Waterborne Polyurethane Matrix Research Articles

Eco-Friendly Waterborne Polyurethane Coating Modified with Ethylenediamine-Functionalized Graphene Oxide for Enhanced Anticorrosion Performance.

This study explores the potential of graphene oxide (GO) as an additive in waterborne polyurethane (WPU) resins to create eco-friendly coatings with enhanced anticorrosive properties. Traditionally, WPU's hydrophilic nature has limited its use in corrosion-resistant coatings. We investigate the impact of incorporating various GO concentrations (0.01, 0.1, and 1.3 wt%) and functionalizing GO with ethylenediamine (EDA) on the development of anticorrosive coatings for carbon steel. It was observed, by potentiodynamic polarization analysis in a 3.5% NaCl solution, that the low GO content in the WPU matrix significantly improved anticorrosion properties, with the 0.01 wt% GO-EDA formulation showing exceptional performance, high Ecorr (-117.82 mV), low icorr (3.70 × 10-9 A cm-2), and an inhibition corrosion efficiency (η) of 99.60%. Raman imaging mappings revealed that excessive GO content led to agglomeration, creating pathways for corrosive species. In UV/condensation tests, the 0.01 wt% GO-EDA coating exhibited the most promising results, with minimal corrosion products compared to pristine WPU. The large lateral dimensions of GO sheets and the cross-linking facilitated by EDA enhanced the interfacial properties and dispersion within the WPU matrix, resulting in superior barrier properties and anticorrosion performance. This advancement underscores the potential of GO-based coatings for environmentally friendly corrosion protection.

Piezoelectric nanocomposite films based on anionic waterborne polyurethane and barium titanate nanoparticle: Fabrication, microstructure, and property characterization

AbstractWe report the fabrication, microstructure, thermal property, and piezoelectric performance of flexible waterborne polyurethane (WPU) nanocomposite films reinforced with barium titanate (BT) nanoparticles with ~50 nm diameter. An anionic segmented WPU was synthesized via bulk polymerization, and its nanocomposite films containing 10–40 wt% BT were fabricated via aqueous dispersion casting and hot pressing. Although the BT nanoparticles interacted with the urethane groups of the WPU hard segment by inducing the separation of the semicrystalline soft segment, they were aggregated in the WPU matrix. Accordingly, the glass transition temperature of the WPU matrix decreased with BT content, but the melting temperature increased. As the BT content increased in the nanocomposite films, the thermal decomposition temperature of the WPU soft segment showed a slight decrease, while the decomposition temperature of the hard segment increased. Additionally, the residue at 600°C increased significantly from 2.0% for neat WPU film to 36.3% for the nanocomposite film containing 40 wt% BT. The piezoelectric outputs attained by the nanocomposite films increased with BT content. Under compressive stress of 23 kPa, the nanocomposite film containing 40 wt% BT was able to achieve the highest piezoelectric voltage of ~0.51 V, a current of ~43.0 nA, and an electric power of ~21.9 nW. For the nanocomposite film, a linear relationship between the piezoelectric out voltage and the applied compressive stress with a slope of ~0.0253 was also observed.Highlights Anionic waterborne polyurethane (WPU) with hard/soft segments is synthesized. Barium titanate (BT) nanoparticles are adopted as a piezoelectric nanofiller. WPU/BT nanocomposites are manufactured by dispersion casting and hot pressing. Specific interactions between BT nanoparticles and WPU hard segments exist. Piezoelectric outputs of nanocomposites increase with BT content and stress.

