UV absorber progenitors: Photo-fries rearrangements of sulfonate esters of hydroxyphenylbenzotriazoles

Benzenesulfonate esters of hydroxyphenylbenzotriazole UV absorbers are described as UV absorber progenitors which can be used in UV-curable coating formulations. During UV exposure, they undergo a photo-Fries rearrangement to form the corresponding o-benzenesulfonyl phenol derivatives. These derivatives are formed in good chemical yield during bulk solution photolyses and are also readily formed in polymer films during exposure to sunlight. The reaction is specific for benzenesulfonate esters; little or no rearrangement takes place with benzyl, naphthyl, or alkylsulfonate esters or with benzoate esters.     

Coating performance and characteristics for UV-curable aliphatic urethane acrylate coatings containing norrish type I photoinitiators

The purpose of this study was to investigate the influence of several Norrish I (α-cleavage) type photoinitiators and UV dose on the curing behavior and coating performance of UV-curable aliphatic urethane acrylate coatings. UV-curable coatings were cured under a high-pressure mercury lamp. The curing behavior and coating performance of the UV-curable coatings that were cured using 2-hydroxy-2-methyl-1-phenyl-propan-1-one or 1-hydroxy-cyclohexyl-phenyl-ketone were superior to those of the UV-curable coatings cured using bis (2,4,6-trimethylben-zoyl)-phenylphosphine oxide or diphenyl (2,4,6-trimethylbenzoyl)-phosphine oxide, when the UV-curable coating was cured in air. Current address: Electronic Chemical Materials R&D Center, CHEIL Industries Inc.     

UV-curable, special coding inks for optical fibers

A UV-curable, special coding ink for optical fibers consists chiefly of UV-curableprepolymers, coloring materials, and a photoinitiator. The UV-curable prepolymers are silicone epoxy benzoic acrylate (SEBA) and alicyclic hydrocarbon epoxy acrylate (ACEA). The coloring materials are disperse red urethane acrylate (RUA), disperse blue urethane acrylate (BUA), acridine yellow urethane acrylate (YUA), or their mixtures. The relationships of component-property of UV-curable, special coding inks were studied. The typical UV-curable, special coding inks were used to color the optical fibers. No. 30 Guan Shan Rd., Wuhan 430074, P.R. China.     

Polydimethylsiloxane (PDMS)-based antibacterial organic–inorganic hybrid coatings

UV-curable antibacterial organic–inorganic hybrid coatings were prepared by sol–gel method. Triethoxysilane-terminated poly(dimethylsiloxane) (TESi-PDMS) as a new coupling agent to improve the compatibility between organic and inorganic phases was synthesized. PDMS-based urethane methacrylate oligomer was obtained by reacting isophorone diisocyanate with hydroxyethyl methacrylate and hydroxyl-terminated PDMS. The formulations were applied onto polycarbonate panels and then cured by UV radiation. Physical properties of UV-cured free films such as gel content, stress–strain, and conversion of acrylate double bond were examined. In addition, the antibacterial effects of the coatings were investigated. Nanosilver-containing formulations exhibited high antibacterial effect against Escherichia coli and Staphylococcus aureus. Thermogravimetric analysis indicated that thermal stability of the hybrids was significantly higher than the organic polymer. Contact angle measurement showed that addition of silane precursor increased the contact angle from 95° to 110°.     

New photoinitiating systems designed for polymer/inorganic hybrid nanocoatings

Conventional UV-curable formulations consist of photoinitiators, multifunctional monomers and oligomers, reactive diluents, pigments, and additives. While photoinitiators are the key components of the formulations and responsible for the absorption of light and relevant performances (e.g., cure speed, high-percent conversion, etc.), the final properties of the cured coating are governed by the other high-volume components. With recent advances in the use of nanomaterials like metals, metal oxides, and silicates in coatings, it is now possible to prepare nanocoatings with enhanced physical, chemical, and biological properties. This is due, in part, to the difference in surface area per unit of volume at the nanoscale. Nanocoatings are usually prepared by UV irradiation of formulations containing dispersed nanoparticles. However, the homogeneous dispersion of these nanoparticles is a key challenge due to their easy agglomeration arising from their high surface-free energy. It is often difficult to obtain well-dispersed formulations providing good transmission of light for a complete cure. In this article, we report several synthetic methodologies for the preparation of epoxy and (meth)acrylate-based nanocoatings containing clay or metal nanoparticles. In the former case, photolysis of intercalated photoinitiator within the layers of montmorillonite clay in the presence of monomers resulted in the in situ formation of exfoliated structures. For the preparation of metal nanocoatings, the formation of silver or gold nanoparticles and crosslinking are accomplished simultaneously by photoinduced electron transfer and polymerization processes. The nanoparticles are homogenously distributed in the network without macroscopic agglomeration. Applicability to both free radical and cationic systems is demonstrated. Moreover, a novel photochemical route for grafting from the self-assembled monolayers on gold is presented.     

