Polyurethane Elastomers Research Articles

Novel bio-based polyurethane elastomers for adjustable room-temperature damping property

The distinctive viscoelastic behavior of elastomeres can be exploited for reducing vibrations and noise. However, the utility of conventional rubber-based elastomers is limited by low glass transition temperature (Tg) and narrow adjustable damping range, which constrain the room-temperature damping property. Moreover, the majority of rubber-based elastomers are sourced from unsustainable petroleum-based resources. Therefore, designing bio-based materials with room-temperature high-damping property to replace conventional rubber-based elastomers is crucial. Herein, a novel bio-based polyurethane (bio-PU) elastomer with an adjustable damping-temperature range and room-temperature high-damping property is successfully synthesized from bio-based poly (trimethylene ether) glycol. The effects of molecular chain structure on the thermal properties, mechanical properties, and adjustable damping-temperature range of the bio-PU elastomers, along with the mechanisms underlying these effects, are elucidated in detail. As the content of hard segment increasing, the Tg of bio-PU elastomers significantly increases from −13.0 to 29.9 °C, effectively encompassing the damping temperature range within the room-temperature working range. This promising strategy for formulating bio-based elastomers with adjustable damping-temperature range can advance the sustainable growth of PU industry and broaden the scope of PU damping applications.

Thermal stimuli response diphenylmethane diisocyanate‐based polyurethane elastomer via adjustable silicon‐induced distinctive microstructure

AbstractThe segment character of polyurethanes (PUs) determines the micromorphology and properties. The effective segment regulation can customize the favorable performance of PUs. Herein, silicon covalent‐modified polyurethanes (MPUs) were prepared by incorporating diphenylmethane diisocyanate (MDI) and diphenyl silanediol (DPSD) into PU molecules as hard segments via a two‐step method. Distinctive microphase separation structures from sheet morphology to radial sheet or withered flower‐like microdomain were formed by adjusting hydrogen bonding of hard segments and post‐treatment techniques. Thus, with the addition of DPSD in hard segments, the thermo‐optic responses for MPUs occurred due to the different microphase evolution under thermal effect. And with the further addition of DPSD, the effect of thermal stimuli on the transmittance gradually weakened. It was very clear that with increasing the temperature, the transmittance of MPUs showed a gradual increase owing to melting the microcrystals or destroying the ordered accumulation of hard segments. Meanwhile, the high mechanical properties were obtained, higher 15 times tensile strength and more than 100 times elastic modulus than those of pure PU as well as the excellent thermal stability. In sum, this study was of great significance for developing new functionalized PU materials.Highlights Polyurethanes were prepared by inducing modified silicon functionality. The distinctive microphase separation evolution of MPUs was found. Thermal stimuli responses showed a gradual decrease due to different structure. High mechanical properties and thermal stability were also obtained.

Preparation of high-performance laminated glass interlayer by modifying epoxy resin composite polyurethane

Laminated glass has been widely used in glass curtain walls, windshields, and other structures due to its high safety, light weight, and aesthetics. The safety of polymer laminated glass depends on the performance of the polymer between the glasses. Polyurethane elastomer (PU) has become a universal polymer material due to its excellent mechanical strength and toughness. The aliphatic thermoplastic polyurethane has attracted people's interest about its application in the field of laminated safety glass due to its transparency and adhesion. In this work, a polyurethane-modified epoxy (EK-PU) composite film with superior bonding strength, mechanical properties, and transparency was successfully achieved. The tensile strength of the PU composite film was confirmed to be 45 MPa, while the bonding strength was 4.73 MPa. The improvement is attributed to the change of microphase separation structure and the introduction of silicone. The excellent impact resistance of the laminated glass based on polyurethane composite film have been confirmed by the falling ball impact test, which is 6.5 times of the common PU film. The laminated glass based on the EK-PU film will be applied in aerospace, defense, and automotive fields.