Deacetylation-controlled chitin derivative imbedded WPU nanocomposite for highly powered and robust triboelectric nanogenerator

For effective triboelectric nanogenerator, it remains a major challenge to improve the intrinsic electron-donating properties of positive materials. We report a positive triboelectric nanocomposite material based on chitin, a biopolymer, embedded in a waterborne polyurethane matrix to improve the output performance, sustainability, and robustness of triboelectric nanogenerators (TENGs). This nanocomposite can increase the output performance via electron donating control through the deacetylation of chitin nanofibers. For the deacetylation of chitin, the exposed amine group can be an attractive electron donor combined with polyurethane, resulting in a higher output characteristic (210 V and 3.2 μA/cm2), as confirmed by Kelvin probe force microscopy measurements. Moreover, this nanocomposite film showed good sustainability (V/V0 = 85%) in a humid environment (85 RH%) owing to its hydrogen bonding with water molecules. The hybridized film exhibited excellent robustness (100,000 cycles of bending test, long-term stability test over 10,000 s) in two types of harsh mechanical environments. This flexible, robust TENG with a nanocomposite film can serve as a self-powered motion sensor for monitoring various human motions, such as contact pressure and sliding speed. Combined with a homemade sodium-ion potentiometric sensor, stable operation of the dehydration monitoring system was successfully demonstrated under sweating conditions.

A simple surface engineering to develop the potential of carbon nitride nanosheets in high-performance polymer nanocomposites conducted by first-principles calculations

The incompatible interface between carbon nitride (CN) nanosheets and polymer resin is a huge challenge to develop high-performance polymer/CN nanocomposites. Recently, the complicated surface functionalization methods reported severely hinder the commercial production and practical application of polymer/CN nanocomposites. Herein, conducted by the first-principles calculations, a simple surface engineering is put forward to change the surface characteristic of CN nanosheets by rapidly introducing oxygen atoms with a chemical oxidation method. Presented by the first-principles calculations, it is found that the introduction of oxygen atoms can enhance the adsorption energy between oxygen-doping carbon nitride nanosheets (OCN) and waterborne polyurethane (WPU) resin. As a result, a stronger interfacial interaction and better dispersion state are presented in WPU/OCN nanocomposites, thus laying the foundation for the properties enhancement. Further, effective suppression effects for thermal pyrolysis and fire hazards of WPU resin are demonstrated by OCN nanosheets. As presented by cone calorimeter results, the peak values of heat release rate and total heat release in WPU/OCN-2 are decreased to 806 kW/m2 and 43.3 MJ/m2, significantly less than those of pure WPU (1028 kW/m2 and 55.9 MJ/m2). Meanwhile, more char residue, lower signal intensity of pyrolysis gas, and a prolonged time for signal peak also confirm that the addition of 2.0 wt% OCN nanosheets can hinder the thermal degradation behavior of WPU resin. In addition, the introduction of oxygen atoms promotes the formation of hydrogen bond interactions between OCN nanosheets and WPU matrix, thus enhancing interfacial compatibility and overcoming the re-stack problem. As a result, break strength and elongation at break of WPU/OCN-2 are up to 621% and 24.4 MPa, respectively. The combination of first-principles calculations and surface engineering opens a new approach for designing and developing high-performance polymer nanocomposites.

EMI shielding, thermal and antibacterial performances of ecofriendly castor oil–based waterborne polyurethane favored by combining carbon nanotube and cetyltrimethylammonium bromide

Many ecofriendly and antibacterial polymer-based shielding nanocomposites have been designed to address the increasingly serious issues of electromagnetic interference (EMI) pollution and antibiotic resistance. These composites contain high amounts of conductive and antibacterial material and exhibit an unsurpassed EMI shielding performance and strong antibacterial properties. However, it is extremely challenging to prepare these materials because of the formation of large aggregates coupled with the high viscosity. Herein, carbon nanotubes (CNTs) and an antibacterial surfactant (cetyltrimethylammonium bromide (CTAB)) are mixed with castor oil–based waterborne polyurethane (WPU) via ultrasonic-assisted solution mixing followed by a freeze-drying approach. Owing to the presence of CTAB, CNTs (at a concentration of 24.3 wt%) are evenly dispersed and connected to each other in the WPU matrix. This morphology and intrinsic characteristics of CNTs enable the resultant CNT/WPU composites to exhibit an excellent electrical conductivity (635.8 S/m) and thermal conductivity (0.308 W/(m·K)) as well as an incomparable shielding effectiveness (SE, 88.81 dB). Notably, the specific SE reaches 997.4 dB/cm, which exceeds those of the reported composites. Moreover, the combination of CNTs and CTAB improves the antibacterial activities of the WPU composites. Due to these merits, the resultant composites have great potential for applications in portable and wearable smart electronics. Overall, this study opens a new way toward the manufacture of ecofriendly and multifunctional polymer composites.

