Synthesis of polyurethane resins and its improvement on dimensional stability and finishing performances of medium‐ and small‐diameter softwoods

This study analyzed the effects of polyurethane (PU) resin treatments on surface homogeneity, dimensional stability, and finishing performances of medium‐ and small‐diameter softwoods produced in Taiwan. Two‐pack PU resins were prepared by combing short castor oil‐modified alkyd resin serving as a polyol with polymeric 4,4′‐diphenymethane diisocyanate (PMDI) serving as a hardener, by the molar ratio of NCO/OH+COOH of 1.2. Four types of short oil‐modified alkyd resins with different polyhydric alcohols (glycerin and pentaerythritol) and polybasic acids (phthalic anhydride and isophthalic acid) were synthesized. Three kinds of medium‐ and small‐diameter softwoods, including China fir, Taiwanina, and Japanese fir with a diameter of 10–15 cm were obtained from Hui‐Sun Forest Station, Taiwan. The wood coating of nitrocellulose (NC) lacquer including sanding sealer and top clear was used. Results show that the surface hardness, homogeneity, moisture excluding efficiency, and antiswelling efficiency of woods were enhanced by PU resin treatments. Among all the PU resins, the isophthalic acid and pentaerythritol‐containing PU resin (IPA‐P‐MDI) achieved the best improved efficiency on dimensional stability of woods. Results of two types of finishing procedure, i.e. NC lacquer sanding sealer plus top clear and top clear only, applied onto the PU‐treated woods revealed that the hardness, adhesion, and durability of NC lacquer films on the PU‐treated wood were superior to those of untreated one, especially for top clear finishing alone. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Epoxy acrylate UV/PU dual‐cured wood coatings

For improving the finishing performances of complicated three‐dimensional coated wood products (e.g., furniture) with some shadow zones in the absence of ultraviolet (UV) light, resulting in incomplete curing of UV coatings, the aim of this study was to investigate the characteristics and effects of curing process on the properties of epoxy acrylate UV/PU dual‐cured resin for wood coatings when compared with traditional UV and polyurethane (PU) coatings. The epoxy acrylate oligomer was synthesized for providing a double bond of acryloyl group and a secondary hydroxyl group. The UV/PU dual‐cured coating was formulated with epoxy acrylate resin/tripropylene glycol diacrylate (TPGDA) monomer by the weight ratio of 80/20, 3% dosage of benzil dimethyl ketal as a photoinitiator, and the NCO/OH mole ratio of 1.0. The aromatic polymeric diphenylmethane diisocyanate was used as a hardener. The films of the dual‐cured coating, obtained from UV‐cured or room temperature‐cured process, showed an excellent tensile strength, elongation at break, impact resistance, and lightfastness when compared with traditional UV and PU coatings; especially, the adhesion of UV/PU dual‐cured coating by UV‐cured process was better than that of traditional UV coating. It can therefore be concluded that the epoxy acrylate oligomer‐based dual‐cured coating could readily be used for complicated wood products finishing. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The effect of different radiation sources for the UV curing of a screen‐printed,water‐based polyurethane acrylate binder

In this paper, titanium‐dioxide‐pigmented printing pastes of water‐borne, UV‐curable polyurethane acrylate binder with two different UV‐curing photoinitiator combinations were prepared and screen printed on a black t‐shirt fabric. The effects of mercury and gallium radiation sources employed either singly or in combination for UV curing and the total energy level on the printing performance were investigated. The cured textile samples were subjected to colour measurements before and after five cycles of washing, and hiding power and changes in chromacity, hue, and colour were determined. Single‐lamp applications of mercury and gallium were not satisfactory, and opaque pigment hindered deep curing, especially at thicker coating levels. It was found that employment of a mercury–gallium lamp system applying an irradiation at medium level can provide pigment printing of opaque white inks with excellent coverage, washing resistance, and medium hardness.     

气相二氧化硅对瓷器文物修复仿釉涂料性能的影响

瓷器文物修复作色上釉时使用的无色透明有机涂料称为仿釉涂料,目前常用于瓷器文物修复的仿釉涂料普遍存在着耐老化性差和硬度不足这两个问题.为了使仿釉涂料更好地满足修复需求,研究使用气相二氧化硅粉体材料,对陶瓷修复常用的三种仿釉涂料(硝基涂料、丙烯酸光油和水性聚氨酯涂料)进行改性实验,并对改性前后涂膜的硬度、光泽度、接触角、附...     