Self-healing and reprocessable biobased non-isocyanate polyurethane elastomer with dual dynamic covalent adaptive network for flexible strain sensor

Owing to the nontoxicity of monomers, non-isocyanate polyurethane elastomers have attracted considerable attention, yet the synthesis and functionalization are still challenging. Herein, self-healing and reprocessable biobased non-isocyanate polyurethane (NIPU) elastomers with dual dynamic covalent adaptive network (DDCAN) by disulfide bonds and dynamic imine bonds were synthesized as substrate for the construction of flexible strain sensor with MXene as conductive substance. The tensile strength and elongation at break of the NIPU elastomer were 3.22 MPa and 234 %, respectively. Thanks to the formation of DDCAN, the NIPU elastomer showed high healing efficiency of 97.5 % after healing at room temperature for 24 h. Interestingly, the NIPU elastomer possessed superior reprocessing capability and the tensile strength after three reprocessing cycles reached 136.1 % of the original one, which was attributed to the increase of crosslinking points caused by topological rearrangement. In addition, the NIPU elastomer-based flexible strain sensor exhibited fast response (response time = 60 ms) and excellent repeatability (1000 bending-releasing cycles) and was successfully applied for human motion detection and speech recognition. The findings in this work conceivably stand out as a new methodology for the preparation of biobased and functional elastomers, which will greatly promote the sustainable development and application of flexible electronics.

Strength Enhancement of Polyurethane Film by Solution Annealing.

Recently, polyurethane elastomer (TPU) has attracted more and more attention depending on its excellent optical, mechanical, and retreatment properties. The high strength of polyurethane has always been pursued, which can enable its application in more fields. In this work, an aliphatic polyurethane elastomer membrane (HRPU6) was successfully synthesized, and its strength was obviously improved by solvent annealing technology. The tensile strength and adhesion strength can reach 64.56 and 2.58 MPa, but 36.55 and 1.57 MPa only before solvent annealing, respectively. The impact strength of laminated glass based on HRPU has also been significantly improved after solvent annealing, confirmed through drop ball impact testing. It has been confirmed that the increase in strength of HRPU6 is attributed to the enhancement of hydrogen bonding and the improvement of the phase separation degree.

TiO2 nano-filler and ionic liquid-blended polyurethane elastomer films for enhanced antistatic applications

TiO2 nano-filler and ionic liquid-blended polyurethane elastomer films for enhanced antistatic applications

Gas–Liquid Mass Transfer Intensification for Selective Alkyne Semi-Hydrogenation with an Advanced Elastic Catalytic Foam-Bed Reactor

The Elastic Catalytic Foam-bed Reactor (EcFR) technology was used to enhance a model catalytic hydrogenation reaction by improving gas–liquid mass transfer. This advanced technology is based on a column packed with a commercial elastomeric polyurethane open-cell foam, which also acts as a catalyst support. A simple and efficient crankshaft-inspired system applied in situ compression/relaxation movements to the foam bed. For the first time, the catalytic support parameters (i.e., porosity, tortuosity, characteristic length, etc.) underwent cyclic and controlled changes over time. These dynamic cycles have made it possible to intensify the transfer of gas to liquid at a constant energy level. The application chosen was the selective hydrogenation of phenylacetylene to styrene in an alcoholic solution using a palladium-based catalyst under hydrogen bubble conditions. The conversion observed with this EcFR at 1 Hz as cycle frequency was compared with that observed with a conventional Fixed Catalytic Foam-bed Reactor (FcFR).

Preparation of highly conductive flexible polyurethane elastomers with low PEDOT:PSS content based on a novel pore collapse strategy

Meeting the requirements of flexible electronic devices remains a challenge in achieving stable and highly conductive polymer composites (CPCs) with minimal loading poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). In this study, PEDOT:PSS based CPCs were prepared using a novel method involving pore collapse of aerogels. Initially, polyurethane aerogels (PUAs) were synthesized with varying pore sizes ranging from 4.14 nm to 5.13 nm based on specific formula ratios. Subsequently, solvent evaporation at 120 °C caused shrinkage and collapse of the PUAs' pore structure, resulting in the formation of a continuous conductive circuit composed of PEDOT:PSS in polyurethane elastomers (CPUEs). CPUEs containing 1.53 wt% PEDOT:PSS exhibited remarkably high conductivity characteristics (1590 S/m). These CPUEs demonstrated excellent mechanical flexibility as they could withstand stretching, bending, and twisting without significant changes in resistance or affecting LED brightness. Moreover, they proved suitable for use as soft electrodes for electrocardiography (ECG) during exercise to monitor heart rate. This work presents an innovative approach for constructing highly conductive networks through pore collapse of aerogels and obtaining low-loading conductive polymers.

