Search

The industry's mechanical equipment often faces a significant demand for damping rubber. Simultaneously improving damping and toughness of rubber materials is a challenging task. It was achieved by incorporating crystal particles into the chlorinated butyl rubber (CIIR) network, inspired by the "sliding crystal mechanism". To create the elastomers with high damping and toughness, polyurethane was used along with polyethylene glycol as a soft segment. The combination factors, including coordination and hydrogen bonds, played a crucial role in facilitating the formation of crystal particles within the material. These crystal particles acted as rigid fillers, enhancing the material's toughness. Additionally, the sacrificial reversible bonds present in the crystal particles allowed for energy dissipation during stress. These bonds can be repeatedly broken and regenerated, enabling the material to dissipate energy efficiently. Comparing these elastomers to pure CIIR, they exhibited a tensile strength and elongation at break of 5.76 MPa and 1973%, a fracture energy of 28.73 MJ/m3, a damping factor of 1.52, and a damping temperature range of 80 °C. These results indicate significant improvements in both damping and toughness properties. This advancement could have valuable implications for the industry's mechanical equipment, which often relies on effective damping rubber. [ABSTRACT FROM AUTHOR]

Effects of xanthene dyes and aerosil nanoparticles on the structure and dynamic characteristics of the cross-linked polyurethane were investigated by the IR-spectroscopy, dynamic-mechanical analysis, and electronic paramagnetic resonance methods. Dye molecule presence causes self-association of urethane groups within polymer rigid segments, weaker interactions between urethane groups and flexible oligoether parts and increased oligoether mobility. Increased mobility of flexible segments by xanthene dyes provides the necessary beam strength due to compensating the nanofiller network effect. The most efficient polyurethane material in the radiation resistance is expected to be a polymer composite with the highest permeability and the lowest modulus of elasticity. [ABSTRACT FROM AUTHOR]

ZnO is considered to be a good catalyst for the synthesis of polyurethanes (PUs) by alcoholysis of bisureas (BUs). ZnO tends to form Zn(NCO)2(NH3)2 in the presence of urea at high temperature, so does it in the alcoholysis of BUs. Here, attempt is made to understand the role Zn(NCO)2(NH3)2 plays in the alcoholysis of BUs. A loading of Zn(NCO)2(NH3)2 at 5 mol% is found to be sufficient to catalyze the polymerization and the reaction time is greatly cut from 40 h (catalyzed by ZnO) to 26 h, with similar chemical structures and properties. The tensile strength, elongation at break, and toughness for PU–Zn‐5 can reach 43.8 MPa, 330%, and 94.0 J cm−3, respectively. One‐pot synthetic strategy is then further introduced to improve the efficiency of the polymerization. Zn(NCO)2(NH3)2, BU, and PU can be synthesized in one‐pot, by adding ZnO, urea, diamine, LiBr, and diol sequentially. The feasibility of this one‐pot method is verified, indicated by the similar reaction time, chemical structures, molecular weight, thermal and mechanical properties. This one‐pot synthetic strategy offers an efficient way to synthesize PUs directly and simply from urea, diamines, and diols, which is beneficial for improving the molecular diversity of PUs. [ABSTRACT FROM AUTHOR]

Polyurethane (PU) is a type of polymer, which exists in various forms in the environment. Very few studies are available concerning the structure or enzymatic mechanism of the microbial community, which can degrade PU. Degradation of PU remains a difficult problem with respect to the environmental and biological disciplines. This study mainly focused on identifying the micro-organisms able to degrade polyurethane and confirming the degradation by performing a plate assay, Sturm test and scanning electron microscopy. Optimal culture conditions for maximum PU degradation were also analyzed through classical methods. A soil burial test was conducted by placing polyurethane films in the soil for one month, and the microbe growing on the surface of polyurethane films—with a maximum degradation of 55%—was isolated and identified as Aspergillus versicolor (ARF5). The culture medium was also optimized with different physical and chemical parameters for maximum PU degradation. The presence of CO2 as a by-product of PU biodegradation was confirmed through the Sturm test. [ABSTRACT FROM AUTHOR]

In this study, the effect of temperature (below and above Tg) on the rate of crack growth and on the fatigue threshold energy release rate of a polyurethane (PU) adhesive is analysed. The effect on the results of the Paris law relation used is also investigated. Tests were performed under a displacement-control strategy and at different temperatures. Out of the experimental data, the threshold energy release rate was determined as a function of temperature, something which up until now has been much more common for adhesive systems other than polyurethane. Results showed that the threshold energy release rate diminishes with increasing temperature, while the crack growth rate increases for a given strain energy release rate. The ratio between the threshold energy release rate and critical strain energy release rate remained constant for tests above the Tg, indicating that fatigue tests need only be performed at one temperature when above the Tg at least for the range of temperatures considered in this study and for the adhesive tested. A Paris law relation taking into account the effect of R-ratio during the displacement-control fatigue tests proved effective in unifying results at different temperatures. [ABSTRACT FROM AUTHOR]

This pilot investigation identifies the influence that changing the process variables of curing pressure, curing temperature, and mix ratio of a polyurethane/agglomerated cork matrix has on the mechanical properties of energy absorption, Young's modulus of elasticity, and spring stiffness in safety helmets intended for micro-transport riders. The results are compared to expanded polystyrene, a material commonly used in micro-transport helmets. Mechanical testing of the various samples found that, over the range tested, curing pressure had no effect on any of the mechanical properties, while increasing amounts of resin caused a stiffer structure, and increasing curing temperature led to increased energy absorption. Consistent with the elastic modulus findings, all polyurethane/agglomerated cork test samples demonstrated higher median levels of spring stiffness, ranging from 7.1% to 61.9% greater than those found for expanded polystyrene. The sample mixed at a 1.5:1 binder/cork ratio and cured at 40 °C displayed the closest spring stiffness to EPS. While the mechanical properties of the eco-friendly polyurethane/agglomerated cork matrix did not match those of expanded polystyrene, the difference in performance found in this study is promising. Further investigation into process variables could characterise this more ecologically based matrix with equivalent energy-absorbing and structural characteristics, making it equivalent to currently used expanded polystyrene and suitable for use in micro-transport helmets. [ABSTRACT FROM AUTHOR]

Fluorinated polyurethane (FPU) is a new kind of polyurethane (PU) material with great applicational potential, which is attributed to its high bond energy C-F bonds. Its unique low surface energy, excellent thermal stability, and chemical stability have attracted considerable research attention. FPU with targeted performance can be precisely synthesized through designing fluorochemicals as hard segments, soft segments, or additives and changes to the production process to satisfy the needs of coatings, clothing textiles, and the aerospace and biomedical industries for materials that are hydrophobic and that are resistant to weathering, heat, and flames and that have good biocompatibility. Here, the synthesis, structure, properties, and applications of FPU are comprehensively reviewed. The aims of this research are to shed light on the design scheme, synthesis method, structure, and properties of FPU synthesized from different kinds of fluorochemicals and their applications in different fields and the prospects for the future development of FPU. [ABSTRACT FROM AUTHOR]

