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The motivation behind this work is the preparation of polyurethane-magnesium aluminum layered double hydroxide (PU-LDH) nanocomposite and its application as a coating for steel protection. The coating was prepared with different doses of LDH, ranging from 0 to 2% of the coating weight. The effect of different concentrations on the mechanical, adhesion, and surface properties of PU coating is studied. Firstly, LDH was prepared via the coprecipitation process and then distributed in PU matrix. The nanocomposites were then crosslinked in the form of coating layers on steel. The preparation of the thermally stable crystalline LDH nanoparticles with 89 nm particle size was confirmed by FTIR, XRD, DLS, and TGA. SEM photos showed the dispersed and intercalated structure. The coating characteristics demonstrate that addition of LDH decreased the drying time and increased the dry film thickness of PU up to 1.5% due to the crosslinking between the large surface area nanofiller and polyurethane matrix. Furthermore, the prepared LDH nanofiller increased the adhesion strength, impact resistance, abrasion resistance, modulus, and flexibility of PU due to the strong polymeric network structure. The 2% nanocomposite coating shows poor properties due to the excess concentration and heterogeneous dispersion of nanoparticles within the PU polymer. The resistance to fire and some chemicals was supported by the thermally and physically stable LDH nanoclay. The former characterizations state that the proposed PU-LDH nanocomposite is an enhanced and applicable coating. [ABSTRACT FROM AUTHOR]

Intensive research is currently being carried out worldwide to replace fossil raw materials with renewable ones or waste based on chemical synthesis. However, it is important that the newly developed raw materials do not conflict with global food production and recommend the use of non-edible or waste raw materials. Therefore, modified non-edible oilseed radish oil was used in the synthesis of polymeric materials. The functionalization of the oil was achieved through one-step, solvent-free transesterification process with triethanolamine, diethylene glycol, polypropylene glycol, ethylene glycol and propylene glycol. Biopolyols with hydroxyl numbers in the range of 237–346 mg KOH/g and different chemical structures were obtained. Open-cell polyurethane foams were produced by replacing 100% of the original petrochemical polyol with the biopolyols. The influence of the chemical structures of the biopolyols on the properties of the thermal insulation materials was analysed. The foams were characterised by low apparent densities of about 16 kg/m3. The type of biopolyol did not have a significant influence on the mechanical strength of the foams. A thermal analysis of the polyurethane biofoams was also carried out. [ABSTRACT FROM AUTHOR]

The release of oil and organic pollutants into water bodies poses a severe environmental concern because they bioaccumulate and are difficult to degrade. In this study, an alternative polyurethane (PU) composite foam containing hydroxylated multi-walled carbon nanotubes (MWCNTs) and polydimethylsiloxane (PDMS) was prepared using a dip-coating method. Adding MWCNTs and PDMS transformed the hydrophilic pristine PU foam to a superhydrophobic PU/CNT-PDMS, as evidenced by the substantial increase in the water contact angle value. Our work evaluated the performance of the foams containing different MWCNTs loading and PDMS concentrations in the oil-water separation process. The foam comprising of 6.97 wt% MWCNTs and 6.52 wt% PDMS, exhibited the highest absorption performance, with the maximum absorption capacity of 33.83 and 44.98 g/g for engine oil and acetone. The recyclability test showed that the PU/CNT-PDMS hybrid foam retained at least 90% of its initial oil absorption capacity after 10 absorption-desorption cycles. The PU/CNT-PDMS hybrid foam produced showed excellent absorption characteristics and was reusable, confirming its potential as a suitable candidate for efficiently removing oil and organic solvents from water. [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]

Polyurethanes (PU) are unique heteropolymers with a wide range of physicomechanical properties, fields of use and high development potential. PU is obtained by condensation of diisocyanate and various polyol compounds. The peculiarities of the structure and synthesis of commercial polyols based on the products of secondary oil processing, namely oligomeric glycols, oxides and dicarboxylic acids are presented. [ABSTRACT FROM AUTHOR]

Plastic pollution undoubtedly is a big global issue for present and future generations. Despite numerous activities in the field, the recycling of thermoset polymers still poses an immense challenge to the chemical industry. The present work proposes a new solution to the plastics pollution issue by developing a novel technology for the transformation of polyurethane (PUR) scraps into value-added polymers. In contrast to conventional methods, which usually involve elaborate but costly methods for sorting and separating different plastics into single-origin material flows, the feasibility of direct upcycling of valueless, mixed PUR-based production scraps into polymer aerogels will be shown. Despite the impurity of the feedstock, the aerogels synthesized in this work possess a well-defined and tuneable meso-porous microstructure and a very low thermal conductivity in the range of comparable high-performance insulation materials. The transfer of this newly developed approach to other polymers as well as bio-based precursors could significantly accelerate the development of holistic circular economies. Highlights: Recovering mixed PUR production scraps without prior sorting is feasible via chemical recycling. Synthesizing aerogels based on recycled feedstock leads to a defined meso-porous network. Tailoring of the nanostructure is possible despite undefined chemical composition. Effective thermal conductivity is on par with state-of-the-art thermal insulation material. [ABSTRACT FROM AUTHOR]

In this study, a bi-layer scaffold combining polyurethane nanofibrous and silicone membrane layers was produced. Chemical, morphological and physical properties of the scaffolds were determined by Fourier-transform infrared spectroscopy, scanning electron microscope (SEM) and Brunauer–Emmett–Teller analyses, respectively. The surface properties were examined with the contact angle test. To evaluate the encapsulation and release behaviour of the scaffolds Rhodamine B and Nile red were used as model drugs. Further, the cytotoxicity and cell proliferation investigations were carried out using mouse embryonic fibroblasts cell lines. 3-(4,5-dimethylthiazoyl-2-yl)-2,5-diphenyltetrazolium bromide assay and SEM were used to investigate the cell viability and cell-scaffold interactions, respectively. The results of the study were evaluated in order to develop a bimodal drug release system that has the potential to be used in tissue engineering applications. [ABSTRACT FROM AUTHOR]

Composite materials in hydrogels state based on collagen and metal-organic frameworks (MOFs) have recently gained attention in tissue engineering due to the enhancement of their mechanical and bactericidal properties. In this work, composite hydrogels based on collagen crosslinked with polyurethane (derived from HDI or IPDI) and MOFs with aluminium as metallic center (MIL53-Al and BHET-Al MOFs) were synthesized by the microemulsion method. The physicochemical properties of these materials were characterized by WAXS, ATR-FTIR, TGA, reticulation by ninhydrin assay, degradation profiles varying pH and using a proteolytic medium, scanning electron microscopy and elemental mapping. At the same time, their in-vitro biocompatibility was tested by the hemolysis test, metabolic activity of fibroblasts by MTT assay, and the inhibition growth of pathogens like E. coli. It was found that the entanglement of collagen, polyurethane and MOFs was made by hydrogen and coordination bonds promoted by the chemical structure of the MOF, leading to a semi-crystalline rough surface with interconnected porosity and aggregates of round-shape, enhancing the mechanical, resistance to thermal degradation and biocompatibility. Interestingly, the better dispersion of MIL53-Al in the collagenic matrix with crosslinker based on HDI leads to a hemolytic capacity of 1.2%, a fibroblast viability of 169.4%, and an E. coli inhibition growth of 96.7%, a potential biomaterial to be used as a wound dressing for chronic wounds in the skin. [ABSTRACT FROM AUTHOR]

