Study of the effect of hyperbranched polyols on cationic UV curable coating properties

Cycloaliphatic epoxide‐based cationic UV curable coatings containing three different hyperbranched polyols (HBPs) were systematically formulated and characterized. Polyether polyols were found to deter epoxide conversion under low UV intensity. For high UV intensity, the cycloaliphatic epoxide conversion increased with polyol content. Coatings with HBPs had better flexibility and solvent resistance than those containing a reference triol. Compared to the triol and polyester HBPs, polyether HBPs imparted lower T_g and hardness but a better flexibilizing effect to the coatings. At higher R values, the coating solvent resistance decreased except for those with one polyether HBP. A two‐peak phenomenon was discovered in the residual thermal reaction heat curve after photoDSC experiments. These two peaks were found to be related to the thermal relaxation behavior of the photocured inhomogeneous film, and the reactivation and reaction of the ‘trapped living cationic species’. The capability of the polyol to lower the high‐temperature‐peak temperature corresponded well with the flexibilizing ability. Copyright © 2006 Society of Chemical Industry     

UV光固化胶黏剂

介绍了UV固化胶黏剂的主要类型与组成。     

UV curable EA-Si hybrid coatings prepared by combination of radical and cationic photopolymerization

A series of UV curable EA-Si hybrid coatings were prepared by a simple approach combining radical and cationic photopolymerization, with epoxy acrylate (EA) as monomer, γ-glycidoxypropyltrimethoxysilane (GPTMS) as inorganic precursor, benzophenone (BP) as free radical photo initiator and a diaryliodonium salt DPIHFP as cationic photo initiator. The chemical structures of EA-Si hybrid coatings were characterized by Fourier transform infrared (FTIR), Raman spectroscopy and X-ray diffraction (XRD). The thermal and optical properties of hybrid coatings were investigated by thermal gravimetric analysis (TGA) and UV–vis transmission spectroscopy, respectively. The results indicated that cross-linked network structure of SiOSi formed in the hybrid coatings, which led to the decrease in crystallinity and of EA-Si hybrid coating. The final conversion of CC bonds was also decreased because of the addition of GPTMS. The thermal stability of EA-Si hybrid coatings was enhanced in the second decomposition stage (300–400 °C) because of the existence of organic–inorganic cross-linked network structures. The transparency of coatings at around 346 nm tended to increase with increasing concentration of inorganic precursor GPTMS.     

Synthesis and cationic photopolymerization of a new fluorinated oxetane monomer

A new fluorinated oxetane monomer (FOX) was prepared using a fluorinated alcohol by phase transfer catalysis in a Williamson ether synthesis. The new fluorinated monomer was used in cationic photopolymerization as comonomer of 3,3′-[oxydi(methylene)]bis(3-ethyloxetane). The presence of the FOX monomer induces a decrease of the glass transition temperature, thermal stabilization and an increase of the final oxetane group conversion. Completely hydrophobic surfaces were obtained with a selective enrichment of the fluorinated comonomer, as confirmed by contact angle and XPS analysis.     

Cationic photopolymerization of epoxides containing carbon black nanoparticles

The active centers responsible for cationic photopolymerizations are essentially non-terminating, and continue to propagate after the illumination is ceased. In this contribution, the mobility of the long-lived cationic active centers is investigated for the cure of epoxides containing carbon black nanoparticles. Concentration profiles for the cationic active centers produced during illumination were coupled with an analysis of the active center reactive diffusion during the post-illumination period, revealing that migration of the active centers leads to cure beyond the illuminated depth. A kinetic analysis yielded predicted cure times for coatings of varying thickness and carbon black loading, showing good agreement with experimental results obtained for photopolymerizations of cycloaliphatic diepoxide coatings containing a monodisperse carbon black with mean hydrodynamic radius of 29.2 nm. These results indicate that the long lifetimes and reactive diffusion of cationic active centers may be used for effective curing of coatings containing carbon black nanoparticles. This comprehensive approach could be applied to other opaque nanocomposite systems.     

