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With the development of science and technology, the need for high performance sensors is more and more urgent to deal with different needs and environments. In this study, a flexible strain sensor with performance of self‐healing is developed based on porous nickel as conductive filler and polyurethane (PU) with hydrogen bonding, disulfide bond, and metal coordination bond as polymer matrix. Porous nickel is prepared by a new biotemplates method, and the effects of reaction temperature and concentration of NiCl2·6H2O on the morphology of porous nickel are studied. Polyurethanes containing hydrogen bonding, disulfide bonds, and metal coordination bonds are prepared, and the mechanical properties and self‐healing properties of polyurethanes with different contents of hard and soft segments are studied. A strain sensor is prepared by mixing porous nickel and polyurethane. The effect of filler content on mechanical properties, self‐healing properties, and electrical self‐healing properties is studied. The sensor is attached to the joints of human limbs, and the peak diagram of time‐relative resistance changes is obtained through the cyclic and repeated movements of the limbs. The sensor has excellent sensitivity. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Cellulose nanocrystal reinforced waterborne polyurethane by blending or in situ addition. • Interactions between cellulose nanocrystal and waterborne polyurethane were formed. • Thermostability of nanocomposites was improved with cellulose nanocrystal addition. Abstract Focusing on eco-friendly materials, cellulose nanocrystal (CNC) extracted from office waste paper was used to reinforce waterborne polyurethane (WPU) with varying content by two incorporation routes including blending method by sonication after WPU synthesis (BCNC/WPU) and the alternative in-situ during the WPU synthesis process (CNC/WPU). The results showed that new interaction between CNC and WPU through hydrogen bonds in the interfacial area was formed and CNC reinforced hard segments effectively. However, the interaction in BCNC/WPU was not as stronger as that in CNC/WPU. Besides, CNC improved thermal stability of WPU remarkably, especially BCNC/WPU. The addition of CNC caused a delay around 50 °C in the start of the degradation process, and a delay of 5–18 °C and 2–20 °C in the temperatures at 10 and 50 wt% weight loss, respectively. These eco-friendly and biodegradable novel materials have potential applications in medical and biologic fields. [ABSTRACT FROM AUTHOR]

Waste polyethylene terephthalate (PET) bottles were collected, cleaned and then depolymerized by glycolysis with neopentyl glycol (NPG) and dipropylene glycol (DPG), in the presence of N-butyl titanate catalyst. The product, named glycolyzed oligoesters, obtained through the depolymerization, were employed respectively in hard segment and soft segment in the synthesis of novel waterborne polyurethane dispersions (PUDs) via a simple and environmentally benign process. In addition, a polyurethane dispersion without glycolyzed oligoesters was synthesized as a comparison. The bulk structure of PET glycolyzed oligoesters and PUDs films were characterized by Fourier transform infrared spectroscopy (FT-IR), H-nuclear magnetic resonance ( 1 H NMR) and Gel permeation chromatography (GPC). The results illustrated that glycolyzed oligoesters were successfully introduced into the hard and soft segment of the polyurethanes. Furthermore, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to investigate the thermal properties of the PET glycolyzed oligoesters and PUDs films. The results showed that the thermal resistance of waterborne polyurethanes obtained with glycolyzed oligoesters increased due to lower degrees of phase separation. X-ray diffraction indicated that all synthesized polyurethanes exhibited reduced degrees of orientation. Due to the balance between hard-/soft-segment of the waterborne polyurethane dispersions, the formulations containing glycolyzed oligoesters within the hard segment sections of the polyurethanes provided the best performance. [ABSTRACT FROM AUTHOR]

Understanding the role of water in waterborne polyurethane synthesis and properties is a central issue. Water may bring some unique and interesting properties and phenomenon for waterborne polyurethane. This paper focus on the impact of the novel water addition procedure on the properties of waterborne polyurethane. The novel poly(neopentyl glycol adipate) (PNA)-based waterborne polyurethane was prepared using the designed in situ water reaction process. As a comparison, waterborne polyurethane was synthesized through the conventional water addition process through prepolymer method. The thermal and crystalline properties of the obtained polyurethanes were detected by XRD, DSC, DMA, POM, TG and SEM. The results indicated that the novel polyurethane dispersion presents unique performance. Furthermore, to explore the application area of the novel polyurethane dispersion, mold resistance experiments were performed. The result suggested that polyurethane dispersion from the novel process is safer and more environmentally friendly than that from conventional water addition process. [ABSTRACT FROM AUTHOR]