In this work, the deposition of high-density polyethylene (HDPE) and polyurethane (PU) particles on polymeric substrates was studied using the finite element analysis software ABAQUS Explicit 2018 at impact velocities ranging between 100 and 500 m/s and temperatures between 20 and 100 °C. The effect of these parameter variations on the particle impact dynamics was quantified by tracking the applied stress, particle temperature, plastic deformation, strain, rebound velocity, and kinetic energy dissipation. The trends observed through variation of these parameters were compared to the experimentally observed window of deposition, which provided important insights into the deposition mechanisms in the cold spray process. The results of the simulations in the present work agreed well with experiments as the lower rebound velocity was associated with the higher deposition efficiency in the cold spray process and vice versa. The results also manifested the importance of the peening effect of the multiple particle collision in the cold spray process, where all of the simulated models showed that the single particle rebounded from the substrate without adhering to it. The peening effect was suggested to play a role in this case because it was eliminated in the single-particle impact simulation of this work. [ABSTRACT FROM AUTHOR]

Although polymer composition of elastomeric material provides excellent performance under different loading cases, the highly nonlinear and rate-dependent behavior of these materials creates serious challenges to investigate the mechanical behavior of them. In this study, the hyperviscoelastic behavior is simulated by implementing the rate-dependent factors into the Mooney–Rivlin strain density potential with nine parameters and material properties are characterized by performing the uniaxial tension loading under different strain rates from 0.001 to 0.33/s for three different shore hardness. In the present study, a developed user-defined subroutine connected to Abaqus commercial finite-element code was employed to simulate the hyperviscoelastic behavior of polyurethane elastomers under dynamic uniaxial tensile loading. The uniaxial tension model is used to predict the hyperviscoelastic behavior and damage evolution of the material. Verification of the FEA simulation model with the experimental data provides a good agreement between the numerical and experimental results. [ABSTRACT FROM AUTHOR]

Polyurethanes have been widely used in many fields due to their remarkable features such as excellent mechanical strength, good abrasion resistance, toughness, low temperature flexibility, etc. In recent years, room-temperature self-healing polyurethanes have been attracting broad and growing interest because under mild conditions, room-temperature self-healing polyurethanes can repair damages, thereby extending their lifetimes and reducing maintenance costs. In this paper, the recent advances of room-temperature self-healing polyurethanes based on dynamic covalent bonds, noncovalent bonds and combined dual or triple dynamic bonds are reviewed, focusing on their synthesis methods and self-healing mechanisms, and their mechanical properties, healing efficiency and healing time are also described in detial. In addition, the latest applications of room-temperature self-healing polyurethanes in the fields of leather coatings, photoluminescence materials, flexible electronics and biomaterials are summarized. Finally, the current challenges and future development directions of the room-temprature self-healing polyurethanes are highlighted. Overall, this review is expected to provide a valuable reference for the prosperous development of room-temperature self-healing polyurethanes. [ABSTRACT FROM AUTHOR]

In the present study, thermoplastic polyurethane (PU) and its nanocomposites have been synthesized using a chain-growth process without a catalyst. The mixture of dual-functionalized multiwalled carbon nanotubes (FMWCNTs) (amino and acid functionalized) was used to enhance chemical and physical interlinking between carbon filler and PU matrix in nanocomposites. The structure of pre-designed synthesized PU and its nanocomposites were confirmed by Fourier transformed infrared analysis, and the degree of crystallinity was analyzed by x-ray diffraction analysis. Scanning electron microscopy morphologies confirm better interfacial interaction between dual-FMWCNTs and PU matrix with very little aggregation at higher loading amount of filler content. Excellent improved thermal stabilities with increase loading amount of functionalized filler were confirmed by thermal gravimetric analysis (TGA). A significant increase in mechanical property of PU-nanocomposites with 3% filler loading was observed 62.4 MPa relative to 32.4 MPa of neat-PU, respectively. The shape recovery (SR) time of thermally triggered nanocomposites was improved significantly due to the better thermal conduction of dual-FMWCNTs. A prompt fast recovery response in less than 10 seconds was recorded for the nanocomposite sample. According to our best knowledge, a fast recovery time of fewer than 10 seconds will be a good approach for high material smart applications which is not reported till somewhere else. [ABSTRACT FROM AUTHOR]

The world production of polyurethanes (PU) currently exceeds 18 mln. tons. Moreover, it is expected that, by 2024, it will become greater than 24 mln. tons. We present a survey of works available from the literature and analyzing the methods of recycling of polyurethanes aimed at the reduction of the amount of PU wastes, environmental protection, and prevention of waste dumping in the landfills. Mechanical processing proves to be the oldest and simple method used for the processing of PU wastes. The process of chemical recycling of polyurethane by glycolysis is regarded as the most environmentally friendly and economically competitive method. Glycolysis of polyurethane is a process of chemical depolymerization based on the reaction of transesterification of polyols and glycols in a molecule of urethane. This process makes it possible to destroy the polyurethane matrix and either to release polyol or to generate new recycled polyol. The possibility of application of different glycols and catalysts in the reaction of catalytic transesterification is demonstrated. [ABSTRACT FROM AUTHOR]

Vacuum casting (VC) is a promising technique used for the production of functional plastic parts due to its fast production of high-quality prototypes. However, the mechanical properties of the fabricated products are affected by the composition of the molding materials. Additive manufacturing (AM) is also widely applied for low-volume prototyping applications. However, the mechanical properties of the fabricated products are affected by both build directions and printing angles. To investigate the difference in flexural strength of parts between vacuum casting and fused deposition modeling, glass fiber (GF) and carbon fiber (CF) are added to the matrix materials of polyurethane (PU) for improving the flexural strength of the molded products and three different printing angles and two build directions were applied in AM process. It was found that the flexure strength of the specimen fabricated by VC is generally greater than that of the specimen fabricated by AM. The highest flexure strength of the specimen fabricated by VC is 141 MPa, whereas the highest flexure strength of the specimen fabricated by FDM is only 102.7 MPa. The addition of short GF to the PU will increase the flexural strength. The flexural strength can be increased by about 41% when the PU is added with 4 wt.% short GF. The flexural strength can be increased by about 4.8% when the PU is added with 1 wt.% long GF. In contrast to above results, the flexural strength will be reduced when the PU is added with more than 2 wt.% long GF. On the contrary, the flexural strength can not be improved when the short CF or long CF is added to the PU. Finally, the flexural strength of the plastic prototype made by VC technology is superior to that of the plastic prototype made by FDM since the mechanical properties of the plastic prototype made by the FDM are affected by the build direction and printing angle. [ABSTRACT FROM AUTHOR]

