Polyurethane Urea Coatings Research Articles

Preparation and characterization of solvent-free anti-corrosion polyurethane-urea coatings

Metal corrosion can cause severe damage to metal facilities, leading to huge economic loss. Anti-corrosion coating is considered to be effective and economic for the protection of metal facilities. Herein, a series of polyurethane-urea coatings were prepared with aromatic isocyanate, amino terminated polyether, castor oil-based polyol and polyaspartic resin as reactants and conductive mica powders as filler. The effect of isocyanate index on the chemical structure, static conductivity and corrosion resistance of the polyurethane-urea coatings were studied, and the micromorphology of the coating layers were observed. With the increase of isocyanate index, the cross-linking degree of the coating increased, while the compactness and electrostatic conductivity decreased, which was caused by the generation of carbon dioxide bubbles in the coating layer. Electrochemical impedance spectroscopy and salt spray test indicated that as the isocyanate index increased, the anti-corrosion ability of the polyurethane-urea coating on the flawless area increased, but that on the defect area decreased. The polyurethane-urea coatings prepared with isocyanate index of 1.0-1.1 possessed good corrosion resistance and electrostatic conductivity. The findings conceivably provided a new strategy to prepare solvent-free anti-corrosion coatings for the protection of metal and metallic facilities and promote the rapid development and practical application of anticorrosive materials.

Synthesis and characterization of castor oil-based branched polyols from renewable resources and their polyurethane-urea coatings

The chemical modifications of castor oil (CO) to develop branched polyols and their polyurethane-urea coatings have been investigated. For this purpose, castor oil-based branched polyols (COBPs) were synthesized from CO by modifying with succinic anhydride followed by reaction with hydroxyl group moieties like petrochemical-based pentaerythritol, trimethylolpropane and bio-based glycerol. The COBPs were characterized by using Fourier transform infrared, 1H and 13C nuclear magnetic resonance spectroscopies, gel permeation chromatography and differential scanning calorimetry. These COBPs were further urethanized with isophorone diisocyanate at OH/NCO ratio of 1:1.6 to get the isocyanate-terminated polyurethane prepolymers. The surplus isocyanate groups of the prepolymer were cured with atmospheric moisture at ambient temperature condition to form uniform film with fast surface drying. The thermo-mechanical, viscoelastic and swelling properties were evaluated for the cured coating films. Properties have been discussed from the viewpoint of branched network and also the urethane segment present in the structure. The glass transition temperatures of the coating films were found to be in the range of 32–64°C. The modified castor oil coating films show better thermo-mechanical and viscoelastic properties in comparison with control (unmodified castor oil) coating films. This work delivers an effective and promising way to synthesize branched moieties in plant oil-based high performance coatings.

Surface morphology of chlorine and castor oil-based polyurethane–urea coatings

The present work deals with surface properties of chlorine containing polyurethane–urea (PU–urea)-coating films. First, isocyanate-terminated pre-polymers were synthesized using castor oil as renewable resource, isophorone diisocyanate, and different weight percentages of 2-chloroethanol and 2,2,2-trichloroethanol. The resultant isocyanate-terminated pre-polymers were cured under atmospheric moisture to obtain chlorine containing PU–urea coatings. The surface properties of the coating films were characterized using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, scanning electron microscopy, and X-ray diffraction. All characterization techniques suggest that the presence of chlorine species on the surface results in different surface properties when compared to control PU–urea (without the chlorine group)-coating film surface. The viscoelastic, swelling, and contact angle (CA) properties were studied for the prepared coating films. The glass-transition temperatures (Tg) were obtained in the region 29.2–35 °C for the coating films. Tg increased by increasing the chlorine content in polyurethane-coating formulations. The CA for the coating films was found to be in the range of 76°–64° and these properties were found to be decreased with increase in the weight percent content of the chlorine moiety in the final coating formulation. Similarly, the higher chlorine content-coating films have shown more water uptake properties. The overall comparative results indicate that the chlorine containing PU–urea-coating films have different surface-coating properties and these depend upon the chlorine content in the final coating formulation as compared with PU–urea surfaces.

