Waterborne Polyurethane Research Articles

Enhancing flame retardancy and multi-functionalization of environmentally friendly cotton fabrics with a polydimethylsiloxane-based polyurethane

Phosphorus-containing flame retardants are prone to result in the buildup of biotoxins, while halogen flame retardants easily lead to hazardous gases. Therefore, it is crucial to develop a multifunctional flame-retardant cotton fabric without phosphorus and halogen. Herein, single-ended hydroxy-terminated polydimethylsiloxane (PDMS-ID) was synthesized through single-ended hydrosilicone oil and 1,4-butanediol, followed by the preparation of a waterborne polyurethane (RWPU) containing side chain polydimethylsiloxane through the reaction of PDMS-ID with isocyanate prepolymer. Characterization data shows that its particle size distribution is relatively dispersed while maintaining good emulsification performance. Based on this, a halogen-free and phosphorus-free multifunctional flame retardant cotton fabric (COF-BBN@RWPU) was successfully prepared through treatment with boric acid/borax/3-aminopropyltriethoxysilane solution and subsequent RWPU encapsulation. In vertical flammability test (VFT), COF-BBN@RWPU has a char length of 57 mm and a limiting oxygen index (LOI) of 42.3 % with a 11 % weight gain while pure cotton was burned through with a LOI of 18.0 %. In addition, the total heat release and total smoke release of COF-BBN@RWPU decreased by 80.0 % and 47.2 %, compared with pure cotton. Additionally, COF-BBN@RWPU can achieve a maximum contact angle of 140.1° with an oil-water separation rate of 98.4 %. This study presents an eco-friendly approach to achieving the multifunctionality of cellulose fabrics.

Percolation network and piezoresistive properties of ultraductile cementitious monitoring coating with A-POSS modified carbon-based nanoconductors

Conventional cement-based sensors are large and often embedded in cast-in-place concrete structures, resulting in poor flexibility, low sensing accuracy, and inability to be replaced after damage. This paper reports a promising health monitoring technology, namely the composite coated sensor (sensing skin) prepared by anionic waterborne polyurethane (WPU)-modified cement, in which N-(2-aminoethyl)-3-amino propyl trime thoxy silane (NAEAPTMS) silsesquioxane modified ettringite (A-POSS) acts as a core modifier. The results showed that a continuous interpenetration polymer network was formed between the WPU and the cement, which greatly improved the crack resistance and balanced the polarisation reaction field. The agglomerated GO-CNT particles self-dispersed into micron/nanometer-sized particles under the co-precipitation of Ca2+/Al3+ and the semi-cage-like POSS structure formed by NAEAPTMS, using AFt as the supporting skeleton. The toughness and bond strength of the sensing skins were improved in the presence of A-POSS and, in particular, the maximum deflection angle exceeded 110°. Meanwhile, the electrical resistivity was reduced by more than 2 orders of magnitude. The effective conductivity inside and outside the interface can be precisely delineated when GO-CNT was perfectly arranged inside WPU-CEMENT. The agreement between the theoretical and experimental results of effective conductivity indicates that the sensing skin had a percolation network with imperfect and tunnel-assisted interfaces. The synergistic effect of WPU and A-POSS gave the sensing skin excellent performance of high sensitivity (80 times larger than strain gauges), low relaxation time (50 ms), and monitoring stability.

A Sustainable Reinforcement Method for Recycled Road Subgrade Demolition Waste as Road Bases Using Waterborne Polyurethane and Fiber

A Sustainable Reinforcement Method for Recycled Road Subgrade Demolition Waste as Road Bases Using Waterborne Polyurethane and Fiber

Preparation and Properties of GMS/HTSF-Modified Waterborne Polyurethane Fluorine-Free Waterproof and Breathable Film.