The development of polymer-based composites with self-healing and recyclable capability has attracted the attention of several researchers for resource recycling and environment protection. In this work, Halloysite nanotubes (HNTs) reinforced polyurethane materials (PU) with self-healing and recyclable ability were constructed by in situ polymerization method. The mechanical, thermal amd morphological properties of PU and related composites were studied. The morphology of samples fracture surface ensured the homogeneous dispersion of HNTs in the polymer matrix. Moreover, thermal stability was improved with the incorporation of the HNTs. The tensile test showed strength increased with HNTs content increased. The tensile strength of composites increases from 23.38 to 34.92 MPa at 2 wt% HNTs. Therefore, the designed strategy provides a simple approach for preparing high mechanical properties, reprocessing and self-healing ability polyurethane composites. [ABSTRACT FROM AUTHOR]

In this study, a novel boric acid-incorporated polyurethane (BPU) foam was synthesized and its several physical and biological properties were investigated. In order to determine the effect of the incorporated boric acid (BA) particles into the foam, mechanical and physical properties (apparent density, contact angle), analytical (Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, inductively coupled plasma optical emission spectrometry), morphological (scanning electron microscopy (SEM), micro-computed tomography), thermal characteristics (thermogravimetric analysis, differential scanning calorimetry) and antibacterial activity were examined. The addition of BA particles to the PU foam improved the thermal and mechanical properties, as BA strengthened the polymeric structure through hydrogen bonds with PU. Mechanical analyses and contact angle measurements revealed that the BPU foam demonstrated better mechanical properties (94.0 kPa) and higher hydrophobicity values (108.52°) with respect to PU foam (52.9 kPa and 37.35°, respectively). According to microscopy analyses, micro-CT images confirmed SEM images in which PU foam has an open cell structure, whereas BPU foam has a closed cell structure. The antibacterial activity test results demonstrate that incorporation of BA to the PU structure significantly improved the antibacterial properties of the PU foam against both of Gram-positive and Gram-negative bacteria. This study suggests that the addition of BA into PU structure enhanced the antibacterial activities of PU foam while improving its physical, mechanical and thermal properties. As a result, BA incorporation should be classified as a promising alternative to improve the properties of PU foams. [ABSTRACT FROM AUTHOR]

The poly(amidoamine) (PAMAM) dendrimer-grafted silica nanoparticles were utilized as a curing and composite agent for epoxy-terminated polyurethane (PU). For this purpose, surface-hydroxylated silica nanoparticles (SiH) were modified with (3-aminopropyl)triethoxysilane to obtain the core for PAMAM dendrimer synthesized via consecutive addition of methyl acrylate and ethylenediamine. Effect of different chain extenders, pyromellitic dianhydride (PMDA) and 1,4-butanediol (BD), on thermal characteristics of the composites was also studied in detail. Successful incorporation of PMDA and BD chain extenders and also epoxy groups to the PU backbone was confirmed by proton nuclear magnetic resonance analysis. Chemical modification of silica nanoparticles via PAMAM dendrimer in each of the generation steps was studied using Fourier-transform infrared spectroscopy and also their thermal degradation characteristics. The thermogravimetric analysis results proved that increasing content of the PAMAM-modified silica nanoparticles in combination with incorporation of PMDA as the chain extender resulted in higher thermal stabilities of the PU composites. The cured epoxy-modified PU with PMDA chain extender showed higher char residue compared with the cured epoxy-modified PU with BD chain extender (7.1 against 0.8%). X-ray diffraction analysis confirmed amorphous nature of silica and the PU composites. Scanning and transmission electron microscopies were also used for morphological investigation of the pure and PAMAM-modified silica in addition to the PU composite. [ABSTRACT FROM AUTHOR]

Newly synthesized polyurethane (PU)–polydopamine (Pda)/CeO2 (cerium oxide) nanocomposite-coated mild steel was investigated for its corrosion protection performance and mechanical properties in 3.5% NaCl by electrochemical techniques. The functionalization of CeO2 nanoparticles by Pda was confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The results derived from the electrochemical impedance spectroscopy (EIS) and polarization studies indicated the superior anticorrosive activity of PU–Pda/CeO2 nanocomposite coatings compared to those of plain PU coatings due to the synergetic effect of Pda/CeO2 and polyurethane. Decreased corrosion current was detected at the scratch of the PU–Pda/CeO2 nanocomposite-coated mild steel surface by scanning electrochemical microscopy (SECM) compared to other studied coatings. Addition of Pda-wrapped CeO2 nanoparticles into the PU coating resulted in the blockage of charge transfer at metal/electrolyte interface which reduced the dissolution of mild steel. It is due to the synergistic effect of Pda and CeO2 which strengthens the anticorrosive property. It was revealed from the SEM/EDX analysis that the formation of the corrosion products at the metal/electrolyte interface behaved as the passive layer which reduced the dissolution of steel. The incorporation of Pda-functionalized CeO2 nanoparticles to PU enhanced the mechanical properties of the coated surface which complimented the electrochemical studies. The superior anticorrosive property of the proposed nanocomposite coatings provides a new horizon in the development of high-performance anticorrosive coatings for various industries. [ABSTRACT FROM AUTHOR]

In this study, organic–inorganic-modified ammonium polyphosphate (APP) flame retardant (FR) was prepared by a sol–gel method that used tetraethoxysilane and vinyltriethoxysilane as precursors. Then modified APP (VTSAPP) was added into polyurethane (PU) to fabricate the FR PU/VTSAPP composites. Crucially, the structure and performance of VTSAPP were systematically characterized. The results showed that a dense hybrid silica gel layer structure was formed on the surface of APP. Ideally, the limiting oxygen index (LOI) value of PU/20VTSAPP composite increased from 19.5% for pure PU to 30% and the vertical burning test (UL-94) reached up to V-0 level. Moreover, the addition of VTSAPP dramatically decreased the released smoke of PU during combustion compared to the counterpart of APP. The FR mechanism of VTSAPP was deeply explored. It is confidently shown that phosphorus and silicon compounds of VTSAPP contributed to the formation of a more continuous and compact char and improved the thermal stability of the char layer. The results of this study distinctly confirmed that VTSAPP was an effective FR agent for PU. Highlights: The modified APP flame retardant was prepared by a sol–gel method that used TEOS and VTES as precursors. The modified APP was added into the PU matrix to prepared flame-retardant PU composites. The modified APP not only enhanced the flame retardancy of PU but also reduced the smoke emission. The flame-retardant mechanism of modified APP in PU was deeply explored. [ABSTRACT FROM AUTHOR]