T-Butyl-Oxycarbonylated Diamines as Building Blocks for Isocyanate-Free Polyurethane/Urea Dispersions and Coatings.

t-Butyl-oxycarbonylated diamines ("di-Boc-carbamates") are investigated as dicarbamate monomers for diamine/dicarbamate polymerizations. Polyureas (PUs) and polyurethanes (PURs) with high molecular weights are prepared from stoichiometric polymerizations of diamines or diols with N-N'-di-t-butyl-oxycarbonyl isophorone diamine (DiBoc-IPDC) using KOt-Bu as a catalyst, while gelation is observed when an excess of DiBoc-IPDC is used with respect to the diamines or diols. Stable dispersions are obtained from PUs and PURs with 3,3'-diamino-N-methyldipropylamine (DMDPA) as internal dispersing agent. The corresponding PU-based coatings exhibit superior mechanical properties and solvent resistances compared to the polyurethane urea coatings synthesized from diols, DiBoc-IPDC, and DMDPA.

One-pot synthesis and physicochemical properties of high functionality soy polyols and their polyurethane-Urea coatings

This paper explores a new approach for the synthesis of highly functional soy polyol (SP) from soybean oil (SBO). A two-step continuous route has been reported for the development of renewable polyols and their polyurethane/urea (PU-Urea) coatings. The methodology includes epoxidation of oils and subsequent hydroxylation to produce polyols. The SBO and SP were characterized by different spectroscopic techniques such as 1H and 13C nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy, Gel permeation chromatography (GPC), Differential scanning calorimetry (DSC) and Thermogravimetric analysis (TGA), and rheological properties were also determined. Through the present approach, we were able to achieve hydroxyl number for SP as high as 231.3mg KOH/g. Additionally, the relative conversion of epoxide value as 0.001% and iodine value under 1.35 (g of I2 100/g) are superior to the past reports. Different PU-Urea coatings obtained by utilization of the high functionality SP, exhibited excellent thermo-mechanical and solvent resistances. It was found that the molecular design of polyisocyanate and functionality of polyol plays an important role on performance properties of the coatings. The coatings were also evaluated for their in-vitro degradation, contact angle and chemical resistance properties. We observed high glass transition (Tg 171.8°C), superior cross-linking density of the PU network, chemical resistance and lower degradation rates. The present work can provide an insight on the design and development of high functionality bio-polyols and their PU-Urea coatings.

Functional polyurethane–urea coatings from sulfur rich hyperbranched polymers and an evaluation of their anticorrosion and optical properties

Solvent free, one pot, multistep synthesis of sulfur rich hyperbranched polyols (SHBPs). SHBPs yielded excellent corrosion resistant, transparent polyurethane–urea coatings.

Sustainability by Converting Waste Polyurethane Foam into Superior Polyurethane Urea Coatings

Recycling is a crucial area of research in Green Polymer Chemistry and developments in recycling are driven by environmental concerns, interests in sustainability and desire to decrease dependence on petroleum based materials. Sustainability refers to the development that meets the needs of present without comprising the ability of future generations. Polyurethane foams (PU) are widely used due to their light weight and superior heat insulation as well as good mechanical properties. However, large quantities of polyurethane foam are discharged during manufacturing/ processing as a waste and hence recycling of PU foam is necessary. In present study polyurethane foam is reacted with an alkanolamines in presence of a catalystin conventional as well as microwave method, but microwaves proved to be fast to depolymerise polyurethanes foam as compared to conventional method. The rate of reaction could be made identified by comparing the hydroxyl values of the two systems. The hydroxyl value increases as the time and microwave power increases. Further the depolymerised product with specified hydroxyl and amine groups is further cured with isocyanates for coating application and the coating formed is evaluated for physical, mechanical and chemical tests.