Self-healing polyurethanes with ultra-high-strength via nano-scaled aqueous dispersion of lignosulfonates

How to overcome the dilemma between self-healing capacity and the mechanical strength for polyurethane materials is an intriguing but challenging topic. Taking advantage of the nano-scaled dispersion of the lignosulfonates in tailored waterborne polyurethane (WPU) emulsion, herein an aqueous dispersion strategy was proposed. Different from the previously reported methods, it is simple, efficient and environmentally friendly. The prepared self-healing polyurethane exhibited an ultra- high tensile strength of 51.4 MPa (higher than previously reported results) combined with a elongation at break of 670% when merely 6 wt% of lignosulfonate was introduced into the WPU system. Upon undergoing three cycles of thermal processing, a tensile strength higher than 30 MPa was still remained. Atomic Force Microscope (AFM) combined with Variable-Temperature Infrared Spectroscopy (V-FTIR) confirmed the existence of the nano-scaled lignosulfonate aggregates within the WPU matrix and the reinforcing mechanism was discussed from a viewpoint of the intermolecular interactions. V-FTIR further revealed the origin of the self-healing from the detected dissociation of the oxime-carbamate bonds with the increased temperature. This nano-scaled aqueous dispersion strategy demonstrates a high potential in designing polyurethane materials with balanced self-healing performance and mechanical properties.

Fabrication of silane and nano-silica composite modified Bio-based WPU and its interfacial bonding mechanism with cementitious materials

Bio-based waterborne polyurethane (WPU) using renewable resources has grown with the increasing scarcity of petroleum resources and people’s awareness of sustainable development and environmental protection. The unfavorable physicochemical properties hinder its further development in the field of concrete protective coatings, also the bonding mechanism between the Bio-based WPU and cementitious materials has little scientific backing. In this work, the environmentally benign bio-based WPU was synthesized by employing soybean oil as the initial raw material, which was prepared by prepolymer method through a series of chemical reactions of epoxidation, hydroxylation and stepwise polymerization. The chemical cross-linking of γ-aminopropyltriethoxysilane(APTES) combined with physical reinforcement of nano-SiO2 strategy was used for the composite modification. The particle size of emulsion, molecular structure, water resistance, tensile and thermal properties, microstructures of the Bio-based WPU were investigated by DLS nanoparticle size measurement, Fourier transform infrared spectroscopy (FT-IR), universal mechanical testing, water immersion, differential scanning calorimetry (DSC) and thermogravimetric analysis (TG), scanning electron microscopy (SEM) respectively. The results shows that the APTES has been successfully grafted into the Bio-based WPU chain and the nano-SiO2 was dispersed homogeneously in the WPU matrix. The Si-O of with low surface energy introduced to the Bio-based WPU by APTES cross-linking and the favourable interfacial covalent bonding between the nano-SiO2 and Bio-based WPU have a synergistic effect in enhancing the water resistance, tensile strength and thermal stability. The pull-off testing shows the cement and interfacial mixed failure was the primary failure mode, the bonding strength of the composite modified Bio-based WPU shows an increasing trend with increasing content of nano-SiO2, which increases by 206.56 % to reach 1.87 MPa compared with Bio-based WPU without modification. The interfacial bonding mechanism of SiO2-SiWPU composite film with cementitious materials are mechanical interlocking effect, coordination bonding, hydrogen bonding and electrostatic adsorption, demonstrating the Bio-based WPU organic–inorganic composites coating can be a promising candidate for concrete protecting.

