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In this paper, polyurethane nanofibers (PU)/chitosan (CS)/zinc oxide nanoparticles (ZnO)/ Glutathione (GSH) were prepared as wound dressings using the electrospinning method. First, the antibacterial effect of ZnO nanoparticles against Escherichia coli and Staphylococcus aureus was investigated. Second, the ability of the nanofibers to release different amounts of antibiotics and nanoparticles to prevent wound infection was investigated. The morphology of the composite nanofibers was investigated using field emission electron microscopy (FESEM). The chemical structure of the nano-wound dressing was examined using infrared spectroscopy (FTIR), and the FTIR spectroscopy results showed that GSH and ZnO nanoparticles were successfully arranged within the nanofibers. with an increase in the amount of GSH (1,3,5 wt%) at a constant voltage of 0.4 V, the amount of current increased by 1.7, 2.1, and 6.2 $\mu$A, respectively. According to the results of electrochemical analysis, the optimal amount of active ingredient is 5 wt%, but according to the images of FESEM analysis, due to the lack of nanofibers with the corresponding morphology, the amount of active ingredient is reduced to 5 wt% PU/Chi/.

A new series of thermotropic polyurethanes containing biphenyl units was synthesized by polyaddition reaction of diisocyanates such as 2,6-tolylene diisocyanate, 2,5-tolylene diisocyanate, 2,4-tolylene diisocyanate, and 1,4-phenylene diisocyanate, with 4,4□-bis(9-hydroxynonoxy)biphenyl (BP9). Structures of the monomer and the corresponding polymers were identified using FT-IR and ¹H NMR spectroscopic methods. BP9 exhibited a smectic type mesophase, however, nematic phase was found for all synthesized liquid crystalline polyurethanes except for 1,4-phenylene diisocyanate/BP9 based polyurethane. Their phase transition temperatures and thermal stability were investigated by differential scanning calorimetry (DSC), optical polarizing microscopy, and X-ray scattering. The infrared study indicated that the hydrogen bonding among urethane linkages attributed to the mesomorphism. Thermal gravimetric analysis (TGA) of synthesized polyurethanes showed that no weight loss of the polymers observed up to 280°C.

In the present study, we prepared and characterized electrically conductive adhesives based on polyurethane filled with two kinds of multiwalled carbon nanotubes (MWCNTs), viz. pristine MWCNTs and acid treated MWCNTs, respectively. The influence of the type of filler on the dispersibility within the polyurethane matrix and the corresponding electrical conductivity is investigated. The electrical conductivity of the prepared specimens was measured using a four-point probe. The morphology and dispersibility of the fillers were observed by field emission scanning electron microscopy and transmission electron microscopy.

A novel microencapsulated flame retardant containing melamine polyphosphate (MPP) and 4,4${}^{\prime }$-oxydianiline-formaldehyde (OF) resin as a core–shell material was synthesized using in situ polymerization. The flame retardant was added to polyurethane (PU) to improve the fire suppression performance of resulting materials. Polyurethane was modified by silane, which was called as Si–PU and MPP was microencapsulated by OF resin, which was OFMPP. The results indicated that the smoke obscuration index (SOI) values of Si–PU, Si–PU/MPP 30% and Si–PU/OFMPP 30% were 6.59, 3.04 and 1.16, respectively, which indicated that the addition of flame retardants causes a significant downward trend in SOI values. The SOI value of Si–PU/OFMPP 30% was lower than that of Si–PU/MPP 30%, indicating that the microencapsulated OFMPP achieved smoke suppression.

Liquid-infused porous surfaces inspired by Nepenthes pitcher plant were fabricated on polyurethane. Five different micro-structures, including pillar (PIL), Sharklet${}^{\circledR }$ (SHK), continuous discrete ridge (DIR), hole (HOL) and networking (NET), were fabricated by soft lithography. Effects of micro-structural geometry on lubricant infiltration capability were investigated by infiltration the micro-structures with two lubricants of different viscosity, Krytox-103 ($\eta$: 0.131 $\mathrm{\text{Pa}}\cdot \mathrm{\text{s}}$) and Krytox-105 ($\eta :0.737\mathrm{\text{Pa}}\cdot \mathrm{\text{s}}$). The lubricant infiltration and retention capability were determined using a confocal laser scanning micro-scopy, and properties of the infused surfaces were evaluated by measuring the speed of water droplet motion at various tilting angles. The results revealed that, for the 80$\mu$m-high micro-structures, infiltration with a less viscous Krytox-103 resulted in more complete infiltration and retention, particularly for the PIL micro-structure. The infused surface exhibited a slippery behavior signified by low sliding angle and good anti-adhesion against chlorophyll fluid and milk yogurt. The lubricant retention capability was significantly reduced for the 7$\mu$m-high micro-structures due to lower aspect ratio and low capillary force. In this case, the PIL infused with a more viscous Krytox-105 provided a slippery surface.