Click Chemistry Engineered Hyperbranched Polyurethane–Urea for Functional Coating Applications

This article reports a facile route for the synthesis of different generations of 1,2,3-triazole-rich hyperbranched polyether polyols using click chemistry and extends their application for the development of moisture-cured polyurethane–urea coatings. Initially, three generations of chlorinated hyperbranched polyether polyols were synthesized by ring-opening polymerization of epichlorohydrin with trimethylolpropane in different mole ratios. These chlorinated polyols on continuous treatments with sodium azide and propargyl alcohol result in three generations of 1,2,3-triazole-rich hyperbranched polyether polyols. Furthermore, these different generations of polyols were reacted with 1-isocyanato-4-[(4-isocyanatocyclohexyl) methyl] cyclohexane (H12MDI) at OH:NCO ratio of 1:1.2 to obtain −NCO-terminated triazole-rich hyperbranched polyurethanes, which were subjected to curing under atmospheric moisture to obtain hyperbranched polyurethane–urea coatings. The coatings showed considerable enhancement in thermal stability, glass transition temperature, and corrosion resistance properties with an increase in generation number. All three generations of coating films show excellent resistance toward various bacterial and fungal attacks.

Synthesis and characterization of triazole rich polyether polyols using click chemistry for highly branched polyurethanes

The present work describes development of moisture cured polyurethane–urea coatings based on 1,2,3-triazole rich polyether polyols. In this paper, two polyether polyols were synthesized by using 1,3-dipolar azide–alkyne cycloaddition reaction and they were named as PL-1 and PL-2 where PL-1 is 9 terminal hydroxyl groups and PL-2 is 6 terminal hydroxyl groups. These polyols were reacted with 4, 4′-diisocyanatodicyclohexylmethane (H12MDI) at OH:NCO ratio of 1:1.2 in order to obtain isocyanate terminated polyurethane prepolymers. The resulted prepolymers were casted on tin foil and cured under atmospheric moisture in order to get completely cured polyurethane–urea free films. The free films were characterized by using Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA) techniques. The TGA and DMTA results showed that these films have good thermal and mechanical stability. Anti-microbial studies proved that these polyurethane films show good resistance towards different bacterial and fungal attacks. These polymers were also coated on mild steel panels in order to evaluate corrosion resistance properties by using salt spray and electro chemical polarization studies.

Development of moisture cure polyurethane–urea coatings using 1,2,3-triazole core hyperbranched polyesters

This article reports the development of moisture cure polyurethane–urea coatings. The coating has been developed using different generations of novel 1,2,3-triazole core containing hyperbranched polyester polyols (THBP). For the synthesis of THBP, the core molecule, tetra hydroxyl-terminated di-triazole (THTD), has been synthesized by click reaction involving ethylene diazide and 2-butyne-1,4-diol. The polycondensation reaction between the core THTD and 2,2-bis (hydroxymethyl) propionic acid (Bis-MPA) at different mole ratios has been used to get first (THBPG-1), second (THBPG-2), and third (THBPG-3) generations of triazole core hyperbranched polyesters. The structural investigations of these THBPs have been carried out by 1H NMR, 13C NMR, and FTIR spectroscopy. The different generations of THBPs were further reacted with 1-isocyanato-4-[(4-isocyanatocyclohexyl) methyl] cyclohexane (H12-MDI) at OH:NCO ratio of 1:1.2 to get –NCO terminated triazole core hyperbranched polyurethanes. They were cured under atmospheric moisture to get hyperbranched polyurethane–urea coatings and were named as THBPUG-1, THBPUG-2, and THBPUG-3. FTIR has been used to confirm the formation of polyurethane coatings. The TGA and DMTA have been used to determine the thermal stability and dynamic mechanical properties of the coatings, respectively. The corrosion resistance properties of the coatings have been studied by salt spray and electrochemical test. The coatings were also evaluated for microbial resistance. The results indicate that the thermal stability, glass transition temperature, and corrosion resistance properties increase with an increase in generation number of THBPs used for coating development. All three generations of coating films show excellent antimicrobial activity. Based on overall combined structure–property relationship study, these types of coatings will be useful as multifunctional applications in marine and moist environments.