Properties of UV-curable solvent-free pressure sensitive adhesive

In this study, the effects of methyl methacrylate (MMA), trimethylolpropane triacrylate (TMPTA), difunctional silicone urethane acrylate oligomer, and UV-dose on the adhesive properties of UV-curable pressure-sensitive adhesives (PSAs) were investigated, for further optimizing the adhesive properties to meet the requirements on high holding power and low peel strength. The results illustrated that increasing the MMA content decreased the peel strength and improved the holding power. The variation of TMPTA content from 1 to 10 wt% significantly enhanced the holding power from 1?h to above 120?h. The gel fraction increased with increasing TMPTA content. This increment was caused by the cross-linking of TMPTA after UV exposure. The peel strength of UV-curable PSAs was reduced to zero when oligomer content was more than 40 wt%, whereas the holding power was significantly enhanced from 5?h to above 120?h as the oligomer content increased up to 70 wt%. When the UV-dose increased, the peel strength decreased and the holding power increased. Therefore, UV-curable PSAs with very low peel strength and high holding power above 120?h were successfully synthesized and they possessed desirable features which could be fabricated to meet the specific requirements for industrial applications.     

UV-curing and thermal stability of dual curable urethane epoxy adhesives for temporary bonding in 3D multi-chip package process

Multi-chip packages (MCP) refers to a packaging configuration, connected via wirebonds to a multilayer circuit board, and protected by either a molded encapsulant or a low-cost ceramic package. As it requires high processing temperature, the adhesives for MCP need to show proper adhesion and thermal stability at high temperature. This study employed semi-interpenetrated (semi-IPN) structured polymer networks using UV-curing with acrylate terminated dual-curable urethane epoxy adhesive, a dipentaerythritol hexacrylate (DPHA), using hydroxydimethyl acetophenone as photo-initiator. UV-curing and thermal stability focused on different photo-initiator contents were investigated using photo-DSC, FTIR-ATR spectroscopy, gel content and TGA. The results show that UV-curable acrylic formulations with different content of photo-initiator affects UV-curing and thermal stability.     

Effects of reactive diluents on mechanical and physical properties of a UV curable acrylated urethane prepolymer

In this study, the dependence of the mechanical properties of a UV curable acrylated urethane on reactive diluent types and their amounts was investigated. The acrylated urethane prepolymer was synthesized from isophorone diisocyanate (IPDI), an aliphatic diisocyanate, and polypropylene glycol monomethacrylate (PPGMMA) by stepwise addition reaction. UV sensitive mixtures containing N-vinylpyrrolidinone (NVP), thiodiethylene glycol diacrylate (TDGDA) and isobornyl acrylate (IBoA) as reactive diluents were irradiated by UV light. An increase in reactive diluent content, either TDGDA or IBoA, caused an increase in tensile strength and a decrease in elongation values. In contrast, above a certain concentration a decrease in tensil strength was observed when NVP was used as reactive diluent. The water absorption capacities of the UV curable acrylated urethane films were observed to depend on type and amount of reactive diluent that was used. Thermooxidative properties of the films were also improved by incorporation of reactive diluents into formulations.     

Properties of UV-curable polyurethane acrylates for primary optical fiber coating

Studies have been made on the effects of the chemical structure of reactive urethane acrylate prepolymers and diluents (reactive monomers) and overall composition of the prepolymer/diluent on the properties of the UV-curable polyurethane acrylates for primary optical fiber coating. We prepared several urethane acrylate prepolymers from two different isocyanates, 4,4′-dicyclohexylmethane diisocyanate (HMDI) or isophorone diisocyanate (IPDI), and two different polyols, polybutadiene diol (PBD) or polypropylene oxide diol (PPG), and 2-hydroxyethyl acrylate (HEA) with dibutyl tin dilaurate as a photoinitiator. UV-curable coating materials were formulated from the prepolymers and 2,2-dimethyl 2-phenyl acetophenone as a photoinitiator with one of four different diluents such as 1-vinyl 2-pyrrolidone (VP), lauryl methacrylate (LMA), acrylic acid 2-ethyl hexyl ester (AEHE), and acrylic acid n-butyl ester (ABE). It was found that AEHE is the desirable diluent in the formulation of the primary fiber-coating material. The desirable composition of PBD, when mixed PBD/PPG diols are used, should be about 50 wt % for optimum formulation. Most of the urethane acrylate prepolymers prepared in this study could be applied in the formulation of primary optical fiber coating and exhibited good properties of buffer functions, including low glass transition temperature, low modulus even at low temperature, say, below ?40°C, high refractive index, and low viscosity. © 1992 John Wiley & Sons, Inc.     