This paper discusses material named Polyurethane bonding which can be used in the stabilization of railroad ballast layer. An experimentation of the static and dynamic response of this material is important in designing appropriate solutions for railroad ballast layer, especially for the transition zone. A comprehensive study on the SHPB testing of Polyurethane bonding is presented in the strain rate range of 1000s${}^{-1}$–4000s${}^{-1}$. Variable power law was used to predict the material response at elevated strain rates as high as 10,000s${}^{-1}$. These results are compared with the material’s quasi-static response. The effects of strain rate on material parameters like Young’s Modulus and Yield Strength were investigated under various high strain rate dynamic experiments. It was found that the yield strength as well as Young’s modulus increased with the strain rate and the trend was more evident at higher strain rates. Quasi-Static Uniaxial Compression tests gave the typical stress–strain relationship of the material. A close investigation of the material response indicates that the behavior of this class of Polyurethane has a close resemblance with PMMA at the quasi-static as well as at various high strain rates.

Native heart valve leaflets are subjected to continuous pulsatile and homodynamic forces and can be as thin as 300 μm. For a proper function of the valve the materials selected for the leaflets need to be biocompatible, robust, flexible, and have comparable mechanical properties to the natural ones.

In this paper, biocompatibility and cell retention ability for gelatin–chitosan polyurethane (PU), polyglycolide (PGA)/PLA and collagen-coated bovine pericardium were examined and their mechanical properties were tested. Endothelial cells, isolated from ovine carotid arteries were seeded onto these materials and exposed to a range of shear-stresses for a period of 1–3 h.

The findings indicated that throughout the exposure time and the shear-stress range tested, a mean cell retention rate of 80% was obtained in the gelatin–chitosan PU group. However, for PGA/PLA and pericardium groups it was found that as the exposure time of shear-stress increased, a significant cell reduction was observed. Noticeably for all the range of physiological flow conditions tested, the electrospun gelatin–chitosan PU demonstrated good biocompatibility and cell retention properties and could be potentially used as a biomaterial for tissue engineering of heart valves.

Organic–inorganic hybridization technique is the recent trend to increase the performance of conventional organic coatings. In this work inorganic nano-Al₂O₃ was incorporated in organic waterborne polyurethane conventional coating (PUA) and applied on mild steel. The problem of lack of interfacial interaction between inorganic nanoreinforcement (nano-Al₂O₃) and organic matrix, agglomeration of high surface energetic nano-Al₂O₃ within the coating need to be solved. In order to obtain stable hybrid coating the organic bi-functional polymers, methyltrimethoxysilane (MTMS) and 3-glycidoxy-propyltriethoxysilane (GPTMS) were grafted on the surface of nano-Al₂O₃ and dispersed in PU coating by ultrasonication which were designated as PUM and PUG respectively. AFM analysis indicates that the grafting of nano-Al₂O₃ significantly reduces the agglomeration problems as well as root mean square surfaces roughness (Rq) of coating. Immersion studies conducted in 3.5 wt.% NaCl solution showed that the dielectric properties (polarization resistance) increases and corrosion rate decreases significantly with grafted coatings as measured by electrochemical technique. The mechanical properties of PUG and PUM hybrid coating showed the much better performance than waterborne Polyurethane (PU) coating.

This study aims to prepare composite materials and improve some of their mechanical properties by using epoxy resin (EP) and polyurethane (PU) as the matrix material and nanoparticles (Al₂O₃) as reinforcing agents in different ratio with weight fractions (5%, 10%, and 15%). The results in the tables show that increasing the weight fraction of nanoparticles leads to an increase in the elasticity coefficient and durability of the impact and absorbed energy, with an increase in the temperature of the composite material reinforced with nanoaluminum oxide particles. The mechanical properties gradually decrease with the increase of the period of immersion in water.

Composite polyurethane (PU)-SiO₂ hollow fiber membranes were successfully prepared via optimizing the technique of dry-jet wet spinning, and their pressure-responsibilities were confirmed by the relationships of pure water flux-transmembrane pressure (PWF-TP) for the first time. The origin for this phenomenon was analyzed on the basis of membrane structure and material characteristics. The effects of SiO₂ content on the structure and properties of membrane were investigated. The experimental results indicated that SiO₂ in membrane created a great many interfacial micro-voids and played an important role in pressure-responsibility, PWF and rejection of membrane: with the increase of SiO₂ content, the ability of membrane recovery weakened, PWF increased, and rejection decreased slightly.