Stearate‐Modified Montmorillonite and Polylactic Acid Synergistically Enhanced the Microcellular of Thermoplastic Polyurethane Elastomer Foam and Improved Its Dimensional Stability

Thermoplastic polyurethane (TPU) elastomer is a commonly used material for foam preparation. However, its application is hindered by significant shrinkage behavior. To reduce the foam shrinkage, polylactic acid (PLA) and calcium stearate‐modified montmorillonite (MMT‐St) are incorporated into the polyurethane matrix. The TPU/PLA/MMT‐St composite foams are formed using an intermittent supercritical carbon‐dioxide‐foaming process. The addition of PLA inhibits the relaxation of TPU chain segments, while the introduction of calcium stearate (GaSt2) improves the dispersion of MMT within the matrix, increases the nucleation sites of cell growth, and improves cell structure. The cell diameter decreases from 10 to 4 μm, while the cell density increased from 4.1 × 1012 to 15.8 × 1012 cell cm−3. In addition, the cell distribution range narrows from 4–19 to 2–6 μm. Incorporating MMT‐St increases the crystallinity and thermal stability of TPU/PLA, mitigates chain relaxation at room temperature, and enhances foam dimensional stability. As a result, this leads to a decrease in shrinkage rate from 27.5% to 5%. As both matrices of the material are thermoplastic, this composite foam possesses recyclability with enhanced material utilization.

RETRACTED: Screening of hindered phenol antioxidants by quantum chemical method for improving the aging properties of polyurethane railpad in railway

Polyurethane material has excellent performance and is widely used as railpad in railway, but it is prone to aging and fatigue during long-term service, resulting in a decrease in its performance. In order to improve the aging and fatigue resistance of polyurethane railpad, as well as the efficiency of screening antioxidant, this paper first used quantum chemical method to calculate three types of grafted hindered phenolic antioxidants. Then, polyurethane elastomer railpads with grafted preferred hindered phenolic antioxidants were prepared, and thermal oxidative aging experiments and thermo-oxygen-fatigue coupling aging experiments were conducted. The research results indicate that 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid molecules have better antioxidant properties. When the degradation rate is less than 20%, the activation energy of polyurethane railpads with grafted hindered phenolic antioxidants is about 20% higher than that of ungrafted materials. After 200 days of thermal oxidative aging, polyurethane railpads with grafted hindered phenolic antioxidants maintain high tensile strength and elongation at break, while maintaining stable static stiffness. Their carbonyl index and loss tangent increase only by 10% and 14.8%, respectively, while unmodified samples increase by 29.4% and 26.4%. Scanning electron microscopy also shows a significant reduction in surface cracks on polyurethane railpads grafted with hindered phenolic antioxidants.

A super strong polyurethane elastomer with efficient self-healing performance enabled by partially mixing reversible hard domains

The reversible chain extender Diels-Alder-diol (DA-diol) containing thermally dissociable Diels-Alder adducts (DA adducts) was synthesized and combined with 1,4-butanediol (BDO) as complexed chain extenders used for preparing a transparent polyurethane elastomer (DAPU) with high mechanical strength and efficient self-healing ability by partially mixing reversible hard domains. The optimal DAPU occupies a desired high tensile strength of 65 MPa, and its elongation at break and toughness are of 1050 % and 216 MJ·m−3, respectively. Meanwhile, the DAPU-0.2 elastomer heals at 110 °C for 2 h with a healing efficiency of 95 %. The desirable mechanical strength and efficient self-healing ability are attributing to the BDO chain extended hard segments ensure the high strength at room temperature, while DA-diol chain extended hard segments endow the as-prepared DAPUs with self-healing ability at an elevated temperature. This work overall points to a strategy in designing self-healing polyurethane elastomers with markedly improved mechanical strength and efficient self-healing ability by partially mixing reversible hard domains.