Synthesis of Carboxyl Cellulose Nanocrystals/Copper Nanohybrids to Endow Waterborne Polyurethane Film with Improved Mechanical and Antibacterial Properties

The multifunctional nanohybrid fillers have attracted widespread attention in the field of polymer nanocomposites. In this study, carboxyl cellulose nanocrystals/copper nanoparticles (TCNC/Cu NP) nanohybrids were prepared by in situ growth of copper ions on the modified carboxyl CNC, and further doped into waterborne polyurethane (WPU) via solution blending. TEM, FTIR, XRD, and UV–vis analysis were used to characterize the morphology, composition, crystallization and structure of the as-prepared nanohybrid. TCNC/Cu NP nanohybrids exhibited good dispersion and interface compatibility in WPU matrix. The nanocomposite film obtained significantly enhanced mechanical, thermal stability and scratch resistance properties, which was attributed to a hydrogen bond network structure formed in the WPU matrix. Additionally, colony count method was performed to test antibacterial properties of various films. Compared to the pure WPU film, all of nanocomposite films showed better antibacterial properties against Escherichia coli and Staphylococcus aureus. The antibacterial ratio of the WPU nanocomposite film with the addition of TCNC/Cu NP (1:1) reach 99%. Furthermore, the results of a copper ion sustained release experiment showed that the nanocomposite film had a long-term release effect, which was ascribed to the strong bonding between TCNC/Cu NP nanohybrids and WPU matrix. Thus, Cu NP was firmly embedded in the hydrogen bonding network structure formed. This work gives a new approach to prepare the antibacterial WPU film with well mechanical properties.

Flexible and Mechanically Enhanced Polyurethane Composite for γ-ray Shielding and Thermal Regulation.

Microencapsulation of paraffin with lead tungstate shell (Pn@PWO) shows the drawbacks of low wettability and poor leakage-proof property and thermal reliability, restricting the application of phase change microcapsules. Herein, a novel paraffin@lead tungstate@silicon dioxide double-shelled microcapsule (Pn@PWO@SiO2) has been successfully constructed by the emulsion-templated interfacial polycondensation and applied in the waterborne polyurethane (WPU). The results indicated that a SiO2 layer with controlled thickness was formed on the PbWO4 shell. The Pn@PWO@SiO2 microcapsules have exhibited superior leakage-proof properties and thermal reliability through double-shelled protection, and the leakage rate decreased by at least 54.11% compared to that of Pn@PWO microcapsules. The SiO2 layer with abundant polar groups ameliorated the wettability of microcapsules and the interfacial compatibility between microcapsules and the WPU matrix. The tensile strength of WPU/Pn@PWO@SiO2-2 composites reached 10.98 MPa, which was over 7 times greater than that of WPU/Pn@PWO composites. In addition, WPU/Pn@PWO@SiO2-2 composites with a latent heat capacity of over 41 J/g exhibited efficient phase change stability and γ-ray shielding properties. Also, the mass attenuation coefficients reached 1.38 cm2/g at 105.3 keV and 1.12 cm2/g at 86.5 keV, respectively. These properties will greatly promote the application of WPU/Pn@PWO@SiO2 composites into γ-ray-shielding devices with thermal regulation.

Cross-linked graphene oxide framework to enhance pervaporation separate property of waterborne polyurethane in food packaging materials

In order to improve separating aromatic/aliphatic group in adhesives or solvents of food packaging materials by pervaporation, an across linked graphene oxide (GO) framework were incorporated into waterborne polyurethane (WPU) membrane. The improved benzene solubility and expanded interlayer pathway of modified membrane have been gained based on three different reduced graphene oxide. Compared to P-phenylenediamine (PPD) and ethane-diamine (EDA) reducing agents, O-phenylenediamine (OPD) showed a relatively mild reducing ability and allowed GO to form a layer-to-layer lamella in the WPU matrix easily. When the dose of GO-OPD was 0.03%, the flux of GO-OPD/WPU membrane was 1.58 times of neat WPU or GO/WPU membranes, while the separation factor was slightly improved. The GO-OPD /WPU membrane also maintained good stability in the continuous pervaporation process of 2700 min.