Low VOC, low viscosity UV cationic radiation-cured ink-jet ink system

Ink-jet inks need to be very low in viscosity to transport the ink through the jet nozzle as well as for drop formation and integrity. The objective of this project was to demonstrate UV-cured systems for ink-jet inks and coatings with zero volatile organic compounds and very low viscosity. Cycloaliphatic epoxy systems were selected as binders of choice for this project due to their low viscosity and ability to be cured using UV-cationic photoinitiators. UV-curable coatings and inks with zero VOC and less than 10 cPs viscosities were formulated using exempt solvent acetone and vinyl cyclohexene diepoxide. UV-curable inks with up to 10% black dye were formulated. Rapid cure was achieved through the use of aryl sulfonium salts of hexafluorophosphoric acid. The presence of dye inhibited the reaction, but adequate cure of dyed formulations was achieved by increasing the concentration of the photoinitiator. Coatings Research Institute, 430 W. Forest Avenue, Ypsilanti, MI 48197.     

Effects of nonreactive resins on the properties of a UV-curable methacrylated urethane resin

The effects of two nonreactive conventional-type resins, a bisphenol-A-based phenoxy resin PAPHEN-301 and aromatic-based PETROLEUM RESIN, on the mechanical, thermal, and physical properties of methacrylated urethane resin-based UV-curable formulations were studied. A methacrylated urethane prepolymer was synthesized from isocyanatoethyl methacrylate (IEM) and polytetrahydrofurandiol (PTHF) via a one-step reaction. An increase in PAPHEN-301 content caused an increase both in tensile strength and elongation values of UV-cured polymeric films. On the other hand, an increase in PETROLEUM RESIN content caused a decrease both in tensile strength and elongation values of the polymeric films. However, thermooxidative properties were not affected by the introduction of either resin. It was also found that the water-absorption capacities of the UV-cured methacrylated urethane films depended on the type and amount of the nonreactive resins. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1837–1845, 1998     

Hydrolytic stabilities of some polyurethane hydrogels

The hydrolytic stability of some polyurethane hydrogels derived from UV-curable urethane prepolymers and hydrophilic monomers was addressed. It was found that polyurethane hydrogels derived from prepolymers with hydrophilic polypropylene glycol soft segments were not stable when the films were cast from nonpolar solvent, whereas they are stable if the films were cast from neat monomer mix. The causes for this instability were analyzed. Spectroscopic and gel permeation chromatographic studies of the water extractables suggested that improper curing of hydrophilic monomers with the urethane prepolymers in nonpolar solvent was mainly responsible for the instability phenomenon.     

Tuning the mechanical properties of UV coatings towards hard and flexible systems

The standard resins of radiation-curable coatings provide either hard or flexible coatings dependent on the type of chemistry used. Whereas aromatic epoxide acrylates usually give hard and brittle coatings, urethane acrylates are known for their flexibility. Since the radiation curable systems should not contain solvents, the desired low viscosity for the specific application is adjusted with reactive monomers. This normally prevents the use of flexible high-molecular-weight polymers. On the other hand, the viscosity of dispersions is determined by the solid content only and not by the molecular weight of the polymers used. Thus, waterbased UV-curable coatings are one strategy out of this dilemma in order to combine the flexibility of higher-molecular-weight polymers with the hardness of highly crosslinked acrylates. The mechanical data of conventional and waterbased UV coatings are discussed in dependency on glass transition temperature and elastically effective chain length between crosslinks.     

氧抑制剂与分子流动性的关系:残余双键是影响初始粘度的函数(英文)

透明涂料的双重固化(热固化和UV固化)为层面涂装和汽车的更多特种部件的发展提供了巨大的发展前景。因为其可能解决紫外固化的屏蔽区的固化不完全的问题[1]。在先前的论文中,已经证实了UV光张度(辐射密度,I0)对暴露膜表面和丙烯酸酯中分子结构的双键转换的深层断面的氧抑制作用的影响[2～6]。近期的研究评价了具有不同玻璃化温度的固态聚合物基体对丙烯酸酯结构中双键转换的影响。探讨了UV固化配方和双重固化配方之间比较的一种直接判断的性能。研究中所使用的固态聚合物基体包括:聚甲基丙烯酸甲酯(PMMA,Tg114℃,平均重均分子质量 MW120000)和聚甲基丙烯酸丁酯(PBMA,Tg15℃,MW=337000)。通过改变单体和齐聚物混合物的分子质量的比以及固态聚合物基体的总含量,调整有氧存在或无氧存在的暴光时间(即固化速度)来进行研究工作,对于这个双重固化配方还用恒定的UV能量辐射评价了残余双键。用FTIR证实了剩余双键。讨论了紫外固化和双重固化配方的自游基迁移性和氧抑制作为配方体系粘度的功能函数。这些研究工作是基础性的而且是非常重要的。其目的是探索双重固化透明涂料的工业应用。     

