Waterborne Polyurethane Coatings Research Articles

Development of fluorosilicon bivalve isocyanate microcapsules for multifunctional coatings with excellent self-repairing properties, enhanced hydrophobicity, and corrosion protection properties

This study first self-made TMP-IPDI tetramer, and then prepared a fluorine-modified silicon dioxide double shell isocyanate type self-healing microcapsule (CBS-X/TMP-IPDI@PU@F-SiO2) using TMP-IPDI tetramer, fluorescent agent 4,4-bis (2-disulfonic acid sodium styrene) biphenyl (CBS-X) as the core material, polyurethane (PU) as the single shell, and fluorine modified silicon dioxide (F-SiO2) as the double shell using interfacial polymerisation method. Then, it was added to waterborne polyurethane (WPU) to prepare self-healing coatings and coatings. The chemical structure, microstructure, self-healing self detection, and mechanical properties of TMP-IPDI, CBS-X/TMP-IPDI@PU@F-SiO2, and composite coatings were characterized by infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR), scanning electron microscopy (SEM), particle size analysis (PSA), X-ray electron spectroscopy (XPS) analysis, contact angle testing, tensile testing, electrochemical impedance testing, and Ultraviolet photograph. The results showed that the TMP-IPDI tetramer was successfully prepared. The average particle size of CBS-X/TMP-IPDI@PU@F-SiO2 prepared is 29 μm. The contact angle, tensile strength, low-frequency impedance and Nyquist curve radius of the repaired spots increased with the increase of the amount of CBS-X/TMP-IPDI@PU@F-SiO2 in WPUs; the increasing trend slowed down when the amount of CBS-X/TMP-IPDI@PU@F-SiO2 was >5 %. When the CBS-X/TMP-IPDI@PU@F-SiO2 dosage is 5 %, the WPU coating has good self-repair and self-detection performance. The stress before and after repair were 12.89 MPa and 20.11 MPa, respectively, with a repair rate of 80.3 %. The contact angle at the repair site can reach 100.8°, and the coating has good corrosion resistance. The microcapsules prepared based on fluorine-modified silica (F-SiO2) as the wall material have good self-healing performance for WPU coatings, achieving secondary protection of the repaired material.

Preparation and application of fluorine-containing acrylate emulsion in two-component waterborne polyurethane coatings

Preparation and application of fluorine-containing acrylate emulsion in two-component waterborne polyurethane coatings

UV-curable acrylic end-capped amphoteric waterborne polyurethane coatings

Waterborne polyurethane dispersions (WPUs) are environmentally friendly coatings since they present low amount of volatile organic compound amounts (VOCs). In the majority of the WPUs the dispersions are balanced with anionic groups and accordingly their stability at low pH is limited. In order to this drawback to be solved, in this work a tertiary amine containing chain extender (triethanolamine, TEOA) was introduced together with a conventional internal emulsifier (carboxylic acid) in acrylic end-capped polyurethane dispersions giving rise to amphoteric UV curable WPUs. After adding a radical photo-initiator and film formation, the coatings were cured under UV irradiation. The properties of amphoteric and anionic dispersions were compared. The best properties were obtained for the samples containing a 1/1 amine/acid molar ratio. Thus, while the anionic dispersions coagulated at low pH values, the 1/1 amphoteric dispersion showed high stability to pH changes. After curing this sample with UV irradiation, the gel content of the film was higher and the water vapour transmission rate was lower than that of the anionic polyurethane because of the strong acid/base interaction. The results showed that the amphoteric WPUs are promising for various applications, offering stability over a wider pH range than traditional formulations.

Oxidative crosslinking induced self-reinforcing waterborne polyurethane with tunable structure as multi-synergistic antibacterial biomimetic composite coating