Two polyurethanes of different molecular weights were prepared by the copolymerization of phenyl diisocyanate and diisopropyl tartrate. The polyurethanes having terminal isocyanate groups were reacted with 3-aminopropyl silica gel to afford two chiral stationary phases. The of the two polyurethanes were 4057 g/mol and 6442 g/mol. The polyurethanes and the corresponding chiral stationary phases were characterized by FT-IR, ¹H NMR and elemental analysis. The loading capacities of the polyurethanes on silica gel were 0.68 mmol units/g and 0.61 mmol units/g, respectively. The separation performance and the influence of additives, triethylamine and trichloroacetic acid, on the separation of chiral compounds were investigated by HPLC. The chiral stationary phase prepared from polyurethane with of 4057 g/mol demonstrated better enantioseparation capability than that with of 6442 g/mol. Additionally, it was found that the addition of triethylamine and trichloroacetic acid in the mobile phases significantly improved the enantioseparation for these two chiral stationary phases.

SMPU (shape memory polyurethane) non-ionomers and ionomers, synthesized with poly(ε-caprolactone) (PCL), 4, 4′-diphenylmethane diisocyanate (MDI), 1,4-butanediol (BDO), dimethylolpropionic acid (DMPA) were measured with cyclic tensile test and strain recovery test. The relations between the structure and shape memory effect of these two series were studied with respect to the ionic group content and the effect of neutralization. The resulting data indicate that, with the introduction of asymmetrical extender, the stress at 100% elongation is decreased for PU non-ionomer and ionomer series, especially lowered sharply for non-ionomer series; the fixation ratio of ionomer series is not affected obviously by the ionic group content; the total recovery ratio of ionomer series is decreased greatly. After sufficient relaxation time for samples stretched beforehand, the switching temperature is raised slightly, whereas the recovery ratio measured with strain recovery test method is lowered with increased DMPA content. The characterization with FT-IR, DSC, DMA elucidated that, the ordered hard domain of the two series is disrupted with the introduction of DMPA which causes more hard segments to dissolve in soft phase; ionic groups on hard segment enhance the cohesion between hard segments especially at high ionic group content and significantly facilitate the phase separation compared with the corresponding non-ionomer at moderate ionic group content.

A kind of novel triblock copolymers of poly(γ-benzyl L-glutamate)-b-poly(tetrahydrofuran)-b-poly(γ-benzyl L-glutamate)s (PBLG-b-PTHF-b-PBLG) was synthesized by using bis(3-aminopropyl) terminated polytetrahydrofuran to initiate the ring-opening polymerization of γ-benzyl L-glutamate N-carboxyanhydride (BLG-NCA). The corresponding multiblock poly(amino acid-urea)s were prepared in one-pot protocol from the chain extension of PBLG-b-PTHF-b-PBLG with MDI. The resulting triblock and multiblock copolymers were characterized by FTIR, ¹H-NMR, ¹³C-NMR and GPC techniques. It is demonstrated that the chain extension has taken place to give rise to the copolymers with the well-defined block composition and narrow molecular weight distribution. A distinct T_g arising from the hard-segments was observed in all the copolymers. Their mechanical properties showed an increasing trend with the molecular weight enhancement of the prepolymers.

Poly(hydroxyl butyrate-co-valerate) (PHBV) is a biopolymer synthesized by microorganisms that is fully biodegradable with improved thermal and tensile properties with respect to some commodity plastics. However, it presents an intrinsic brittleness that limits its potential application in replacing plastics in packaging applications. Films made of blends of PHBV with different contents of thermoplastic polyurethane (TPU) were prepared by single screw extruder and their fracture toughness behavior was assessed by means of the essential work of fracture (EWF) Method. As the crack propagation was not always stable, a partition method has been used to compare all formulations and to relate results with the morphology of the blends. Indeed, fully characterization of the different PHBV/TPU blends showed that PHBV was incompatible with TPU. The blends showed an improvement of the toughness fracture, finding a maximum with intermediate TPU contents.

With the development of society, oil pollution has become more and more serious, it is becoming a global issue to separate oil and water mixture. Currently, a variety of functional materials have been successfully prepared for oil/water separation. Among them, polyurethane is an attractive candidate due to its low cost, wear-resistance and excellent mechanical properties. This report summarizes the design strategy of polyurethane-based materials and their applications in oil/water separation. The progress made so far will guide further development of polyurethane-based materials for oil/water separation.