Conventional paint spraying processes often use small molecule organic solvents and emit a large amount of volatile organic compounds (VOCs) that are highly toxic, flammable, and explosive. Alternatively, the spraying technology using supercritical CO2 (scCO2) as a solvent has attracted attention because of its ability to reduce VOC emissions, but the flow characteristics of coatings have not been thoroughly studied. Therefore, we numerically simulate the spraying process based on the actual process of scCO2 spraying polyurethane coatings by computational fluid dynamics (CFD). The effects of inlet pressure and volume fraction of scCO2 on the fluid motion parameters inside the nozzle as well as the atomization effect of droplets outside the nozzle are investigated. The simulated results show that a fluid with a large volume fraction of scCO2 will obtain a smaller density, resulting in a larger velocity and a larger distance for the spray to effectively spray. Higher coating content and bigger inlet pressures will result in higher discrete phase model (DPM) concentrations, and thus a bigger inlet pressure should be used to make the droplets more uniform across the 30° spray range. This study can provide theoretical guidance for the process of scCO2-sprayed polyurethane resin. [ABSTRACT FROM AUTHOR]

Two polyurethanes (PUs) were similarly synthesized by reacting a cycloaliphatic isocyanate with 1,4-butanediol and two polyols of different nature (polyester, polycarbonate diol) with molecular weights of 1000 Da. Only the PU synthesized with polycarbonate diol polyol (YCD) showed intrinsic self-healing at 20 °C. For assessing the mechanism of intrinsic self-healing of YCD, a structural characterization by molecular weights determination, infrared and X-ray photoelectronic spectroscopies, differential scanning calorimetry, X-ray diffraction, thermal gravimetric analysis, and dynamic mechanical thermal analysis was carried out. The experimental evidence concluded that the self-healing at 20 °C of YCD was due to dynamic non-covalent exchange interactions among the polycarbonate soft segments. Therefore, the chemical nature of the polyol played a key role in developing PUs with intrinsic self-healing at 20 °C. [ABSTRACT FROM AUTHOR]

Protein-stable coverage of the artificial implant is a key problem for biocompatibility. In the present study, a protein layer was attached covalently to a polyurethane surface treated by an ion beam. A plasma system consisting of a vacuum chamber (0.8 Pa pressure) with a high voltage electrode powered by a short pulse (20 μS pulse duration and 200 Hz pulse repetition) generator was designed. Polyurethane with a formulation certified as a material for medical implants was treated by nitrogen ions with an energy of 20 keV and 5 × 1014–1016 ions/cm2 fluence range. Wettability measurements, X-ray photoelectron, Raman, Fourier transform infrared attenuated total reflection, and ellipsometry spectra showed a significant change in the structure of the surface layer of the treated polyurethane. The surface of the treated polyurethane contained a carbonised layer containing condensed aromatic clusters with terminal free radicals. The surface energy of polyurethane surface increased from 33 to 65 mJ/m2. The treated polyurethane surface became capable of adsorbing and chemically binding protein (fibrinogen). The designed system for ion beam treatment can be used for surface activation of biomedical polymer devices, where a total protein coverage is required. [ABSTRACT FROM AUTHOR]

Plastic degradation by biological systems emerges as a prospective avenue for addressing the pressing global concern of plastic waste accumulation. The intricate chemical compositions and diverse structural facets inherent to polyurethanes (PU) substantially increase the complexity associated with PU waste management. Despite the extensive research endeavors spanning over decades, most known enzymes exhibit a propensity for hydrolyzing waterborne PU dispersion (i.e., the commercial Impranil DLN-SD), with only a limited capacity for the degradation of bulky PU materials. Here, we report a novel cutinase (CpCut1) derived from Cladosporium sp. P7, which demonstrates remarkable efficiency in the degrading of various polyester-PU materials. After 12-h incubation at 55°C, CpCut1 was capable of degrading 40.5% and 20.6% of thermoplastic PU film and post-consumer foam, respectively, while achieving complete depolymerization of Impranil DLN-SD. Further analysis of the degradation intermediates suggested that the activity of CpCut1 primarily targeted the ester bonds within the PU soft segments. The versatile performance of CpCut1 against a spectrum of polyester-PU materials positions it as a promising candidate for the bio-recycling of waste plastics. IMPORTANCE Polyurethane (PU) has a complex chemical composition that frequently incorporates a variety of additives, which poses significant obstacles to biodegradability and recyclability. Recent advances have unveiled microbial degradation and enzymatic depolymerization as promising waste PU disposal strategies. In this study, we ident ified a gene encoding a cutinase from the PU-degrading fungus Cladosporium sp. P7, which allowed the expression, purification, and characterization of the recombinant enzyme CpCut1. Furthermore, this study identified the products derived from the CpCut1 catalyzed PU degradation and proposed its underlying mechanism. These findings highlight the potential of this newly discovered fungal cutinase as a remarkably efficient tool in the degradation of PU materials. [ABSTRACT FROM AUTHOR]

Polyurethane/2-hydoxyethyl methacrylate (PU/2-HEMA) hybrids with the modifying properties of unsaturated polyester resin (UPR) were prepared through two steps of polymerization. In the first step, polyurethane prepolymers (PUA) were prepared with an NCO/OH ratio of 2.2 by a polyaddition reaction based on isophorone diisocyanate (IPDI), polyoxypropylene glycol (PPG 2000), and PPG 2700. In the second step, the hybrid was prepared by adding and mixing different contents of 2-hydroxyethyl methacrylate (2-HEMA) to prepolymer polyurethane (PUA). The effect of PUA and PUA/2-HEMA hybrid on the physicomechanical properties of UPR films was studied, including viscosity, compressive strength, hardness, thixotropy, and gamma radiation resistance. The addition of PUA/2-HEMA hybrids improved the physical and mechanical properties of UPR more than the addition of PUA owing to the existence of functional groups derived from PUA and PUA/2-HEMA, such as NCO, double bonds, and NH, which can establish cross-linking between UPR and PUA, as well as between UPR and PUA/2-HEMA. The findings demonstrate that the mechanical properties improve with dose, indicating cross-linking involving the double bonds of 2-HEMA, NH, C=O, as well as the ether group over oxidative degradation. However, an increase in 2-HEMA content in PUA hybrids increases the gamma radiation resistance, tensile, and compressive strengths demonstrating that cross-linking leads over oxidative degradation. This is attributed to the formation of the polymeric network as a result of cross-linking between PUA and 2-HEMA as indicated in the experimental results shown in Table 3 and Schemes 2 and 3. [ABSTRACT FROM AUTHOR]

Polyurethane elastomers are among the most versatile classes of industrial polymers—typically achieved through a two-step synthesis of segmented block copolymers, comprising very long and soft segments that provide elasticity and significantly long and hard segments that provide strength. The present research focused on the design of a single-step synthesis of a new segmented polyurethane consisting of very short soft and hard segments, crosslinked by preferentially side-reacted hierarchical tertiary oligo-uret network structures, thus exhibiting significant strength, elasticity, and toughness. Despite the theoretically linear structure, both FTIR and solid-state 13C NMR spectroscopy analyses indicated the quasi-equal presence of urethane groups and tertiary oligo-uret structures in the resulting polymer, indicating a preferential consecutive side reaction mechanism. Thermal analysis indicated the significant crystallization of soft segments consisting of only four ethylene oxide units, which was, hereby, demonstrated to occur via an extended chain mechanism. Tensile mechanical properties included significant strength, elasticity, and toughness. Increasing the soft segment length led to a decreased tertiary oligo-uret secondary crosslinking efficacy. The preferential hierarchical side reaction mechanism was, hereby, further confirmed through the synthesis of a completely new type of hyper-branched polymer via diisocyanate and a mono-hydroxy-terminated reagent. The structure–property relations and reaction mechanisms demonstrated in the present research can facilitate the design of new polyurethanes of enhanced performance and processing efficacy for a variety of novel applications. [ABSTRACT FROM AUTHOR]

