Photooxidative stability of electron-beam and u.v.-cured di- and triacrylate resins. Influence of resin/initiator structure

The post-cured photooxidative stabilities of electron-beam and u.v.-cured di- and triacrylate based resins have been examined using i.r. and second order derivative u.v. spectroscopic techniques. Using hydroxyl index at 3450 cm¹ as a measure of the rate of photooxidation of the resin films, their stabilities were found to be strongly dependent on the curing process and structure of the residual photoinitiator. The structure of the resin also played a major role in influencing the development of potentially active intermediate chromophores. Resins containing a terminal secondary amine group developed a strong absorption band at 250–300 nm during photooxidation, which paralleled the production of i.r. bands at 1680 and 1605 cm¹. The development of this chromophore is strongly influenced by the nature of the curing process and residual photoinitiator and is shown to be produced through an oxidative mechanism. The chromophore is associated with an α,β-unsaturated carbonyl species and is considered to be a key intermediate in the process of photoyellowing. Resins with no terminal secondary amine groups exhibited no such characteristic spectral changes. Possible mechanistic schemes are proposed to account for the observations.     

新型红外光引发剂的激光光聚合研究

目前对紫外区敏感的光聚合体系的研究已经比较成熟 ,并且在工业生产中得到了实际应用 .对可见光区的光聚合体系的研究也已引起了不少研究者的关注 .而有关近红外 /红外区敏感的光聚合体系的报道还很少 .已经商业化的红外半导体激光器具有体积小、价格便宜、操作简便、性能稳定等特点 ,配合计算机布线技术 ,可大大提高生产效率 ,这些优点使得与之匹配的对红外区域敏感的光聚合体系具有广阔的应用前景[1 ] ,尤其是在计算机直接制版 (Ｃｏｍｐｕｔｅｒ ｔｏ ｐｌａｔｅｓ,ＣＴＰｓ)领域[2 ] .Ｃｈａｔｔｅｒｊｅ等曾经研究了用阳离子菁染料与不…     

可聚合二苯甲酮类光引发剂的合成及其光聚合性能研究

以4-(2,3-环氧丙氧基)二苯甲酮(EBP)和丙烯酸为原料,通过开环反应合成了含有不饱和双键的可聚合光引发剂4-(丙烯酸-2-羟基丙酯-3-氧基)二苯甲酮(AEBP).采用红外光谱(FT-IR)、核磁共振氢谱(¹HNMR)对其结构进行表征,利用紫外吸收光谱对AEBP的紫外吸收波长进行表征,通过实时红外(RT-IR)研究了AEBP引发丙烯酸酯单体的光聚合动力学.采用萃取法对比了BP与AEBP引发固化体系后的迁移性.结果表明,随AEBP浓度增加,单体最终转化率增加;当助引发剂N,N-二甲氨基苯甲酸-乙酯(EDAB)浓度为1.2%时,单体最终双键转化率最高;AEBP对双官能度单体的引发效率较之三官能度单体的好;聚合速率随光照强度的增强而变快;固化后AEBP的迁移性比传统的BP大大降低.     

INFLUENCE OF MOLECULAR STRUCTURES OF SECONDARY AMINE TERMINATED POLY（ESTER-AMINE）S ON THE CURING PERFORMANCE WITH EPOXY RESIN

Five secondary amine terminated poly(ester-amine)s(defined as PEA)with controlled molecular structures were synthesized through reacting excessive piperazine with phthalicdiglycol diacrylate(PDDA)and 1,1,1-trimethylolpropane triacrylate(TMPTA)at a constant secondary amine/acrylate group ratio of 1.5/1 and at different PDDA/TMPTA molar ratios. Both IR and ~(?)H-NMR spectra indicated that all acrylate groups were consumed in the reaction,based on which the structural parameters were calculated from the ~(?)H-NMR spectra.With decreasing PDDA/TMPTA ratio,the content of secondary amine,degree of branching,molecular weight,T_g and T_d increased accordingly.These polymers were further used as both crosslinkers and flexibilizers for a linear epoxy resin E51 to form cured films under ambient condition.The gel content, relative hardness and T_g of the resulting films increased as PEA molecules changed from linear to highly branching structures.Due to the flexibility of PEA molecules,all the films possessed excellent mechanical performance.     