Waterborne polyurethane dispersions in nanoparticles were synthesized from poly (propylene glycol), isophorone diisocyanate, and dimethylolpropionic acid in a modified prepolymer process. Three groups of specimens with variations in hard-to-soft segment molar ratios were synthesized in Group A experiments to confirm the recipe of waterborne polyurethane, whose particles have the smallest mean particle size and the narrowest particle size distribution. Group B experiments, which consist of five samples, were designed based on the results of Group A experiments. The variable of each sample was one kind of raw materials’ content compared with the confirmed recipe in Group A experiments. Relationships among variations in viscosity, mean nanoparticle size, and nanoparticle size distribution over time were analyzed. It was found that the viscosity of all samples increased, mean nanoparticle size remained constant or decreased, and nanoparticle size distribution became narrow over time. Our work provides a new recipe for the preparation of waterborne polyurethane of nanoparticles with excellent stability. Moreover, aging time is considered to be a key index to viscosity, particle size, and particle size distribution in the polyurethane dispersion. [ABSTRACT FROM AUTHOR]

Highlights: [•] The new synthesis process combines prepolymer isocyanate with acetone process. [•] Nanoparticles with no conglomeration and a good stability were obtained easily. [•] The polyurethane has low crystallinity and good thermal resistance. [•] The polyurethane with good performance could be used as water-based ink binder. [Copyright &y& Elsevier]

• The preparation of robust polyurethane particles is discussed in detail. • The PU nanoparticles formation processes were simulated. • The mechanism of the homo-/hetero-aggregation of PU nanoparticles are presented. Polyurethane has been significantly developed for decades due to the valuable thermoplastic, elastomeric and thermoset behavior on the basis of the block chains consisting of hard and soft segments. With the advances of green chemistry and nanoscience, the synthesis of green, homogenous novel polyurethane products with high performance have gained great attention. In this review, we firstly introduced recent synthesis processes of waterborne polyurethane particles with various shape and size. Then, the impact factors on the morphology of polyurethane particles were discussed and analyzed. Thirdly, the nanoparticles formation and aggregation processes were simulated to illustrate the diverse polyurethane nanoparticles bulk structures. Finally, the robustness and free-standing properties of nanoparticles were presented significantly to broaden applications of polyurethane in carriers of drug, binder, coatings, adhesives, stabilizer and surfactant areas, etc. In a word, the preparation of polyurethane particles in aqueous is necessary and urgent, as well as the mechanism. [ABSTRACT FROM AUTHOR]

• A facile and green process was designed to prepare aqueous functional composite. • The composite propertratio has a monotonic dependence on L D ies were influenced by WPU via non-covalent interactions. • Lysozyme might adsorb CNTs to form orientation under charge-π interaction. The composite preparation combining carbon nanotubes, biological systems and polymers to form homogenous and stable assemblies is an innovative research area with great significant for practical application of carbon nanotubes in printing, packaging and sensors areas. In this work, multi-walled carbon nanotubes (MWCNTs) was dispersed in lysozyme solution via sonification process, and then mixed with waterborne polyurethane (WPU) through a facile process. The non-covalent interaction among lysozyme, MWCNTs and WPU chains was investigated using the methods of scanning electron microscopy, transmission electron microscopy, UV–vis spectroscopy, Raman spectroscopy, fluorescence anisotropy, and X-ray diffraction. It suggests that lysozyme may adsorb nanotubes to form a certain orientation with the function of charge-π interaction, and there may be 2∼5 lysozyme biomolecules bound to hemi-CNTs side. Moreover, the homogeneous, stable and spherical nanoparticles of WPU are significantly stimulative for the stability of the MWCNTs/lysozyme/WPU composite through non-covalent interactions. [ABSTRACT FROM AUTHOR]

An amendment to this paper has been published and can be accessed via a link at the top of the paper. [ABSTRACT FROM AUTHOR]

Poly(propylene carbonate) (PPC) is gaining significant momentum as a biodegradable polymer using CO2 as an abundant, low-cost and renewable feedstock. Yet, PPC suffers from unsatisfactory thermal and mechanical properties, and its blends with other synthetic polymers as the second component typically exhibit poor compatibility. Herein, novel furan-based non-isocyanate polyurethanes (NIPUs) with high molecular weights and narrow distributions have been synthesized starting from 5-hydroxymethylfurfural (HMF) via a four-step procedure including reduction, glycidylation, carbonation of CO2 and step-growth polymerization with diamines. Owing to the structural similarity and intermolecular hydrogen bonding interactions, furan-based NIPUs display good compatibility with PPC. A sea-island morphology can be observed in SEM images of PPC/NIPU blends, where the NIPU phases are randomly dispersed in the PPC matrix. Moreover, the blends exhibit only one Tg (higher than both that of PPC and the corresponding NIPU) on the DSC curves, which first increase and then decrease when increasing the content of NIPUs from 0 wt% to 15 wt%. Notably, the physical crosslinking formed by hydrogen bonding interactions, coupled with the rigidity of furan rings, confer simultaneous improvements of elongation at the break and tensile strength, affording high-performance CO2-based biodegradable polymeric materials with low carbon footprint, good sustainability, and ideal biocompatibility. [ABSTRACT FROM AUTHOR]