Polyurethanes (PUs) are versatile polymers used in industries at large scale. PUs are in used in the form of foam, elastomers, adhesives, fibers, thermosets, thermoplastics, etc. Polyols and isocyanates are the two compounds used to synthesize PU. Day by day increasing price of crude oil and its destructive impact on the environment motivate researchers to develop bio‐PU. Seed oils are attracting nowadays because of their renewability and low cost. They are the best substitutes for fossil fuel‐based polyol used in the preparation of PUs. However, these bio‐based PUs show lower thermal, mechanical properties, which needs improvement to further their utilization. The need to maintain a cleaner environment for the survival of both aquatic and terrestrial lives including human beings is very crucial and is a subject of increasing concern to the environmentalists. The removal of heavy metals, dyes, and organic pollutants from wastewater before their discharge in the environmental is very important due to its polluting effect on the underground water. This review article emphasizes on to provide insight on the developments in the field of chemistry, types, and synthesis of various PUs, as well as on the components used to synthesize bio‐based PUs and water treatment applications. Additionally, details on the PU's environmental friendliness are highlighted, with a focus on their potential to recycling and recovery. This review also highlights the details of the synthesis, uses, and potential futures of PU composites. [ABSTRACT FROM AUTHOR]

In this study, carbon-carbon double bonds and catechol groups modified oligochitosan (OCS)/photocurable polyurethane composite films (OPU) were prepared for wound dressing application. Methacrylic anhydride (MA) was used to modify oligochitosan. The effect of the ratio of amino groups on OCS to MA on the properties of the composite films was investigated. The results showed that the OPU films possessed the best overall performance in hydrophilicity, mechanical strength, adhesion properties, and antibacterial activity when the ratio of amino groups on OCS to MA was 4:2. The prepared films may show potential application as wound dressings. [ABSTRACT FROM AUTHOR]

A new method of ballast stabilization wherein a layer of geogrid is placed toward the bottom of the ballast layer, and the top zone of ballast beyond the geogrid influence zone is treated with polyurethane, was investigated in this study. The deformation and degradation behavior of geogrid–polyurethane composite-stabilized ballast (CSB) was assessed based on large-scale cyclic tests conducted at a frequency (f) of 32 Hz. The test results indicated that the CSB had significantly reduced vertical and lateral deformations, by about 63% and 65.9%, respectively, compared with those of unstabilized ballast (USB), and by 38.8% and 26% compared with those of geogrid-stabilized ballast (GSB). Furthermore, the composite stabilization helped to improve the resilient modulus from 216.75 to 280.83 MPa, the damping ratio from 0.230 to 0.340, and the track stiffness from 41.33 to 68.13 MN/m compared with the values for USB. The breakage of ballast also was reduced significantly owing to ballast–polyurethane bonds that remained intact even after 250,000 load cycles. It was found that the geogrid placement location and its corresponding influence zone play a significant role in the overall performance of CSB. The test results further indicated that the geogrid when placed 76 mm from the ballast–subballast interface and a polyurethane treatment depth of 152 mm measured from the sleeper soffit exhibited significantly improved performance under cyclic loading. [ABSTRACT FROM AUTHOR]

The acquisition of clean drinking water in regions with limited power sources has been a challenge of paramount concern. Solar stills have emerged as a popular and sustainable option for obtaining clean water in such regions. This process involves employing solar radiation to heat up water, which is then condensed to obtain potable water. The present study introduces a solar still system that is both cost-effective and energy-efficient, while simultaneously ensuring sustainability. Fabric-coated polyurethane rollers with capillary action enhance evaporation area, leading to notable performance improvements. Water vapour condensed on the cooling chamber's inclined aluminium plate and collected in the distillate chamber within the solar still. The thermal, energetic, and economic performance and productivity of the proposed model were evaluated. The fabricated solar still boasted maximum instantaneous system efficiency and exergy efficiency of approximately 62.16% and 7.67%, respectively. This system's cost-effectiveness and performance improvements are particularly noteworthy. The daily average distillate productivity of the proposed still was estimated at 1.14 L/m2, resulting in an annual production rate of 416.54 L/year. The estimated cost of producing 1 L of distillate was 0.023 $. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to extend the pot life without altering the qualities and performance of the coating, which is important to increase when manufacturing polyurethane coatings. Design/methodology/approach: An acrylic polyol from a mixture of different monomers of hydroxypropyl methacrylate, methacrylic acid, 2-ethylhexyl acrylate, methyl methacrylate and n-butyl methacrylate was prepared with different ratios of 2,4-pentanedione as a pot life extender. The reaction takes place in presence of di-tert-butyl peroxide as initiator with samples (T1–T7). The physical properties of prepared acrylic polyol were characterized. Then, coating polyurethane varnish was prepared from the prepared acrylic polyol with an aliphatic polyisocyanate in a 1:1 equivalent ratio of OH:NCO at room temperature, in presence of paint thinner (diluents/solvent) and dibutyltin dilaurate as a catalyst to give samples (T1C–T7C). This coating was evaluated via Fourier-transform infrared spectroscopy, drying time, hardness and gloss, distinctness of image and reflected image quality. Findings: The coating has a prolonged pot life while still maintaining the other qualities, thanks to the greater 2,4-pentanedione content. Originality/value: It is desired to have a paint which has a satisfactory pot life, short curing time and reduces many drawbacks such as inefficient working and deterioration of the paint before application. [ABSTRACT FROM AUTHOR]

The chemical structure, polymer mobility and mechanical properties are studied for a cross-linked amorphous poly(ether urethane) (PU) from glass transition to rubber elasticity for juvenile dry samples and for water-saturated states after exposure to humid air (r.h. = 29, 67, 95, 100%) at 60 ∘ C during 1 y of ageing. For saturated samples, network chain cleavage is the chemical ageing mechanism, but it is too weak and slow to affect on the physical properties significantly within 1 y. Water acts primarily in a physical manner. Within 1 d, H 2 O molecules replace part of the weak urethane H-bonds by H 2 O –urethane H-bonds and reduce all other physical interactions between network chains by solvating hydrophilic segments. Thus, the cooperative polymer mobility strongly amplifies: The gain of specific conformational entropy doubles across the caloric glass transition, which shifts by −17 K. A H 2 O concentration of only c H 2 O ≈ (0.4 ... 0.5) c H 2 O , max suffices for the major part of these fast rearrangements. Some part of the water slowly forms (during 3–4 months) a finely dispersed water-rich mixed phase with the PU chains. Except the new phase, these molecular processes of physical ageing strongly affect the mechanical properties at damage-free deformation. For dry PU in the glass transition, the shear modulus, μ relaxed (T), after viscoelastic stress relaxation only depends on the deformation-induced entropy change—like in the rubber elastic state. Within one month, water drastically decreases the viscoelastic response, as expected for plasticisation. However, μ relaxed (T) slightly grows in wet PU. H 2 O molecules cause these opposite trends by boosting the cooperative mobility (i.e. extension of the accessible conformational space and entropy by reduction in energy barriers) and by occupation of free volume compartments. Water quickly reduces the fracture parameters by about 50%. We explain that embrittlement by the H 2 O -induced facilitation of cooperative network chain motions, which let fracture proceed with less energy. In summary, our findings provide a detailed conception of the molecular effects the H 2 O molecules have on the PU network, and they explain the consequences for the mechanical properties. [ABSTRACT FROM AUTHOR]

