Newly UV-curable polyurethane coatings prepared by multifunctional thiol- and ene-terminated polyurethane aqueous dispersions: Photopolymerization properties

A novel approach toward the preparation of newly UV-curable polyurethane coatings composed of multifunctional thiol- and ene-terminated polyurethane aqueous dispersions is presented. By a synergistic combination of polyurethane dispersions synthesis and thiol-ene chemistry, strategies for the preparation of newly UV-curable polyurethane coatings are developed. Photo-DSC, real-time FTIR, DMA and tensile tests measurements are used to investigate the photopolymerization and mechanical behaviors of newly UV-curable polyurethane coatings. The newly polyurethane coatings have 1.5 times higher polymerization rate and final 99% functional groups conversion in air conditions compared to current urethane-acrylate based UV-curable polyurethane dispersions coatings. UV-cured polyurethane films prepared by this method are also found to exhibit increase in Young's modulus and tensile strength at break by 25% and 10%, respectively. These experiment facts suggest that the incorporation of thiol-ene chemistry to the polyurethane dispersion coatings increase their polymerization rate, producing a high degree of cross-linking. This confirms the preparation of the targeted novel UV-curable polyurethane coatings and reveals the dramatic effect that changes in incorporation of thiol-ene chemistry can have on the photopolymerization behaviors of UV-curable polyurethane dispersions coatings systems.     

Soy-based UV-curable thiol–ene coatings

Novel soy-based thiols and enes were synthesized and characterized. Then, soy-based thiol–ene UV-curable coatings were formulated and their coating physiochemical properties were investigated in detail. The use of biorenewable resources, combined with environmentally friendly UV-curable technology, provides a “green + green” solution to the stricter regulations in the coatings industry. Novel soy-based thiols and enes were synthesized through the Lewis acid-catalyzed ring opening reaction of epoxidized soybean oil with multifunctional thiols or hydroxyl functional allyl compounds. FTIR and NMR confirmed the formation of the target compounds. The soy-based thiols and enes were formulated with petrochemical-based enes and thiols, respectively, to make thiol–ene UV-curable coatings. Typical coating film properties, thermal properties, and photopolymerization kinetics of these coatings were studied. Soy-based thiol–ene coatings having lower functionality thiols and enes have poor UV curability and coating properties, which was attributed to the lower crosslink density. Soy-based thiols and enes with higher functionality can be UV-cured in combination with petrochemical-based enes or thiols even without the presence of free radical photoinitiators. Better coating film properties were obtained from these higher functionality thiol–ene systems that were toughened by commercial hyperbranched acrylates.     

Facile synthesis of waterborne UV-curable polyurethane/silica nanocomposites and morphology,physical properties of its nanostructured films

Waterborne UV-curable polyurethane (WUPU)/silica nanocomposites were prepared by in situ method using aqueous silica sol. SEM examinations of hybrid films indicated that the nanosilica were well dispersed in the matrix. Atomic force microscopy revealed that the microphase separation between polyurethane and silica was significantly affected by the amount of silica incorporated. DMA analysis showed that the nanocomposite films with silica nanoparticles showed a single tan δ peak, which implies that soft and hard segments of polyurethane are well phase mixed. The nanostructure films displayed enhanced storage modulus, tensile strength without sacrificing high elongation at break. The resulting transparent hybrid films are promising for a number of applications, e.g. for high performance water-based UV-curable coatings.     

Morphology and mechanical properties of UV-curable castor oil-based waterborne polyurethane/organic montmorillonite nanocomposites

Water resistance is a unique advantage of castor oil-based polyurethane, permitting the application of coatings in humid environments. However, its low thermal decomposition temperature remains a limitation. Here, to demonstrate a simple method to improve the thermal stability of cured films, we prepared an organic montmorillonite dispersion utilising 3-(methacryloyloxy)propyltrimethoxysilane and protonated 3-aminopropyltriethoxysilane for modifying the clay. The method was put into practice by directly mixing the dispersion with a UV-curable castor oil-based waterborne polyurethane dispersion. The inclusion of organic molecule chains from the silane coupling agents noticeably improves the compatibility of polyurethane with organic montmorillonite, which imparts the composite latex with better thermal stability and mechanical properties when the organic montmorillonite additive is 5.0?wt-%.     