Cell survival of thick engineered scaffolds is often compromised due to limited oxygen diffusion. Therefore, the design of oxygen-delivering nanofibrous polyurethane (PU)-calcium peroxide (CPO) scaffolds was investigated in this study. The average size of CPO nanoparticles was $57.7\pm 7.33$nm. The average diameter of PU fibers was $0.51\pm 0.23\mu$m, which was increased to $0.68\pm 0.27$, $0.98\pm 0.47$, and $1.68\pm 1.14\mu$m upon incorporation of 0.1wt.%, 0.5wt.% and 1wt.% CPO, respectively. The CPO-containing scaffolds could produce oxygen for at least 13 days. Samples containing 0.5% CPO showed the highest oxygen release without a significant change in pH. For this sample, the addition of ascorbic acid as an antioxidant to counteract the possible formation of ROS, reduced the fiber diameter to $0.64\pm 0.50\mu$m and increased the oxygen release. Adding 0.5% CPO improved the cell viability on the fifth day. In addition, the PU-CPO composite scaffold showed strong antibacterial activity. Overall, designed scaffolds could be useful in different tissue engineering applications to overcome the limited oxygen availability early after implantation.

The effect of substrate chemistry on surface phase separation of polyurethane films were investigated by using self-assembled monolayer (SAM) with chemically different modifications, i.e. hydroxy (–OH) and methyl (–CH₃) end groups. Results showed that hydrophilic (–OH) and hydrophobic end groups (–CH${}_3)$ could respectively promote the aggregation of hard and soft segments at polyurethane–substrate interface, which further regulates the phase separation of polyurethane surface that contacts the substrate. The aggregation of hard segments tended to enhance the surface smoothness of polyurethane films, especially on hydrophilic substrates with hydroxy modification. Further analysis of tensile testing revealed that the regulation of surface phase separation had no effect on the shape memory effect of polyurethane films. These findings suggest that the chemical properties of the substrates could regulate the phase separation and may provide some guidance on the design of specific polyurethane with desired morphology and properties.

In this paper, a functional ternary slurry consisting of polyurethane (PU) microspheres, graphene oxide (GO) nano platelets and silicon oxide (SiO₂) abrasives was used to carry out the polishing process on Si face of 4H-SiC wafers. The processing parameters of the slurry include graphene weight fraction in slurry GO1–GO7 (0.1–0.7wt.%), pH value (3–5), and sonication time T5–T15 (5–15min). Polishing process is conducted with two kinds of polishing pads A and B, PU and PC (polycarbonate). Results show that material removal rate (MRR) increases with increasing GO weight fraction up to GO5; besides, MRR also increases with increasing sonication time up to T10, and with increasing pH value. Using PU pad, the GO5-T10-pH5-A slurry leads to highest MRR 102.220nm/h of the polished SiC wafer. On the other hand, surface roughness improvement rate (SRIR) increases with increasing GO weight fraction up to GO5, and increases with increasing sonication time up to T15. But SRIR is not affected by pH value. Regarding effect of pad type, on average the PU pad results in higher MRR and better SRIR compared with the PC pad. Using PC pad, GO5-T10-pH5-B leads to lower MRR of 87.627nm/h. The addition of GO as the ternary slurry demonstrates its better effect on polishing SiC wafers by comparing with the counterpart binary slurry without GO. For example, MRR by the counterpart slurry SiO₂12-pH5-A is 58.411nm/h, which is lower than 102.220nm/h by the ternary slurry GO5-T10-pH5-A. Both XPS and Raman spectra demonstrate that the wafer polished by the functional ternary slurry can effectively produce the softer SiO₂ reactant layer on SiC wafer, and result in better polishing performance.

4D printing technology endows printed samples with self-driven performance that increasingly show strong application prospects. Polyurethane, as a typical shape memory polymer, is widely used in 4D printing. Current researches on 4D printed polyurethane materials are focused on investigating polyurethane composites or novel printing techniques to optimize the shape memory properties of the printed samples. In this study, the effects of pre-programmed 4D printing process parameters on the shape memory properties of polyurethane were systematically investigated. The higher printing speed, higher printing temperature, and lower fill rate result in faster response time of the biomimetic samples with thermal stimulation. Based on the programming of process parameters (e.g., printing temperature, printing speed and filling rate), the biomimetic flowers and hands were processed to achieve a controlled behavior of sequential deformation. It was successfully achieved that only one printing material could demonstrate the shape memory effects with a sequential response process. The adjustable sequential deformations further enlighten the application of 4D printing technology in specific engineering fields such as aerospace, biomedicine, robot and military engineering, where parts must undergo a sequence of deformations to serve practical requirements.

In this article, the enhanced radiation crosslinking of polyurethane via double-bond capping method were discussed in detail. Meanwhile, the Enhanced radiation crosslinking of polyurethane based on polyimide as hard segment were emphasized. In addition, the preparation of radiation crosslinking foam by introducing terminal double-bond were introduced.