全球辐射固化材料近期市场分析（一）

辐射固化技术于20世纪60～70年代,在欧美市场上初步确立了自身的产业地位,成为全球经济体系中的一个组成部分.各种专业分工不同的企业（原材料生产供应商、化学配方产品生产供应商、装置设备制造供应商和下游客户）,共同构建了UV/EB固化产业的价值链.近年来,世界三大主要地区（北美、欧洲和亚洲）辐射固化市场以近两位数的速度在增长,尽管全球经济形势持续低迷.2012年,全球辐射固化市场配方产品的消耗量据统计大约为457000t.亚洲市场消耗量已超过欧美市场而居全球首位.辐射固化配方产品在世界三大主要地区市场中应用的重点领域虽然各不相同,然而工业涂料在全球的市场份额中仍然比例最大.本文还列出了辐射固化原材料在不同市场中的消费量与价格.     

A novel ferrocenium salt as visible light photoinitiator for cationic and radical photopolymerization

A novel hybrid photoinitiator for visible light photopolymerization, (η⁶-3-benzoyl-4-chlorodiphenylamine) (η⁵-cyclopentadienyl) iron hexafluorophosphate (Fc-NBP), was synthesized and studied. Its absorption in the UV and visible light regions showed much stronger activity than those of either the commercialized cationic photoinitiator I-261 or the conventional free radical photoinitiator benzophenone, especially above wavelengths of 350 nm. When exposed to visible light, the photoinitiator under study initiates both cationic polymerization and radical polymerization. The photoinitiator's abilities in the photopolymerization of acrylates and epoxides were evaluated by near infrared (NIR) spectroscopy. The results from NIR clearly indicate that Fc-NBP exhibited high efficiency in photopolymerizing acrylate monomers. In the same lamp, however, benzophenone showed no photoinitiating ability. The photopolymerization rate of the diglycidyl ether of the bisphenol-A epoxy (DGEBA) oligomer was found to be slower than that of acrylates when using Fc-NBP as the photoinitiator. This study shows that the polymerization of epoxide DGEBA can be speeded up by adding a photosensitizer benzoyl peroxide (BPO), but BPO and tertiary amines do not affect the free radical photopolymerization of tripropylene glycol diacrylate (TPGDA). We conclude by providing a possible photoinitiation mechanism.     

Synthesis of novel highly reactive silicone-epoxy monomers for cationic photopolymerizations

A series of novel cationically photopolymerizable silicone-epoxide monomers bearing substituted benzyl ether groups were prepared. Monomers with methoxy groups on the aromatic ring of the benzyl ether group were synthesized by sequential hydrosylation reactions of 1,1,3,3-tetramethyl disiloxane. Kinetic studies using real-time infrared spectroscopy of the cationic photopolymerizations of these novel monomers showed that those monomers with methoxy groups exhibited elevated rates of photopolymerization. The acceleration effect was explained on the basis of synergistic effects of two mechanisms, namely, the normal ring opening polymerization catalyzed by a Brönstead acid, and the cationic photopolymerization induced by the redox interaction between the free radicals formed in the backbone of the monomer and the onium salt used as photoinitiator. The methoxy groups on the aromatic ring of the benzyl ether enhance the stabilization of the carbocation formed in the structure of the monomer. Silicone-epoxy monomer with 2,5-dimethoxybenzyl ether group exhibited the higher photopolymerization rate. The latter compound can also be used as accelerator of the cationic photopolymerization of commercial silicone-epoxy monomer when used in low concentrations.     

Novel visible photoinitiators systems for free-radical/cationic hybrid photopolymerization

Free radical/cationic hybrid photopolymerization of acrylates and epoxides was induced using an initiator system comprised of the dye derivative 5,12-dihydroquinoxalino[2,3-b]quinoxaline or 5,12-dihydroquinoxalino[2,3-b]pyridopyrazine as the sensitizers and hexafluoroantimonate triarylsulfonium salt as the initiators. The curing experiments were carried out in the presence of air and the consumption of each monomer upon VIS-radiation was monitored in situ by real-time infrared spectroscopy. Hardness (H), elastic modulus (E) and the H/E ratio of the coatings obtained by visible-initiated acrylate/epoxide hybrid photopolymerization were determined using nanoindentation. DSC measurements show that the initiator system presented here may produce an interpenetrating polymer network. The pencil hardness of the obtained coatings indicates that the dye/hexafluoroantimonate triarylsulfonium salts systems studied here may have practical applications as visible-light hybrid initiators.     

