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This study focuses on producing polyurethane dispersion (PUD)/carboxylated nitrile butadiene rubber (XNBR) blends with different types of crosslinkers without both accelerators and sulphur. Two types of crosslinkers: epoxide crosslinker and organo-modified siloxane, are introduced in the PUD/XNBR (blending ratio of 80:20). The zeta potential and particle size of the PUD/XNBR blends were determined using a dynamic light-scattering nanoparticle analyser. The chemical interaction and surface roughness of the PUD/XNBR blends were evaluated using Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM). The zeta potential and particle size of the PUD were influenced by XNBR blending and the types of crosslinkers. FTIR observations indicate that the XNBR and the crosslinkers facilitated intermolecular hydrogen bonding and different extents of ordered hydrogen bonding. A higher degree of ordered hydrogen bonding can be associated with a higher surface roughness of the PUD/XNBR blends. Nevertheless, the hybrid crosslinkers can be used to achieve reasonable surface roughness for the easier donning of latex gloves. The research findings can be applied to design glove products with desirable surface roughness and intermolecular bonding. [ABSTRACT FROM AUTHOR]

The development of skin-compatible polyurethane materials with excellent wide-temperature range and anti-aging self-healing properties is considered crucial for modern applications. However, few polyurethane materials can achieve these characteristics simultaneously because of the chemical bond activity. Here, we report a wide-temperature range and antiaging self-healing polyurethane material with superior mechanical features. At -40 °C, the polyurethane exhibits a selfhealing efficiency of 72.6%, with a tensile strength of ~7.4 MPa and elongation at break of ~1424.5%. At 60 °C, its selfhealing efficiency reached 93.6%, with an elongation at break of 1922.2% without significant reduction of the tensile strength. Notably, its low-temperature self-healing efficiency was 79.3 and 72.6%, respectively, at -20 and-40 °C, and the samples showed some degree of self-healing, even at -60 and -80°C. Meanwhile, the polyurethane showed excellent anti-aging performance, and its self-healing properties were sufficiently high after aging at 60 °C for 7 days. The designed polyurethane is expected to offer a promising platform for fabricating materials for electronic skin applications, wearable electronic devices, flexible displays, and soft robotics. [ABSTRACT FROM AUTHOR]

The high versatility of polyurethanes (PU's) is encouraging the development of new formulations for new applications, like their use as a matrix for structural composites. PU's based technology offers some advantages, such as fatigue resistance and fast curing cycles. However, their high reactivity hinders some manufacturing processes like Resin Transfer Moulding (RTM). This work aimed to achieve a PU resin (PUR) formulation with the required latency and reactivity for the RTM. For this purpose, different catalytic systems based on an epoxide and LiCl were investigated. The reactivity of the systems was evaluated through Differential Scanning Calorimetry (DSC) and rheology tests, and the curing reaction and viscosity were modelled. Furthermore, the RTM process of a representative composite part was simulated. Results demonstrated the processability improvements when the LiCl was incorporated into the isocyanate component of the formulation combined with a monool or a diol. It was observed that these combinations contribute to the encapsulation of the LiCl between the as formed urethane groups by hydrogen bonding, providing the desired latency and acting as a delayed action catalyst. Once the reaction started and the encapsulation was deactivated, an alkoxide was formed to act as a catalyst. Encapsulation was more effective with the diol, providing a higher latency. [ABSTRACT FROM AUTHOR]

Scalable preparation of flexible, porous, and microstructure membrane for triboelectric nanogenerators (TENGs) with controllable thickness and high contact surface area using cost-effective methods is still a great challenge. Herein, we developed a novel, cost-effective, and scalable fabrication procedure for the preparation of a lightweight, flexible, thin, and porous polyurethane (PU) membrane for a TENG device. Importantly, the thickness and pore size of the PU membrane can be tuned easily. The PU-based TENG device fabricated with a porous PU membrane of 5 μm thickness and 15 μm pore size (PU-5-15) generated a maximum peak to peak output voltage was 58.5 V with a corresponding peak to peak current was 1.37 μA at 4 N and power density of 9.7 mW/m². The device was systematically used to energize 24 green commercial lightemitting diodes (LEDs) in brighter condition connected in series and to turn on the LCD of a portable timer clock within 51 s and glow for 1 s after 187 taps. The developed TENG device also exhibited stable cyclic charging and discharging property that is very important for real applications. Furthermore, the energy-harvesting performance of the device was also tested with human body movements. The developed industrially compatible method is very easy and convenient, and mass production is possible. Compared to other studies, in this novel study, we achieved a higher electrical performance at the desired lower thickness for the porous PU membrane-based TENG device. The developed fabrication method will pave the way for the facile and scalable industrial processing of PU membranes for energy-harvesting applications. [ABSTRACT FROM AUTHOR]

In the present work, a new strategy for preparing authentic two-way shape memory polymer was proposed by using a conventional crosslinked polyurethane (PU) containing crystalline poly(e-caprolactone) (PCL) as the proof-ofconcept material. Lauroyl peroxide (LPO) was added as a chemical crosslinker for inducing secondary crosslinking during the programming. Having been stretched and heat treated without additional ingredients and chemicals, the trained PU showed the desired two-way shape memory effect. The crosslinking network created by LPO was successfully converted into internal stress supplier, which represents the core progress of this research. As the temperature changed, the reversible melting/re-crystallization of the crystalline phases elaborately cooperated with the compressed crosslinking network, leading to the implementation of two-way shape memory effect. Through the optimization of the LPO quality, an average reversible strain of up to ~21% in the direction of stretching was measured. In principle, all semi-crystalline polymers can be imparted with two-way shape memory effect following the above-proposed method. Given the great convenience of material selection, preparation, programming and application, the current research may have opened a new way for the production and usage of the smart materials in practice. [ABSTRACT FROM AUTHOR]