Waterborne polyurethane (WPU) coatings with antibacterial properties have attracted extensive attention. Herein, we proposed a molecular design strategy was used to establish a series of castor oil/tung oil based WPU antibacterial coatings. By introducing conjugated double bonds of tung oil into WPU skeleton, electrostatic interaction by zwitterion and bacterial division inhibition by conjugated double bonds achieved the synergistic antibacterial effects. To our delight, inspired by lotus leaves, the scanning electron microscope test revealed the bionic micro-nano embedded structure was constructed on the surface of WPU using siloxane-modified nanocellulose (CNC@MTES). The destruction of the phosphorus layers and superhydrophobicity grant the material to have quadruple synergistic antibacterial effects. The antibacterial rates of WPU coatings on E. coli and S. aureus were more than 99.6% and played the mildew protection effect. What's more, peroxy bond formed by unique oxidative cross-linking induced self-reinforcing to enhanced the mechanical properties (the stress and Young's modulus of coating enhanced by 122.06% and 2368% respectively). Strong bonding between CNC@MTES and WPU ensured the durability of the coating, which was still effectively antibacterial and hydrophobic after 400 friction cycles. This research offered an innovative and effective method for coating to be widely used in product packaging, medical devices, smart glass and other fields.

Bio-inspired self-healing and anti-corrosion waterborne polyurethane coatings based on highly oriented graphene oxide

In the face of ubiquitous corrosion threats, the development of high-performance elastomer protective materials with active self-healing functions is extremely challenging and significant. We propose an approach by combining WPU elastomer with GO to create the multifunctional pearl layer structured polymers with interface hydrogen bonds. By crosslinking the polycaprolactone diol (PCL) chain with a hydrogen bond array, the elastomer with high mechanical strength, extensibility, elasticity, excellent damage resistance, and healing properties was successfully synthesized. The elastomer exhibits remarkable mechanical properties, including a tensile strength of 39.89 MPa, toughness value of 300.3 MJ m−3, and fracture energy of 146.57 kJ m−2. The enhanced damage resistance of the elastomer can be attributed to the decomposable hydrogen bond array as well as the strain-induced crystallization of PCL fragments, which effectively dissipate energy. Importantly, due to the reversibility of the hydrogen bonding array, the fractured WPU can easily heal and restore its original mechanical properties when subjected to heating at 50 °C. Moreover, the photothermal properties of GO enable the biomimetic polymer coating to achieve damage recovery after being irradiated with NIR for 30 s. The obtained biomimetic coating exhibits a highly oriented lamellar structure, thereby greatly enhancing physical barrier performance and anti-corrosion performance. Electrochemical impedance spectroscopy (EIS) shows that the impedance modulus is one order of magnitude higher than that of the blank coating. Additionally, scanning vibrating electrode (SVET) confirmed that the self-healing performance and protection effect of the biomimetic coating in 3.5 wt% NaCl solution were also reliable. This highly reliable biomimetic coating presents a revolutionary solution for creating multi-functional, high-performance smart material in harsh environments.

Facile fabrication of waterborne polyurethane coatings with good hydrophobicity and antifouling properties by leveraging fluorinated polysiloxane

The unsatisfactory water and fouling resistance of waterborne polyurethane (WPU) coatings have significantly hampered their practical applications. Herein, a simple strategy to prepare a novel industrial WPU hydrophobicity and antifouling coating (FSiWPU) was employed. The FSiWPU coating was prepared by a facile polycondensation reaction to introduce hydroxyl-terminated siloxane fluoride (HTFSi) into polyether-type WPU. The study demonstrated that the coating material exhibited excellent hydrophobicity (with a water contact angle of 107.9°), water resistance (with a water absorption of 8.7 %) and considerable mechanical strength (35.6 MPa). More importantly, due to the surface enrichment of low-surface-energy HTFSi chain segments, the coating exhibited excellent antifouling and substrate shielding protection against various contaminating liquids and corrosive chemicals. The approach provided a promising candidate for the large-scale production and practical application of waterproof and anti-fouling waterborne polyurethane coatings.

Synthesis of Silanated Coconut Oil-Based Waterborne Polyurethane Coating for Corrosion Protection

In this study, an eco-friendly coconut oil-based polyol blend was synthesized for bio-based waterborne polyurethane (WBPU) and WBPU-silane composite coatings. It was demonstrated that an increase in silane content incorporated into the WBPU matrix significantly enhanced the corrosion protection of WBPU coatings. Results also show a fourfold increase in the adhesion strength of WBPU-silane composite coatings as compared to that of bare WBPU coatings. Further, the water contact angle revealed that hydrophobic properties increase as the silane content incorporated into the WBPU matrix increases. This work provides a novel route for enhanced corrosion protection utilizing a bio-based polyol blend.