Polyurethane (PU) is one of the most important plastics in the world plastic industry. Industrial production of PU is generally carried out by bulk or solution polymerization with homogeneous catalysts. Poly(2-diethylamino ethylacrylate) (P(DEAEA)) and poly(2-diethylamino ethylacrylate-co-2-hydroxy ethylmethacrylate) (P(DEAEA-co-HEMA)) gels were synthesized by free radical polymerization. The swelling behavior of the synthesized gels in toluene at 25 °C was examined. Subsequently, the catalytic effects of these catalysts on the synthesis of (PU) by both bulk and solution polymerizations were investigated. Optimum particle diameter and catalyst amount were determined for catalysts used in PU synthesis reaction. Both gels were found to be more effective in the PU synthesis reaction than triethylamine (TEA), which is currently used commercially. In addition, it was found that the gels retained 95% of their efficiency, despite being reused 30 times in the PU synthesis reaction. Finally, the kinetics of PU synthesis reactions with catalysts were studied. [ABSTRACT FROM AUTHOR]

Shape memory polymers are the materials that can recover their original shape after a large deformation when exposed to an external stimulus such as electric field, pH, temperature, light, magnetism or humidity. With these properties, it is possible to use them in many areas in the industry. In this study, a shape-memory polymer compound was developed which is capable of changing its shape when subjected to an external voltage. Electroactive shape memory polymer compound was prepared by mixing commercially available and economically viable thermoplastic shape memory polyurethane (SMPU) with carbon black (CB), which has low cost and high electrical conductivity, by adding at various proportions. Conductivity, structural, morphological, homogeneity, thermal, rheological and shape memory characterizations of the SMPU/CB blend were carried out by four-probe measurements, ATR-FTIR spectroscopy, x-ray diffraction analysis, scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analyses, melt flow index (MFI), and a thermal camera imaging methods, respectively. The effects of CB loading ratios on these characteristics of SMPU/CB blends were investigated. It was concluded that SMPU/20CB blend can be used as a commercial material having shape memory characteristics. [ABSTRACT FROM AUTHOR]

Polyurethanes (PU) are multifunctional polymers, used in automotive industry, in coatings, rigid and flexible foams, and also in biomimetic materials. In the same way as all plastic waste, the incorrect disposal of these materials leads to the accumulation of polyurethanes in the environment. To reduce the amount of waste as well as add value to degradation products, bioremediation methods have been studied for waste management of PU. Enzymes of the hydrolases class have been experimentally tested for enzymatic degradation of PU, with very promising results. In this work, two enzymes that can degrade polyurethanes were studied by molecular dynamics simulations: a protease and an esterase, both from Pseudomonas. From molecular dynamics simulations analysis, it was observed the stability of the structures, both in the simulations of the free enzymes and in the simulations of the complexes with a PU monomer. Hydrogen bonds were formed with the monomer and the enzymes throughout the simulation time, and the interaction free energy was found to be strongly negative, pointing to strong interactions in both cases. [ABSTRACT FROM AUTHOR]

Hypopharyngeal tissue engineering is increasing rapidly in this developing world. Tissue damage or loss needs the replacement by another biological or synthesized membrane using tissue engineering. Tissue engineering research is emerging to provide an effective solution for damaged tissue replacement. Polyurethane in tissue engineering has successfully been used to repair and restore the function of damaged tissues. In this context, Can polyurethane be a useful material to deal with hypopharyngeal tissue defects? To explore this, here ester diol based polyurethane (PU) was synthesized in two steps: firstly, polyethylene glycol 400 (PEG 400) was reacted with lactic acid to prepare ester diol, and then it was polymerized with hexamethylene diisocyanate. The physical, mechanical, and biological testing was done to testify the characterization of the membrane. The morphology of the synthesized membrane was investigated by using field emission scanning electron microscopy. Functional groups of the obtained membrane were characterized by fourier transform infrared spectroscopy spectroscopy. Several tests were performed to check the in vitro and in vivo biocompatibility of the membrane. A highly connected homogeneous network was obtained due to the appropriate orientation of a hard segment and soft segment in the synthesized membrane. Mechanical property analysis indicates the membrane has a strength of 5.15 MPa and strain 124%. The membrane showed high hemocompatibility, no cytotoxicity on peripheral blood mononuclear cell, and susceptible to degradation in simulated body fluid solution. Antimicrobial activity assessment has shown promising results against clinically significant bacteria. Primary hypopharyngeal cell growth on the PU membrane revealed the cytocompatibility and subcutaneous implantation on the back of Wistar rats were given in vivo biocompatibility of the membrane. Therefore, the synthesized material can be considered as a potential candidate for a hypopharyngeal tissue engineering application. [ABSTRACT FROM AUTHOR]

Highlights: Carbon nanotubes/polymerizable ionic liquid copolymer (CNTs/PIL) provides nucleation sites and inhibits the combination of microcellular structures. The increase in evaporate time improves the conductive network of composite foams. Electromagnetic interference shielding effectiveness (EMI SE) and specific EMI SE of the composite foam displays 69.9 dB and 211.5 dB/(g cm−3). Polarization, conduction and magnetic loss attenuate microwave energy.Lightweight microcellular polyurethane (TPU)/carbon nanotubes (CNTs)/ nickel-coated CNTs (Ni@CNTs)/polymerizable ionic liquid copolymer (PIL) composite foams are prepared by non-solvent induced phase separation (NIPS). CNTs and Ni@CNTs modified by PIL provide more heterogeneous nucleation sites and inhibit the aggregation and combination of microcellular structure. Compared with TPU/CNTs, the TPU/CNTs/PIL and TPU/CNTs/Ni@CNTs/PIL composite foams with smaller microcellular structures have a high electromagnetic interference shielding effectiveness (EMI SE). The evaporate time regulates the microcellular structure, improves the conductive network of composite foams and reduces the microcellular size, which strengthens the multiple reflections of electromagnetic wave. The TPU/10CNTs/10Ni@CNTs/PIL foam exhibits slightly higher SE values (69.9 dB) compared with TPU/20CNTs/PIL foam (53.3 dB). The highest specific EMI SE of TPU/20CNTs/PIL and TPU/10CNTs/10Ni@CNTs/PIL reaches up to 187.2 and 211.5 dB/(g cm−3), respectively. The polarization losses caused by interfacial polarization between TPU substrates and conductive fillers, conduction loss caused by conductive network of fillers and magnetic loss caused by Ni@CNT synergistically attenuate the microwave energy. [ABSTRACT FROM AUTHOR]