This study focuses on anti-trauma mats designed for buffaloes' comfort, using as raw materials rubber powder from end-of-life tyres (ELTs) and an isocyanate-based polyurethane resin binder. The first part of the study focused on mat formulation. Whilst it was possible to select a unique combination of raw materials and design features, it was necessary to investigate the relationship between three critical parameters affecting mat consistency and therefore buffalo comfort: binder quantity, mat thickness, and desired final mat density (bulk). In order to quantitatively assess the variation in hardness, various combinations were investigated within well-defined ranges based on the relevant literature. The results obtained from nine selected combinations indicate that increases in the three critical parameters do not induce a real phase transition in the final product consistency, although the hardness suggests an increasing trend. The mats consistently exhibited a moderately soft/hard consistency, offering environmental benefits in terms of increased rubber usage and potentially reduced chemical binder, depending on the desired thickness. The selected mixture showed excellent resistance to heavy chemical loads, suggesting reliability for frequent cleaning operations. The second part of the study involved field trials of the mats with calves. This involved monitoring their weight gain and appetite levels over a 90-day period. The results showed excellent growth performance compared to uncoated grids (i.e., weight gain was approximately 20% higher at the end of the observation period); this was similar to that achieved with the use of straw bedding. However, compared to straw bedding, the mats (i) exhibit long-term durability, with no signs of wear from washing or trampling over the months of the trial, (ii) allow for quick and efficient cleaning, and (iii) enable companies to save on labour, material (straw), and waste disposal costs, while maintaining (or even improving) the same welfare levels associated with the use of straw. [ABSTRACT FROM AUTHOR]

This work describes the preparation of thermally curable benzoxazine-modified polyurethanes with pendant carboxylic acid moieties, which have potential as organic coatings with enhanced thermal stability and electrical insulation properties. Thermoplastic poly(urethane-co-benzoxazine)s (PUBs) were synthesized via the polyaddition reaction of a benzoxazine diol chain extender with isocyanate-terminated urethane oligomers made from poly(tetramethylene ether)glycol at various molecular weights, dimethylol propionic acid, and toluene diisocyanate. Spectroscopic methods were utilized to characterize the proposed structures of the starting materials and final polymeric coatings and confirmation of co-presence of urethane bonds and benzoxazine rings. The curing temperature of the cross-linked PUBs (XPUBs) was evaluated using differential scanning calorimetry analysis. A catalytic effect of free carboxylic acids was observed, resulting in a lowering of the curing temperature by up to 30 °C. The XPUBs exhibited excellent thermal stability and reduced flammability compared to common polyurethane due to the formation of phenolic cross-linked linkages. The tensile strength and modulus of the XPUBs were also improved, while the extensibility of the polymeric coatings was mostly preserved. The key parameters that determine the possible application of these materials as electrical insulator coatings were very promising. The XPUBs displayed high dielectric strength of up to 38 kV/mm, low dielectric constant of less than 3, and a dissipation factor of approximately 6. [ABSTRACT FROM AUTHOR]

Polyurethanes, an important class of polymers, are used extensively for preparing various apparel, shoesoles, etc. This paper reports that polyurethanes could be prepared conveniently after blocking the precursor molecule toluene diisocyanate (TDI)with 4-bromo-1H-pyrazole to form blocked toluene diisocyanate (TDI). The blocked adducts were characterized by FTIR, NMR, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and CHNS analysis. Particularly, spectroscopic analysis was used to confirm the complete blocking. The DSC thermogram showed that the blocked adducts deblock at 238 °C, regenerating TDI and blocking agent 4-bromopyrazole. At 238 °C, regenerated TDI reacted with polyolsof different molecular weights to form polyurethane under solvent-free conditions. The polyurethanes were further characterized by FTIR, NMR, thermogravimetric analysis, differential scanning calorimetry, and contact angle study. FTIR study shows that there is no peak at 2250–2270 cm−1. So it confirms the absence of NCO peaks. Contact angle measurements of various polyurethanes showed the values in the ranges of 27–50 °C, indicating generally hydrophilic natures of samples. DSC thermogram indicates the presence of glass transition temperature of synthesized polyurethanes at − 30 to − 40 °C. Viscosity measurements of polyurethanes in chloroform at different temperatures indicated decrease in viscosity at higher temperature. [ABSTRACT FROM AUTHOR]

This work presents the synthesis and characterization of new TPUs obtained by melt polyaddition using 1,1′-methanediylbis(4-isocyanatocyclohexane) (HMDI, Desmodur W®), a new unconventional chain extender, i.e., (methanediyldibenze-ne-4,1-diyl)dimethanediol, and five types of soft segments differing in structure and molar masses. The structure of the obtained polymers was determined (by using the Fourier transform infrared spectroscopy and X-ray diffraction methods), and the physicochemical (reduced viscosity, density), optical (UV-VIS), processing (MFR) and thermal (DSC and TGA-FTIR) as well as surface, antibacterial and cytotoxic properties were determined. Based on the results obtained, it can be stated that the type of soft segment used significantly affects the properties of the obtained polymers. The most favorable properties for use in medicine were demonstrated by materials based on a polycarbonate soft segment. [ABSTRACT FROM AUTHOR]

In the present research, a single-step electrospinning technique was implemented to develop homogeneous hydrophilic nanostructures with a self-cleaning characteristic based on non-woven polyurethane (PU) altered by quaternary ammonium salts (QAS). By transferring the nanofibrous structures to the polyethylene terephthalate substrate, the filtering membranes were fabricated. The fabricated PU and PU/QAS membranes were compared and characterized for assessing their self-cleaning properties. The synthesized nanofibers were mechanically tested and also characterized by scanning electron microscopy. At low trans-membrane pressure of 7.5 kPa, water permeation flux and biofouling effect of electrospun nanocomposite membrane performance were primarily studied by means of dead-end filtration. Following a 5-day filtration, the modified nanofibrous structure displayed promising results in the recovery of the flux after a day 3 and inhibited the development of biofilm as well. The tensile strength and modulus of PU-QAS were 7.5MP and 31.7% higher compared to PU membrane. The pore size was also observed to be 360n in PU, while for PU-QAS, it was observed as 340 nm. It was concluded that the developed PU/QAS membrane can be restored to its original flow properties by cleaning with tap water. [ABSTRACT FROM AUTHOR]

Left ventricle leads are designed for the purpose of long-term pacing in the left ventricle. This study investigated the leads that use polyurethane as an outer insulator and SI-polyimide as an inner insulator. Polyurethane is commonly used for the outer insulation of cardiac leads due to its flexibility and biocompatibility. SI-polyimide (SI-PI) is a high-performance material known for its electrical insulation properties and is used for the inner insulation to maintain the integrity of the electrical pathways within the lead. Ten leads were received from the Wright State University Anatomical Gift Program. The duration of in vivo implantation varied for each lead, from less than a month to 108 months, with an average in vivo duration of 41 ± 31 months. We used the Test Resources Q series system for conducting our tests, as well as samples prepared to ensure compliance with the ASTM Standard D 1708-02a and the ASTM Standard D 412-06a. During the test, the load was applied to the intact lead. Before conducting individual tests, each lead was carefully inspected for surface defects. After conducting the tests, the load to failure, percentage of elongation, percentage of elongation at 5 N, ultimate tensile strength, and modulus of elasticity were calculated. There was no significant difference in load to failure, the percentage of elongation to failure, ultimate tensile strength, and modulus of elasticity (p-value = 0.82, p-value = 0.62, p-value = 0.82, and p-value = 0.12), respectively, when compared to in vivo exposure time. On the other hand, the percentage of elongation at 5 N force showed a significant difference (p-value = 0.0066) after 60 months in an in vivo environment. As the duration of in vivo exposure increased, the load to failure, percentage of elongation, ultimate tensile strength, and modulus of elasticity decreased insignificantly. The residual properties of these left ventricle leads remained relatively stable after 108 months of in vivo exposure duration, with no statistically significant degradation or changes in performance. [ABSTRACT FROM AUTHOR]