Degradable Waterborne Polyurethane with Flame Retardancy and High Mechanical Strength via Synergy of Hydrogen Bonds

Waterborne polyurethane (WPU) with degradability is critical to the environment. Especially, degradable WPU with high mechanical strength and flame retardancy features various important industrial applications, while the increased flame retardancy often leads to reduced mechanical strength. Herein, we report the simultaneous realization of degradability, flame retardancy, and high mechanical strength into one design. The tensile strength of degradable WPU is up to 39 MPa and can be tuned by the ratio of soft segments. The strong synergistic hydrogen bond interactions of different components confirmed by FTIR and XPS as well as molecular dynamics simulation are responsible for the excellent mechanical strength. Moreover, WPU achieves the highest “V0” level of flame retardancy. The simultaneous realization of the stress of 35 MPa and a limiting oxygen index of 27.55% is obtained by changing the flame retardant contents. Importantly, WPU possesses degradability with a mass loss rate of 37% after natural burial in soil for 3 months. The dense WPU coatings can be adhered to different substrates and also have good anticorrosion ability. This work provides a promising strategy for high-performance biodegradable materials and expands the industrial application of polyurethane.

Waterborne polyurethane composite coatings as UV-light converter and directional infrared light barrier for light and heat management in greenhouse

Light and heat management in greenhouses are important for crops yield and quality. Here, we created waterborne polyurethane (WPU) composite coatings for greenhouse films, which can act both as ultraviolet (UV) light down-conversion and directional infrared light barrier for the light and temperature conditions in pepper greenhouses. Rare-earth organic complexes (REOC) that can convert UV light to red light were mixed with WPU by ball-milling. The REOC nanoparticles presented good dispersion in WPU coatings, which were determined by atomic force microscopy, and the coating with 1 wt% REOC still remained comparably high transparency. The luminescence properties were increased with REOC loadings. The coatings with REOC showed lower infrared (IR) light transmittance and higher IR light reflectance than those of the pristine film and WPU coatings. The preferable location of the composite coatings on inner side of films acted as IR light barrier and facilitated the maintenance of heat inside the greenhouses, increasing the temperature. Simulation was performed to testify the temperature increase using IR barrier covered layer. Small and big greenhouses with different films were built and the temperatures were recorded. The results show that the film containing REOC increase the temperature in the greenhouses by >2 °C compared to traditional agricultural films. Finally, due to light conversion and IR light barrier, the yields of green peppers can be increased by 35 %. The mass of single fruits can also be increased by 8 g.

The functionalization of film materials for grafting WPU with polystyrene hollow microspheres

Surface coating expresses the most appealing quality of a product. Multifunctional waterborne polyurethane (WPU) coatings with thermal insulation, matting, UV resistance and hydrophobicity are one of the targets of advanced materials manufacturing. In this study, polymer hollow microspheres with polyhydroxy groups on the surface, called HM-OH, were prepared by emulsion polymerization. Through TEM and SEM observations, it was confirmed that the HM-OH has a cavity (approximately 207 nm in diameter) with an average diameter of 726 nm. The relative content of the hydroxyl group on its surface is 9.1 %, and it has good dispersibility and thermal stability. A multifunctional low-gloss WPU nanocoating was prepared by grafting onto HM-OH, called WPU-g-HM. The emulsion stability test showed that WPU-g-HM basically solved the problem of blending incompatibility between HM and WPU, and the tensile strength and elastic modulus of WPU-g-HM reached their best values when the amount of HM-OH was 2.5 %. UV–vis testing showed that the HM-OH made the prepared nanocoating have unique UV shielding properties. Furthermore, it was observed by SEM and AFM that the rough surface morphology of the nanocoating was the main reason for the decrease in the gloss of WPU-g-HM compared with WPU. The thermal conductivity of WPU-g-HM was 0.0347 W/(K·m), and the water contact angle was 100.3°, which indicated that the multifunctional WPU composite coating was successfully prepared.