The development of new technologies to produce three-dimensional and biocompatible scaffolds associated with high-end cell culture techniques have shown to be promising for the regeneration of tissues and organs. Some biomedical devices, as meniscus prosthesis, require high flexibility and tenacity and such features are found in polyurethanes which represent a promising alternative. The Poly(PCL–TMC)urethane here presented, combines the mechanical properties of PCL with the elasticity attributed by TMC and presents great potential as a cellular carrier in cartilage repair. Scanning electron microscopy showed the presence of interconnected pores in the three-dimensional structure of the material. The scaffolds were submitted to proliferation and cell differentiation assays by culturing mesenchymal stem cells in bioreactor. The tests were performed in dynamic flow mode at the rate of 0.4 mL/min. Laser scanning confocal microscopy analysis showed that the flow rate promoted cell growth and cartilage ECM synthesis of aggrecan and type II collagen within the Poly(PCL–TMC)urethane scaffolds. This study demonstrated the applicability of the polymer as a cellular carrier in tissue engineering, as well as the ECM was incremented only when under oriented flow rate stimuli. Therefore, our results may also provide data on how oriented flow rate in dynamic bioreactors culture can influence cell activity towards cartilage ECM synthesis even when specific molecular stimuli are not present. This work addresses new perspectives for future clinical applications in cartilage tissue engineering when the molecular factors resources could be scarce for assorted reasons. [ABSTRACT FROM AUTHOR]

Background: Understanding the mechanical response of elastomers to applied deformation at different strain rates and temperatures is crucial in industrial design and manufacture; however, this response is often difficult to measure, especially at high strain rates (e.g. > 100 s− 1), and more predictive methods to obtain constitutive relationships are required. Objective: The objective of the research described in this paper is to develop such methods. Method: The paper outlines a novel approach combining quasi-static monotonic tests in tension and compression, quasi-static cyclic tests in tension, and high strain rate tests in compression, with dynamic mechanical analysis and time-temperature superposition. A generalized viscoelastic model incorporating continuum damage is calibrated. Results: The results show that a model calibrated using data from quasi-static compression and dynamic mechanical analysis can be used to adequately predict the compressive high strain rate response: hence, this paper provides an important step in the development of a methodology that avoids the requirement to obtain constitutive data from high strain rate experiments. In addition, data from FE models of the dynamic mechanical analysis experiments are provided, along with a discussion of data obtained from tensile and cyclic loading. Conclusions: The paper demonstrates the effectiveness of 'indirect' predictive methods to obtain information about high rate behaviour of low modulus materials. [ABSTRACT FROM AUTHOR]

Developing efficient sorbent materials is of worldwide importance to protect the environment against frequent oil spills and chemical leakage accidents. A simple and low-cost process was adopted to prepare hydroxylated BN bonded with SiO2 sol and then embed BN/SiO2 on polyurethane (PU) foam(BN/SiO2@PU) via dip-coating. BN/SiO2@PU could float on water due to its hydrophobicity. Absorption tests were performed to test its performance using various organic solvents or oil. Comparing with BN/SiO2 aerogel, BN@PU and SiO2@PU, BN/SiO2@PU had a high absorption rate and a high absorption capacity for both organic solvents and oil, and could absorb as much as 40 times its weight. It was also able to selectively absorb oil or organic solvents from an oil–water mixture with separation efficiency higher than 95% and had good recyclability of 20 absorption cycles even towards commercial waste oil. Furthermore, BN/SiO2@PU with high temperature stability can be used under harsh condition. The performance of the prepared adsobent reported is competitive and superior to other reported materials, confirming its potential application in water treatment. [ABSTRACT FROM AUTHOR]

In this study, we evaluated polyurethane foam (PF), volcanic rock (VR), and a modified plastic cap (MPC) as supports for the immobilization of organophosphorus (OP) pesticide-degrading actinobacterial strains. The colonization and activity of four streptomycetes were favoured by PF, which was selected as the carrier to use in a continuous stirred tank bioreactor (CSTR) that can be operated at increasing inflows of a pesticide mixture that contains the insecticides chlorpyrifos (CP) and diazinon (DZ). Our results demonstrate that the CSTR can be operated at flow rates of 10 and 40 mL h−1 with greater than 85% removal of the pesticides in the short term. A significant decrease in the efficiency of CP removal was observed at the highest inflows into the reactor. The CP and DZ loading rates in the bioreactor ranged from 0.44 to 1.68 mg L−1 h−1 and from 0.50 to 2.17 mg L−1 h−1, respectively. Although the treated wastewater exhibited moderate toxicity for Raphanus sativus, a bioreactor inoculated with a mixed culture formed by Streptomyces spp. strains AC5, AC9, GA11 and ISP13 may provide an effective biotechnological strategy for the reduction of OP pesticide residues produced during agronomic and manufacturing practices and therefore prevent environmental pesticidal pollution. [ABSTRACT FROM AUTHOR]

Plastic bottles are non-biodegradable material made up of Polyethylene Terephthalate (PET) and takes around 450 years to get decomposed. In Malaysia, near 13.2% of plastics contribute to municipal solid waste, where 2.5% is PET. To reduce the waste, interlocking bricks manufacture by waste plastic bottles are used to replace the conventional bricks that use cement and clay. The purpose of this research is to reuse plastic bottles comprised of Polyethylene Terephthalate and Polyurethane binder, by manufacturing interlocking brick that helps to reduce the waste on landfills and the pollution. The plastic bottles were shredded and grinded to a size of 0.75 mm and mixed with the Polyurethane (PU) and the Polymer. The mixed later casted and compacted in the interlocking brick machine mould. The tests performed on the interlocking bricks were compressive strength, impact, flexural strength and thermal conductivity for obtaining the mechanical and thermal properties. The tests values were then keyed into the Response Surface Methodology (RSM) to obtain the optimal PET and PU to verify reliability. Based on the results it is concluded that PET/PU of 60/40 ratio is suitable as non-load bearing masonry brick and recommended to be used as partition walls. [ABSTRACT FROM AUTHOR]

Density reduction has become a topical issue in wood composite materials for application in building and furniture. In this study, lightweight wood–polyurethane (W–PU) composite foams with the addition of 30 wt% wood particles were prepared. Industrial kraft lignin was used as bio-polyol to substitute partial petroleum-based diethylene glycol (DEG) to synthesize rigid W–PU foams. The effect of varying lignin contents (5, 10, 15 and 20 wt% based on DEG mass) on the reactivity, morphology, density, compressive properties, water absorption and thermal stability of the foams was evaluated. Fourier transform infrared (FTIR) analysis confirmed the formation of characteristic urethane linkages in all the foam samples. With the incorporation of lignin, the foam cellular shape became irregular with formation of large cells. W–PU foams exhibited poor cellular structures with a larger number of open cells. The density of W–PU foams increased from 47 to 96 kg/m3 as the lignin content increased from 0 to 20%. Although the foam reactivity was decreased by the incorporation of lignin, both the compressive strength and modulus were increased upon the incorporation of lignin. Furthermore, the specific compressive strength and modulus of W–PU foams increased by 55% and 48% with lignin content increasing from 0 to 20%, and the 20-day water absorption decreased by 38%. Thermal gravimetric analysis showed that the incorporation of lignin did not significantly affect the thermal degradation behaviour of foam, but it rather increased the mass of char residue. This study provides a promising method for value-added utilization of technical lignin in W–PU lightweight composites. [ABSTRACT FROM AUTHOR]