Adsorption of Cu2+ and Pb2+ from Municipal Wastewater by Intercalation Polymerization Modified Kaolin

Adsorption method has attracted extensive attention in heavy metal wastewater treatment due to its low cost, abundant sources, and simple operation. Kaolin is utilized as raw material, waterborne polyurethane is utilized as dispersion medium, and dimethyl sulfoxide (DMSO) is utilized as intercalation agent, to prepare intercalation polymerization modified kaolin material (KBEP). It is then characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetry (TG), and other methods. The polymer is utilized for static adsorption of Cu2+ and Pb2+, and the kinetic analysis of the adsorption process is carried out. The results show that the layer spacing of kaolin increases substantially (from 0.69 nm to 0.81 nm) after modification. When the content of kaolin is less than 1.7%, kaolin exists in intercalation or stripping state in waterborne polyurethane matrix. When the content of kaolin is higher than 1.7%, kaolin can exist in the form of agglomeration with waterborne polyurethane matrix. Compared with pure polyurethane, the composite’s thermal stability is improved, and the maximum thermal weight loss of the hard section is increased by 50 °C. When kaolin content is 2.5%, the temperature of the hardness and the fastest thermal decomposition rate of the soft section increases by 30 °C and 26 °C, respectively. The adsorption test reveals that the Cu2+ elimination rate reaches 93.7% when the addition amount of the prepared material reaches 1.5 g/L. When the addition amount of the prepared material reaches 0.6 g/L, the Pb2+ elimination rate reaches 95.8%. With the increase of the dosage of kaolin composite, the adsorbability of the polymer to the two metal ions decreases gradually. Kinetic experiments show that the adsorption of Cu2+ and Pb2+ is in line with the pseudo-second-order kinetic (PSOK) equation. The adsorbability of Cu2+ and Pb2+ is 75.3 mg/g and 268.6 mg/g, respectively. The adsorption way is mainly chemical adsorption.

Waterborne polyurethane/silica nanocomposites based on electrostatic interaction: Interfacial interactions and properties

To study the effect of electrostatic interaction on the interface and mechanical properties of nano-composites, two kinds of silica nanoparticles with positive and negative charges were prepared and introduced into waterborne polyurethane (WPU) emulsion with negative charges to prepare composite emulsion and film. Molecular dynamics simulation and instrumental characterization were used to investigate the properties of nanoparticles and hybrid films. Molecular dynamics simulation results showed that WPU/SiO2(+) nanocomposite demonstrated higher interfacial free energy, lower free volume fraction and diffusion coefficient than those of WPU/SiO2(−) nanocomposite. The mechanical properties of the composite films indicated that there is no positive effect on the mechanical properties as the charges of SiO2 and WPU keep the same. Therefore, the mechanical properties of the composite films can be effectively enhanced by introducing positively charged SiO2, and the optimized introduction amount is 1 %. SEM images of the cross-section for the film show that SiO2(+) exhibits higher interfacial interaction strength with the WPU matrix than SiO2(−). Accordingly, molecular dynamics simulation and instrumental analysis afford similar results.

Experimental and numerical investigation on the mechanical and electrical properties of multiwalled carbon nanotube/waterborne polyurethane coated 3D printing carbon fiber reinforced composites

AbstractMechanical–electrical properties and failure behavior of 3D printed carbon fiber reinforced composites with multiwalled carbon nanotube (MWCNT)/waterborne polyurethane (WPU) conductive coating were studied to develop a performance monitoring method for composites. The results indicated that the coating materials could obtain good mechanical–electrical properties and sensitivity factor. Scanning electron microscopy images show that multiple conductive channels exist in the coating. The coating is well bonded to the composites. In order to obtain more details, mechanical–electrical coupling simulation was conducted. The experiment and simulation are in good agreement. The correlation between the strain of composite part and the electrical resistance change rate of the coating is validated. Furthermore, the multi‐scale observations reveal the failure mechanism including composite‐coating debonding, brittle fracture of polyamide matrix, fiber breakage, and pull‐out in the composite part, as well as ductile fracture of WPU matrix and MWCNT pull‐out in the coating part. This study can provide some insights for structural health monitoring of composites.