A Review of Waterborne Polyurethane Coatings and Adhesives with Polyester Polyol from Poly(Ethylene Terephthalate) Waste

A Review of Waterborne Polyurethane Coatings and Adhesives with Polyester Polyol from Poly(Ethylene Terephthalate) Waste

Boron-Based Mildew Preventive and Ultraviolet Absorbent Modification of Waterborne Polyurethane Coatings on Laminated Bamboo

In order to improve the outdoor exposure performance of laminated bamboo, boric acid/borax and UV absorbents, including triazole (UV1130), nano–TiO2, and nano–SiO2, were used to modify waterborne polyurethane (WPU) coatings, respectively. The physical and chemical properties of the coatings with and without modification were evaluated by adhesion strength, contact angle, wear, and temperature-resistance experiments. The antimildew properties of the coatings were evaluated by the bacteriostatic zone method, and the pyrolysis characteristics were investigated through TG–FTIR analysis. The results showed that, when compared with the unmodified WPU coating, the coatings with different modifications had stronger wear resistance; the mass loss of the best C4 coating was only 0.0078 g, which was 0.0203 g less than that of the unmodified C0 coating. However, when compared to the unmodified coating, the wettability of the modified coating increased to different degrees, and the contact angle of the C4 coating with the most obvious effect was only 36.50°. During the curing process of the modified coatings, the UV absorbents and boric acid/borax would interact with the C–N, C–O, and C=O bonds in the coating and change the molecular structure of the WPU. The thermal stability of the coatings with different modifications was enhanced. The best result, a 76.27% weight loss, was observed in the modified coating with boric acid/borax and 1.0% nano–TiO2. Different modified coatings had a certain degree of control effect on Aspergillus Niger, and the reason for this was considered the combined effect of boric acid/borax and UV absorbents.

Preparation and corrosion resistance of KTNT–waterborne polyurethane coatings

In this study, titanate nanotubes (TNTs) were prepared through the hydrothermal method and then modified with γ-aminopropyltriethoxysilane (KH550) to obtain KTNTs with good dispersion properties. A KTNT–waterborne polyurethane (WPU) composite coating was prepared by blending KTNTs with WPU. Fourier transform infrared spectroscopy was used to characterize TNT compositions before and after modification. Thermogravimetric analysis and electrochemical impedance spectroscopy were used to test the thermal stability and corrosion resistance of the composite coating. The results showed that KH550 was successfully connected to the TNT surface. This improved the thermal stability and corrosion resistance of the KTNT–WPU coatings. The fastest thermal decomposition rate for the 0.5% KTNT composite coating was 2%/min lower than that of the pure WPU coating. At the same time, the impedance of the composite coating could reach 7.58 × 107 Ω cm2, the corrosion current density was 3.20 × 10−9 A/cm2 and the corrosion inhibition rate reached 99.87%. The composite coating had an effective corrosion protection time of 120 h, and the protective effect of the coating weakened when the immersion time exceeded 360 h.

Self-healing waterborne polyurethane coatings with high transparence and haze via cellulose nanocrystal stabilized linseed oil Pickering emulsion

Protection coatings with self-healing ability can significantly enhance their anti-corrosion properties and service life. In this study, self-healing waterborne polyurethane (WPU) coatings with high transparence and haze were facile fabricated via cellulose nanocrystal (CNC) stabilized linseed oil (LO) Pickering emulsion. Sustainable CNCs displayed outstanding emulsifying ability and stability to stabilize LO Pickering emulsion. The size of LO Pickering emulsion droplets decreases with the CNC concentration, while the emulsion fraction and surface coverage by CNCs increase with CNC concentration, leading to a more stable Pickering emulsion. The self-healing rates of WPU coatings at varied time, temperature, CNC and catalyst concentration were investigated. Higher temperature, larger emulsion droplets, and with driers employed as catalysts generally lead to faster self-healing rate. The WPU self-healing coatings displayed much better abrasion resistance and mechanical properties than pristine WPU due to the incorporation of CNCs. Moreover, the WPU self-healing coatings show a high transparence and haze due to light scattering, and their applications as coatings of lamp covers and glass to achieve uniform light distribution and privacy protection with high light transmission were further demonstrated.