Pre-insulated district heating (DH) pipes have been in use for more than 40 years. The thermal performance of these pipes decreases over time as a result of thermal and mechanical aging, which leads to higher heat energy losses. A non-destructive method based on a cooling method is under development for assessing the thermal performance of a DH network. The method utilizes the copper wire, which is already embedded in the polyurethane insulation for detection of water leakage, as a sensor for measuring the temperature at the position of the copper wire. The method involves a shutdown of a selected part of a network for less than 2 h and evaluating the cooling process by measuring the supply pipe temperature and the temperature of the copper wire. The method was applied in a DH network during heating season. The thermal conductivity calculated by the method [0.027 W/(m K)] was in good agreement with the reference value [0.026 W/(m K)]. The cooling of the network can be measured at a valve or at other more easily accessible steel parts. It was also shown that the method is applicable for DH networks without a copper wire. However, a temperature measurement is needed on the casing pipe. [ABSTRACT FROM AUTHOR]

Thin-walled (D/t > 30; D, initial outer diameter; t, initial wall thickness) bent tubes with large diameter (D > 100 mm) and small bending radius (R/D < 3; R, centerline radius) are difficult to form integrally using traditional bending methods. In this paper, using a novel loading method, a modified push-bending (MPB) process with polyurethane as mandrel was developed. A stainless steel bent tube with extreme geometrical specification (D = 144 mm, D/t = 72, and R/D = 1.94) was formed integrally by MPB. Based on analytical and finite element (FE) method, the internal pressure, i.e., contact pressure between polyurethane and tube (CPPT) were investigated. The results show that the CPPT decreases linearly from the back end to the front end of polyurethane rod and increases with smaller μ1 (the coefficient of friction between polyurethane and tube) and larger L (the center axis length of polyurethane rod), and the increase of CPPT is helpful to decrease the ovality of the bent tube. [ABSTRACT FROM AUTHOR]

The aim of this research is to develop a novel non-leaching antimicrobial waterborne polyurethane (WPU) leather coating material with covalently attached quaternary phosphonium salt (QPS). The structure of the QPS-bearing WPU has been identified, and their thermal stability, mechanical property, and antimicrobial performance have been investigated. The results reveal that the incorporation of QPS slightly reduces the thermal stability of WPU material but would not affects its usability as leather coating. Despite the presence of hydrophobic benzene in QPS structure, the strong hydration of its cationic groups leads to the increased surface contact angle (SCA) and water absorption rate (WAR) of the films, suggesting that the water resistance of the films needs to be improved for the purpose of leather coatings. Antibacterial tests demonstrate that when the QPS content is 20 wt%, QPS-bearing WPU shows effective antimicrobial activity against bacteria. The WPU containing QPS prepared in this study is a non-leaching antimicrobial material and has great potential application as leather coating. [ABSTRACT FROM AUTHOR]

We investigated the effect of gelation solvent, monomer type, and monomer concentration on the physical properties of freeze-dried poly(urethane)-poly(isocyanurate) (PUR-PIR) aerogels, with particular emphasis on their thermal conductivity. It was found that the gelation solvent considerably affects aerogel morphology and physical properties. Aerogels with the lowest thermal conductivity were obtained using a mixture of tetrahydrofuran (THF) and acetonitrile, in a 50% volume ratio. The influence on thermal conductivity of polyol and isocyanate structure and of their concentration was also investigated. Rigid precursors, phloroglucinol (POL), and an aromatic polyisocyanate based on toluene diisocyanate (Desmodur RC) yielded the lowest thermal conductivity. Our results were compared with recent work reporting on parameters that could be used as predictors of thermal conductivity and other physical properties of organic aerogels. None of these parameters were found to be satisfactory predictors of aerogel properties. For example, no systematic correlation between solvent solubility parameters and aerogel properties was observed. We also examined the role of the K-index. This index, defined as the ratio between porosity and contact angle, was shown recently to be a good predictor of the properties of polyurea aerogels. While the thermal conductivity scaled with the K-index, the scaling was different for each of the isocyanate monomers considered in our experiments. Thermal conductivity, instead, scaled well with the product of density and shrinkage of aerogels, independent of monomer type. The reasons of this dependence on shrinkage and density are discussed, and the use of these parameters to guide experimentation on other systems is discussed. Physical properties such as static and dynamic compression modulus and thermal stability of the most promising formulations were also examined. [ABSTRACT FROM AUTHOR]

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MoS2-multi-walled-carbon-nanotube (MWCNT) hybrids containing two-dimensional MoS2 and one-dimensional MWCNTs were synthesized through a one-step hydrothermal reaction. X-ray-diffraction and transmission-electron-microscopy results demonstrated that MoS2 nanosheets were successfully synthesized, and uniformly anchored on the MWCNTs' surfaces. Furthermore, the effects of the MoS2-MWCNT hybrids on the tribological performances of polyurethane composite coatings were investigated using a UMT-2MT tribo-tester. Friction and wear test results revealed that the friction coefficient and wear rate of a 3 wt% MoS2-MWCNT-1 filled polyurethane composite coating were reduced by 25.6% and 65.5%, respectively. The outstanding tribological performance of the MoS2-MWCNT-1 reinforced polyurethane composite coating was attributed to the excellent load-carrying capacity of the MWCNTs and good lubricant ability of MoS2. The surface morphologies of the worn surfaces and counterpart ball surfaces were investigated to reveal the wear mechanisms. [ABSTRACT FROM AUTHOR]

In this paper, the effect of chemical treatments on date palm fibers (DPFs) properties was studied; DPFs were first treated with a 5 wt% NaOH aqueous solution for 1 h and then modified using two types of silane coupling agents (3-Mercaptopropyltrimethoxysilane and 3-Aminopropyltrimethoxysilane) with various concentrations (0.1, 0.5, 1 and 2 wt%) to improve the interfacial properties of DPFs with polymeric matrices. SEM observations showed the formation of silane layers on the alkalized surface of DPFs. The Fourier-transform infrared (FTIR) results showed that the salinization was successfully performed by forming covalent Si-O-C bonds between DPF and silane coupling agent. The pull-out behavior of treated fibers was also investigated using two matrices; polyurethane (PU) and epoxy. The obtained results showed that the treatments have successfully improved the interfacial bond characteristics of DPF-PU and DPF-Epoxy systems. [ABSTRACT FROM AUTHOR]