Although epoxy resin has been extensively used in the field of wind turbine blades, polyurethane has attracted much attention in recent years, due to its potential value of better fatigue resistance, lower processing viscosity and higher strength than epoxy resin blades. Herein, we construct a dense cross-linking structure in polyurethane (PU) based on different amounts of hydroxypropyl methacrylate (HPMA) with low processing viscosity and excellent mechanical properties. By increasing the content of HPMA, the thermal stability of PU is enhanced, but the micro-morphology does not change significantly. When the content of HPMA is 50 g (in 200 g copolymer), the PU sample PH-50 exhibits a viscosity of 70 MPa·s and a gelation time of 120 min at 25 °C, which is sufficient to complete processes like pouring and filling. By post-curing the PH-50 at 80 °C for 2 h, the heat distortion temperature can reach 72 °C, indicating the increase of temperature resistance. The PU copolymers also have excellent mechanical and dynamic thermo-mechanical properties due to the cross-linking structure between PU chains and poly-HPMA chains. Additionally, the PU copolymer has excellent compatibility with various glass fiber fabrics (GFF), showing a good match in the vacuum infusion experiment and great properties in the mechanical test. By compounding PH-50 with GFF, the composite with high strength is easily prepared for a wind turbine blade in various positions. The tensile strengths of the composites are all over 1000 MPa in the 0° direction. Such composites are promising for the future development of wind turbine blades that meet the stringent requirements for outstanding processing and mechanical properties. [ABSTRACT FROM AUTHOR]

In this study, a new epoxidized oil from Citrullus colocynthis seed oil (CCSO) was obtained for a potential application in the formulation of polyurethane coatings. Initially, the fatty acid composition of CCSO was determined by gas chromatography–mass spectrometry (GC–MS). Subsequently, the epoxidation of CCSO was performed with in situ generated peracetic acid, which was formed with hydrogen peroxide (30 wt.%) and glacial acetic acid and catalyzed with sulfuric acid. The reaction was continued at a molar ratio of 1.50:1.0 of hydrogen peroxide to double bond (H2O2:DB) for 6 h at a controlled temperature of 60 °C. The resulting epoxidized oil was then used to produce a bio-based polyol by hydroxylation. The molar ratio of epoxy groups to methanol and distilled water was maintained at 1:11:2, and the reaction was carried out for 2 h at a controlled temperature of 65 °C. The major functional groups of the epoxidized oil and its polyol were validated by Fourier-transform infrared (FT-IR) and proton nuclear magnetic resonance (1H NMR) spectroscopies. A polyurethane (PU) coating was produced from the synthesized polyol and 3HDI isocyanurate, keeping the molar ratio of NCO:OH at 1:1. The resulting PU coating was then applied to glass and aluminum panels (Al 1001). After the film was cured, the properties of the PU coating were evaluated using various techniques including pencil hardness, pendulum hardness, adhesion, gloss, chemical resistance, and EIS tests. The results show that the PU coating obtained from CCSO is a promising new raw material for coating applications. [ABSTRACT FROM AUTHOR]

Optimizing the energy efficiency of hydraulic cylinder modern sealing systems requires, among other things, minimizing the developed friction forces. This can be achieved by manufacturing seals from polymer-based polytetrafluoroethylene-type materials (Virgin PTFE and filled PTFE) or from thermoplastic polyurethane elastomers. This paper presents a procedure for calculating and experimentally determining the friction forces developed in the coaxial sealing systems of hydraulic cylinders pistons. Three sealing systems made from different materials were tested under varying conditions of pressure and velocity on an experimental test stand set up by the authors. The paper concludes with data and recommendations for the selection of the optimum seal material in order to maximize energy efficiency. Our comparative research conducted on the seal materials led to the conclusion that for reducing friction forces in hydraulic cylinders, Virgin PTFE is the most adequate. [ABSTRACT FROM AUTHOR]

The search for innovative and sustainable solutions to improve the energy efficiency of the construction industry has been a hot topic for researchers due to the tremendous impact of insulator materials in the thermal comfort of buildings. In the present work, an innovative lightweight composite material with thermal insulation properties was developed, for the first time, by using cardoon particles and polyurethane. The formulation of the composite material was optimized in terms of cardoon fraction and the polyol/isocyanate ratio, to achieve the best compromise between internal bond (IB) strength and thickness swelling (TS). The best performing composite was PU75-CP45, with 45 wt% of cardoon particles and 75% of isocyanate, achieving an IB of 0.41 MPa and a TS of 5.3%. Regarding insulation properties, the PU75-CP45 composite material exhibits a promising performance when compared to conventional construction industry materials by tuning its thickness. Additionally, the composite material presented very low emissions of volatile organic compounds and formaldehyde (bellow to legislation levels) and high resistance to biological degradation. [ABSTRACT FROM AUTHOR]

Polymer materials are widely used in medicine due to their mechanical properties and biological inertness. When ion-plasma treatment is used on a polymer material, a carbonization process occurs in the surface nanolayer of the polymer sample. As a result, a surface carbonized nanolayer is formed, which has mechanical properties different from those of the substrate. This layer has good biocompatibility. The formation of a carbonized nanolayer on the surface of polymer implants makes it possible to reduce the body's reaction to a foreign body. Typically, to study the properties of a carbonized layer, flat polymer samples are used, which are treated with an ion flow perpendicular to the surface. But medical endoprostheses often have a curved surface, so ion-plasma treatment can occur at different angles to the surface. This paper presents the results of a study of the morphological and mechanical properties of a carbonized layer formed on a polyurethane surface. The dependence of these properties on the directional angle of the ion flow and its fluence has been established. To study the surface morphology and elastic properties, methods of atomic force microscopy and methods of elasticity theory were used. The strength properties of the carbonized layer were studied using a stretching device combined with a digital optical microscope. [ABSTRACT FROM AUTHOR]

Covalent adaptable networks (CANs) represent a pioneering advance in polymer science, offering unprecedented versatility in materials design. Unlike conventional adhesives with irreversible bonds, CAN-based polyurethane adhesives have the unique ability to undergo chemical restructuring through reversible bonds. One of the strategies for incorporating these types of reactions in polyurethanes is by functionalisation with Diels–Alder (DA) adducts. By taking advantage of the reversible nature of the DA chemistry, the adhesive undergoes controlled crosslinking and decrosslinking processes, allowing for precise modulation of bond strength. This adaptability is critical in applications requiring reworkability or recyclability, as it allows for easy disassembly and reassembly of bonded components without compromising the integrity of the material. This study focuses on the sustainable synthesis and characterisation of a solvent-based polyurethane adhesive, obtained by functionalising a polyurethane prepolymer with DA diene and dienophiles. The characterisation of the adhesives was carried out using different experimental techniques: nuclear magnetic resonance spectroscopy (NMR), Brookfield viscosity, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and T-peel strength testing of leather/adhesive/rubber joints to determine the adhesive properties, both before and after the application of external stimuli. The conversion of both the DA and retro-Diels–Alder (r-DA) reactions was confirmed by 1H-NMR. The adhesive properties were not altered by the functionalisation of the adhesive prepolymer, showing similar thermal resistance and good rheological and adhesive properties, even exceeding the most demanding technical requirements for upper-to-sole joints in footwear. After the application of an external thermal stimuli, the bonded materials separated without difficulty and without damage, thus facilitating their separation, recovery and recycling. [ABSTRACT FROM AUTHOR]