Developing a fluorine-free, durable, high-performance waterproof breathable film for fabrics remains a formidable challenge. In this paper, a strategy for the preparation of fluorine-free, durable, and high-efficiency fabric waterproof and breathable membranes using glyceryl monostearate (GMS)/double-ended hydroxy silicone oil (HTSF)-modified waterborne polyurethane was proposed. The orderly orientation of GMS and HTSF gives the fabric excellent water-repellent properties, and the polyurethane macromolecular chain ensures strong adhesion of long-chain alkanes and silicones to the fabric surface. In this paper, the effects of different GMS contents on the stability, chemical structure, particle size, viscosity, water absorption performance, surface morphology, and XPS of a waterborne polyurethane fluorine-free waterproof and breathable membrane (GHWPU) were studied. At the same time, the application properties of GHWPU-treated fabrics, such as waterproof performance, antifouling performance, surface energy, morphology, and air permeability, were discussed. Through the analysis of SEM and XPS, it was found that the folds on the surface of the film were more and more orderly with the increasing content of GMS, and this orderly distribution of water-repellent groups endowed the film with excellent water-repellent ability. When the GMS content was 28 wt %, the finished fabrics had excellent comprehensive properties such as static contact angle of 141.6°, hydrostatic pressure of 96.7 KPa, resistance to more than 30 washes, and air permeability of 119.3 mm/s.

Preparation and characterization of UV-curable coatings based on waterborne polyurethane acrylate/g-C3N4 co-crosslinked network for wood materials

Wood materials are often damaged due to exposure to environmental factors including humidity changes, temperature fluctuations, and ultraviolet radiation, resulting in surface aging, deformation, and cracking. Therefore, developing a new wood coating with good mechanical properties and weather resistance is conducive to improving the usability and service life of wood as an outdoor material. In this study, graphitic carbon nitride (g-C3N4) with a characteristic crystal structure was synthesized using melamine as raw material. By constructing a g-C3N4 /polyurethane acrylate co-crosslinked network, a UV-curable wood coating with excellent interfacial adhesion was prepared, which retained the natural aesthetic texture of the wood and imparted good wear resistance, anti-wetting property, and aging resistance to the wood material. Subsequently, the formation process and cross-linking reaction mechanism of the coating were revealed by XRD, FTIR and XPS measurements. Compared with untreated samples, coatings with a cross-linked network structure exhibited enhanced resistance to external environmental changes. As the content of the g-C3N4 increased (>1.0 %), the mechanical properties were significantly improved, with the mass loss rate and damaged area decreasing by 56.9 % and 60.0 %. Meanwhile, with the increased cross-link density of the coating, the water and heat resistance of the wood increased by 22.77 % and 260 %, respectively. After a seven-day UV aging resistance test, the ΔE values only changed by 10.28 %, showing good weathering resistance. This design and synthesis of wood coating provides an effective technology for the long-term use of outdoor wood material.

Self‐Healing Waterborne Polyurethanes as a Sustainable Gel Electrolyte for Flexible Electrochromic Devices

Self‐healing polymers are promising for diverse applications in wearable technology and electronic skin. Polyurethanes are versatile polymers that can incorporate various monomer structures. Waterborne polyurethanes (WPUs) emerge as an environmentally conscious choice due to water usage instead of organic solvents, thereby minimizing the generation of volatile organic compounds. This study introduces a novel approach to enhance the self‐healing properties of WPUs by integrating disulfide bonds. These dynamic disulfide bonds undergo exchange reactions upon heating, facilitating the renewal of cross‐links on damaged film surfaces. Self‐healing WPUs with a low glass transition temperature achieve excellent self‐healing efficiency under mild conditions. Self‐healing adhesives applied to various flexible substrates retain stable peel strength, which confirms their potential as self‐healing solutions. Furthermore, the WPU hydrogel electrolyte is prepared with dihydroxyhexyl viologen (DHHV), and the prepared electrochromic gel exhibits good ionic conductivity while maintaining high transparency. The flexible electrochromic device exhibited excellent performances, including low coloration voltage, high coloration efficiency, and long‐term stability. The transmittance difference is exceptional, with over 99%, and no decay after repeated bending cycles is observed. The current results demonstrate the feasibility of self‐healing WPUs in improving the operation and durability of high‐performance flexible electrochromic devices.