Bamboo tar‐based polyurethane wood coatings

Bamboo tar is a natural resource of aromatic polyol obtained from a residue of by setting or distilling crude bamboo vinegar. In this study, the two‐packed polyurethane (PU) coatings were prepared by blending bamboo tar and castor oil varying with different weight ratios and polymeric toluene diisocyanate (PTDI) was used as a hardener at the NCO/OH molar ratio of 1.0. Six kinds of PU coatings were formulated and the viscosity, pot‐life, drying time, mechanical properties (hardness, tensile strength, impact resistance, adhesion, and abrasion resistance), gel content, durability, lightfastness, FTIR, thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA) were characterized. The results indicated that the bamboo tar containing PU film appearance is semitransparent yellow‐brown color and the wood texture could be kept after finishing. All PU films possessed excellent adhesion as well as durability. The increase in bamboo tar content led to shorten drying time of coatings and to increase in hardness, tensile strength, lightfastness, and thermal stability of films. From these results and due to a light smell flavor, it is suggested that the bamboo tar‐based PU coatings is suitable to be used as an exterior wood coatings. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

UV curing and matting of acrylate nanocomposite coatings by 172 nm excimer irradiation

For UV-curable acrylate coatings reinforced by silica nanoparticles, the effect of 172 nm excimer irradiation on the surface roughness has been studied. A dual UV lamp set-up consisting of a 172 nm excimer lamp and a mercury arc lamp allowed obtaining gloss levels down to 0.5 units (at 60°) depending on the acrylate formulation and curing conditions. Moreover, UV matt-finished sample showed enhanced surface hardness and increased chemical resistance. It is assumed that 172 nm excimer irradiation resulted in a higher network density via additional cross-linking reactions.To study the depth profile of acrylate conversion for coatings cured by the combination of a 172 nm excimer lamp (accountable for surface curing) and a mercury arc lamp (responsible for through curing), FTIR microscopy as well as (Ge)ATR-FTIR having an IR penetration depth of less than 0.5 μm have been applied. Providing the presence of a photoinitiator as well as the absence of oxygen inhibition, similar degrees of double bond conversion of about 90% were observed on the entire area of the cross-section of the coating, i.e. the wavelength of UV irradiation was found to have no significant impact on acrylate conversion.     

Adhesion failure of antiscratch coatings on polycarbonate under UV irradiation

The adhesion failure of antiscratch (AS) coatings on unmodified and plasma‐modified polycarbonate (PC) substrate was studied using both chemical and physical methods while considering the surface and interface changes between coatings and PC under ultraviolet (UV) irradiation. The differences in the wettability and surface elemental compositions of the PC surface (PCs) and AS coatings after UV ageing were evaluated by contact angle and Fourier transform infrared (FTIR) measurements. The nanoindentation technique was employed for the quantitative assessment of the changes in the nanomechanical properties of both PCs and AS coatings under UV irradiation. The adhesion of coating on plasma‐modified PC was found to be significantly better than that of unmodified substrates. The hydrophilicity and polarity of PCs covered by AS coatings were significantly increased because of the photodegradation of PCs, whereas silicon coatings remained invariant. Nanoindentation tests revealed an obvious enhancement in stiffness of the coating and exposed PC after ageing. Based on these experiments, we proposed that adhesion failure under UV irradiation may be caused by two reasons: first, the photodegradation that occurred at the PCs covered by AS coatings; and second, the stress induced by the changes in stiffness of both AS and PCs under UV ageing. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40507.     

Effect of Irradiation on Structural Changes of Levan

Levan, as a biocompatible and renewable biopolymer with anticancer properties, is a promising candidate for a wide range of applications in various fields of industry. However, in the literature, there is a lack of information about its behavior under the influence of UV irradiation, which may limit its potential application, including medical science. Therefore, this study describes the effects of irradiation on the structural properties of levan. This type of fructan was subjected to stability tests under radiation conditions using LED and polychromatic lamps. The results showed that the photodegradation of levan irradiated with a polychromatic light occurs faster and more efficiently than the photodegradation of levan irradiated with an LED lamp. Furthermore, AFM analysis showed that the surface became smoother after irradiation, as evidenced by decreasing values of roughness parameters. Moreover, UV irradiation causes the decrease of total surface free energy and both its components in levan; however, more significant changes occur during irradiation of the sample with a polychromatic lamp.     