Nanocellulose-reinforced polyurethane as flexible coating for cork floor

Cork materials have the property of elastic deformation under pressure due to their unique closed, porous, cell structure with thin cell wall; and they accordingly need a surface coating that matches their deformation during there being used as floor materials. However, traditional wood coatings are hard, brittle, and mostly suitable for stiff wood surfaces, which are difficult to be directly adapted to the requirements of flexible cork. Although waterborne polyurethane (WPU) has the advantage of property tailorability, its fully applicable to cork materials are still a challenge. Herein, this study utilized a simple physical blending of waterborne polyurethane and nanocellulose with high aspect ratio, to develop a high-strength coating that matches the elastic deformation requirements of cork materials. When both two kinds of nanocellulose, poplar wood nanocellulose (WCNF) with an aspect ratio of 800 and bacterial nanocellulose (BCNF) with an aspect ratio of 2000, was individually added into the WPU emulsion at 0.5 wt%, the tensile strength and elastic modulus of the nanocellulose-modified polyurethane coating increased by 48.58 % and 118.88 %, 54.50 % and 120.48 %, respectively, compared to those of the pure WPU coating (14.09 MPa and 312.74 MPa). It is notable that both the nanocellulose-modified coatings showed no signs of damage on the cork surface even they underwent continuous bending over 2000 cycles, which indicates their excellent flexural fatigue resistance. Interestingly, such nanocellulose-modified coatings maintain comparable transparency, gloss, adhesion, solvent resistance and even present slightly improved hardness and wear resistance than their pure WPU coatings. Overall, the two nanocelluloses are comparative to the modification of the coatings, both of which could match the elastic deformation requirements of cork materials. Therefore, the nanocellulose physically blended polyurethane technology provides a simple and effective solution for the design and property tailoring of flexible coatings for cork floor.

Improvement of Mechanical Properties and Solvent Resistance of Polyurethane Coating by Chemical Grafting of Graphene Oxide.

Waterborne polyurethane coatings (WPU) are widely used in various types of coatings due to their environmental friendliness, rich gloss, and strong adhesion. However, their inferior mechanical properties and solvent resistance limit their application on the surface of wood products. In this study, graphene oxide (GO) with nanoscale size, large surface area, and abundant functional groups was incorporated into WPU by chemical grafting to improve the dispersion of GO in WPU, resulting in excellent mechanical properties and solvent resistance of WPU coatings. GO with abundant oxygen-containing functional groups and nanoscale size was prepared, and maintained good compatibility with WPU. When the GO concentration was 0.7 wt%, the tensile strength of GO-modified WPU coating film increased by 64.89%, and the abrasion resistance and pendulum hardness increased by 28.19% and 15.87%, respectively. In addition, GO also improved the solvent resistance of WPU coatings. The chemical grafting strategy employed in this study provides a feasible way to improve the dispersion of GO in WPU and provides a useful reference for the modification of waterborne wood coatings.

Bio-Based Waterborne Polyurethane Coatings with High Transparency, Antismudge and Anticorrosive Properties.

Green and environment-friendly preparation are of the utmost relevance to the development of transparent antismudge coatings. To prepare a waterborne polyurethane (WPU) coating with antismudge property, it is challenging to balance the stability of dispersion and the antismudge property of coating. Herein, we prepare a transparent bio-based WPU coating grafted with a minor proportion of poly(dimethylsiloxane) (WPU-g-PDMS) using renewable castor oil, monocarbinol-terminated PDMS, hexamethylene diisocyanate trimer, and 2,2-bis(hydroxymethyl)propionic acid as raw materials. Effects of the dosage of monocarbinol-terminated PDMS, the curing temperature, and the curing time on the antismudge performance were studied. Results showed that rigorous stirring (3000 rpm) is necessary to obtain a stable WPU-g-PDMS dispersion with a storage time longer than 6 months. A high curing temperature (>160 °C) and a period of curing time (>1 h) are indispensable to obtain the excellent antismudge property because they would facilitate the grafted low-surface-tension PDMS chains to migrate from the interior to the coating surface. The facts that simulated contaminated liquids such as water, HCl solution, NaOH solution, artificial blood, and tissue fluid could slide off easily and cleanly, and marker ink lined on the coating surface could shrink, indicated that the WPU-g-PDMS coating has good antismudge properties, which could be self-compensated shortly after deterioration. Due to the high cross-linking degree caused by multifunctional polyol and isocyanate, the WPU-g-PDMS coating has high hardness and good anticorrosive performance. The antismudge functionalization and waterborne technology of bio-based polyurethane coatings proposed in this work could be a promising contribution to the green and sustainable development of functional coatings. This kind of WPU-g-PDMS coating is expected to protect and decorate electronic screens, vehicles, and buildings, especially endoscopes.