Background: This study explores how different post-processing methods affect the mechanical properties and degree of conversion of 3d-printed polyurethane aligners made from Tera Harz TC-85 resin. Methods: Using Fourier-transform infrared (FTIR) spectroscopy, the degree of conversion of liquid resin and post-processed materials was analyzed. This investigation focused on the effects of various post-curing environments (nitrogen vs. air) and rinsing protocols (centrifuge, ethanol, isopropanol, and isopropanol + water). The assessed mechanical properties were flexural modulus and hardness. Results: The degree of conversion showed no significant variance across different groups, though the polymerization environment influenced the results, accounting for 24.0% of the variance. The flexural modulus varied considerably, depending on both the rinsing protocol and the polymerization environment. The standard protocol (centrifugation followed by nitrogen polymerization) exhibited the highest flexural modulus of 1881.22 MPa. Hardness testing revealed significant differences, with isopropanol treatments showing increased resistance to wear in comparison to the centrifuge and ethanol rinse treatments. Conclusions: This study conclusively demonstrates the adverse effects of oxygen on the polymerization process, underscoring the critical need for an oxygen-free environment to optimize material properties. Notably, the ethanol rinse followed by nitrogen polymerization protocol emerged as a viable alternative to the conventional centrifuge plus nitrogen method. [ABSTRACT FROM AUTHOR]

The use of alternative raw material sources in polyurethane chemistry is necessary given the limited supply of fossil fuels, their rising prices and the concern for sustainability. The production of biopolyols from edible vegetable oils such as rapeseed oil, soybean oil or sunflower oil is often proposed. In order to avoid conflict with the global food economy, non-edible or waste oils are hoped to find application in chemical synthesis. The possibility of using oils from selected fruit seeds to obtain biopolyols is analyzed in this manuscript. Five biopolyols were obtained from watermelon, cherry, black currant, grape and pomegranate fruit seeds using the transesterification reaction of the oils with triethanolamine. Thermal insulating polyurethane foams were then obtained by replacing 75% of petrochemical polyol with the biopolyols in polyurethane systems. Based on an analysis of the foaming process, it was found that the incorporation of triethanolamine molecules into the biopolyols causes a catalytic effect. The use of such biopolyols allows eliminating the catalyst from a polyurethane foam formulation. The polyurethane biofoams obtained with the pomegranate-seed-based biopolyol were characterized by the highest content of closed cells (45 vol.%). The lowest content was found for the foams containing the currant-seed-based biopolyol (9%). The foams were characterized by thermal conductivity coefficients between 32 and 35 kW/m·K and densities of approximately 40 kg/m3. Good dimensional stability and compressive strength between 100 and 250 kPa make them suitable for use in construction. [ABSTRACT FROM AUTHOR]

Polyurethanes (PUs) pose great potential in diverse applications, including the functionalization of fabrics, owing to their promising mechanical characteristics and biological compatibility. Here, a green synthesis of PUs has been carried out using the dispersion polymerization technique. The process includes the production of soybean oil-polyol through epoxidation, the preparation of PUs through the formation of polyurethane pre-polymer using an aromatic diisocyanate, i.e., toluene-2,4-diisocyanate, and different mole ratios of sodium alginate used as chain extender. Polyurethane dispersions were obtained by adding specific amount of distilled water. Further, structural attributes of soybean-sodium alginate-based waterborne polyurethanes (SO-SA-PUAro) were identified using an ATR-based Fourier Transform Infrared (FTIR) spectrophotometer, and physico-chemical properties like solid contents, physical appearance, and dispersion stability were observed and co-related with other outcomes. Moreover, synthesized polyurethane dispersions were applied to the plain weaved polyester-cotton blended textile substrate using pad-dry-cure methods. Significant gradual improvements in textile attributes like tensile strengths (from 873 N/m to 989 N/m on warp and 639 N/m to 729 N/m on warp and weft side of fabrics respectively), rubbing fastness (from 3 to 4/5 and 2 to 4 for dry and wet rubbing tests respectively), washing fastness (from 3–4 to 4–5), anti-pilling property (from 2–3 to 4–5), crease recovery angle (from 1.96 cm to 2.74 cm and 1.95 cm to 2.62 cm on warp and weft sides of the fabrics respectively), bending lengths (from 98° to 122° and 88° to 114° on warp and weft sides of the fabrics respectively), and anti-microbial tests (26 mm for E.coli and 27 mm for Cocci bacterial strains) were observed with increasing moles of sodium alginate as chain extender. However, a decreasing trend in tear strengths (from 12.89 lbf/in to 11.65 lbf/in and 10.12 lbf/in to 8.92 lbf/in on warp and weft sides of the fabrics) of the treated fabrics was noted. The outcomes of the study demonstrated that polyurethanes synthesized through bio-based polyol and chain extender have considerably enhanced the textile attributes of fabric and are good alternatives to replace petroleum-based raw materials. [ABSTRACT FROM AUTHOR]

The objective of this study was to coat negatively charged polymer brushes covalently onto the surface of thermoplastic polyurethane (TPU) using a simple conventional surface free-radical polymerization technique. The coated surfaces were assessed with contact angle, protein adsorption, cell adhesion and bacterial adhesion. Bovine serum albumin (BSA) and bovine fibrinogen (BFG) were used for protein adsorption evaluation. Mouse fibroblasts (NIH-3T3) and Pseudomonas aeruginosa (P. aeruginosa) were used to assess surface adhesion. Results show that the TPU surface modified with the attached polymer brushes exhibited significantly reduced contact angle, protein adsorption, and cell as well as bacterial adhesion, among which the negatively charged polymers showed the extremely low values in all the tests. Its contact angle is 5°, as compared to 70° for original TPU. Its BSA, BFG, 3T3 adhesion and P. aeruginosa adhesion were 93%, 84%, 92%, and 93% lower than original TPU. Furthermore, the TPU surface coated with negatively charged polymer brushes exhibited a hydrogel-like property. The results indicate that placing acrylic acids using a simple surface-initiated free-radical polymerization onto a TPU surface and then converting those to negative charges can be an effective and efficient route for fouling resistant applications. Graphical Abstract [ABSTRACT FROM AUTHOR]

In this paper, starch was first liquefied using sulfamic acid as catalyst, and then the starch-based polyurethane coating was prepared. The optimum ratio between the hydroxyl group of liquefied starch and isocyanate group of PM200 was determined to be 1:1.3. Differential scanning calorimetry was used to study the curing reaction kinetics of starch-based polyurethane, and the result showed that the initial temperature (Ti), peak temperature (Tp) and end temperature (Tf) of thermostatic curing reaction were 23.31 °C, 83.15 ℃ and 199.75 ℃, respectively. According to the Kissinger model, the calculated activation energy and preexponential factor of the curing reaction system were 44.34 kJ mol−1 and 7.36 × 103 s−1, respectively. Meanwhile, the Crane model indicated that the order of curing reaction was 0.88. The curing kinetic equation was also established to provide a theoretical basis for the actual curing process of starch-based polyurethane materials. [ABSTRACT FROM AUTHOR]