Cholesteric liquid crystal (CLC) compound present in egg yolk is extracted and characterized by polarized optical microscope, differential scanning calorimetry, scanning electron microscopy, dynamic light scattering and electro-optical measurements, confirming its potential use as an active material in the fields such as flexible liquid crystal displays. Emulsion polymerization is used to fabricate a flexible polyurethane shell with different thicknesses over CLC nanoparticles. Finally, thin films of prepared core-shell nanoparticles and poly(vinyl alcohol) as the binder are fabricated on the indium tin oxide substrates via knife-coating method and their electro-optical properties are evaluated. The films responded to applied potentials (4-18 V) by a 46-100% change in transmittance levels. The high shell thickness (5-45 nm) caused the need for higher voltages, because of the difficulty in feeling of the external field by liquid crystal (LC) core through the polymer shell. In the case of very thin or no polymer shell, the LC core becomes damaged or deformed under the electric field. [ABSTRACT FROM AUTHOR]

Abstract: Three polyurethane formulations were prepared on the basis of siloxane; two formulations contained 1% and 3% of a hydroxyl functionalized polyhedral oligomeric silsesquioxane [POSS (ROH)2] nano-particles (as a co-chain extender) and one was without nano-particle. Structures of the polyurethanes were characterized by FTIR and SEM. The effect of POSS nano-particles on properties of the synthesized PUs was examined for vascular applications by tensile test, contact angle, SEM, AFM and endothelial cells viability evaluation. Properties of the polyurethane with 1% POSS were compared with those of PU without POSS and the results showed 66% increase in the elongation-at-break, 53% increase in tensile strength and 33% increase in modulus, 9.45% increase in contact angle, 76.7% reduction in surface roughness and 9.46% increase in cell viability. It was also shown that a polyurethane containing 1% of POSS nano-particles in its structure developed the highest hydrophobicity, which resulted in its lowest potential for thrombosis.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Abstract: Two series of polyurethane (PU), based on polycaprolactone (PCL) as soft segments with two different molecular weights (2000 and 530 Da), and hexamethylene diisocyanate (HDI) and 1,4-butandiol (BDO) as hard segments were synthesized to fabricate curcumin-loaded electrospun nanofibrous PCL-based PU substrate. Chemical structures of the synthesized PUs were characterized by FTIR and NMR spectroscopy techniques. The thermal properties were analyzed by differential scanning calorimetry (DSC) and surface hydrophilicity was studied by static contact angle and bulk hydrophilicity was evaluated by water uptake test. Thereafter, bead-free PU nanofiberous substrate containing curcumin was fabricated by electrospinning and morphology of the mats was observed by scanning electron microscopy (SEM). Mechanical properties of the electrospun mats in comparison with polymeric films were assessed by a universal test machine. The in vitro release of curcumin was studied by UV–Vis spectroscopy. The optical density of the bacterial solutions was used to evaluate the antibacterial activity of the curcumin-loaded nanofibrous mats against Escherichia coli (E-coli ATCC: 25922). The results showed that curcumin-loaded PU synthesized by PCL with molecular weight of 2000 Da displayed better mechanical properties as well as better antibacterial properties in wound dressing application.Graphical abstract: [ABSTRACT FROM AUTHOR]

Photo-oxidative degradation of polyurethanes based on hexamethylene diisocyanate with different oligoether components was investigated using IR spectroscopy and dynamic mechanical analysis. The cross-linking density of highly cross-linked polyurethane based on an oligoether triol of molecular mass 500 tended to increase during photo-oxidation. A polyurethane containing esters was more stable than that based on an oligoether diol of similar molecular mass. [ABSTRACT FROM AUTHOR]

A series of composites of commercial waterborne polyurethane and hybrid silica were prepared by the sol-gel process through in situ synthesis. Mechanical properties, small angle X-ray scattering and differential scanning calorimetry measurements were performed to evaluate the effects that hybrid silica has on the properties of the resulting polyurethane composites. A series of 13 different organosilanes differing in polarity and alkyl chain length was studied. Under the present evaluated conditions, composites bearing hybrid silica were more likely to exhibit a reduction in mechanical resistance when compared to bare polyurethane. Samples also exhibited a negligible variation in glass transition temperature and a reduction in ΔCp. The enthalpy of the crystallization process exhibited an increase. Based on the small angle X-ray scattering measurements, the composites exhibited a small reduction in the interdomain spacing and an increase in the degree of phase separation. Graphical Abstract: [ABSTRACT FROM AUTHOR]

In polishing process, polishers must have a number of proprieties inter alia elasticity to perform their function, which is the achievement of a minimum roughness and a correct form. During the process, the polishers are subjected to compression stress generated by the technological parameters of the process. The efficiency of the polishers and the obtained quality will be influenced when they lost their mechanical properties after some hours of use. This work aims to characterize the polisher's compression behavior and its influence on the surface quality and the effectiveness during the optical polishing process. The subjects are to define polishers wear reasons and thus to define their lifetime, in addition to the identification of the relationship between the compression behavior and the polishing quality and efficiency. For that, polishing, compression and hysteresis tests were conducted on polyurethane polishers before and after their use and the obtained results were discussed. The found results after 2 h of polishing showed the difference of the elastic properties of the polishers without a big influence on their total wear. Consequently, a very low surface roughness was obtained, with high shape accuracy. [ABSTRACT FROM AUTHOR]

Adhesives used to bond the wood panels are petroleum-based and has volatile organic compound, VOCs. Harmful substance when inhaled by human being and can cause different problems, such as cancer. As an alternative to replace these adhesives is to use the polyurethane derived from castor oil (PU), a renewable resource that can be used to structural applications, indoor and outdoor environments. It is weather resistant and has good mechanics properties. The aim of this paper is to evaluate the mechanical resistance of glued joint with PU biding MDF panels. It was produced raw MDF samples glued two by two with 0.05 g of adhesive in 1 cm. Where 6 samples were used with PVA adhesive, 6 with contact adhesive and 6 with PU. After 72 h it was applied a mechanical analysis technique of shear bond strength, according to the standards ASTM D 3983-93 and ASTM D897-95A. The results shows the shear average resistance of PU was 12.67 ± 2.26 MPa, whereas for the PVA adhesive was 2.55 ± 0.19 MPa and the contact adhesive was 3.26 ± 0.63 MPa. It is conclusive the polyurethane derived from castor oil can be used to bind MDF panels, due to its superior shear average resistance compared to PVA and contact adhesives. [ABSTRACT FROM AUTHOR]

