The former can be obtained by performing geometrical analysis on rough strain measurements of the CCFPI in OECST. The latter can be derived by implementing the strain–displacement conversion on the accurate distributed strain measured by the DOFS-S in OECST. The method has been investigated experimentally. The findings from the study have demonstrated that the proposed OECST can measure the cross-sectional deformation of shield tunnels with a satisfactory accuracy, which can be used to assess the health condition of tunnels.