光敏性含磷丙烯酸酯的合成和性能研究

将三氯氧磷分别与乙二醇及一缩乙二醇反应合成了2种双磷酸酯酰氯,将其再进一步与丙烯酸羟乙酯反应,制备了2种四官能度的UV固化含磷丙烯酸酯,通过1H-NMR和FT-IR对最终产物结构进行了表征。研究了中间反应物配比对产物收率的影响,2种含磷丙烯酸酯对UV固化体系中C==C双键转化率的影响,固化膜的热稳定性和UV固化体系的物理力学性能。结果表明:双磷酸酯酰氯与丙烯酸羟乙酯物质的量比为1:3.94～3.97时,产物收率98.9%。2种含磷丙烯酸酯25℃下黏度较低(280mPa.s),固化膜800℃残炭率较高(5.5%),附着力1级,硬度5H,剪切强度12.7MPa,是优良的紫外光固化促进剂。     

An in situ intercalative polymerization method for preparing UV curable clay–polymer nanocomposites

A novel in situ intercalative polymerization technique was used to disperse clay mineral in a precursor resin for use in UV curing by performing an in situ ion exchange reaction during polyesterification. Unmodified montmorillonite (MMT) was added to a reaction mixture composed of monomers and methyl, tallow, bis‐2‐hydroxyethyl ammonium (MTEtOH) during the synthesis of unsaturated polyesters to create resins containing highly dispersed, organically modified MMT. UV‐curable clay–polymer nanocomposite (CPN) films were then prepared utilizing donor–acceptor chemistry through reactions of the unsaturated polyester resin with triethylene glycol divinyl ether. Functional group conversion improved up to 15% by the incorporation of clay mineral into the polymer matrix through the in situ polymerization method. The CPNs also had improved barrier, mechanical, and thermal properties over a control film containing no clay mineral. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42601.     

Visible light sensitive photoinitiating systems: Recent progress in cationic and radical photopolymerization reactions under soft conditions

Although there have been many reports on photoinitiating systems adapted to visible lights for radical photopolymerization, the challenge for the design and development of photoinitiating systems for cationic photopolymerization or concomitant radical/cationic photopolymerization (for interpenetrating polymer network IPN synthesis) with visible lights still remains open. Particularly, the recent development of cheap and easily accessible LEDs operating upon soft visible light irradiations has opened new fields for polymer synthesis. Since 2011, many novel photoinitiating systems based on organic and organometallic compounds with excellent visible light absorption have emerged and exhibited outstanding photoinitiating abilities especially for cationic photopolymerization. In this review, recent progress (mainly from 2011 to early 2014) in applications of photoinitiators and sensitive photoinitiating systems under visible lights are reported. In addition, their relative efficiencies in the photopolymerization of different monomers are exemplified and discussed.     

结构型紫外线固化胶粘剂的研究

介绍了结构型紫外线固化胶粘剂的特征及应用，重点研究了影响结构型紫外线固化胶粘剂粘接强度的因素。     

Film formation from cationic electropaint systems containing resins with different glass transition temperature

Some phenomena in the deposition process of electropainting have not been well elucidated till now. In this paper, to investigate an influence of glass transition temperature (T_g) on film formation, the deposited film was observed with an atomic force microscope and the electrochemistry was investigated, using two kinds of cationic acrylate resin with different T_g (methyl methacrylate system (MMAs): T_g=70°C, and methyl acrylate system (MAs): T_g=5°C). Electrodeposition was performed under constant voltage or current condition.

At constant voltage, the deposition behavior in the two resin systems differed extremely. The MMAs, the resin with high T_g, produced a high resistance film. The MAs, the resin with low T_g, was deposited forming a film at a voltage lower than 20 V. At constant current, the film formation did not result in a rise in voltage. It behaved like a conductive film. When the resin with high T_g was used, particulate deposits were observed by AFM even in the induction period. The resin with low T_g formed flat deposits. These results suggest that paint deposition is initiated once electrolysis of water starts. In addition, there are two types of film formation on the cationic electropainting: high resistance film formation for the resin with high T_g, and ion-permeable film formation for the resin with low T_g. In both cases, film growth occurs at the film/bulk solution interface.     