光敏有机硅聚氨酯丙烯酸酯预聚体性能的研究

考查了光引发剂、活性单体对光敏有机硅聚氨酯丙烯酸酯预聚体（PSUA）胶膜的耐水性、拉伸强度、伸长率、硬度、柔韧性和热稳定性的影响。结果表明，胶膜具有优良的耐水性，吸水性低于4％。含单官能度单体的PSUA胶膜的接触角大于含多官能度单体的，含有IBOA的体系接触角达103．6°；当选择引发效率高的裂解型光引发剂，用量为0.5％～1％时，胶膜具有较高的接触角。含多官能度单体胶膜的拉伸强度高于含单官能度单体的体系，但伸长率较小。含TMPTA体系的胶膜的硬度最大，为0．575。胶膜具有较好的柔韧性和热稳定性，其柔韧性达到1mm级，在300℃时失重为4.61％。     

Characterization of Radiation-Induced Thin Films of Urethane Oligomer

Forty different formulations were developed with urethane diacrylate (M1200) oligomers (containing an aliphatic backbone chain) in the presence of eight different functional monomer diluents additives and five co monomers (co additives). Thin films, prepared with these formulations under ultraviolet (UV) and electron beam (EB) radiations, were characterized. The theological properties were correlated with glass transition temperature (T _g) of the co monomer diluents. Results obtained with M1200 under UV and EB radiations are discussed and compared with those of aromatic urethane (M1100) films, previously reported.     

Synthesis and characterization of uv-curable acrylated urethane prepolymers,I. Effects of reactive diluents and relative humidity on physical properties

A UV-curable acrylated urethane prepolymer was synthesized from tolylene-2,4-diisocyanate (TDI), a polyether polyol (Arcol 1131) and endcapped with 2-hydroxyethyl methacrylate (HEMA) by addition reaction in the presence of dibutyltin dilaurate as catalyst. UV curing was performed with either diethylene glycol diacrylate or thiodiethylene glycol diacrylate as reactive diluent. The effects of reactive diluent types, their concentrations and the humidity of environment on mechanical properties of cured films were investigated. Changes in the tensile strength, elongation and Young's modulus values of the cured films upon addition of reactive diluents with different concentrations were related to the effect of the diluent on the crosslinking density of cured films. The increase of relative humidity from 50 to 95% caused a decrease of tensile strength and Young's modulus values of cured films. It is proposed that the decrease of these physical properties in high relative humidity is due to the formation of hydrogen bonding in polymer chains caused by water molecules.     

Improvement of jute fiber through ultraviolet-cured films of urethane acrylate

Formulations were developed with urethane acrylate in combination with different monomers. The role of plasticizers used as coadditives in the formulations was investigated. Physical and mechanical properties of the UV-cured films were studied. Hessian cloths made with jute fibers were coated with these formulated solutions and cured under UV radiation. Though plasticizers decrease the tensile properties of the UV-cured films, but they substantially enhance both tensile strength by 80% and elongation of the coated hessian cloths by more than 300%. Uptake of water and moisture at different relative humidity conditions decreases significantly by the hessian cloths when coated with these formulations. © 1994 John Wiley & Sons, Inc.     

New developments in radiation-curable powder coatings

Radiation-curable powder coatings are now in the early stages of commercialization. For years, the coatings industry has sought ways to lower the curing temperature of powder coatings. UV-curable powder coatings offer the possibility of curing powder coatings at temperatures as low as 120°C. Radiation-curable powder coatings also offer high cure speed and relatively low energy consumption. As each application requires its own coating performance, two different maleate-vinyl ether-based binders for UV-curable powder coatings have been developed. With these binders the balance between flexibility and hardness of the coating can be adjusted with proper formulation. In this paper, the curing characteristics and coating performance of several UV-powder coating formulations are described. In addition, a comparison between conventional powder coatings and UV-powder coatings is provided. Presented at the 26th International Waterborne, High-Solids, and Powder Coatings Symposium, February 10–12, 1999, New Orleans, LA. P.O. Box 615, 8000 AP Zwolle, The Netherlands.     

Modification of cotton,rayon, and silk with urethane acrylate under ultraviolet radiation

Ten different formulations were developed with Ebcryl 264, a urethane acrylate in combination with other monofunctional monomers in the presence of some additives and coadditives. Thin films prepared from these formulations under ultraviolet (UV) radiation were characterized. Natural fibers such as cotton, rayon, and silk were treated with the formulations and cured under UV radiation. Their physical and mechanical properties were studied. It was found that the tensile strength (TS) of cotton, rayon, and silk was significantly increased as a result of this treatment under UV radiation (TS_cotton = 150%, TS_rayon = 30%, and TS_silk = 40%). Elongation of cotton and silk increased to 380 and 50%, respectively. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1703–1711, 1997