Waterborne Polyurethane Coatings Research Articles

Facile synthesis of copper/ reduced single layer graphene oxide as a multifunctional nanohybrid for simultaneous enhancement of antibacterial and antistatic properties of waterborne polyurethane coating

Development of a surface with simultaneous antibacterial and antistatic properties is necessary for some special environments like operating rooms and high-tech industries. Multifunctional copper/ reduced single layer graphene oxide (Cu/ rSLGO) nanohybrid has been developed to induce these simultaneous properties in waterborne polyurethane coatings (WPU). The Cu/ rSLGO nanohybrid was synthesized through the in-situ reduction of Cu+2 ions and single layer graphene oxide nanosheets without using any secondary reducing reagent. FESEM, TEM, FTIR, XRD, EDX, UV–vis, and TGA analyses were used to characterize morphological, structural, crystallographic, and thermal properties of the prepared nanohybrid, and the modified WPU coatings were studied by SEM, AFM, contact angle, TGA, DLS, and mechanical properties analyses. The results of the colony counting method exhibited that the Cu/ rSLGO nanohybrid has a strong antibacterial activity with 92% and 80.66% of the loss of viability for S. aureus and E. coli bacteria, respectively. Moreover, adding 3%wt Cu/ rSLGO nanohybrid and the creation of sufficient conductive pathways throughout the WPU matrix lead to the electrical surface resistance of the modified coating reaches 4.8 × 10+9 Ω/sq which falls into the electrical surface resistance range of commercial antistatic coatings. Furthermore, utilizing the Cu/ rSLGO in the WPU coating not only provided thermal resistance but also, enhanced its mechanical properties compared with the coating made of pristine waterborne polyurethane.

Coaxial electrospun fibres with graphene oxide/PAN shells for self-healing waterborne polyurethane coatings

Encapsulation of linseed oil, a self-healing agent, in graphene oxide reinforced PAN shells was realized by coaxial electrospinning. The electrospun fibres were embedded in waterborne polyurethane coatings to prepare self-healing coatings. When cracks/microcracks occurred and caused the rupture of the core-shell fibres, the core material, linseed oil, would be released and filled in the cracks. Linseed oil will react with oxygen and solidify, so that the cracks/microcracks can be healed autonomously. The addition of graphene oxide in the PAN shells increased the thermal stability of the shells. The thickness of the fibre shells was 30–50 nm, suggesting that the microcracks in submicron-scale may trigger the self-healing process. The loading capacity of the fibres was about 45 wt%. The self-healing properties of the waterborne polyurethane coatings were improved with increasing content of the core-shell fibres.

Polyhedral Oligomeric Silsesquioxane (POSS) as Reinforcing Agent for Waterborne Polyurethane Coatings on Wood

Polyhedral oligomeric silsesquioxane (POSS) was added as a reinforcing agent in waterborne polyurethane (WPU)-based coatings to improve their properties. The morphology, structure, thermal stability as well as mechanical properties of the resulting WPU and WPU/POSS hybrid films were investigated. The good compatibility of POSS in the WPU matrices was demonstrated by transmission electron microscopy. Furthermore, Fourier-transform infrared spectroscopy analysis (FTIR) suggested the successful bonding of POSS and WPU matrices. The thermal stability of WPU/POSS hybrids was improved than that of pure WPU according to thermal gravimetric analysis (TGA). The results also revealed the enhancement of the pencil hardness and abrasion resistance of the hybrid films compared with WPU. However, the pull-off adhesion slightly decreased from Grade 0 to Grade 2.

Weathering Resistance of Waterborne Polyurethane Coatings Reinforced with Silica from Rice Husk Ash.

Waterborne polyurethanes (WPUs) are interesting materials for coatings when compared to solvent-based polyurethanes, once that reducing the concentration of volatile organic compounds that are harmful for human health and the environment. However, the WPU has low weathering resistance. In order to improve this behavior among others properties, inorganic fillers has been added in these systems. SiO2 particles from various sources, mainly, from agro-industrial waste, as rice husk has attracted the scientific and technological interest. In this study, the accelerated weathering essay was performed in waterborne polyurethane (WPU)/ silica (from rice husk ash) composites in order to evaluate the thermal and physical changes in these materials. These composites were prepared by two distinct methods: in situ polymerization and blending method. The highest resistance to thermal degradation and to accelerated weathering was reached with WPU/silica composites obtained by blending method due the interactions between SiO2 particles and the polymer matrices. Blending method for preparation WPU/silica composites proved to be a simpler and faster method, with no drawback for large scale application.