2-(4-甲氧基苯基)-4,6-双(三氯甲基)-S-三嗪光引发剂的合成及其光聚合动力学性能研究

以对甲氧基苯甲腈和三氯乙腈为原料合成了光引发剂2-(4-甲氧基苯基)-4,6-双(三氯甲基)-S-三嗪(MBTT),通过傅里叶红外光谱仪、核磁共振仪和紫外吸收光谱对所合成的产物结构进行了表征.并利用实时红外(RT-IR)对该引发剂进行了光聚合反应动力学研究,考察了单体、引发剂浓度和光强对引发速率及单体转化率的影响.结果表明,MBTT是一种高效的紫外光引发剂,在引发剂用量为0.1%时光聚合的单体转化率就能达到90%;随着光强的增大,单体的双键转化率和最大反应速率都增大,诱导期缩短;双丙烯酸酯类单体的双键转化率比三丙烯酸酯类单体的双键转化率要高.     

Preparation and properties of epoxy resins cured with silyl esters of phenol novolak and cresol novolak

The curing agents of epoxy resin, trimethylsilyl ethers of phenol novolak (TMSPN) and cresol novolak (TMSCN) were prepared by refluxing phenol novolak and cresol novolak respectively, with the mixture of hexamethyldisilazane and chlorotrimethylsilane in THF. The curing reaction of epoxy resin with these curing agents and the thermal properties of cured resins were examined. The Tg values of epoxy resins cured with TMSPN were a little higher than those cured with TMSCN. The maximum of Tg is 118°C for TMSPN-cured epoxy resin against 112°C for TMSPN-cured epoxy resin. The water absorption of hydrophobic epoxy resins cured with TMSPN was a little lower than those cured with TMSCN. The clear decrease of water absorption is attributed to the difficulty of the micro-void formation caused by the more tight primary structures of TMSPN. The water absorption at 25°C containing trimethylsilyl groups is about one-tenth of that of epoxy resins cured with conventional curing agents and even one-half of that of the epoxy resins cured with active esters. The low water absorption is attributed to the presence of trimethylsilyl groups, which are more hydrophobic than ester groups, and to the absence of hydroxyl groups of the cured resins. This revised version was published online in July 2006 with corrections to the Cover Date.     

Novel,highly efficient polymeric benzophenone photoinitiator containing coinitiator moieties for photopolymerization

A novel polymeric photoinitiator P(MPBP‐co‐DMAEMA), bearing side‐chain benzophenone (BP) and coinitiator amine, was synthesized through free radical copolymerization of a polymerizable photoinitiator, 4‐[(4‐maleimido)phenoxy]benzophenone (MPBP), and a polymerizable coinitiator amine, N, N‐dimethylaminoethyl methacrylate (DMAEMA). In order to find out the influences of coinitiator amine on photopolymerization, a polymeric coinitiator amine, P(DMAEMA), was also synthesized for comparison. FT‐IR, ¹H NMR, and GPC analyses confirm the structures of polymers. The UV‐Vis spectra of polymeric photoinitiator P(MPBP‐co‐DMAEMA) and polymerizable photoinitiator MPBP are similar, and both exhibit high red‐shifted maximal absorption as compared with BP. The photopolymerization of 1,6‐hexanediol diacrylate (HDDA) and trimethylolpropane triacrylate (TMPTA), initiated by MPBP/DMAEMA, MPBP/P(DMAEMA), and P(MPBP‐co‐DMAEMA) systems, was studied by photo‐DSC. The results indicate that P(MPBP‐co‐DMAEMA) is most efficient for the polymerization of both HDDA and TMPTA, and MPBP/P(DMAEMA) is the least efficient of the three photoinitiating systems. Copyright © 2009 John Wiley & Sons, Ltd.     

Highly efficient,polymerizable, sulfur‐containing photoinitiator comprising a structure of planar N‐phenylmaleimide and benzophenone for photopolymerization