UV-curable waterborne polyurethane acrylate modified with octavinyl POSS for weatherable coating applications

UV-curable waterborne polyurethane acrylate (WPUA) modified with octavinyl polyhedral oligomeric silsesquioxane (OVPOSS) was prepared via photopolymerization between OVPOSS and WPUA. Structural and morphological features of WPUA/OVPOSS coatings were assessed using Fourier transform infrared spectroscopy, transmission electron microscopy and X-ray diffraction. Thermal properties of the WPUA/OVPOSS hybride coatings have been improved over the pure waterborne polyurethane acrylate analyzed by thermal gravimetric analysis. Performance of the coatings was also evaluated using water absorption, hardness, contact angle, X-ray photoelectron spectroscopy (XPS). The data showed that the WPUA/OVPOSS coatings possessed better water resistance and thermal oxidative stability in comparison with pure WPUA.     

Thiourethane thermoset coatings from bio‐based thiols

Three bio‐based thiols were synthesized via the thermal thiol‐ene reactions between sucrose soya ester (SSE) and multifunctional thiols; then, thiourethane coatings were produced from these thiols and their coating properties were studied. A series of high bio‐renewable content thiol oligomers were synthesized according to the previously reported thermal thiol‐ene reaction. Fourier transform infrared spectra (FTIR) confirmed the complete consumption of the double bonds in SSE, and gel permeation chromatography confirmed the formation of high‐molecular‐weight oligomers. The viscosity of these oligomers remained low due to their compact and branched structures. Thermoset thiourethane coatings were prepared from these thiol oligomers and polyisocyanate trimer resins with dibutyltin diacetate as the catalyst. FTIR spectra confirmed the formation of the thiourethane group. However, coatings based on isophorone diisocyanate (IPDI) polyisocyanate resin showed a lower degree of cure because of the decreased resin mobility due to the rigid cyclohexane ring. Generally, all the coatings showed good adhesion to aluminum panels, and had high gloss. However, they exhibited low tensile strength, modulus and chemical resistance due to the flexibility of the fatty acid chain. Coatings based on more rigid IPDI‐based polyisocyanate showed higher T_g, hardness and direct impact resistance compared with the hexamethylene‐diisocyanate (HDI) based polyisocyanate counterparts. Thermogravimetric analysis results showed that coatings based on mercaptanized soybean oil have better thermal stability than those from di‐pentene dimercaptan or glycol di‐3‐mercaptopropionate. Two T_g values were found by both differential scanning calorimetry and dynamic mechanical thermal analysis of thiourethanes from HDI‐based polyisocyanate and di‐pentene dimercaptan or glycol di‐3‐mercaptopropionate based oligomers due to phase separation resulting from the poor compatibility between HDI‐based polyisocyanate and the respective oligomers. Copyright © 2011 Society of Chemical Industry     

UV固化超支化聚氨酯丙烯酸树脂的研究进展

超支化聚氨酯是一种新型的功能性树脂,UV固化超支化聚氨酯丙烯酸树脂作为一种新型的涂料成膜物质,具有固化速度快、涂膜性能好、环境污染小等优点,对制备环境友好、性能优异的产品以及用其改性普通的UV光固化树脂具有实际意义,展现出良好的发展前景。本文就国内外有关UV固化超支化聚氨酯丙烯酸树脂的制备方法、固化动力学和固化流变行为等方面的研究工作进行了综述,并介绍了UV固化超支化聚氨酯丙烯酸树脂在改善涂膜力学性能和阻尼性能等方面的应用研究现状,提出完善UV固化超支化聚氨酯丙烯酸树脂的基础研究和在此基础上的相关产品的开发将是今后研究的主要发展方向。     