Crosslinking chemistries occupy an important position in polymer modification with a particular importance when triggered in response to external stimuli. Enediyne (EDY) moieties are used as functional entities in this work, known to undergo a pericyclic Bergman cyclization (BC) to induce a triggered crosslinking of polyurethanes (PU) via the intermediately formed diradicals. Diamino‐EDYs, where the distance between the enyne‐moieties is known to be critical to induce a BC, are placed repetitively as main‐chain structural elements in isophorone‐based PUs to induce reinforcement upon heating, compression, or stretching. A 7‐day compression under room temperature results in a ≈69% activation of the BC, together with the observation of an increase in tensile strength by 62% after 25 stretching cycles. The occurrence of BC is further proven by the decreased exothermic values in differential scanning calorimetry, together with characteristic peaks of the formed benzene moieties via IR spectroscopy. Purely heat‐induced crosslinking contributes to 191% of the maximum tensile strength in comparison to the virgin PU. The BC herein forms an excellent crosslinking strategy, triggered by heat or force in PU materials. [ABSTRACT FROM AUTHOR]

The expansion of nanofiller‐based polymers has been rapidly increasing in contemporary society due to their wide range of applications owing to their diverse physicochemical characteristics. This review focuses on a polymer nanocomposite in which graphene is incorporated as a nanofiller and polyurethane is used as a polymer. As polyurethane is well known for its shape memory behaviour and the reinforcement of graphene‐based nanomaterial sparks the physicochemical properties of the fabricated nanocomposites which makes it more adaptable and useful for a wide array of applications. The review provides insights into the recent synthesis approaches to the fabrication of graphene‐based polyurethane nanocomposites. Further, efforts were also made to cover the recent studies done on the use of these nanocomposites as an advanced shape memory material. Rather than merely serving as descriptive content, this article is intended to serve as a comprehensive guide for researchers seeking to harness the potential of graphene‐based nanomaterial reinforcement in polyurethane for high‐performance applications. By providing a detailed overview of the latest research in this domain, the review aims to propel the development of novel and sophisticated materials, unlocking new horizons in smart shape memory technologies. [ABSTRACT FROM AUTHOR]

Surface modification of polyester fabric was done using dielectric barrier discharge (DBD) with the aim of improving the adhesion properties using polyurethane (PU) polymer as an adhesive. The change in adhesion strength with respect to various plasma powers and treatment durations was examined. For analysing the adhesive bond strength of the coated fabric the T-peel off strength was investigated. After plasma treatment, an improvement in adhesion was observed compared to the untreated sample. The effect of oxygen gas on adhesion with PU adhesive was also studied. Surface wettability after plasma treatment was studied by wicking measurements. Changes in surface morphology were analysed using a scanning electron microscope (SEM) and an atomic force microscope (AFM). X-ray photoelectron spectroscopy (XPS) and ATR-FTIR were used to study the surface chemistry of plasma-treated samples. SEM, AFM, and XPS results reveal the surface roughening and incorporation of functional groups, such as C–O, C–OH, O–C=O, and COOH. No adverse effect on the mechanical strength of the plasma-modified polyester fabric was seen. [ABSTRACT FROM AUTHOR]

A series of robust energetic polyurethane binders was developed by in situ grafting reactive spiranes to achieve the migration-resistant processing aid and compensate for the energy output. The reactive grafting spiranes (RGSs), bearing two highly ring-strained spiranes, were synthesized sequentially to provide a promising ring strain energy up to a maximum value of 290 kJ mol−1. The thermodynamic compatibility of the RGS with uncured glycidyl azido polymer (GAP) was studied quantitatively by analyzing the glass transition temperature of their blendings. The reactivity study of the catalyst-free click reaction with respect to spacer-dependent species was amplified by tracing the extent of the reaction and measuring the activation energy. The faster reactivity of propargyl species was evident from two experimental approaches, which were verified further by theoretical predictions. Interestingly, the energy gap difference in the frontier molecular orbitals agreed well with the difference in activation energy between the two types of spacer-dependent species. The mechanical and thermochemical enhancements of GAP-based polyurethane with RGS were basically gained from those highly ring-strained moieties. [ABSTRACT FROM AUTHOR]

In this study, hydroxyl-terminated carborane polyarylates were directly reacted with isocyanates by direct main chain introduction method. Three carborane polyurethane resins were prepared by using polyarylates and isocyanates. The best curing process conditions were determined through curing kinetics research and experiments. TGA, DSC, XRD and variable temperature infrared spectroscopy were used to investigate the thermal properties. The combustion performance was studied by heat release rate (HRR), total heat release (THR) and limiting oxygen index (LOI). The surface morphology after heat treatment of carborane polyurethane resin and traditional polyurethane was observed by SEM method and focused on the stability of carborane polyurethane resin. [ABSTRACT FROM AUTHOR]

In this study, novel hollow nanofiber materials were produced by the coaxial electrospinning method from polyurethane (PU)/poly(lactic acid) (PLA) blend nanofibers of different weight ratios (80:20, 60:40, 50:50, 40:60, and 20:80). Thus, the tissue scaffolds as dermal wound dressing materials which can absorb the exudate liquid formed on the wet wound and dry quickly, providing patient comfort with high mechanical properties, showing high biocompatibility, and supporting fibroblast cell growth were developed. Moreover, the characteristics of hollow PU/PLA nanofibers were compared in detail with the characteristics of solid PU/PLA nanofibers in our previous study. Hollow PU/PLA nanofibers were observed 2–4 times thinner than solid PU/PLA nanofibers. The production of hollow nanofibers in the range of 235–518 nm was achieved. It was reported that the hollow PU/PLA (50/50, w/w) nanofiber has the highest tensile strength with a value of 7.19 MPa, and the hollow PU/PLA (60/40) w/w) nanofiber has the highest percentage elongation with a value of 63.78%. It was determined that the biomedical material, which has the highest liquid absorption capacity with a value of 756% and can dry in 10 min, is H5PU5PLA nanofiber. As a result, the highest value of fibroblast cell viability with 92.38% by cytotoxicity test was observed for hollow PU/PLA (20/80, w/w) nanofiber. [ABSTRACT FROM AUTHOR]

Wound plaster polyurethane can make using glycerol from waste cooking oil (WCO). Wound plasters should contain antibacterial ingredients in addition to covering the sore. Traditionally various plants have been used to treat sore and contain sundry antibacterial chemical compounds amid Moringa oleifera Lam. Therefore, it is very potential to make polyurethane wound plasters from glycerol produced from WCO combined with Moringa leaf extract obtained from wound plasters from natural ingredients. Maceration with 96 % ethanol yielded moringa leaf extract. Then, a transesterification reaction carries out by using KOH-methanol at 60 °C to get glycerol and tested by FTIR spectrophotometry. Polyurethane wound plasters were made with a mixture of methylene 4,4 diphenyl diisocyanate, polyethylene glycol (PEG) and various formulas with variations of glycerol 0, 3, 6, 9, 12, 15 and 18 drops. A characteristic test enforced with swelling test to find the best formula and functional group analysis using FTIR spectrophotometry. Into the best wound plaster, improved Moringa leaf ethanol extract at an intensity of 1 - 5 %. An antibacterial activity test carries out on the Moringa leaf ethanol extract and plasters obtained by the agar diffusion method. The FTIR spectrophotometer test showed the formation of glycerol from WCO. The results of the characteristics test for polyurethane wound plaster preparations obtained the best formula using 3 drops of glycerol. The antibacterial activity test results at a concentration of 500 mg/mL Moringa leaf extract produced a muscular inhibition zone of 19.2 mm against Staphylococcus aureus and Antiseptic solution of 17.3 mm; Pseudomonas aeruginosa of 14.3 mm and Antiseptic solvent of 16.2 mm. Antibacterial activity of polyurethane wound plaster against Staphylococcus aureus contains 5 % ethanol extract of 10.3 mm, Plaster Merck X of 11.2 mm, Pseudomonas aeruginosa, only gave resistance at 5 % concentration of 8.3 mm and Plaster Merck X of 9.2 mm. [ABSTRACT FROM AUTHOR]