Improved adhesion of TiO2‐based multilayer coating on HDPE and characterization of photocatalysis

Multilayered photocatalytic TiO₂‐based coating was prepared by spin coating on a high‐density polyethylene (HDPE) substrate. The multilayered coating consisted of a polyurethane (PU) barrier layer and two layers of TiO₂ nanoparticles bound with PU. The adhesion between the HDPE substrate and protective PU coating was enhanced by oxygen plasma treatment of the substrate. The improved adhesion contributed to the photocatalytic degradation of palmitic acid. Long‐term activity of the photocatalytic coating in degradation of palmitic acid under UV illumination was followed by FTIR‐ATR. The catalytic activity of the coating was maintained in three identical cycles where palmitic acid was added and UV‐irradiated for 6 h. According to FTIR measurements, the palmitic acid was almost completely decomposed after 6 h, but gas chromatography (GC) analysis showed total decomposition to require 12 h UV illumination (∼ 97% of palmitic acid decomposed in 12 h). Study of the degradation of palmitic acid by GC as a function of time indicated that the degradation kinetics was pseudofirst order, and the rate constant obtained was 0.31 h⁻¹. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of nitrocellulose on the properties of PU–NC semi‐IPN wood coatings

Wood coatings of PU–NC semi‐interpenetrating polymer networks (semi‐IPNs), made from blown castor oil (BCO), aromatic polyisocyanate (PTDI), and nitrocellulose (NC), were prepared by sequential polymerization method. To investigate the effects of NC on the properties of PU–NC semi‐IPNs wood coatings, three different viscosities of NC (½‐sec, ¼‐sec, and ${1\over 16}$ ‐sec), and a PU catalyst [dibutyltin dilaurate (DBTDL)] were synthesized in this study. The results revealed that the PU–NC semi‐IPNs with ½‐sec NC‐containing coating had the shortest drying time, and their films had the best tensile strength, elongation at break, lightfastness, and solvent resistance. Dynamic mechanical analysis showed that PU–NC semi‐IPNs with ½‐sec NC or ${1\over 16}$ ‐sec NC had good interpenetration between PU and NC, whereas PU–NC semi‐IPNs with ¼‐sec NC had a slight separation phase between PU and NC. In both PU–NC semi‐IPNs with ¼‐sec NC and those with ${1\over 16}$ ‐sec NC, the addition of 0.2% DBTDL could effectively reduce the drying time of the coating and improve the film properties, including tensile strength, elongation at break, and lightfastness. In addition, the miscibility of PU and NC was examined in PU–NC semi‐IPNs with ¼‐sec NC. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2157–2162, 2003     

Effect of pigment colour on the printing performance of synthetic leather using a ultraviolet‐curable water‐borne polyurethane acrylate binder

The effect of pigment colours, cyan (C), magenta (M) and yellow (Y), and a blend of these (CMY blend) on the printing performance of synthetic leather using a ultraviolet (UV)‐curable water‐borne polyurethane acrylate binder and two types of photoinitiators was investigated. The curing process was carried out at different radiation doses using gallium and mercury UV lamps in combination. The performance of the prints was evaluated with abrasion resistance, crock fastness, gloss and hardness values and K/S. Chemical changes in the cured film structures due to UV curing were analysed by Fourier Transform–infrared spectroscopy measurements. The highest hardness values for clear and pigmented cured films were obtained with a gallium and mercury lamp combination at the highest energy density (1529 mJ/cm²). The highest K/S was obtained for the sample printed with the formulation including the C pigment and cured under a gallium and mercury lamp combination at low energy density (398 mJ/cm²). The M‐pigmented film displayed the highest hardness and abrasion resistance, whereas lower values were obtained with films pigmented with Y and C, and CMY blend, successively. The highest dry and wet crock values were obtained with the formulation including the M pigment. CMY‐pigmented film showed the highest gloss values at all energy densities. The pigment colour affected the curing degree of printed films due to the different absorption/transmission intervals of each colour in the UV spectrum.     