UV固化丙烯海松酸聚氨酯丙烯酸酯的合成及应用

以2,4-甲苯二异氰酸酯(TDI)、丙烯海松酸二甘醇聚酯二元醇和丙烯酸羟丙酯(HPA)为主要原料合成了可紫外光固化的涂料用丙烯海松酸聚氨酯丙烯酸酯(APAPUA)低聚物。对产物进行了红外表征,并考察了其光固化行为。测试了APAPUA固化膜的硬度、柔韧性及其他力学性能,同时考察了其热稳定性。结果表明,该低聚物固化膜铅笔硬度达到4H,附着力1级,耐冲击性55 cm,初始分解温度245℃,具有固化速度快,力学性能及耐热性优良等特点,可以作为价格低廉的耐热性低聚物应用于光固化涂料。     

光固化环氧全氟辛酸酯聚氨酯的研究

以环氧树脂、全氟辛酸、聚乙二醇、异佛尔酮二异氰酸酯(IPDI)和甲基丙烯酸羟乙酯为原料,通过四步反应合成了一种新型的可光固化的聚氨酯大分子单体。利用1H-NMR、IR、接触角、XPS、DSC、TGA、TEM等分析测试手段对单体的结构以及含氟聚合物的表面特性,热性能和断面形貌进行了研究。接触角和XPS的结果表明由于含氟聚合物中的全氟链段容易向表面迁移,使得固化膜表面对H2O和CH2I2的接触角可以达到108.9°和92.3°,具有低的表面自由能,能够有效地改善涂膜的耐水、耐油等性能;热性能以及断面形态分析发现该聚合物表现出较好的热性能和柔韧性。     

Preparation, characterization and properties of UV-curable waterborne polyurethane acrylate/SiO2 coating

The UV-curable waterborne polyurethane acrylate (UV-WPUA) oligomer was first prepared based on isophorone diisocyanate (IPDI), polyether polyol (NJ-220), dimethylol propionic acid (DMPA), and hydroxyethyl methyl acrylate (HEMA) via an in situ method. With the different content tetraethoxysilane (TEOS) and 3-glycidyloxypropyltrimethoxysilane (GLYMO) as coupling agents, a series of waterborne UV-WPUA/SiO₂ oligomers were prepared by the sol?Cgel process. The physical and mechanical properties of the UV-WPUA and UV-WPUA/SiO₂ hybrid coating materials were measured. The UV-WPUA and WPUA/SiO₂ hybrid materials were characterized using FTIR spectra, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray diffraction (XRD) measuring apparatuses to determine their structures, thermal properties, surface morphologies, etc. The results showed the SiO₂ particles of the hybrid materials had wide dispersion, forming a good interfacial bonding layer on surfaces. The tensile strength, water resistance, and thermal properties of the hybrid materials were better than those of the UV-WPUA. The resulting UV-WPUA/SiO₂ hybrids are promising for a number of applications, e.g., for high-performance water-based UV-curable coatings.     

Glossy topcoat exterior paint formulations using water-based polyurethane/acrylic hybrid binders

The development of glossy topcoat one-pot exterior paint formulations using water-based polyurethane/acrylates hybrid binders as well as the assessment of its properties through different conventional tests is discussed in this work. Polyurethane (PU) anionomer having 2-ethoxymethacrylate terminal groups was prepared following a prepolymer mixing process. This prepolymer was chain extended in aqueous solution and after addition of acrylic monomers radical polymerized. Paints were prepared using titanium dioxide as unique pigment. Panels coated with air-dried paints with three pigment to volume concentration (PVC) values were subjected to standardized tests including adhesion, flexibility, gloss and color determination. Accelerated weathering tests were carried out to evaluate changes in properties, especially gloss and color, of painted panels. Solvent-based acrylic and polyurethane paints were included as high gloss quality reference coatings. It was found that air-dried formulations based on hybrid polyurethane/acrylic with up to 50 wt.% of acrylic component, show a gloss as high as 70 and the relative gloss change after accelerated weathering test is lower than the pure solvent-based acrylic and polyurethane paints.     