Mechanical evaluation of elastomeric thermoplastic polyurethane additively manufactured triply periodic minimal surface area lattice structures for adjustable cushioning properties

PurposeCushioning is a useful material property applicable for a range of applications from medical devices to personal protective equipment. The current ability to apply cushioning in a product context is limited by the appropriateness of available materials, with polyurethane foams being the current gold standard material. The purpose of this study is to investigate additively manufactured flexible printing of scaffold structures as an alternative.Design/methodology/approachIn this study, this study investigates triply periodic minimal surface (TPMS) structures, including Gyroid, Diamond and Schwarz P formed in thermoplastic polyurethane (TPU), as a possible alternative. Each TPMS structure was fabricated using material extrusion additive manufacturing and evaluated to ASTM mechanical testing standard for polymers. This study focuses attention to TPMS structures fabricated for a fixed unit cell size of 10 mm and examine the compressive properties for changes in the scaffold porosity for samples fabricated in TPU with a shore hardness of 63A and 90A.FindingsIt was discovered that for increased porosity there was a measured reduction in the load required to deform the scaffold. Additionally, a complex relationship between the shore hardness and the stiffness of a structure. It was highlighted that through the adjustment of porosity, the compressive strength required to deform the scaffolds to a point of densification could be controlled and predicted with high repeatability.Originality/valueThe results indicate the ability to tailor the scaffold design parameters using both 63A and 90A TPU material, to mimic the loading properties of common polyurethane foams. The use of these structures indicates a next generation of tailored cushioning using additive manufacturing techniques by tailoring both geometry and porosity to loading and compressive strengths.

Fabrication of multifunction polyurethane with robust, self-healing and anti-corrosion performance based multiple dynamic bonds strategy

Polyurethanes (PUs) containing multiple dynamically have been extensively studied, however combining their mechanical, self-healing and anti-corrosion ability remains a significant challenge. Therefore, this paper successfully prepared PU coating (PU-SS-Salen-Ni) by introducing Ni2+ coordinated Salen and bis(4-hydroxyphenyl) disulfide chain extenders. PU-SS-Salen-Ni with quadruple dynamic bonding exhibited excellent tensile strength (15.4 MPa), toughness (72 MJ·m−3) and superior self-healing efficiency (86.8 %) after being held at 80 °C for 4 h. Meantime, the |Z|f=0.01Hz of PU-SS-Salen-Ni coating reached at 9.35 × 106 Ω·cm2 at the beginning of immersion, and even maintained at 6.99 × 106 Ω·cm2 after 28 days immersion due to the synergistic effect of multiple dynamic bonds. This study provides insight into the design of PU elastomers with sustainable self-healing, excellent mechanical properties and corrosion protection.

Self-Healing Polyurethane Elastomers with Superior Tensile Strength and Elastic Recovery Based on Dynamic Oxime-Carbamate and Hydrogen Bond Interactions.

The preparation of self-healing polyurethane elastomers (PUEs) incorporating dynamic bonds is of considerable practical significance. However, developing a PUE with outstanding mechanical properties and high self-healing efficiency poses a significant challenge. Herein, this work has successfully developed a series of self-healing PUEs with various outstanding properties through rational molecular design. These PUEs incorporate m-xylylene diisocyanate and reversible dimethylglyoxime as hard segment, along with polytetramethylene ether glycol as soft segment. A significant amount of dynamic oxime-carbamate and hydrogen bonds are formed in hard segment. The microphase separated structure of the PUEs enables them to be colorless with a transparency of >90%. Owing to the chemical composition and multiple dynamic interactions, the PUEs are endowed with ultra-high tensile strength of 34.5MPa, satisfactory toughness of 53.9MJ m-3, and great elastic recovery both at low and high strains. The movement of polymer molecular chains and the dynamic reversible interactions render a self-healing efficiency of 101% at 70°C. In addition, this self-healing polyurethane could still maintain high mechanical properties after recycling. This study provides a design strategy for the preparation of a comprehensive polyurethane with superior overall performance, which holds wide application prospects in the fields of flexible displays and solar cells.