Self‐healing waterborne polyurethane coating by pH‐dependent triggered‐release mechanism

ABSTRACTIn this study, effect of high‐loaded silica capsules with corrosion inhibitor on thermal degradation and self‐healing properties of waterborne polyurethane (WPU) was investigated. Silica capsules were synthesized using an oil in water (O/W) microemulsion and WPU was prepared via the prepolymer method. Assembled capsules demonstrated pH dependent release of their core. Incorporating silica capsule as an inorganic component resulted to improve thermal and barrier properties of WPU coatings. WPU coating with 1% silica capsules demonstrated better barrier quality in corrosive media and adding more than that resulted a rapid deterioration in barrier properties. Furthermore, such coatings possess an excellent adhesive strength with steel substrate. Electrochemical impedance spectroscopy was used in corrosion monitoring and healing procedure. Moreover, capsule morphology and thermal degradation of the WPU coating has been investigated separately by scanning electron microscopy and thermal gravimetric analysis. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47082.

Eco-friendly waterborne coating from bio-based polyester amide resin

The vegetable oil-based waterborne polyurethane coatings have gained significant interest due to low volatile organic compounds, and hence, this has been considered as a proper substitute to the commonly used solvent-borne coating systems. In the present work, we have developed the polyurethane coatings from diethanolamide of fatty acid and dicarboxylic acid (sebacic acid and succinic anhydride)-based poly(esteramide) resin as a diol along with 2,2′-dimethylol propionic acid and isophorone diisocyanate. The chemical structure of bio-based diol and PU coatings was elucidated by FTIR and 1H NMR spectroscopy. The polyurethane dispersions (PUDs) prepared were analysed by particle size analysis and stability. The mahua oil-based PUDs were coated on the metal panels and the cured material obtained was characterized by the physico-mechanical, chemical resistance and the thermal properties which were compared with the petroleum resource-based PUDs. The PUD coatings showed good physico-mechanical properties, chemical resistance and thermal stability. Hence, the dispersion prepared from bio-based diols may find application as eco-friendly coatings.

Preparation and corrosion performance of healable waterborne polyurethane coatings containing isophoronediisocyanate loaded silica capsules

Abstract The preparation and application of silica encapsulated isophoronediisocyanate (IPDI) as the active healing agent in the coatings fabricated by using of waterborne polyurethane (WPU) is reported. Prepolymer method was used to synthesize WPU, and IPDI loaded silica capsules (SCs) were prepared via interfacial emulsion polymerization. An almost complete recovery of scratches on the coatings containing synthesized SCs loaded with IPDI has been observed. Incorporating of the IPDI loaded SCs not only grants self-healing properties but also improves the thermal stability of WPU coatings. Scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and thermal gravimetric analysis (TGA) were used for detection of healing procedure and monitoring of thermal degradation as well as SCs loading content.

Preparation and Properties of Split Microfiber Synthetic Leather

A split microfiber synthetic leather using split microfiber nonwoven as the base and waterborne polyurethane (WPU) coating as the polymer coating was prepared by a dry transfer-coating method. First, the nylon/polyester (N/P) split microfiber nonwoven was manufactured, and the structure and properties were investigated. FESEM analysis indicated fiber diameter size was between 2.2~5.5 μm, and performance attaributes met the demands of textiles-nonwovens for synthetic leather. Then the effect of coating-forming temperature, foaming agent concentration and foaming ratio on the structure and performance of WPU coatings were systematically studied. Finally, the structure and properties of the split microfiber synthetic leather were analyzed. The results showed that the split microfiber synthetic leather arranged in a three-layer configuration, and its air permeability, tensile strength, elongation at break, tear strength, peeling strength and creasy recovery angle were better than knitted synthetic leather and real leather.