Colour and gloss properties of pigment‐printed synthetic leather using an ultraviolet‐curable water‐borne polyurethane acrylate binder and two photoinitiators at different ratios

This study reports on the colour and gloss properties of pigment‐printed polyurethane‐based synthetic leather using an ultraviolet (UV)‐curable water‐borne polyurethane acrylate binder and two types of photoinitiators (Omnirad 819 DW and Omnirad 500) at different ratios. The UV curing of printed synthetic leather samples was conducted with gallium and mercury lamps, either singly or in combination, at three different power levels. Chemical changes in the cured films because of the polymerisation of the UV‐curing process were analysed by Fourier Transform‐infrared spectroscopy, which showed that the polymerisation reaction occurred after UV curing in both the clear and in the pigmented films. The Omnirad 500 photoinitiator is more effective in surface curing and the Omnirad 819 DW photoinitiator is more effective in deep curing. The Omnirad 500 photoinitiator caused the gloss values to drop significantly, especially in the formulation including both photoinitiators, Omnirad 819 DW and Omnirad 500, at a 1:2 ratio, respectively. In the formulation including a higher ratio of the Omnirad 819 DW photoinitiator, higher gloss values were obtained compared with the formulation including a higher ratio of the Omnirad 500 photoinitiator. Considering all the results, the highest gloss value of 20.96 was obtained with samples printed with the formulation of the two photoinitiators at an equal ratio (1:1) cured under a gallium/mercury lamp combination at a power level of 90 W/cm. Moreover, the highest K/S value of 10.86 was obtained with samples printed with the formulation of the two photoinitiators at an equal ratio cured under the gallium lamp at 90 W/cm.     

Sea Buckthorn Oil Tocopherol Extraction's By‐Product Utilization in Green Synthesis of Polyurethane Coating

The focus of the present study is to utilize a by‐product obtained during extraction of tocopherols, a valuable vitamin E compound, from sea buckthorn (SBT) oil and in doing so find a reliable alternative to petrochemical based polyols. Bio‐based polyurethane (PU) is prepared by using SBT oil based fatty acid methyl ester polyesteramide polyols (SBTPEP) with toluene diisocyanate (TDI). The fatty acid methyl ester is converted to the corresponding fatty amide by reaction with diethanolamine. The formed fatty amide is then esterified with phthalic anhydride to synthesize polyesteramide polyol. Characterization techniques used to evaluate polyesteramide polyol are Fourier‐transform infrared spectroscopy (FTIR) and NMR. The cured PU coating is also put through various mechanical tests to analyze the physical properties. The cured PU coating shows good surface and mechanical properties. It shows a gloss value of 87.4 and passes impact, adhesion, and chemical resistance tests. It is hydrophobic which is evident from its contact angle of 100.2°. It has good thermal stability which is evident by its glass transition temperature of 53.9 °C. Use of phthalic anhydride contributes to the bio‐based characteristics of synthesized PU. Practical Application: The present study presents a synthesis route which has minimal dependence on hazardous feedstock by utilization of green feedstock. The results obtained from physical and mechanical evaluations favor the use of this PU formulation in the coating sector. The adhesion and impact strength test results show potential application in the industrial sector coatings where the applied coat must be able to withstand high levels of physical stress and strain. The presence of aromatic rings and oil‐based moiety, that is the fatty acid hydrocarbon chain, contributes to the hydrophobic nature of the PU coating. Hydrophobic coatings have tremendous application in various fields such as marine coatings, automotive, electronics, and decorative coatings. These are potential fields of application for the synthesized green PU coating obtained from tocopherol extraction by‐products.     

Synthesis of polymeric dyes based on self-colored network of castor oil-based waterborne polyurethane

The development of vegetable oil-based polymers was particularly suitable for the era of increasingly scarce petroleum. Self-colored castor oil-based waterborne polyurethanes (PUs) were successfully synthesized based on castor oil and 1-amino-4-hydroxy-2-(6-hydroxyhexyl) anthraquinone (DR) as polyols. The UV–Vis spectrum showed that the addition of carboxylic acid groups make the spectrum of the PU produce the hyperchromic effect under alkaline conditions. Castor oil-based waterborne colored PUs possessed excellent stability under weak alkaline conditions. The connection of castor oil caused the PU to constitute soft polymer networks. PU coatings on cotton fabrics possessed excellent color properties. The urethane groups in the PUs formed hydrogen bonds with the hydroxyl groups on the cotton fibers and the polymer network structure formed by the PU coating itself made the color fastness of the cotton coatings reached grade 5. With the increase of castor oil content, the degradation rate of castor oil-based waterborne colored PU increased from 3.45% to 3.65%. This work provides a way to impart excellent color properties and fastness to PU coatings by inserting dye molecules and vegetable oils into the PU macromolecular chain.     