A facile and on-demand optimizing strategy for polyurethane elastomers via programmable hydrogen bonding

Polyurethane elastomers address important significance in a wide range of applications. The mechanical properties including strength and toughness are of great importance, which are closely related to their unique hydrogen bonding structure. Unfortunately, the poor designability of hydrogen bonding structure in existing polyurethane severely restricts the on-demand regulation of their properties. Herein, a facile, universal and efficient modifying strategy based on stimuli-responsive polyphenol aggregates was proposed. Through precisely manipulated heat-induced aggregate division and/or photo-induced interfacial hydrogen bonding upgrading, programmable strengthening and toughening effect on the derived polyurethane elastomers could be achieved with high precision. Typically, the tensile strength and toughness of our proposed polyurethane elastomers could be enhanced by 3.23 and 2.22 times comparing with neat samples, respectively. The relevant results were supported by various characterizations and mathematical modeling. In addition, our polyurethane exhibited unique selective biocompatibility, rapid self-healing capability and recyclability, which could fulfill varieties of functions. Our proposed modifying strategy by using polyphenol aggregates can not only programmatically optimize the comprehensive properties of polyurethane, but also inspire programmable regulation of polymer performance through programmable design of its certain microstructure in the future.

Preparation and performance characteristics study of thermoplastic polyurethane elastomer (TPU) for basketball shoe soles

Thermoplastic Polyurethane Elastomer (TPU) materials have found extensive applications in the preparation of basketball shoe soles, owing to their excellent elasticity, lightweight properties, and durability. However, TPU materials still face challenges related to breathability, temperature sensitivity, and weather resistance, necessitating further research and improvement. This paper primarily investigates the advancements in E-TPU materials with high rebound foam particles tailored for basketball shoe sole applications. It emphasizes the factors influencing their performance and presents performance control methods from the perspectives of synthesis, molding, and usage. This research provides innovative approaches and methodologies for basketball shoe sole design.

Incorporation of self-heating effect into a thermo-mechanical coupled constitutive modelling for elastomeric polyurethane

Elastomeric polyurethane (EPU) is characterised by distinctive mechanical properties, including high toughness, low glass transition temperature, and high impact resistance, that render it indispensable in diverse engineering applications from soft robotics to anti-collision devices. This study presents a thermo-mechanically coupled constitutive model for EPU, systematically incorporating hyperelasticity, viscoelasticity, thermal expansion, and self-heating effect in a thermodynamically consistent manner. Experimental data, obtained from previous studies, are then used for parameter identification and model validation, including iterative updates for temperature parameters considering the self-heating effect. Subsequently, the validated model is integrated into finite element codes, i.e., user subroutine to define a material’s mechanical behaviour (UMAT) based on the commercial finite element software ABAQUS, for the computation of three-dimensional stress-strain states, facilitating the analysis of the structural response to various mechanical loads and boundary conditions. The results obtained from simulations are compared with analytical solutions to confirm the precision of Finite Element Method (FEM) implementation. The self-heating effect is further analysed under different strain rates and temperatures. To validate the engineering significance of the FEM implementation, a plate with a hole structure is also simulated. In conclusion, this research provides a robust tool for engineers and researchers working with soft materials, enhancing their understanding and predictive capabilities, notably addressing the self-heating effect in thermo-mechanical behaviours.