Thermostability and flame retardance of green functional two-component waterborne polyurethane coatings with nanoparticles

A new kind of green and functional two-component flame-retardant waterborne polyurethane and its coating were synthesized through adding polyurethane polyol dispersions, hydrophilic nanoTiO2 and hydrophilic curing agent. The properties and analysis were characterized via FTIR, laser particle analyzer, rheometer, TEM, TGA, TGA-FTIR, LOI tester, SEM, UV–vis spectrum, water and solvent resistance. The results showed the tensile strength counld reach 22.3 MPa. And the nanoTiO2 delayed speed of thermal decomposition to improve thermostability of two-component waterborne polyurethane. Larger quantities of hydrophilic nanoTiO2 did not produce a larger unbroken carbon yield surface or thicker carbon layers, but effectively produced a condensed phase flame-retardant effect with OP550 during burning. Besides, LOI and UL-94 also reached over 29.4% and V–0 respectively. The UV and visible light shielding noticeably increased with the adding nanoTiO2. The 0.5% content of nanoTiO2 had the optimal properties in green and functional two-component waterborne polyurethane coatings.

Enhancement of thermal conductivity of PEG-PPG-based waterborne polyurethane coating by incorporating ordered polyethylene glycol fragment

With the respect to research the effects of polyethylene glycol (PEG, Mw = 1000), an ordered hydrophilic fragment, on thermal conductivity of waterborne polyurethane coatings (WPUCs), the PEG–polypropylene glycol (PPG, Mw = 2000)–based WPUCs (PEG-PPG-based WPUCs) were synthesized with different combinations of PEG and 2,2-bis(hydroxymethyl)propionic acid (DMPA). The total amount of hydrophilic agent was fixed. Experiment found that the PEG-PPG-based WPUC synthesized with 13% PEG and 2% DMPA showed a highest thermal conductivity (∼0.675 W/m‧K). The phase separation, crystallinity and thermal conductivity were increased with the increasing of PEG. A number of characterizations were carried out through FTIR, TG, DSC, DMA, AFM and XRD to study the association of chemical structures and thermal conductivity at the basis of multiple combinations. The results showed that the ordered PEG fragments incorporated into WPUCs could increase the crystallinity and thermal conductivity, which was owing to the more ordered structures formed in hard phase and soft phase, and that facilitated the phonon propagation in free pathways, as a result.

Weathering resistance of thermally modified wood finished with coatings of diverse formulations

Thermal modification processes significant affect the chemical configuration of the wood matrix improving moisture-related properties and material durability. In addition, the distinctive dark tones of heat-treated timber increase the economic value of several light-colored species. However, these treatments alter the substrates and it could influence the performance of coating products, necessary to maintain the surface features in certain end-use sectors. Ash wood (Fraxinus excelsior L.) samples industrially treated at 192 °C, 202 °C and 212 °C were coated with decorative waterborne polyurethane and industrial UV-hardened coatings. Afterwards, the samples were subjected to accelerated weathering. The resulting surface topography was assessed with a 3D scanner and a profilometer, revealing slight changes in the texture. Color changes were quantified with hyperspectral imaging by generating surface color maps in CIE Lab coordinates. The results indicate acceptable photostability of thermally modified wood. Changes in wettability, surface free energy, work of adhesion and cohesion were determined by contact angle. Higher hydrophilicity after weathering was observed, but with an acceptable overall performance. At the same time, polar and dispersive shares were redistributed depending on the applied coating. It was demonstrated that heat-treated wood could be an optimal substrate for innovative wood-based products, suitable for use outdoor and exposure to changing weather conditions.

8-Hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) based high fluorescent, pH stimuli waterborne polyurethane coatings

8-Hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS), a water-soluble pyrene dye, was used to develop highly fluorescent waterborne polyurethane (WPU) by physical dispersion in WPU matrix. The presence of negatively charged sulfonate ions in HPTS moiety assisted in homogeneous dispersion of HPTS in WPU matrix. The optical properties of HPTS-WPU emulsion and films were characterized by UV-Vis and PL spectroscopy and observed to exhibit high fluorescence property both in emulsion state as well as in solid state even at very low concentration. The fluorescence intensity was found to increase with increasing weight % of the HPTS dye in WPU matrix. Further, pH sensing behavior of these films was also investigated by exposing to trifluoroacetic acid (TFA) vapor (pka = 0.23) and ammonia (NH3) vapor (pkb = 9.25). Observations revealed that HPTS retained not only its highly green fluorescent nature in WPU matrix but also exhibited pH sensing behavior. The overall analysis suggested that HPTS-WPU could be used to develop an environmentally friendly high fluorescent smart coatings and textiles inheriting real-time pH sensing property.