Curing and combustion properties of a PU‐coating system with UV‐reactive phosphazene

A UV‐curable polyurethane (PU)‐coating system containing phosphorus is formulated by the combination of photoinitiator, PU acrylate oligomer, and UV‐reactive phosphazene monomer. PU acrylate oligomer is prepared by the addition of 2‐hydroxyethylmethacrylate (HEMA) to NCO‐terminated PU prepolymer. UV‐reactive phosphazene monomer is derived from the HEMA substitution reaction to hexachlorocyclotriphosphazene (NPCl₂)₃. The curing reaction of this PU‐coating system is carried out by UV irradiation. The resultant UV‐cured PU‐coated films demonstrated better performance properties than those of original UV‐cured PU acrylate (UV‐PU) without UV‐reactive phosphazene monomer. Furthermore, their thermal properties are investigated by a thermogravimetric analyzer and a dynamic mechanical thermal analyzer, respectively. The combustion behaviors of these UV‐cured PU‐coated films are evaluated by the measurements of a limiting oxygen index and a cone calorimeter. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1980–1991, 2002     

聚氨酯涂料技术在中国的发展

聚氨酯技术在德国兴起,在中国涂料行业中飞速发展。以聚氨酯为原料的涂料系统已经渗透到中国涂料行业的各个应用领域内。本文重点阐述了聚氨酯技术在汽车OEM涂料及修补漆、木器涂料、防腐蚀涂料、塑料涂料和建筑涂料中的应用。鉴于中国政府正在不断对环保型和低VOC释放量的产品出台严格的法律法规,因此水性或高固含的聚氨酯涂料产品尤其令中国涂料行业关注。本文还论述了水性聚氨酯涂料及辐射固化聚氨酯涂料的发展。     

Solar reflectance,surface adhesion,and thermal conductivity of wood/natural rubber composite sheet with Tio2/polyurethane topcoat for roofing applications

Effects of titanium dioxide (TiO₂) dosage in polyurethane (PU) coating and PU coating thickness on solar reflectance, surface adhesion, crack resistance to bending, and thermal conductivity of wood/(natural rubber) (WNR) composite sheet were studied before and after prolonged UV aging. The TiO₂ powder content added to the PU coating was varied from 0 to 15 parts per hundred parts of PU. The average PU coating thickness on the WNR composite sheet was altered from 127 ± 10 to 315 ± 10 μm. The experimental results suggested that the solar reflectance slightly increased with increasing TiO₂ powder but did not change upon varying the PU coating thicknesses. The presence of TiO₂ in the PU coating caused a slight decrease in thermal conductivity because of porosities occurring due to the presence of voids, but increasing the TiO₂ powder content in the coating resulted in a progressive increase in thermal conductivity of the composite sheet. In a UV‐accelerated weathering tester (UVB 313 nm), the lightness of the PU coating slightly increased owing to PU discoloration, whereas the solar reflectance, PU/WNR layer adhesion, and crack resistance to bending remained unaffected with increasing UV aging time. J. VINYL ADDIT. TECHNOL., 18:184–191, 2012. © 2012 Society of Plastics Engineers     

Effect of hyperbranched acrylates on UV‐curable soy‐based biorenewable coatings

Utilization of biorenewable components in UV‐curable coating formulations is both economically and environmentally beneficial, particularly when compared to their petrochemical‐based counterparts. To produce UV‐curable coatings of high biorenewable content with enhanced performance, acrylated epoxidized soybean oil (ASBO) was combined with biorenewable reactive diluent tetrahydrofufuryl acrylate, adhesion promoters, photoinitiator and hyperbranched acrylates (HBAs) as synthetic tougheners. The HBAs were found to impart high functionality and low viscosity, thus increasing crosslinking in the coating network and improving mechanical and thermal properties such as film hardness, adhesion, solvent resistance, impact resistance, tensile modulus and toughness, glass transition temperature and thermal stability. Real‐time Fourier transform infrared spectroscopy showed decreased acrylate conversion when compared with a reference formulation without HBAs, which was attributed to earlier coating network vitrification during UV irradiation. ASBO‐based coatings were also thermally annealed to allow further reaction of unreacted components in the vitrified network. As a result, coating properties were further improved. Overall, the addition of HBAs as synthetic tougheners to UV‐curable ASBO‐based biorenewable coating systems was shown to greatly improve the corresponding coating properties. Copyright © 2010 Society of Chemical Industry     

塑料用水性涂料的研究进展

水性涂料作为一种环境友好型涂饰材料,具有广泛的应用前景.综述了水性丙烯酸、水性聚氨酯和UV固化3种主要的塑料用水性涂料的发展现状;介绍了目前存在的问题,并提出了其今后的发展趋势和研究方向.