Dynamic healing-assembly for biocompatible, biodegradable, stretchable and self-healing triboelectric nanogenerators

Triboelectric nanogenerators (TENGs) have great potential as power sources for on-skin and implantable electronics. However, most existing TENGs are not suitable for the above applications due to limited material choices, often characterized by rigidity, susceptibility to damage, biological incompatibility, and non-biodegradability. Herein, we developed a simple self-healing assembly strategy based on introducing dynamic Cu(II)-dimethylglyoxime-urethane groups into a biocompatible and biodegradable polyurethane elastomer, to simultaneously address the above obstacles. The coordination of Cu2+ with dynamic bonds significantly enhanced the mechanical properties of elastomer, resulting in a modulus of 9.4 MPa and toughness of 40.2 MJ/m3. These bonds also gave the elastomer skin-like self-healing capabilities, achieving a healing efficiency of 77.5 % at 80 °C. Subsequently, a highly stretchable and integrated triboelectric nanogenerator (Cu-POU TENG) with self-healing capabilities was developed. The Cu-POU TENG with an effective area of 1.5 × 1.5 cm2 produced an open-circuit voltage of 38 V in single-electrode mode. The Cu-POU TENG could restore its original electrical properties through self-healing after mechanical damage. Furthermore, the Cu-POU TENG exhibited biocompatibility and biodegradability, making it suitable for on-skin and implantable electronics. Notably, the Cu-POU TENG maintained a stable voltage output throughout the degradation process. The integration of self-healing feature enabled a sophisticated structure, allowing the Cu-POU TENG to function effectively as a motion sensor for tracking body movement. This Cu-POU TENG holds great potential for applications in on-skin and implantable electronics.

Self‐healing waterborne polyurethane elastomers based on synergistic hydrogen, disulfide and borate bonding for composite conductors

AbstractAs a functional material, polyurethane elastomers have found different applications in a variety of fields such as flexible electronics and smart coatings, but due to the damage during use, they are often endowed with self‐healing properties. However, conventional intrinsically self‐healing polyurethanes often don't balance excellent mechanical and self‐healing properties, so it has become crucial to prepare polyurethane elastomers with excellent self‐healing properties and high mechanical properties. In this study, a self‐healing waterborne polyurethane elastomers (IP‐DTDAx‐BAy‐WPU‐n) was synthesized based on 4, 4‐diaminodiphenyl sulfide (DTDA) boronic acid (BA). The disulfide bond has high motility at low temperatures and induces molecular‐level healing at the damaged interface, contributing to good repair under mild conditions. The borate ester bond limits intermolecular chain slippage and improves the mechanical properties as a dynamic cross‐linking point, while its dynamic reversible effect can synergistically improve the self‐healing ability. The results show that the synthesized elastomer films have good mechanical properties (strength 23.21 MPa, elongation at break 1259.08%, toughness 83.28 MJ m−3), good elastic recovery and self‐healing properties (93%). Furthermore, a composite conductors (IP‐DTDAx‐BAy‐WPU/AgNWs) with self‐healing properties was prepared by compositing AgNWs nanowires with polyurethane elastomers, which laid the foundation for its application in flexible electronic devices and wearable sensing devices.

Synthesis and molecular dynamics simulation of biobased “bottle-brush” polyfarnesene via aqueous radical polymerization

The farnesene monomer, obtained through bio-fermentation, offers a unique long side chain structure that serves as an excellent platform for the synthesis of bottle-brush polymers with exceptional thermal properties. Such polymers have immense potential in the production of polyurethane elastomers and adhesives. Molecular dynamics simulations of polyfarnesene were performed using Materials Studio to calculate pivotal mechanical parameters like glass transition temperature (Tg), cohesive energy density (CED), and free volume. The Tg was verified by comparing the results from the simulations with measured values obtained through experimental tests. Additionally, hydroxyl-terminated polyfarnesene was cured with a variety of isocyanate cross-linking agents, using a cross-linking script, to evaluate its mechanical and energetic characteristics. The results from the simulation of trans-1,4-polyfarnesene exhibited a Tg of 202 K, which was in close agreement with the Tg (197 K) obtained from differential scanning calorimetry (DSC) measurements. Moreover, the mechanical properties of hydroxyl-terminated polyfarnesene were significantly enhanced through cross-linking, with the multi-isocyanate (N100) curing system demonstrating the highest efficacy. These findings demonstrate the usefulness of molecular dynamics (MD) simulations in providing a thorough qualitative and quantitative understanding of the intricate connection between the properties and structure of polymers.