Preparation and Characterization of Efficient Flame-Retardant and Thermostability Two-Component Aqueous Varnish Coatings

A method to prepare efficient flame-retardant two-component waterborne polyurethane coatings by combining polyepichlorohydrin, polypropylene glycol, isocyanate, chain-extender and curing agent was developed. The structures and properties of latexes and films were determined by grain size, viscosity, FTIR, differential scanning calorimeter, mechanical properties, thermogravimetry, flame-retardant and applicant measurements. The results illustrated that the more the hydrated double electric layer of two-component varnish coatings latex particles was, the better the resulting mechanical and chemical stability was. The grain size increased and viscosity decreased as stoichiometric ratio of –OH to –NCO became larger. The lower T gs and higher T gh were attributed to the polar extender which hindered aggregation of soft segment in order to accelerate the more drastic movement of the polymer chain. The nonflammability of char layer was weakened as stoichiometric ratio of –OH to –NCO became larger, thus reducing flame-retardant and thermal stability. The limit oxygen index values of all materials exceeded 30%. The two-component varnish coatings had a pretty good water and solvent resistance.

Waterborne Polyurethane Coatings with Covalently Linked Black Dye Sudan Black B.

Colored waterborne polyurethanes have been widely used in paintings, leathers, textiles, and coatings. Here, a series of black waterborne polyurethanes (WPUs) with different ratios of black dye, Sudan Black B (SDB), were prepared by step-growth polymerization. WPU emulsions as obtained exhibit low particle sizes and remarkable storage stability at the same time. At different dye loadings, essential structural, statistical and thermal properties are characterized. FTIR (fourier transform infrared) spectra indicate that SDB is covalently linked into waterborne polyurethane chains. All of the WPUs with covalently linked SDB show better color fastness and resistance of thermal migration than those with SDB mixed physically. Besides, WPUs incorporated SDB covalently with different polymeric diols, polytetramethylene ether glycol (PTMG), polypropylene glycol (PPG), poly-1, 4-butylene adipate glycol (PBA) and polycaprolactone glycol (PCL), were prepared to obtain different properties to cater to a variety of practical demands. By a spraying method, the black WPUs can be directly used as metal coatings without complex dyeing process by simply mixing coating additive and other waterborne resins, which exhibit excellent coating performance.

Synthesis and Characterization of Multifunctional Two-Component Waterborne Polyurethane Coatings: Fluorescence, Thermostability and Flame Retardancy.

Fluorescent and flame-retardant two-component waterborne polyurethane coatings were synthesized using 1,5-dihydroxy naphthalene, a halogen-free polyphosphate and a hydrophilic curing agent, and their properties were systematically characterized. The average particle sizes and zeta potential values were below 170 nm and −30 mV. Meanwhile, the multifunctional two-component waterborne polyurethane coatings had strong fluorescence intensities. When comparing with the coatings with 0.5 wt % 1,5-dihydroxy naphthalene, the coatings with 1.0 wt % 1,5-dihydroxy naphthalene had a stronger microphase separation. Interestingly, the thermostability of the multifunctional coatings was remarkably improved through 1.0 wt % 1,5-dihydroxy naphthalene, and besides it belonged to nonflammable materials. Additionally, all of the coating films passed the solvent resistance testing. These samples with different amounts of 1,5-dihydroxy naphthalene are environmental friendly, especially applications that require transparent and fluorescent coatings.

Self-assembled graphene oxide microcapsules in Pickering emulsions for self-healing waterborne polyurethane coatings

A self-assembly process was employed to prepare the graphene oxide microcapsules (GOMCs), containing linseed oil as the healing agent. The nanometer-thick shells of GOMCs were built by the liquid crystalline assembling of graphene oxide (GO) sheets, forming at liquid–liquid interface in Pickering emulsions. The GOMCs were embedded into waterborne polyurethane matrix, enabling the facile fabrication of self-healing composite coatings on hot-dip galvanized steel surfaces. The inclusion of GOMCs in the composite coatings not only imparted self-healing properties to the coatings, but also improved their anticorrosion properties because of the physical barrier of the GO shell, leading to much better survival to the weather/marine environment and surface wear.