UV固化胶粘剂应用研究进展

论述了当前UV固化胶粘剂的应用现状,对UV固化胶粘剂配方中的主要原料预聚物、单体、光引发剂等的研究进展做了详细的阐述。     

Oxygen mediated and wavelength tunable cationic photopolymerization reactions under air and low intensity: A new concept

A new concept which allows efficient cationic photopolymerization reactions under air, at any excitation wavelength in the UV–visible range and under low light intensities (conventional Xe lamp and/or laser diodes) is presented. It is based on the use of a versatile free radical promoted cationic process for the photoinitiation step which only requires a radical source, a silane and an usual iodonium salt and takes advantage of the presence of oxygen. The tunable character of the absorption is connected with the choice of the radical source. The oxygen enhancement is due to the particular role played by the silane. In every case, the silylium cation is the most efficient structure for the cationic ring opening reaction. Examples of the performance achieved (e.g. a conversion close to 100%) with such systems over the 390–580 nm range using various irradiation devices is shown and discussed.     

Specific cationic photoinitiators for near UV and visible LEDs: Iodonium versus ferrocenium structures

Two iodonium salts based on a coumarin chromophore are investigated for polymerization upon light emitting diode irradiations (LEDs). They work as one‐component photoinitiators. They initiate the cationic polymerization of epoxides (under air) and vinylethers (laminate) upon exposure to violet LEDs (385 and 405 nm). Excellent polymerization profiles are recorded. Their efficiency is quite similar to that of a ferrocenium salt. Interpenetrating polymer networks can also be obtained through a concomitant cationic/radical photopolymerization of an epoxy/acrylate blend monomer. The light absorption properties of these new salts as well as the involved photochemical mechanisms are investigated for the first time through electron spin resonance, laser flash photolysis, steady state photolysis experiments. Molecular orbital calculations are also used to shed some light on the initiation mechanisms. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42759.     

紫外光固化有机硅隔离剂的研究

以氯丙基聚硅氧烷和丙烯酸-3-羟丙酯（HPA）在三乙胺催化作用下得到丙烯酰氧烃基改性聚硅氧烷．然后使之与活性稀释剂共混,在紫外光照射下固化成膜讨论了投料比、促进利用量、不同光引发剂、稀释剂用量对光固化反应的影响。     

紫外光固化胶粘剂的粘接强度研究

以二官能团PUA(聚氨酯丙烯酸酯)为基体树脂、四氢呋喃丙烯酸酯为稀释单体、γ-缩水甘油醚基丙基三甲氧基硅烷(KH-560)为偶联剂、HCPK(1-羟基环己基苯基甲酮)为光引发剂和nano-SiO2(纳米二氧化硅)为填料,成功制备出一种UV(紫外光)固化胶。将UV固化胶用于PC(聚碳酸酯)塑料片材的胶接,并以该胶接件的T型剥离强度作为考核指标,采用单因素试验法优选出制备UV固化胶的较佳配方。结果表明:当w(二官能团PUA)=64%、w(HCPK)=3.0%、w(KH-560)=1.00%、w(四氢呋喃丙烯酸酯)=30%和w(nano-SiO2)=2.0%时,UV固化胶的剥离强度达到甚至超过市售同类产品(loctite3106)。     

Effects of preparation method on microstructure and properties of UV‐curable nanocomposite coatings containing silica

UV‐curable nanocomposites were prepared by the blending method or the in situ method with nanosilica obtained from a sol–gel process. The microstructure and properties of the nanocomposite coatings were investigated using ²⁹Si‐NMR cross‐polarization/magic‐angle spinning, transmission electron microscopy (TEM), Fourier transform IR (FTIR), differential scanning calorimetry (DSC), and UV–visible (UV–vis) spectra, respectively. The NMR and TEM showed that during the blending method, tetraethyl orthosilicate (TEOS) completely hydrolyzed to form nanosilica particles, which were evenly dispersed in the polymer matrix. However, for the in situ method, TEOS partially hydrolyzed to form some kind of microstructure and morphology of inorganic phases intertwisted with organic molecules. FTIR analysis indicated that the nanocomposites prepared from the in situ method had much higher curing rates than those from the blending method. DSC and UV–vis measurements showed that the blending method caused higher glass‐transition temperatures and UV absorbance than the in situ method. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1119–1124, 2005