A super-cooling solar reflective coating with waterborne polyurethane for asphalt pavement

To construct highly cooling solar reflective coatings with excellent abrasive resistance, a crosslinkable absorbing heat waterborne polyurethane (WPU) was synthesized and used to prepare a solar reflective coating for asphalt pavement. The super-cooling effect of WPU based on solar reflective coating was evaluated by comparing to that of waterborne epoxy (WEP) and polyacrylate emulsion (WMMA). Due to formation of numerous PBA microcrystals in WPU matrix, the heat absorbing behavior of WPU was confirmed by DSC results. The melting of microcrystals occurred at -2–105 °C, and the fusion enthalpy was 48 J/g. Although the solar reflective coatings based on the three resins had similar total reflectance, according to temperature experiment, WPU reflective coating (WPURC) still had the best cooling performance and could reduce the inner temperature of asphalt concrete by 7–11 °C. In the presence of numerous PBA microcrystals, WPURC showed effective and stable super-cooling effect during cyclic temperature experiment. Additionally, during abrasive test, WPURC not only had excellent anti-abrasive performance, but also effectively reduced threat of abrasion to cooling performance. Herein, the heat absorbing WPU constituted a major breakthrough for efficient cooling and functional durability of the reflective coating.

Electrical and magnetic network design for improving electromagnetic interference shielding performance of waterborne polyurethane fabrics

Waterborne polyurethane (WPU) fabrics containing multiwalled carbon nanotubes (CNTs) and Ni coated multiwalled carbon nanotubes (Ni@CNTs) were successfully fabricated through emulsion mixing and drop-coating method. Carbon-based nanofillers were distributed in the conformal WPU matrix and fabric substrate, and intertwined with each other to form electric/magnetic network. The electromagnetic interference shielding effectiveness (EMI SE) of PU/10Ni@CNTs/10CNTs fabric reaches 77.2 dB, batter than that PU/20CNTs fabrics due to the synergistic effect of electrical, dielectric, and magnetic loss.

Preparation and characteristics of sepiolite-waterborne polyurethane composites

Abstract A kind of organic/inorganic composite material composed of waterborne polyurethane and sepiolite was prepared in this work. Sepiolite was organically modified by three kinds of silane coupling agents, and then compounded with waterborne polyurethane through layer-by-layer method in order to prepare composite materials. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) show the crystal and chemistry structure of sepiolite samples, and confirmed the preparation of organic sepiolite. Scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) showed the surface microstructure and elemental content of sepiolite and organic sepiolite, and was consistent with the XRD results. Transmission electron microscope (TEM) examination of waterborne polyurethane composites surfaces showed that sepiolite particles were regularly dispersed in the waterborne polyurethane matrix. Thermal resistance of waterborne polyurethane composites was determined by thermogravimetry analyzer (TG) and derivative thermogravimetry analyzer (DTG), differential scanning calorimetry (DSC), gas chromatography (GC), and mass chromatography (MS). Mechanical behavior was examined by tensile strength tester, showed higher break strength than that of the control waterborne polyurethane. Therefore, organically modified sepiolite was considered to be a kind of wonderful inorganic material that could be used to improve the thermal stability and mechanical property of polymer.