Nanoscale polyurethane emulsion which synthesized in previous work was used as polymer modifying agent herein to prepare modified asphalt by gentle agitation method. Rheological properties, storage stability, microstructure and polymer dispersibility of WPU-modified asphalt were investigated using dynamic shear rheological (DSR), segregation test, and fluorescence microscopy. Due to the reaction of active NCO groups in WPU and active hydrogen atoms in asphalt, the modified asphalt system can be stable stored at high temperature. In addition, the nano-particle size of polyurethane emulsion makes polymer uniformly dispersed in modified asphalt and work better. [ABSTRACT FROM AUTHOR]

Polyurethane has attracted the great attention of scientists because of its lightweight, high toughness, good wear resistance and corrosion resistance. In the past, polyurethane was mainly used in low‐end products because of its single function. With the development of science and technology, ordinary polyurethane has been unable to meet the diverse needs of people. In recent years, scientists have developed a lot of functional polyurethane: self‐healing polyurethane, antifouling polyurethane, antibacterial polyurethane, shape memory polyurethane and electromagnetic shielding polyurethane. Polyurethane with a single function has been reported by many people, while polyurethane with multiple functions has been rarely reported. This review comprehensively reviews the structural design and applications of functional polyurethane. In addition, the advantages and disadvantages of chemical grafting functional polyurethane are introduced emphatically. Finally, challenges and future research directions of functional polyurethane are also discussed. [ABSTRACT FROM AUTHOR]

To evaluate the effect of polymers and nanomaterials on asphalt after thermo-oxidative aging, the aging resistance of thermoplastic polyurethane modified asphalt (PU-MA), polyurethane/graphene oxide composite modified asphalt (PU/GO-MA) were discussed through experiments and molecular dynamics (MD) simulations. The molecular composition and self-healing ability of aged asphalt were investigated. Base asphalt and virgin asphalt were used as control. The aging experiments of base asphalt, PU-MA and asphalt modified with PU and different content of GO composites were carried out by rolling thin-film oven test. The differential scanning calorimeter, thermal gravimetric analyzer, viscous flow deformation, bending beam rheometer and Fourier transform infrared spectrometer tests were carried out. The molecules and cracks models of asphalt were simulated by MD. The parameters such as mean square displacement, fractional free volume, dipole moment and viscosity were calculated. The results show that PU/GO can affect the transformation among components, increase the melting temperature of asphalt, improve the migration ability of asphalt molecules, enhance the self-healing diffusion movement of asphalt molecules and reduce the energy and viscosity of aged asphalt. In brief, nano and chemical synergistic modification has effects on the properties of asphalt after aging. [ABSTRACT FROM AUTHOR]

Abstract: Hyperbranched poly(urea-urethane)-grafted multi-walled carbon nanotubes (HPU-MWCNTs) were incorporated in a polyurethane (PU) matrix based on poly(ethylene oxide-tetrahydrofuran) and aliphatic polyisocyanate resin as curing agent. The 9–12nm thick HPU shell formed on the MWCNTs improved the dispersion of MWCNTs and enhanced the interfacial adhesion between the PU matrix and MWCNTs, leading to improvements in storage modulus and Tg of the composites and enhancement of the thermal stability of PU. Thus, composites with 0.5–1wt% MWCNTs increased the thermal conductivity by about 60–70% when compared to, and retained the high electrical resistivity of, neat PU. [Copyright &y& Elsevier]

Highlights • Castor oil-based waterborne polyurethane/sodium alginate composites were prepared. • The effect of sodium alginate content on the properties of the polymers was studied. • The formation of interpenetrating networks leads to the properties improvement. • Increasing sodium alginate content improves thermal stability of the composite films. Abstract In this paper, bio-based waterborne polyurethane dispersions were successfully prepared from castor oil using 2, 2-dimethylolbutanoic acid as the chain extender. Then, a series of bio-based composite dispersions and films were prepared by blending different amounts of sodium alginate aqueous solution with these bio-based polyurethane dispersions. The chemical structures, thermo-mechanical properties, thermal stability, and mechanical properties of the resulting composite films were characterized and discussed. The results show that the tensile strength and storage moduli of the composite films increase while the elongation at break of the composite films decrease with increasing the sodium alginate content. In addition, the contact angle and thermal stability of the composite films also increase with increasing sodium alginate content. These improvements are related to the increase of the crosslink density and the formation of interpenetrating networks with introduction of sodium alginate macromolecule. [ABSTRACT FROM AUTHOR]