Creating Safe, Biodegradable Nanofibers for Food Protection: A Look into Waterborne Polyurethane Electrospinning

Creating Safe, Biodegradable Nanofibers for Food Protection: A Look into Waterborne Polyurethane Electrospinning

A sulfonated hyperbranched bio-based waterborne polyurethane sizing coating for the enhancement of mechanical properties and surface wettability of carbon fibres

Wet-weaving and cluster braiding in industrial production processes generate irreversible defects and grooves in carbon fibre (CF) filaments, which reduce the service life and mechanical properties of the fibres. Additionally, the fibre surface covered with numerous inactive carbon-containing groups and presents chemical inertness, which limits the prospects of CF applications. Hence, the hyperbranched bio-based waterborne polyurethanes (SWPU) possessing the synergism of sulfamate and carboxylate complex hydrophilic units were adopted as sizing coatings to improve the flexural and tensile strengths of CF, as well as fibre surface roughness and wettability. The SWPU is designed on dihydroxymethylbutyric acid and sulfamates (A95) as per- and post-chain extenders, respectively, trimethylolpropane (TMP) as an intramolecular cross-linker, and plant-extracts castor oil (CO) replacing petroleum-based petrochemicals as the soft-segments. The construction of CO-TMP hyperbranched cross-linking networks and the strengthened hydrogen-bonding effects of the polar sulfamates positively affect the intermolecular interactions and configuration stability of SWPU sizing coatings. SWPU revealed favourable thermo-mechanical properties achieving a T5% decomposition temperature and toughness of 297.83 °C and 35.24 MJ/m3. The coating effects of the bio-based sizing agents not only repaired defects and improved surface roughness on CF, but the polar groups in SWPU comprising SO3Na, carbamate and polyurea promoted the chemotactic activity and wettability of the fibres. The surface energy and tensile strength of the SWPU sized CF reached 43.75 mN/m and 5.68 GPa, respectively, which were 45.4 % and 30.7 % higher compared to original CF. The research contributes to the development and industrial production of high-performance, eco-friendly bio-based sizing coatings.

Effects of NIR-reflective pigments on waterborne polyurethane coatings and their thermal insulation performance

Waterborne coatings have garnered much attention and gradually occupied the coating market recently due to the significant advantages in volatile organic compound emissions compared with solvent-borne coatings. Waterborne polyurethane coatings are a majority portion of waterborne coatings. Unlike solvent-borne coatings, the film formation of waterborne coatings occurs in an inhomogeneous phase, which brings a challenge for pigmentation in waterborne coatings. However, the influence of pigment on film formation and the property of waterborne polyurethane coating remain unclear. In this study, the different contents of commercial black near-infrared (NIR) reflective pigments were incorporated into both commercial and synthetic waterborne polyurethane systems. The film formation process was monitored by multispeckle diffusing wave spectroscopy. The impact of the pigment content on dry films was assessed through scanning electron microscope, color and gloss measurements, dynamical thermal analyzer, and tensile testing. Furthermore, the thermal insulation performance of the waterborne polyurethane coatings was evaluated to study the function of the NIR reflective pigments. Our findings reveal that the addition of black NIR reflective pigments yields a multifaceted effect on film formation and coating morphology and improves thermal insulating property. Elevated pigment content correlated with increased crosslinking density, tensile stress, and Young's modulus.