Effect of NCO/OH ratio and Ce‐Zr nanoparticles on the thermo‐mechanical properties of hyperbranched polyurethane urea coatings

AbstractThe present study describes the effect of NCO/OH ratio and addition of Cerium (Ce)‐Zirconium (Zr) mixed oxide nanoparticles on the properties of Hyperbranched Polyurethane Urea (HBPUU) Coatings. Initially a hydroxyl terminated hyperbranched polymer (HTBP) was synthesized through A3 + CB2 approach. The HTBP and Ce‐Zr nanopowder dispersed HTBP, both were reacted with hexamethylene diisocyanate (HDI) separately; at various NCO/OH eq. ratios to get different NCO terminated HBPU and HBPU/Ce‐Zr hybrid prepolymers. These prepolymers were used for the preparation of HBPUU and HBPUU/Ce‐Zr hybrid coating films through moisture curing. The techniques such as 1H NMR, 13C NMR, FT‐IR, and XRD have been used for structural information while Dynamic mechanical and thermal analyzer (DMTA), Thermogravimetric analysis (TGA) and Universal testing machine (UTM) have been used for evaluation of thermo‐mechanical properties. The combined spectroscopic investigations results indicate the formation of HBPUU network with a degree of branching of 76% while FT‐IR deconvolution results indicates the formation of more hydrogen bonded structure with increasing NCO/OH ratio. The XRD and FT‐IR studies confirm the presence of Ce‐Zr mixed nanoparticles in the HBPUU hybrids. As per TGA and DMTA analysis the thermal stability, char residue, storage modulus (E', material stiffness) and glass transition temperature (Tg), increases with increasing NCO/OH ratio and Ce‐Zr nanoparticle loading in HBPUU coatings. In general, UTM data suggest that the tensile strength increases and per cent elongation at break decreases with increasing the NCO/OH ratio and addition level of nanoparticles in HBPUU coatings. Copyright © 2009 John Wiley & Sons, Ltd.

Soybean Oil–Isosorbide‐Based Waterborne Polyurethane–Urea Dispersions

A series of soybean oil-based amide diol-isosorbide waterborne polyurethane-urea (PUU) dispersions have been successfully prepared, with amounts of isosorbide ranging from 0 to 20 wt % of the total diol content. The thermal and mechanical properties of the resulting PUU films have been characterized by dynamic mechanical analysis, differential scanning calorimetry, thermogravimetric analysis, and mechanical testing. The results reveal that the glass transition temperature is increased with increased amounts of isosorbide, and the mechanical properties are improved significantly with the incorporation of isosorbide. For example, the Young's modulus increases from 2.3 to 63 MPa and the ultimate tensile strength increases from 0.7 to 8.2 MPa when the isosorbide amount is increased from 0 to 20 wt %. The thermal stability decreases slightly with the incorporation of isosorbide. This work provides a new way of utilizing biorenewable materials, such as isosorbide and a soybean oil-based amide diol, for the preparation of high-performance polyurethane-urea coatings.

Synthesis and characterization of hyperbranched polyurethane–urea coatings

A series of hyperbranched polyurethane (HBPU)–urea coatings were synthesized by a systematic two-step reaction process. Initially, isocyanate terminated PU prepolymers were prepared from a hyperbranched polyester polyols with isophorone diisocyanate at NCO/OH ratio of 1.6:1 for 5 h at 70–80 °C. The excess NCO content after the synthesis of NCO terminated HBPU prepolymer was completely reacted with atmospheric moisture. The obtained HBPU–urea networks were characterized with Fourier transform-infrared (FT-IR) spectroscopy for the quantitative evolution of the extent of urethane and urea bonds as well as to study the structure-property relationship. In order to find out the changes and types of intermolecular H-bonding interaction in the HBPU–urea films with the variation in polyester structure, the deconvolution of FT-IR spectra were carried out using Origin 6.0 software through Gaussian curve-fitting method. The viscoelastic properties and thermal stability of the synthesized coatings were determined by dynamic mechanical and thermal analyzer and thermogravimetric analyzer, respectively. For HBPU–urea samples glass transition temperature and thermal stability increased with the generation number from the first to the third. Polyester samples showed single step decomposition profile and HBPU–urea samples showed two-steps decomposition with good thermal stability.