Mussel‐inspired synthesis of silver nanoparticles as fillers for preparing waterborne polyurethane/Ag nanocomposites with excellent mechanical and antibacterial properties

AbstractSilver nanoparticles (AgNPs) were synthesized by a facile, mild and green method using dopamine as a reducing and stabilizing agent and were introduced to waterborne polyurethane (WPU) via an in situ emulsification method to prepare antibacterial nanocomposite films. The formation of AgNPs was characterized by UV–visible spectroscopy and XRD. The dispersion of AgNPs was confirmed by TEM and the thermal stability of WPU/Ag nanocomposites was confirmed by TGA. The results showed that AgNPs were uniformly dispersed in the WPU matrix. The introduction of AgNPs significantly improved the thermal stability of WPU films. With incorporation of 0.1 wt% AgNPs, a five‐fold increase in the tensile strength was achieved without sacrificing the ultimate strain. The WPU/Ag nanocomposite films showed antibacterial activity against Escherichia coli and Staphylococcus aureus. © 2021 Society of Industrial Chemistry.

Computational simulation a system of waterborne polyurethane matrix by β-C induction with ZnO and CaCO3 particles

This work includes the search for the development of a composite of a WPU (waterborne polyurethane), β-CD (β-Cyclodextrin), PZnO (zinc oxide particles), and the presence of CaCO3, to obtain new properties such as adhesion to multiple substrates of organic and inorganic origin. Therefore, a development sequence was proposed: Computational development: conformation of the polymeric matrix (with the intermediary polymers) and simulation of the interaction between β-CD and PZnO and Ca+2 and CO3-2 ions, as well as insertions in β-CD, computational simulations were carried out with the help of ACD LABS™ (free version) software and by molecular dynamics with GROMACS™. With the above, we were able to determine properties such as interfacial tensions, surface tensions, and contact angles, and degrees of solvation and stability in waterborne emulsions. Therefore, it is important to point out that one of the main contributions of this research proposal is that there are no studies that combine these materials.

Fabrication of high transparent, mechanical strong, and flame retardant waterborne polyurethane composites by incorporating phosphorus‐silicon functionalized cellulose nanocrystals

AbstractTo manufacture transparent waterborne polyurethane composite coatings that possess desirable mechanical and flame retardancy properties is still a challenge. Herein, we first synthesized phosphorus‐silicon functionalized cellulose nanocrystals (FCNC) filler, and further introduced it into waterborne polyurethane (WPU) matrix to prepare composite. The phosphorus‐silicon‐containing components were grafted covalently on the surface of FCNC, and the FCNC showed good dispersion level in water and WPU matrix. Moreover, the inserted FCNC could not only maintain the high transparency of WPU‐FCNCs composites, but also remarkably enhancing the mechanical and flame retardancy performances. Noticeably, the WPU‐FCNC3 composite containing 3 wt% of FCNC showed balanced mechanical (σb = 16.7 MPa, εb = 557.5%), limiting oxygen index (22.9%), and a UL‐94 rating of V‐2 among prepared films. Additionally, WPU‐FCNC3 composite exhibited significantly reductions in heat release during combustion, and also showed a high transmittance of 92.2%. The present research supplies promising way for developing transparent, toughness, and flame retardant composite coatings.

Nanocomposites Based on Waterborne Polyurethane Matrix and Fe3O4 Nanoparticles: Synthesis and Characterization

Herein, the feasibility of producing waterborne polyurethane nanocomposites containing magnetic nanoparticles (MNPs) by casting method, to obtain films with potential magnetic properties, is shown. The characterization of the resulting nanocomposites is carried out using infrared spectroscopy, thermal analysis, colorimetry, tensile tests, microscopy and magnetic tests. The films become opaque and dark colored when MNP is incorporated. The mechanical behavior of the nanocomposites is that of tough plastics, with Young's modulus in the range of 106–143 MPa, increasing with the MNP concentration. Aggregation of the MNP takes place at concentrations above 1.5 wt%, as observed in scanning electron microscopy (SEM) images of the fracture surfaces. Magnetization saturation increases with the concentration of MNP. A small coercivity indicates the presence of a fraction of blocked particles whose size exceeds the critical size for superparamagnetism at the temperature of the measurements.