In a continuation of research on chemically bonded photoinitiators comprising a structure of planar N‐phenylmaleimide (NPMI) and benzophenone (BP), a novel, highly efficient, polymerizable, sulfur‐containing photoinitiator, 4‐[(4‐maleimido)thiophenyl]benzophenone (MTPBP), was synthesized by the introduction of an NPMI group into BP. Another chemically bonded photoinitiator, 4‐[(4‐maleimido)phenoxy]benzophenone (MPBP), was selected to evaluate its photoefficiency. The results showed that MTPBP possessed a greatly redshifted UV maximal absorption and a very weak fluorescence emission. Electron spin resonance spectra indicated that the C? S bond in its molecule underwent photolysis reactions to generate radicals to initiate the polymerization. Three representative types of different functionality monomers—methyl methacrylate, 1,6‐hexanediol diacrylate, and trimethylolpropane triacrylate—were chosen to be initiated through dilatometry and differential scanning photocalorimetry with unsaturated tertiary amine N,N‐dimethylaminoethyl methacrylate as the coinitiator. The results showed surprisingly high efficiency of MTPBP due to the mutual influence between NPMI and BP as in their physical mixtures and photolysis reactions at the C? S bond. Both MPBP and MTPBP behaved with similar regularity toward different monomers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3738–3750, 2006     

Thermoanalytical study of an epoxy resin crosslinked with an aliphatic polyamine

Samples of the cured resins were prepared in the form of cast sheets. The concentration of the amine curing agent (triethylenetetramine) in the epoxy resin (bisphenol-A diglycidylether) was varied between 25 and 100% of the stoichiometric quantity. The cured resins were examined by differential scanning calorimetry, penetration under load as a function of temperature, and dynamic mechanical analysis. It is found that all of these methods provide a useful means of monitoring crosslinking through changes in the glass transition temperature. The dependence of some characteristic secondary relaxation temperatures, and the change in heat capacity at the glass transition, on the concentration of the amine were also investigated.     

A novel epoxy methacrylate resin containing phthalazinone moiety for UV coatings

A novel phthalazinone modified epoxy acrylate resin for the high temperature resistant ultravioet (UV) curable coating was synthesized. The methacrylated epoxy resins obtained were utilized to UV radiation curing by taking 2.5% (wt%) of photoinitiator in combination with 20% (wt%) of diluent, and generated the interpenetraring polymer networks. The cured film had good thermal and chemical stability.     

Rapid and sensitive determination of the conversion of UV-cured acrylic ester resins by pyrolysis-gas chromatography in the presence of an organic alkali.

The double-bond conversion of UV-cured resins prepared from pentaerythritol triacrylate (PETA) was determined by pyrolysis-gas chromatography in the presence of an organic alkali, tetramethylammonium hydroxide (TMAH). The pyrogram of the uncured prepolymer compound, consisting of PETA and a photoinitiator, 2,2-dimethoxy-2-phenylacetophenone, contained specific products reflecting the original acrylate structure, such as methyl acrylate (MA) and methyl ethers of pentaerithritol. Meanwhile, in pyrograms of the UV-cured PETA, the yields of MA considerably decreased. The double-bond conversions of the cured resins, irradiated with various UV dosages, were calculated based on the relative yields of MA among specific products in the pyrograms. The conversions determined by this approach were analyzed by comparing them with those estimated by Fourier-transform infrared spectroscopy.     

Synthesis and photoinitiating behavior of hyperbranched polymeric photoinitiators bearing coinitiator amine

A series of benzophenone (BP)‐terminated hyperbranched polyester (BoltornTM P1000), bearing amine moieties as synergists by reacting with piperidine, were synthesized as yellowish liquids with low viscosity, and used as polymeric photoinitiators (HPPIs). For comparison, acrylate groups were introduced to the terminals of hyperbranched polyester for obtaining a polymerizable photoinitiator. The chemical structures were characterized by FTIR and ¹H NMR spectroscopy. HPPIs and BP exhibited the similar absorptions by UV–vis spectroscopy. The photoinitiating behavior of HPPIs with trimethylolpropane triacrylate (TMPTA) as a trifunctional monomer was investigated by using photo‐DSC analysis. The results indicated that the maximum photopolymerization rate and unsaturation conversion of TMPTA initiated by HPPIs were both lower than that by BP. Among them, the HPPI with double tertiary amine moiety of BP moiety was found to be the most efficient photoinitiator. Additionally, the films cured with bisphenol A epoxy acrylate EB605 initiated by HPPIs were uniform and possessed high T_g from DMTA. Copyright © 2010 John Wiley & Sons, Ltd.     