Properties of sodium molybdate-based compound corrosion inhibitor for hot-dip galvanized steel in marine environment

Abstract Sodium molybdate (Na2MoO4) was selected as the corrosion inhibitor, compounded with benzimidazole, in order to prolong the service life of the hot-dip galvanized steel (HDGS) in the marine environment in this article. XRD, SEM/FESEM and EDS were used to characterize the micro-morphology and elemental composition of HDGS. Immersion corrosion test, Tafel polarization and EIS test were carried out to study the effect of compound inhibitor on the corrosion resistance of HDGS in the marine environment. The best proportion of compound inhibitor was added to the self-made waterborne polyurethane coating (WPUC), aiming to evaluate its influence on the coating performance in the marine environment by immersion corrosion test and EIS test. The results showed that Na2MoO4, as a passivation type corrosion inhibitor, bounded Zn at the active sites of HDGS coupons and created structural defects. Benzimidazole, as an adsorption type corrosion inhibitor, was attracted by electricity and adsorbed at the structural defects. Under the premise of 1 wt% total content, the optimal ratio of Na2MoO4 & benzimidazole was 9:1 and the corrosion inhibition efficiency was 99.62%. The corrosion current density of HDGS in the simulated seawater with compound inhibitor was 5.650 × 10−8 A/cm2, while that of HDGS in the simulated seawater without compound inhibitor was 1.483 × 10−5 A/cm2. The WPUC containing compound inhibitor had a small decrease in corrosion resistance due to defects created by doping at the beginning of immersion, then the compound inhibitor would play an active role in the corrosion process to make more than double the service life of WPUC.

Anti-Fouling and Anti-Biofilm Performance of Self-Polishing Waterborne Polyurethane with Gemini Quaternary Ammonium Salts.

Biofilms are known to be difficult to eradicate and control, complicating human infections and marine biofouling. In this study, self-polishing and anti-fouling waterborne polyurethane coatings synthesized from gemini quaternary ammonium salts (GQAS), polyethylene glycol (PEG), and polycaprolactone diol (PCL) demonstrate excellent antibiofilm efficacy. Their anti-fouling and anti-biofilm performance was confirmed by a culture-based method in broth media, with the biofilm formation factor against Gram-positive (S. aureus) and Gram-negative bacterial strains (E. coli) for 2 days. The results indicate that polyurethane coatings have excellent anti-biofilm activity when the content of GQAS reached 8.5 wt% against S. aureus, and 15.8 wt% against E. coli. The resulting waterborne polyurethane coatings demonstrate both hydrolytic and enzymatic degradation, and the surface erosion enzymatic degradation mechanism enables them with good self-polishing capability. The extracts cyto-toxicity of these polyurethane coatings and degradation liquids was also systematically studied; they could be degraded to non-toxic or low toxic compositions. This study shows the possibility to achieve potent self-polishing and anti-biofilm efficacy by integrating antibacterial GQAS, PEG, and PCL into waterborne polyurethane coatings.

A Self-Matting Waterborne Polyurethane Coating for PVC Artificial Leather

A type of polyester-based self-matting waterborne polyurethane (ESMWPU) with an excellent matte effect of 0.8° and transmittance of 78.5% for PVC artificial leather was synthesized. The influence of synthesis parameters, including R value, crosslinking and hydrophilic group content, on coating gloss and transmittance was investigated. Meanwhile, the properties necessary for applying water-based resins to plasticized PVC were detailed. The results demonstrated that R value, crosslinking degree and hydrophilic group content synergistically decided the morphological changes of latex particles during their film-forming process in three aspects: particle stiffness, three-dimensional structure and particle size, respectively. With optimized parameters of R = 1.9, TMP = 2 wt% and DMPA = 1.75 wt%, ESMWPU latex particles stabilized their spherical shapes without collapsing in the film-forming process and created a rough surface, resulting in a matte effect. In terms of application performance, good wetting and adhesion for ESMWPU to a plasticized PVC surface was achieved with a 2 wt% leveling agent load. Moreover, due to the high cohesion energy of ester bonds and intermolecular hydrogen bonds, this type of polyester-based ESMWPU also depicted admirable thermal adhesion resistance. All aforementioned results distinctly demonstrate a feasible yet promising paradigm for applying ESMWPU on PVC artificial leather.