Properties of UV-curable polyurethane acrylates using nonyellowing polyisocyanate for floor coating

UV-curable polyurethane acrylates for poly(vinyl chloride) (PVC) floor coating were prepared using nonyellowing polyisocyanates. The effects of the chemical structure of the polyisocyanates and hydroxyacrylates, and the compositions of the prepolymer/diluent on the properties of the UV-curable polyurethane acrylates were investigated. Several different urethane acrylate prepolymers from four different polyisocyanates, isophorone diisocyanate (IPDI) adduct, hexamethylene diisocyanate (HDI) adduct, HDI biuret, and HDI isocyanurate, and two different hydroxyacrylates, hydroxyapropyl acrylate (HPA), polycaprolactone modified hydroxyethylhexylacrylate (PCMHEA). UV-curable coating materials were formulated from the prepolymers and 1-hydroxycyclohexylphenyl ketone as a photoinitiator with polyethylene glycol diacrylate (PEGDA) as a diluent. The polyurethane acrylates prepared with HDI isocyanurate and the equimolar mixture of HPA and PCMHEA showed balanced coating properties such as tensile properties, hardness, weatherability, and good adhesion. The dynamic mechanical studies showed the properties of those polyurethane acrylates were well correlated with their glass transition temperature behaviors. It was also found that the adhesion was best as a PVC floor coating with the appropriate viscosity (below 150 P at 25°C) when 35% PEGDA as a diluent was used. © 1996 John Wiley & Sons, Inc.     

可紫外光固化聚氨酯乳液的合成与性能研究

对可紫外光固化的芳香族水分散性聚氨酯的合成与性能进行了初步的探讨。利用聚醚多元醇，甲苯二异氰酸酯和丙烯酸羟丙酯合成了稳定的可紫外光固化的水分散和性聚氨酯乳液。发现随着光照时间延长和丙烯酸羟丙酯用量的增加，所得聚氨酯薄膜的拉伸强度增加，断裂伸长率下降，在有机溶剂中的溶胀度也下降。     

Electrochemical characterisation of multilayer organic coatings

The protective properties of eight high performance commercial multilayer organic coatings for aeronautical use (based on polyurethane, epoxy and polyurethane-compatible epoxy resins) on anodised 2024-T3 Al alloy were evaluated in neutral aerated 3.5% NaCl aqueous solution using the electrochemical impedance spectroscopy (EIS) technique. The investigation was performed on specimens supplied and prepared from Alenia in accordance with their technical specifications. Results obtained in this paper show that all coating systems exhibit excellent protective properties even after prolonged immersion in the test solution (one year). Although the dielectric properties of all multilayer coatings are quite similar, EIS was proved to be able to discriminate among them, making possible a rank of these protective systems to prevent or to reduce corrosion. Capacitance measurements performed on the same coatings allow their behaviour to be forecasted.     

气相二氧化硅对紫外光固化光纤涂料性能的影响

用聚氨酯丙烯酸酯与环氧丙烯酸酯预聚物按一定比例共混制备出性能较好的紫外光固化光纤涂料。着重研究了气相二氧化硅填料的加入对光纤涂料性能的影响。研究发现：气相二氧化硅填料的适量加入能有效降低涂料的吸水性，而对涂料的光固化速度等性能无明显的影响。此外，还探讨了聚合物涂层中气相二氧化硅微粒改善光纤疲劳与老化性能的作用机理，发现2％（质量分数）的气相二氧化硅填料使氧合物涂层的吸水率最小，从而降低光纤表面的侵蚀速率。     

纳米二氧化硅水溶胶改性UWPU的研究

通过丙酮法合成光固化水性聚氨酯丙烯酸酯预聚体,用三乙胺中和后在乳化过程中原位引入纳米二氧化硅水溶胶(Wv33、R900、R301)制备二氧化硅/光固化水性聚氨酯(SiO2/UWPU)纳米复合乳液,并进一步通过紫外光固化制备了SiO2/UWPU复合膜。通过电子扫描显微镜(SEM)和电子拉力机研究了不同纳米二氧化硅水溶胶对UWPU/SiO2复合膜的微观结构和力学性能的影响。SEM分析表明表面有机改性的pH值接近中性的硅溶胶(Wv33)较pH为酸性或碱性的硅溶胶在聚氨酯基体中有较好的分散性;应力-应变曲线分析表明Wv33能有效实现对复合膜的增强,即提高了复合膜的储存模量、拉伸强度和邵A硬度。     