High resolution solid‐state 13C‐NMR study of as‐cured and irradiated epoxy resins

This article presents the effects of strong ionizing radiations on the physico‐chemical modifications of aliphatic or aromatic amine‐cured epoxy resins based on diglycidyl ether of bisphenol A (DGEBA). Such epoxy resins have a considerable number of applications in the nuclear industrial field and are known to be very stable under moderate irradiation conditions. Using extensively high resolution solid‐state ¹³C‐NMR spectroscopy we show that the aliphatic amine‐cured resin (DGEBA‐TETA) appears much more sensitive to gamma rays than the aromatic amine‐cured one (DGEBA‐DDM). On the one hand, qualitative analyses of the high resolution solid‐state ¹³C‐NMR spectra of both epoxy resins, irradiated under similar conditions (8.5 MGy), reveal almost no change in the aromatic amine‐cured resin whereas new resonances are observed for the aliphatic amine‐cured resin. These new peaks were interpreted as the formation of new functional groups such as amides, acids and/or esters and to alkene groups probably formed in the aliphatic amine skeleton. On the other hand, molecular dynamics of these polymers are investigated by measuring the relaxation times, T_CH, T_1ρH and T_1C , before and after irradiation. The study of relaxation data shows the formation, under irradiation, of a more rigid network, especially for the aliphatic amine‐cured system and confirms that aromatic amine‐cured resin [DGEBA‐4,4′‐diaminodiphenylmethane(DDM)] is much less affected by ionizing radiations than the aliphatic amine‐cured resin [DGEBA‐triethylenetetramine(TETA)]. Moreover, it has been shown that the molecular modifications generated by irradiation on the powder of the aliphatic‐amine‐cured resin appear to be homogeneously distributed inside the polymers as no phase separations can be deduced from the above analyses. Copyright © 2001 John Wiley & Sons, Ltd.     

正离子光固化聚硅氧烷的合成及其环氧树脂复合固化膜的性能

以含氢聚硅氧烷(PMHS)分别与甲基丙烯酸六氟丁酯(HFMA)和烯丙基缩水甘油醚(AGE),经氯铂酸催化硅氢加成反应将甲基丙烯酸六氟丁酯和烯丙基缩水甘油醚引入聚硅氧烷的侧链,合成了3种含氟量不同的含氟代烃侧基/环氧侧基聚硅氧烷(EFPS),用FTIR、1H-NMR和13C-NMR进行了结构表征,将这类聚硅氧烷与环氧树脂...     

Organic-inorganic gels based on silica and multifunctional acrylates

Rigid, microporous silica rods, prepared previously by the sol-gel process, were infiltrated with three triacrylate monomers to give sequential interpenetrating networks (IPNs). The three commercially available triacrylate monomers are glycerol propoxy triacrylate (GPTA), trimethylolpropane triacrylate (TMPTA) and pentaerythritol triacrylate (PETA). Each solution containing a photoinitiator was allowed to infiltrate the silica rod, after which the sample was UV irradiated to polymerize the triacrylate monomer. Emphasis was placed on establishing the infiltration and polymerization conditions leading to optically transparent composites. For comparison, one of the triacrylates (GPTA) was introduced into a hydrolyzing sol-gel formulation containing TEOS, ethanol, water and acid catalyst, to effect a simultaneous IPN. The sequential IPN and the simultaneous IPN samples gave similar transmission curves, despite differences in skeletal density.1992 Fulbright Visiting Scholar, on leave from Marie Curie Sklodowska University, Lublin, Poland.     

含2,2′,4-三(2-氯苯基)-5-(3,4-二甲氧基苯基)-4′,5′-二苯基-1,1′-双咪唑光引发体系的光聚合动力学研究

2,2′,4-三(2-氯苯基)-5-(3,4-二甲氧基苯基)-4′,5′-二苯基-1,1′-二咪唑(CZ-HABI)是一种高效的光引发剂,其结构通过傅里叶红外光谱仪、核磁共振仪、紫外吸收光谱进行表征.复合引发体系(PI)由光引发剂CZ-HABI、增感剂4,4′-双(二乙氨基)苯甲酮(EMK)、供氢体N-苯基甘氨酸(NPG)组成,利用实时红外(RT-IR)对该复合光引发体系进行了光聚合反应动力学研究,结果表明:在没有供氢体条件下,基本上没有引发效果,增加供氢体后,引发效率大幅增加;增加复合光引发体系用量能提高光聚合反应的双键转化率,且最大聚合速率与[PI]1/2成正比;随着光强的增强,单体的双键转化率与最大反应速率均增大;复合光引发体系引发双丙烯酸酯类单体的最终双键转化率比三丙烯酸酯类单体要高.复合光引发体系的引发效率比ITX/EDAB光引发体系的引发效率高,与1-羟基环己基苯基甲酮(184)、2-羟基-2-甲基-1-苯基-1-丙酮(1173)的引发效果相近.     