Edge-glued panels are composed by the lateral and top gluing with adhesives of solid battens. These panels use small pieces of wood, offering an optimal usage of forest resources and the development of higher value-added products. The adhesive generally used to produce the panels are the synthetic ones (PVA or EPI). The polyurethane derived from castor oil may arise an alternative to replace the adhesives derived from non-natural origin, because it has no solvent in its composition, is a biodegradable material and it comes from a renewable resource. The bonding quality of this panel was performed according to BS EN 13353, which specify the minimum resistance values for panels under different humidity and temperature conditions applied to the international market. In this context, the aim of this paper was to evaluate the lateral gluing quality of Pinus taeda panels using the polyurethane derived from castor oil, as well as assess the pressing time effect on the bonding quality. The adhesive was applied into the battens surface in weight of 180 g/m. The panels were put into a cold press machine for 1, 2, 4, 8 and 24 h, totalizing five conditions and eight together/replications. The bonding quality of this panel was performed according to BS EN 13353 and BS EN 13354, under different humidity and temperature conditions. The results were submitted to statistical analysis by outlier tests, normality test, homogeneity variance, analysis of variance and mean comparison, all with 95 % reliability. The polyurethane showed acceptable values to EN-13353 for 4 h in the press machine. The test for critical humidity and temperature conditions showed a reduction in the adhesive bond strength, but still acceptable to EN-13353. Under these circumstances, it is concluded that the polyurethane derived from castor oil may be an alternative to produce lateral glued panels for dry conditions and internal and external applications for humid conditions. [ABSTRACT FROM AUTHOR]

Background: In this study, polyurethane (PU) films from palm kernel oil-based polyester (PKO-p) incorporated multi-walled carbon nanotubes (MWNTs) were prepared via evaporative casting method. Nanoparticle fluid dispersions containing 0.01, 0.04 and 0.08 % wt. of MWNTs were added into PKO-p-based resin and mixed by digital probe sonicator for 20 min followed by mixing with isocyanate to produce PU-MWNTs composite films. The mechanical properties, water resistance, water vapor transmission rates (WVTR), biocompatibility, and antibacterial activities of the PU-MWNTs composite films were examined. Results: Results show that PU containing 0.01 wt. % of MWNTs demonstrated optimum mechanical properties as it possessed high tensile strength, modulus, and good flexibility compared to PU film and other PU-MWNTs composite films. There are no significant difference in swelling values as well as water vapor transmission rates for PU film and PU-MWNTs composite films. All the films showed low swelling values (17-23 %) and WVTR values in the range 181-269 g m d. Cell studies revealed that PU and PU-MWNTs composite films are non-cytotoxic to human skin fibroblast cells (CRL2522) and the cell proliferation was increased after incubation of 72 h. The in vitro qualitative antibacterial results showed both PU and PU-MWNTs composite films exhibited bactericidal effect against Gram-positive ( Staphylococcus aureus and Bacillus cereus) and Gram-negative bacteria ( Escherichia coli and Klebsiella pneumonia). Conclusions: In summary, incorporation of MWNTs improved the mechanical properties of the polyurethane films with no cytotoxic effect against normal human skin fibroblast cells. [Figure not available: see fulltext. Caption: Fluorescence microscope images of the cell viability of normal human skin fibroblast cells (CRL2522, ATCC) which changed their morphology to elongated/spindle-like shape after being cultured for 72 h on polyurethane (PU) film, PU-MWNT01, PU-MWNT04, and PU-MWNT08 composite films.] [ABSTRACT FROM AUTHOR]

Polyurethane is widely used, with its two major applications, soft furnishings and insulation, having low thermal inertia, and hence enhanced flammability. In addition to their flammability, polyurethanes form carbon monoxide, hydrogen cyanide and other toxic products on decomposition and combustion. The chemistry of polyurethane foams and their thermal decomposition are discussed in order to assess the relationship between the chemical and physical composition of the foam and the toxic products generated during their decomposition. The toxic product generation during flaming combustion of polyurethane foams is reviewed, in order to relate the yields of toxic products and the overall fire toxicity to the fire conditions. The methods of assessment of fire toxicity are outlined in order to understand how the fire toxicity of polyurethane foams may be quantified. In particular, the ventilation condition has a critical effect on the yield of the two major asphyxiants, carbon monoxide and hydrogen cyanide. [ABSTRACT FROM AUTHOR]

High-pressure injection injuries (HPII) caused by water swelling sealant are rare at present. The patient generally has small-sized skin lesions, and the misleadingly benign presentation may cause delayed treatment at the early stage of management. In addition, radiographic examination may be underestimated. Subsequently, the inadequate surgical intervention may cause tissue necrosis and poor prognosis. Furthermore, the early recognition of water swelling sealant injected into tissue and emergent surgical intervention are the key to successful management for the patient with HPII caused by injecting water swelling sealant to tissue. [ABSTRACT FROM AUTHOR]

The sorption of Ag ions by polyurethanes (PU) of various chemical structure was investigated. It was shown that the sorption capacity of the polymers can be increased by introducing complexing fragments (urea or amino groups). The possibility of forming complexes with strong coordination ability between Ag ions and PU fragments was established. It was shown that complex formation leads to an increase in the 'effective' cross-linking density of the matrix. [ABSTRACT FROM AUTHOR]

Among various nanofillers for composite systems, carbon-based fillers such as graphite, carbon fibers, carbon black, carbon nanotubes, graphene, etc. are attracting great attention in both academia and industry for the advent of highly integrated electronic devices. The objective in fabricating such composite materials is to obtain distinct properties evolved from the synergistic effects of the component materials that may be exploited for various applications such as electronics and optical devices. In the present work, polyurethane/graphite composites have been synthesized with the aim of using them for electromagnetic shielding applications. The polyurethane/graphite composites were prepared through an in situ polymerization method in the presence of graphite nanoparticles. The prepared composites were characterized by scanning electron microscope, transmission electron microscope (TEM), and x-ray diffraction techniques. The shifting of the major peak of graphite nanoplatelets (GNPs) in prepared nanocomposites towards the left from 26.336° d-spacing = 3.381 Å to 25.374° d-spacing = 3.507 Å on a 2 θ scale indicates the intercalation type of dispersion in the prepared nanocomposites. This was further validated with the TEM characterization. The introduction of GNPs in polyurethane (PU) during in situ polymerization creates an electrical network in the resulting composite, which therefore makes it highly conductive. The prepared nanocomposite showed an electrical network at 2.2 vol.% of the percolation threshold in DC condition and a similar percolation threshold was found at 100 Hz in AC conditions. The maximum conductivity found at 6.5 vol.% of filler loading was 0.01 S/cm. The resulting composites were evaluated for electromagnetic interference (EMI) shielding at different filler loadings. The prepared PU/GNPs composites were found to be highly effective with shielding effectiveness of 19.34 dB, and with electromagnetic interference shielding materials at 0.9-1 GHz. [ABSTRACT FROM AUTHOR]