Preparation of Ultra-Sensitive flexible temperature sensors with thermal responsive waterborne polyurethane for enhanced temperature sensing performance

Flexible temperature sensors with superior resolution and reliable repeatability are crucial in the burgeoning field of electronic skins (e-skins). In this study, we synthesized thermo-responsive materials with mechanical flexibility by incorporating multi-wall carbon nanotubes (MWCNT) into waterborne polyurethane (WPU) matrix via covalent bonding. The thermal movement of WPU chain segments serves as the driving force, endowing the resultant material with excellent temperature response properties and stability. The MWCNT@WPU sensor demonstrates ultra-high sensitivity (−5.63 % K−1), high accuracy (0.1 °C), rapid response (mere 4.5 s), and long-term durability (up to 30 days) for temperature sensing within the range of 30 to 60 °C. Importantly, the temperature coefficient of resistance (TCR) can be tailored by adjusting the molecular weight of WPU soft segments and the ratio of hard segment to soft segment in WPU. Moreover, the developed sensor exhibits outstanding detection accuracy and stability in practical applications such as continuous water temperature monitoring, breathing rate measurement, and human skin temperature sensing, highlighting its immense potential in the e-skins field, catering to applications in healthcare monitoring, intelligent robotic platforms, and environmental surveillance.

Property improvement of epoxy emulsified asphalt modified by waterborne polyurethane in consideration of environmental benefits

Waterborne epoxy modified emulsified asphalt (EMEA) has the shortcomings of insufficient toughness and poor aging resistance, which limits its application of low-carbon cold-paving technology in plateau zones. To obtain a cold-mix asphalt binder with excellent performance, waterborne polyurethane (WPU) was utilized to modify EMEA in this work. Properties, modification mechanism, action process, environmental benefits, and cost-benefit of composite-modified emulsified asphalt (CMEA) were analyzed. Results show that CMEA had good rutting resistance, low-temperature rheological, tensile toughness, adhesion with aggregate and moisture damage resistance, and aging resistance properties. These were closely related in that WPU was cross-linked with the waterborne epoxy resin (WER) to form an interpenetrating polymer network (IPN) structure, when the space network structure of WER and the soft and hard segments of WPU worked together. Based on the above results, it was recommended that EA containing 4.0 wt% WER was modified by 7.5 wt% WPU to achieve the best pavement properties. Furthermore, it was discovered that a physical process by which WER and WPU modified EA, served as a skeleton connection and toughening agent. CMEA has excellent performance and is especially suitable for use in low-temperature and strong aging areas, while can bring good environmental benefits.

A Highly Effective Self-Healing Waterborne Polyurethane Vitrimer Containing Conjugated Schiff Base Bonds Driven by Photothermal

A Highly Effective Self-Healing Waterborne Polyurethane Vitrimer Containing Conjugated Schiff Base Bonds Driven by Photothermal

Liquefaction of banana peel as the source of renewable and sustainable polyols for preparation of waterborne polyurethane

A set of waterborne polyurethane (WPU) were prepared with the bio-polyol synthesized from the liquefaction of banana peel. The effect of the bio-polyol amount on water adsorption ability, tensile strength and elongation at break of WPU films was evaluated. The WPU prepared using 12 g bio-polyol exhibited a low water adsorption ability of 5.37 %, high tensile strength of 32.5 MPa, and appropriate elongation at break of 259.5 %.

Characterization and Comparison of Anammox Immobilization in Polyvinyl Alcohol, Polyethylene Glycol and Water-Borne Polyurethane

Anammox bacteria were embedded with different mass fractions of polyvinyl alcohol (PVA), polyethylene glycol (PEG) and water-based polyurethane (WPU) materials. The embedded immobilized pellets with different particle sizes of about 2.8–3.2 mm were prepared. The effects of the mass fraction of the embedding material (PVA 6–12%, PEG 6–9%, WPU 10%) and the concentration of activated carbon added in the embedding process (0–4%) on the pellet was investigated. The performance of pellet formation, sedimentation rate, mechanical strength, expansion coefficient, and elasticity were compared and analyzed under different immobilization conditions, and the parameters of each embedding step were optimized. Anammox immobilized pellets prepared with 10% polyvinyl alcohol (PVA), 2% sodium alginate (SA), and 2% powdered activated carbon were proposed. The effects of salinity on anammox were investigated through a batch test, and the optimal reaction conditions were selected to carry out the operation test. The functional groups of embedded and unembedded anammox sludge were detected using the infrared spectrum. A continuous flow sequencing batch reactor (SBR) demonstrated stable operation with immobilized anammox. Scanning electron microscopy revealed that the immobilized anammox pellets appeared as irregular particles, with each micro-unit predominantly being spherical. Additionally, a minor presence of rod-shaped bacteria was also noted. After 30 days of stable operation of the reactor, the ammonia nitrogen removal rate reached 84.7%.