An experimental study of ignition and flame front propagation during spark initiation in a hydrogen–air mixture in a semi-open channel with a porous coating is reported. The bottom surface of the channel was covered with a porous layer made of porous polyurethane or steel wool. The measurements were carried out for a stoichiometric mixture (equivalence ratio ER = 1.0) and for a lean mixture (ER = 0.4) of hydrogen with air, where ER is the molar excess of hydrogen. The flame front was recorded with a high-speed camera using the shadow method. Depending on the pore size, the velocity of the flame front and the sizes of disturbances generated on the surface of the flame front were determined. Qualitative features of the deflagration flame front at ER = 0.4, consisting of disturbances resembling small balls of flame, were discovered. The sizes of these disturbances significantly exceed the analytical values for the Darrieus–Landau instability. The effect of coatings made of porous polyurethane or steel wool is compared with the results obtained for an empty smooth channel. Depending on the hydrogen concentration in the hydrogen–air mixture, the velocity of the flame front compared to a smooth channel was three times higher when the channel was covered with steel wool and five times higher when the channel was covered with porous polyurethane. [ABSTRACT FROM AUTHOR]

Low-noise pavements, particularly polyurethane pavements with sound absorption and vibration reduction characteristics, are an effective way to reduce traffic noise. However, the noise reduction performance of polyurethane porous elastic mixtures (PPEM) gradually deteriorates owing to void clogging and thermal-oxidative aging. This study investigates and characterizes the noise reduction performance of PPEM influenced by these factors. The tire noise reduction performance of a prepared PPEM was measured based on void-clogging, thermal-oxidative aging, and tire noise tests. The results indicate that the pavement performance of the PPEM meets the Chinese specification requirements, and its dynamic stability can be up to 120,000 times/mm. The void ratio was found to be the most important factor affecting the noise reduction performance of the mixture, and, at a constant void ratio, the PPEM outperformed a porous asphalt concrete mixture. With increased thermal-oxidative aging time, the noise reduction performance of the PPEM first increases and then decreases and is likely to gradually decrease owing to the aging of polyurethane and crumb rubber. [ABSTRACT FROM AUTHOR]

As the number of patients suffering from cardiovascular diseases and peripheral vascular diseases rises, the constraints of autologous transplantation remain unavoidable. As a result, artificial vascular grafts must be developed. Adhesion of proteins, platelets and bacteria on implants can result in stenosis, thrombus formation, and postoperative infection, which can be fatal for an implantation. Polyurethane, as a commonly used biomaterial, has been modified in various ways to deal with the adhesions of proteins, platelets, and bacteria and to stimulate endothelium adhesion. In this review, we briefly summarize the mechanisms behind adhesions, overview the current strategies of surface modifications of polyurethane biomaterials used in vascular grafts, and highlight the challenges that need to be addressed in future studies, aiming to gain a more profound understanding of how to develop artificial polyurethane vascular grafts with an enhanced implantation success rate and reduced side effect. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of a series of polyurethane ionenes using a non‐isocyanate approach is disclosed. Imidazole‐capped, urethane‐containing prepolymers are prepared by first reacting carbonyl diimidazole (CDI) with several poly(propylene glycol) (PPG) diols with variable molecular weight, followed by subsequent reaction with 3‐aminopropylimidazole (API). Polymerization with 1,4‐dibromomethylbenzene followed by anion exchange resulted in the desired polyurethane ionenes bearing the [NTf2] counteranion as a series of viscous liquids. NMR and FTIR spectroscopy are used to characterize the intermediates and final ionenes, including molecular weight determination by end‐group analysis. A single glass transition temperature (Tg), as determined by differential scanning calorimetry (DSC), is observed for each ionene (−38 to −64 °C) with the Tg decreasing with increasing PPG molecular weight. Thermogravimetric analysis (TGA) indicated a two‐step decomposition for each ionene, with the first being degradation of the PPG segment, followed by the urethane/ionic segment. Microphase separation is observed from x‐ray scattering profiles with Bragg distances that increased with increasing PPG molecular weight. Ionic conductivity is found to be inversely dependent upon DSC Tg at lower temperatures (RT and below); however, at higher temperatures, conductivity appears to be more dependent upon the ability of ionic aggregates caused by phase separation to interact. [ABSTRACT FROM AUTHOR]

When it comes to grouting in coal mines, polyurethane (PU) is often utilized. However, it is of vital importance to consistently improve the mineral PU, considering the significant amount of environmental deterioration to which it is prone. Laboratory experiments were used to model various coal mine conditions. Additionally, a workable technique for PU strengthening using ultrasonic waves was proposed. Compression tests and scanning electron microscopy (SEM) were used to describe the PU–gangue material's induration characteristics. The results showed that ultrasound has a positive impact on PU's mechanical strength. The final strength of the PU was significantly impacted by the size of the coal gangue particles, the amount of dust, and the amount of water. The induration made of gangue and PU with the same mass but differing particle sizes was noticeably different in its compressive strength. The strengthening mechanism showed that the average size of the rigid foam after the ultrasound treatment was smaller, and the 'honeycomb'-structured space in the inner section was more compact, resulting in the rigid PU foam having a higher compressive strength after ultrasound treatment. Furthermore, the dust content and water content of coal mines need to be controlled within a specific range to ensure the effective use of PU grouting materials. [ABSTRACT FROM AUTHOR]

In recent years, the incidence of cardiovascular disease has increased annually, and the demand for artificial blood vessels has been increasing. Due to the formation of thrombosis and stenosis after implantation, the application of many materials in the human body has been inhibited. Therefore, the choice of surface modification process is very important. In this paper, small-diameter polyurethane artificial blood vessels were prepared through electrospinning, and their surfaces were treated with plasma to improve their biological properties. The samples before and after plasma treatment were characterized by SEM, contact angle, XPS, and tensile testing; meanwhile, the cell compatibility and blood compatibility were evaluated. The results show that there are no significant changes to the fiber morphology or diameter distribution on the surface of the sample before and after plasma treatment. Plasma treatment can increase the proportion of oxygen-containing functional groups on the surface of the sample and improve its wettability, thereby increasing the infiltration ability of cells and promoting cell proliferation. Plasma treatment can reduce the risk of hemolysis, and does not cause platelet adhesion. Due to the etching effect of plasma, the mechanical properties of the samples decreased with the extension of plasma treatment time, which should be used as a basis to balance the mechanical property and biological property of artificial blood vessels. But on the whole, plasma treatment has positive significance for improving the comprehensive performance of samples. [ABSTRACT FROM AUTHOR]