Biodegradable amphiphilic polyurethane films (bio-PUs) were synthesized by solvent free polyaddition reaction of hydrophilic poly(ethylene glycol) (PEG) and hydrophobic poly(caprolactone) (PCL) as macrodiols with hexamethylene diisocyanate. Samples were subsequently heat cured in order to obtain 3D crosslinked structure. Different PCL/PEG ratios allowed controlling the toughness of the resulting bio-PUs. Significant enhancement of Young's modulus, strength and elongation at break was observed at a PCL/PEG molar ratio above 3. The change in the bio-PU mechanical behavior was ascribed to the formation of crystalline PCL domains in the bio-PU network. The presence of PEG increased both the ability to absorb water and the rate of hydrolytic degradation, while PCL increased the cell viability. Prepared solvent free bio-PUs may advantageously be used in medicine as elastic resorbable material applicable against post-surgical adhesions. [ABSTRACT FROM AUTHOR]

The microstructures of Estane 5703 aged at 70°C in dry and wet air have been studied by small-angle neutron scattering. The samples were swollen in deuterated toluene for enhancing the contrast. The scattering data show the characteristic domain structure of polyurethanes consisting of soft and hard segments. Debye-Anderson-Brumberger function used with hard sphere structure factor, and the Teubner-Strey model are used to analyze the two-phase domain structure of the polymer. The combined effects of temperature and humidity have a strong disruption effect on the microstructures of Estane. For the sample aged at 70°C in wet air for 1 month, the domain size, described by the correlation length, increases from 2.3 to 3.8 nm and their distance, expressed by hard-sphere interaction radius, increases from 8.4 to 10.6 nm. The structure development is attributed to degradation of polymer chains as revealed by gel permeation chromatography. The hydrolysis of ester links on polymer backbone at 70°C in the presence of water humidity is the main reason for the changes of the microstructure. These findings can contribute to developing predictive models for the safety, performance, and lifetime of polyurethanes. [ABSTRACT FROM AUTHOR]

A series of novel acetic acid lignin-containing polyurethane (LPU) films coupled with aminopropyltriethoxy silane (APTS) (LPUSi) or the mixture of APTS and trimethylol propane (TMP) (LPUSiT) were prepared. With 2% APTS addition, the crosslinking density increased, and the resultant films were endowed with good mechanical properties and water resistance. It was also found that the hydrogen bonding interaction between -NH and -C=O of urethane was destroyed, and new hydrogen bonds between APTS and LPU were formed. However, when APTS content was greater than 4%, significant phase aggregation were detected, resulting in poor mechanical properties and water resistance. In contrast, the crosslinking density, tensile strength and water resistance can be further improved with TMP addition at 2% APTS. The simultaneous addition of APTS and TMP was beneficial for phase mixing and the formation of uniform network. And the surface morphology of LPUSiT films became smoother and more homogeneous. [ABSTRACT FROM AUTHOR]

A series of polyurethane nanocomposites were synthesized from thermoplastic polyurethanes (with different hard segment ratios) and two types of organically modified montmorillonites (OMMT) - Cloisite® 10A and Cloisite® 20A. The thermal behavior was examined by non-isothermal thermogravimetry (TG, DTG), Differential Scanning Calorimetry (DSC) and Dynamic-Mechanical Thermal Analysis (DMTA). The results of X-ray analyses showed that the OMMT produced the intercalated polyurethane nanocomposites. It has been proven that the thermal stability and tensile properties of these new systems were higher when the organoclay was present within the polymer matrix. Moreover, these properties depend on both the OMMT loading and the type of gallery cations of the organically modified montmorillonites. [ABSTRACT FROM AUTHOR]

Novel blends of acrylonitrile butadiene rubber (NBR) and polyurethane-silica (PU-SiO2) hybrid networks have been prepared by melt blending. The PU-SiO2 hybrid networks were formed via the reaction of NCO groups of NCO-terminated PU prepolymer and OH groups of SiO2 in the absence of an external crosslinking agent (i.e. alcohols and amines) during the curing process of NBR. Both in the neat PU-SiO2 system and the NBR/(PU-SiO2) system, the NCO-terminated PU prepolymer could be crosslinked by SiO2 to form PU-SiO2 hybrid networks. The effects of PU-SiO2 introduction into the NBR, on the properties of the resulting blends were studied. It was found that the vulcanization was activated by the incorporation of PU-SiO2. Transmission electronic microscopy (TEM) studies indicated that the interpenetration and entanglement structures between NBR and PU-SiO2 increased with increasing PU-SiO2 content and the quasi-interpenetrating polymer networks (quasi-IPN) structures were formed when the PU-SiO2 was 50 wt% in the NBR/PU-SiO2) systems. The microstructures formed in the blends led to good compatibility between NBR and PU-SiO2 and significantly improved the mechanical properties, abrasion resistance and flex-fatigue life of the blends. [ABSTRACT FROM AUTHOR]

The authors report that during tensile stress relaxation test of a polyurethane crosslinked by catechol-iron coordination bonds, the stress gradually increases with time after the initial drop, which differs from the documented behaviors of other materials. Based on model experiment and structural characterization, water triggered rapid increase of dynamic crosslinkages accompanied by Poisson's contraction is found to be responsible for the stress intensification effect. In addition, the influential factors are carefully discussed. The findings might help to develop novel polymeric materials with improved application performance under loading conditions. [ABSTRACT FROM AUTHOR]