Degradable cellulose acetate-based waterborne polyurethane sand-fixing agents for sand control in desert regions

In hot and arid desert regions, degradable chemical sand-fixing agents are efficient in dealing with problems caused by wind-blown sand movement without damaging the environment. This study aimed to develop a set of biodegradable sand-stabilizing substances, cellulose acetate (CA)-based waterborne polyurethane (WPU), utilizing CA as a partial hydroxyl provision through an acetone-based technique. The findings demonstrate that all the CA/WPU sand-fixing agents had unique, evenly spherical particles and were fully capable of degradation. The CA/WPU-2 sand-fixing agent contained 20 % polypropylene glycol (PPG) of CA. It showed strong viscosity, thermal stability, and water resistance. Furthermore, seed germination will be hindered by the CA/WPU-2 sand-fixing agent due to its superior sand-fixing capability compared to pure WPU. Consequently, it is suitable for application in arid regions where plant survival is difficult. CA/WPU-6 contained 120%PPG of CA. it showed outstanding O2 permeability and hydrophilicity due to its significant use of cellulose acetate. In addition, it demonstrated higher wind-blown sand resistance compared to popular commercial sand-fixation production. Furthermore, it sustained a consolidation strength lower than the highest penetration capability for herbaceous plant seeds. Therefore, CA/WPU-6 is a suitable option for establishing vegetation in dry situations. The results of this study address the demand for sustainable production and cost reduction, offering significant potential for industrial applications.

Performance and Morphology of Waterborne Polyurethane Asphalt in the Vicinity of Phase Inversion.

Waterborne polyurethane asphalt emulsion (WPUA) is an environmentally friendly bituminous material, whose performance is highly dependent on the phase structure of the continuous phase. In this paper, WPUAs in the vicinity of phase inversion were prepared using waterborne polyurethane (WPU) and asphalt emulsion. The chemical structures, thermal stability, dynamic mechanical properties, phase-separated morphology and mechanical performance of WPUAs were studied. Fourier-transform infrared (FTIR) spectra revealed that there are no -NCO bonds in either the pure WPU or WPUAs. Moreover, the preparation of WPUA is a physical process. The addition of WPU weakens the thermal stability of asphalt emulsion. WPU improves the storage modulus of asphalt emulsion at lower and higher temperatures. The glass transition temperatures of the WPUA films are higher than that of the pure WPU film. When the WPU concentration increases from 30 wt% to 40 wt%, phase inversion occurs; that is, the continuous phase shifts from asphalt to WPU. The WPUA films have lower tensile strength and toughness than the pure WPU film. However, the elongations at break of the WPUA films are higher than that of the pure WPU film. Both the tensile strength and toughness of the WPUA films increase with the WPU concentration. Due to the occurrence of phase inversion, the elongation at break, tensile strength and toughness of the WPUA film containing 30 wt% WPU are increased by 29%, 250% and 369%, respectively, compared to the film with 40 wt% WPU.

Water‐Based Polyurethane Heating Film with Double‐Layer Conductive Network for a Rapid Electrothermal Response