Effect of functionalized multiwalled carbon nanotubes on weather degradation and corrosion of waterborne polyurethane coatings

A series of waterborne polyurethane/functionalized multiwalled carbon nanotube (WBPU/f-MWCNT) nanocomposite dispersions was prepared using three defined concentrations of 0.5, 1.0 and 2.0 wt% carboxyl functionalized multiwalled carbon nanotubes (f-MWCNTs). All dispersions were coated on mild steel and exposed under natural weather condition for a maximum of 365 days. Both exposed and unexposed coatings were characterized by potentiodynamic polarization (PDP) and X-ray photoelectron spectroscopy (XPS) analyses. The pristine WBPU coating showed slight degradation and corrosion protection. Inclusion of a higher content of f-MWCNTs significantly improved both the degradation and corrosion protection efficiencies of the coatings. Maximal degradation and corrosion protection was observed when 2.0 wt% f-MWCNT was mixed with WBPU for all of the coatings.

Preparation and properties of high storage stability polyester polyol dispersion for two-component waterborne polyurethane coating

A new type of polyester polyol dispersion with good storage stability was prepared based on a hydrophilic monomer 5-sodium sulfodimethyl isophthalate (5-SIPM), and frequently-used monomers such as neopentyl glycol (NPG), dimethyl terephthalate (DMT), dimethyl phthalate (DMP) and trimethylolpropane (TMP) by the transpolycondensation and polycondensation method. The polyester polyol dispersion was characterized by FTIR and GPC. The proper content of these monomers were determined by the performance of polyester dispersion: the content of TMP was 15wt%, the content of NPG was 7.5wt% and the hydrophilic monomer 5-SIPM content was 5wt%. Two-component waterborne polyurethane (2K-WPU) coatings were prepared by Bayhydur® XP2487/1 and polyester polyol dispersions, which were stored before and after at 40 ° for 6 weeks, the prepared films have no differences in drying time, adhesion, pencil hardness, gloss and chemical resistance, the result also reveals that the polyester polyol dispersion have excellent storage stability resistance.

Fabrication and evaluation of Rb2Co(H2P2O7)2·2H2O/waterborne polyurethane nanocomposite coating for corrosion protection aspects

Here we investigate the influence of new acidic pyrophosphate (Rb2Co(H2P2O7)2·2H2O) (DP) incorporation in waterborne polyurethane (WBPU) coatings on the corrosion protection efficiency of WBPU coatings for carbon steel in 3.5% NaCl solution.

Antibacterial sustained-release coatings from halloysite nanotubes/waterborne polyurethanes

Abstract Natural and safe antibacterial nanoparticles based on carvacrol loaded halloysite nanotubes and their waterborne polyurethane nanocomposite coatings with antibacterial and antibiofilm properties are presented. Halloysite nanotubes are natural clay nanoparticles with a hollow tubular structure that allows loading and sustained release of active agents. In this study, halloysite nanotubes were efficiently loaded with carvacrol, the active agent of essential thyme oil. Encapsulated carvacrol molecules were demonstrated to be released from halloysite nanotubes in a sustained manner over one week and effectively inhibit the growth of a pool of pathogenic microorganisms. Carvacrol loaded halloysite nanotubes were further investigated as antibacterial nanofillers in polymeric nanocomposites by incorporating them into waterborne polyurethane coatings. Polyurethane nanocomposite films containing 5 wt.% carvacrol loaded halloysite nanotubes showed uncompromised thermal and mechanical stability as compared to neat polyurethane films. Carvacrol/halloysite nanotubes/polyurethane films demonstrated sustained release of carvacrol and antibacterial activity on representative pathogens, Aeromonas hydrophila , as evidenced by growth inhibition in agar diffusion assays and reduction in bacterial count upon exposure to nanocomposite films. Furthermore, these nanocomposite films inhibited bacterial colonization on their surfaces at least for two days demonstrating their applicability as anti-biofilm surface coatings. Composed of safe and natural components, the sustained-release antibacterial coatings presented here have strong potential for being widely utilized to prevent and mitigate bacterial infections on materials surfaces without raising toxicity concerns.