Anticorrosive polyurethane paints with nano- and microsized phosphates

Two types of phosphate fillers (nanosized aluminum phosphate and microsized aluminum–zinc phosphate) were tested as anticorrosive fillers in 2 K solvent-borne polyurethane paints based on commercial acrylic resin with OH groups and an isophorone diisocyanate-type hardener. Three coating compositions containing commercial fillers (mica/quartz, TiO₂, wollastonite, talc) and also mentioned nanosized aluminum phosphate or microsized aluminum–zinc phosphate were prepared using a pearl-mill as well as a laboratory dissolver, applied onto a steel substrate and cured at room temperature for 14 days. An influence of the type and content of a phosphate filler on properties of polyurethane paints and coatings has been investigated. Incorporation of nanosized aluminum phosphate into coating compositions increases their viscosity while cured paints exhibit reduced adhesion to steel substrates. The results of corrosion tests in a salts spray chamber as well as immersion in an aqueous NaCl solution indicated that the paint system with 9.8 wt.% of applied nanofiller had similar protective properties to a polyurethane coat containing a higher dose (i.e. 15.6 wt.%) of commercial microsized aluminum–zinc phosphate.     

Effect of silica nanoparticles on structure and properties of waterborne UV-curable polyurethane nanocomposites

UV-curable waterborne polyurethane (WUPU)/silica nanocomposites were prepared using various silica by phase-inversion emulsification method. TEM examinations of nanostructured films indicated that the organic modified nanosilica was well dispersed in the WUPU matrix, while the acid and alkaline silica formed much less compact, or densely aggregated structure. DMA analysis demonstrated that the WUPU/silica nanocomposite films had a broadening of the tanδ peak and shifted to higher temperature. The WUPU/silica nanocomposite films displayed enhanced storage modulus, Shore A hardness, tensile strength without sacrificing high elongation at break compared to that of the pure WUPU film. The resulting nanocomposite films are possibly interesting for the generation of waterborne UV-curable transparent coatings with scratch-resistance.     

The effect of thiol and ene structures on thiol-ene networks: Photopolymerization, physical, mechanical and optical properties

The photopolymerization of four different types of ene monomers with both primary and secondary multifunctional thiols has been evaluated. To understand the effect of ene monomer structures on polymer properties, a comprehensive investigation of the basic physical, mechanical and optical properties was conducted for the secondary and primary thiol-ene networks. The results indicate that ene structure and functionality can significantly affect the rigidity and the physical and mechanical properties of the thiol-ene networks. The heat capacity in the rubber state correlates with the network crosslink density and flexibility of the ene component. Networks formed from the secondary thiol-ene systems are basically equivalent to those made from primary thiol-enes with respect to physical, mechanical and optical properties. The secondary thiol monomer samples evaluated were found to have exceptional storage stability and relatively low odor.     

Recent developments in aqueous two-component polyurethane (2K-PUR) coatings

In the field of environmentally friendly coatings waterborne two-component polyurethane systems represent a new technology, combining the good film properties of solventborne two-component polyurethane coatings with the low VOC values of waterborne technology. Recently, waterborne two-component polyurethane coatings have matured to the point that they offer realistic alternatives to the corresponding solventborne systems in various application fields.

For industrial finishing and automotive refinish we are introducing rapid drying coatings exhibiting well-balanced range of properties at low VOC level. We developed high-performance OEM-clearcoats which combine good chemical resistance with excellent mar resistance. Waterborne soft-feel lacquers are already well established in the market.

Development of a new generation of water dispersible polyisocyanates as well as improvements in application technology have contributed substantially to this. Additionally, progress in understanding the fundamental principles of aqueous two-component-PUR systems like side reactions during pot life and film formation or the cause of blistering supported our developments.

We expect that waterborne two-component polyurethane coatings will gain a significant share of the market where high-performance coatings are demanded.