Carbon‐based composite materials have garnered widespread attention in the field of personal thermal management (PTM). In these applications, constructing conductive fillers with a highly cross‐linked network is key to achieving the rapid electrothermal conversion of materials. Herein, a novel carbon‐based composite material is successfully developed using screen printing technology, with a waterborne polyurethane (WPU) matrix embedded with carbon nanotubes (CNTs) and calcein‐modified graphene nanosheets (CAG). Due to the strong π–π conjugation interactions present in the highly cross‐linked carbon‐based network, the resulting CAG‐CNTs/WPU composite forms a 3D conductive network, which not only demonstrates a significant synergistic effect but also facilitates efficient transport of electrons and phonons. Experimental results show that the CAG‐CNTs/WPU composite possesses excellent electrothermal conversion properties and an upper high thermal conductivity (3.10 W m−1 K−1). At a low voltage of 5 V, the composite exhibits a rapid response, increasing to 50 °C in 20 s. This research not only highlights the importance of adopting environmentally friendly preparation methods but also emphasizes the synergistic role played by 2D graphene nanosheets and 1D CNTs in building an efficient 3D electrothermal network, which has significant scientific and application value in advancing PTM applications.

Interconnected Multifunctional Waterborne Polyurethane Binder for Structural Robustness of Si Anodes in Lithium-Ion Batteries

Interconnected Multifunctional Waterborne Polyurethane Binder for Structural Robustness of Si Anodes in Lithium-Ion Batteries

Transparent Superhydrophobic and Self-Cleaning Coating.

Surface roughness and low surface energy are key elements for the artificial preparation of biomimetic superhydrophobic materials. However, the presence of micro-/nanostructures and the corresponding increase in roughness can increase light scattering, thereby reducing the surface transparency. Therefore, designing and constructing superhydrophobic surfaces that combine superhydrophobicity with high transparency has been a continuous research focus for researchers and engineers. In this study, a transparent superhydrophobic coating was constructed on glass substrates using hydrophobic fumed silica (HF-SiO2) and waterborne polyurethane (WPU) as raw materials, combined with a simple spray-coating technique, resulting in a water contact angle (WCA) of 158.7 ± 1.5° and a sliding angle (SA) of 6.2 ± 1.8°. Characterization tests including SEM, EDS, LSCM, FTIR, and XPS revealed the presence of micron-scale protrusions and a nano-scale porous network composite structure on the surface. The presence of HF-SiO2 not only provided a certain roughness but also effectively reduced surface energy. More importantly, the coating exhibited excellent water-repellent properties, extremely low interfacial adhesion, self-cleaning ability, and high transparency, with the light transmittance of the coated glass substrate reaching 96.1% of that of the bare glass substrate. The series of functional characteristics demonstrated by the transparent superhydrophobic HF-SiO2@WPU coating designed and constructed in this study will play an important role in various applications such as underwater observation windows, building glass facades, automotive glass, and goggles.

An adaptive waterborne fluorocarbon coatings with Anti-Flashing Rust, Antibiofouling, and Self-Repairing properties

Waterborne fluorocarbon coatings are gaining popularity as a more environmentally friendly replacement for traditional solvent-based coatings because of its corrosion resistance and antibiofouling properties. However, the environmental unfriendliness of small molecular emulsifiers used, the occurrence of flash rusting, and the inability to self-repair after accidental damage restrict its application in the marine industry. Here, a redox-responsive copolymer (PMx) was synthesized by the amphiphilic nature of waterborne polyurethane as microreactors, which was employed as coatings (PMx/WPU) with anti-flashing rust, antibiofouling, and self-repairing functions. The copolymer was polymerized from chlorotrifluoroethylene (CTFE), vinyl acetate (VA), and a special monomer conjugated to the corrosion inhibitor 2-benzothiazolethiol (MBT) through disulfide bonds, in which MBT can be released through disulfide bond breaking in a reducing environment, effectively preventing the occurrence of flash rusting. The combination of the repelling properties of the fluorinated groups and the bactericidal action of the MBT results in PMx/WPU coatings with excellent antibiofouling properties. Additionally, the reversible hydrogen bonds in the polyurethane provide the PMx/WPU coatings with excellent self-repairing ability (93.9%). Our study presents a new approach to polymerize fluoro-substituted ethylene monomers using polyurethane as microreactors, enabling the preparation of waterborne fluorocarbon coatings with anti-flashing rust, antibiofouling, and self-repairing properties for practical applications.