With the wide application of electronic equipment, the demand for the efficient performance of electromagnetic interference (EMI) shielding materials has become increasingly urgent to meet different requirements and electromagnetic environments. In this study, a flexible composite with both self-healing and reliable EMI shielding functions was facilely developed. Firstly, we synthesize Ag@Carbon fiber (CF) by electroless plating method, and we can see that the silver layer wrapped CF completely by scanning electron microscope (SEM). Then we synthesize polyurethane (PU) with disulfide, and mix Ag@CF with PU mechanically to prepare Ag@CF/PU composite. Ag@CF/PU achieved satisfactory mechanical properties, EMI shielding performance and self-healing performance. When the filler content was 3 wt%, the tensile strength of composite was 1.63 MPa, the highest EMI shielding effectiveness (SE) was 10.3 dB at X-band, and self-healing efficiency of tensile strength was 96%. With the increase of filler content, the tensile strength and EMI SE of composite improved, and self-healing efficiency decrease. When the filler content was 20 wt%, the tensile strength was 7.95 MPa, the highest EMI SE was 26 dB and self-healing efficiency of tensile strength was 28%. This work demonstrated a self-healing flexible EMI shielding composite material that ensured reliability. [Display omitted] [ABSTRACT FROM AUTHOR]

Nanocrystalline cellulose (CNC) produced from waste paper by direct acid hydrolysis without any alkali or bleaching treatment was used to reinforce polyurethane elastomer (PU). By comparison, traditional cellulosic sources such as microcrystalline cellulose and waste cotton were also used to extract CNC and prepare polyurethane nanocomposites. The result showed that CNC extracted from waste paper had the largest aspect ratio, crystallinity and thermal stability. Three kinds of CNC all built interactions with polyurethane matrix through hydrogen bonds and covalent bonds. Amongst, polyurethane nanocomposites with CNC extracted from waste paper had the largest thermodynamic properties and stiffness. Briefly, CNC extracted from waste paper was comparable with CNC isolated from traditional cellulosic sources and could be used for stronger reinforcement of PU with lower cost. This work realized recycling of waste paper with a simple method and prepared a thermally resistant PU with low cost. [Display omitted] • Nanocrystalline cellulose was prepared with a simple method without any pretreatment. • Waste paper could be utilized for nanocrystalline cellulose production. • Nanocellulose from waste paper was comparable to that from traditional cellulosic source. • Realization of thermal modification of polyurethane by nanocellulose addition. • Economically heat resistant polyurethane from waste paper cellulose was achieved. [ABSTRACT FROM AUTHOR]

[Display omitted] • The prepared PU/GO composite modified asphalt was uniformly dispersed. • Synergy effect of polymer and nano-modification improved the performance of asphalt. • Molecular simulation and experiment completely revealed mechanism of modified asphalt. In this paper, reactive polyurethane and graphene oxide were used to prepare polyurethane/graphene oxide (PU/GO) nanocomposite, which were polymerized in situ and then were sheared at high-speed in asphalt. The uniform dispersion of nanocomposite modified asphalt system with PU and GO was obtained. The macroscopic properties and microscopic changes of modified asphalt binders were studied from the aspects of mechanics, physical structure and composition. The relationship between the structure and properties of modified asphalt system was discussed. The molecular models of base asphalt, polyurethane modified asphalt and PU/GO nanocomposite modified asphalt were built in Materials Studio, which were simulated by molecular dynamics. The structural changes under the interaction of each molecule were analyzed. The solubility parameters, mean square displacement, radial distribution function, radius of gyration and glass transition temperature of these models were calculated. The results show that GO is well dispersed in PU and polymer particles are more uniform. The polymer particles with GO achieve good dispersion in the asphalt system. Synergy effect of polymer and nano modification was realized in the dispersed modified asphalt material and properties were improved. [ABSTRACT FROM AUTHOR]

• A series of bio-based polyurethanes were prepared from different plant oil based polyols. • Increasing OH numbers of the polyols increases T g s and tensile strengths of the polyurethanes. • Polyurethane from linseed oil based polyol exhibits the highest tensile strength of 50.7 MPa. • Thermal stability of the polyurethanes decreases with increasing OH numbers of the polyols. The replacement of petroleum based polymers with the environmental-friendly counterparts derived from renewable resource has received much attention due to the growing concern toward the depletion of the world crude oil stock and environmental problem. In this study, a series of biobased polyurethanes were successfully prepared from polyols obtained by thiol-ene reaction of different plant oils (olive, rice bran, grape seed and linseed oils). Their properties were characterized by dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and tensile test. Their thermomechanical and mechanical properties were compared and discussed to reveal the structure-property relationship. The results show that as the hydroxyl values of the polyols increase, T g s and tensile strengths of the corresponding polyurethanes increase linearly while the thermal stability decrease. Furthermore, polyurethane from linseed oil had the highest T g of 65.2 °C and tensile strength of 50.7 MPa. The resulting polyurethane films with tunable thermomechanical performance are promising to find application in coatings, leather, adhesive and so on. [ABSTRACT FROM AUTHOR]