A phosphate-based epoxy resin for flame retardance: synthesis, characterization, and cure properties

A phosphorus-containing oligomer, bis(3-hydroxyphenyl) phenyl phosphate (BHPP), was synthesized through the reaction of phenyl dichlorophosphate and 1,3-dihydroxybenzene, and characterized by elemental analysis, Fourier transform IR spectroscopy, and ¹H NMR and ³¹P NMR spectroscopy. Consequently, the phosphate-based epoxy resins with a phosphorus content of 1 and 2 wt % were prepared via the reaction of diglycidyl ether of bisphenol-A with BHPP and bisphenol-A, and were confirmed with Fourier transform IR spectroscopy and gel permeation chromatography. Phenolic melamine, Novolak, and dicyanodiamide were used as curing agents to prepare the thermoset resins with the control and the phosphate-based epoxy resins. Thermal properties and thermal degradation behavior of these thermoset resins were investigated by using differential scanning calorimetry and thermogravimetric analysis. The thermoset resins cured with phenolic melamine exhibited higher glass-transition temperatures than the other cured resins owing to the high rigidity of their molecular chain. Thermogravimetric analysis studies demonstrated that the decomposition temperatures of the thermoset resins cured with Novolak were higher than those of the others. A synergistic effect from the combination of the phosphate-based epoxy resin and the nitrogen-containing curing agent can result in a great improvement of the flame retardance for their thermoset resins.     

丙烯酸酯类吸油树脂的合成与性能研究

以丙烯酸酯、甲基丙烯酸酯为主要单体,二丙烯酸丁二醇酯为交联剂,过氧化二苯甲酰为引发剂,采用悬浮聚合方法,合成聚丙烯酸酯类高吸油树脂.研究了分散剂、引发剂、交联剂用量及单体配比等因素对树脂吸油性能的影响.结果表明,分散剂用量为单体质量的0.12%,引发剂用量为1.0%,交联剂用量为1.5%时树脂的吸油能力最佳,吸甲苯倍率可达15倍,吸汽油倍率可达10倍,吸机油倍率可达近9倍.     

UV curing behaviors and hydrophilic characteristics of UV curable waterborne hyperbranched aliphatic polyesters

A series of waterborne hyperbranched polyesters (WBHPs) endcapped with methacrylic and salt-like groups in different ratios have been investigated as UV curable resins. The kinetic studies of the drying step and UV curing were carried out by FT-IR measurements. The drying of the film of 100 μm thickness was completed in less than 6 hr at 70°C or within 10 hr at 50°C in an oven. The influence of different photoinitiators and their concentrations, extent of unsaturation and acid content of WBHP on final unsaturation conversion was studied. The surface free energy is a critical character, which affects the surface properties of a cured film. So one method based on the measurement of contact angle of a pure liquid on a solid surface was applied to determine the polar and dispersive components of the surface energy of UV cured films. The investigations of surface energy of WBHPs illustrated that those with more acid content and thus higher polar component are more sensitive to water, while those containing less acid content and thus lower polar term are less water sensitive. Moreover, the UV cured films of WBHPs and their blends with commercial waterborne resins (trade name EB 210, EB 2002, EB 11 and IRR 160) have acceptable pendulum hardness varying from 55 to 180 sec. Copyright © 2003 John Wiley & Sons, Ltd.     

UV curing kinetics and mechanism of a highly branched polycarbosilane

The UV curing process in both air and nitrogen atmosphere for the highly branched polycarbosilane system was investigated by differential scanning photo calorimeter. The UV cured products were characterized by Fourier‐transform infrared spectrometry (FTIR). By comparison with the FTIR results of the uncured liquid mixture and the cured samples, the possible cross‐linking reactions were determined. The kinetics of the curing systems was studied. The rate constant k was calculated based on the experimental results. The activation energies in different curing conditions were obtained. According to these results, it was learned that the mechanism for the UV curing in nitrogen was controlled by the photolysis of photoinitiator. Comparably, the UV curing process in air was complicated. It was affected by not only the photolysis of photoinitiator, but also oxygen and tripropane glycol diacrylate. Copyright © 2008 John Wiley & Sons, Ltd.