UV-cured Films Research Articles

A variation in wrinkle structures of UV-cured films with chemical structures of prepolymers

Spontaneously wrinkled films can be easily obtained from UV-crosslinkable liquid prepolymers under special UV-curing conditions. They vary wrinkle structures of the UV-cured films and, however, cannot be precisely controlled. Here, five different UV-crosslinkable prepolymers are synthesized to study the chemical structure effect of prepolymers on wrinkle formation and modulation of the UV-cured films irrespective of the UV-curing conditions. Both wavelength and amplitude of the wrinkles are tuned with the different liquid prepolymers from 4.10 to 5.63µm and from 1.00 to 1.66µm, respectively. The wrinkle structures of the UV-cured films are faded by adding a solid prepolymer to a liquid prepolymer due to interference from it in the shrinkage of the liquid prepolymer layer. The wrinkles completely disappear in the UV-cured films fabricated from the formulated prepolymers containing over 50wt% of the solid prepolymer.

Rapid preparation of epoxy acrylate-clay nanocomposite: Simultaneous acrylation/nanoclay dispersion under ultrasonication

Abstract The main theme of the present study was to prepare the epoxy acrylate-clay nanocomposite through the simultaneously acrylation reaction of epoxy resin and dispersion of clay nanoparticles under ultrasonic irradiation. The acrylation of diglycidyl ether of bisphenol-A epoxy resin was carried out through the reaction with acrylic acid in the presence of different nanoclays. In addition to UV-curing agents, two different types of commercial organoclays namely, Cloisite 15A and Cloisite 30B were used in nanocomposite films. The degree of epoxy acrylation and the UV-curing process of nanocomposite films were monitored by the corresponding absorption bands in FTIR spectroscopy. The degree of epoxy acrylation reached up to 85% for 30 min ultrasonication with a rather good degree of dispersion for both organoclays as evidenced in XRD patterns and SEM and TEM micrographs. The comparative study of different UV-cured nanocomposites films were carried out by means of different thermal and mechanical test such as DSC, TGA, DMTA and the surface hardness. The significant improvements in glass transition temperature and the thermal stability of different nanocomposites were attributed mainly to effective interactions between clay platelets and epoxy acrylate chains which result in proper dispersion of clay platelets.

UV-cured multifunctional coating resins prepared from renewable thiolactone derivatives

Abstract A set of multifunctional UV-cured thiol-ene polymer resins were systematically prepared from thiolactone containing monomers and different amine compounds. Aminolysis of the thiolactone moiety enabled the introduction of different side chains and cross-linkers into the polymers. The glass transition temperature of the polymers varied between 22 and 90 °C, depending on the type and molar ratio of amine-containing compounds relative to the monomer. The properties of the UV-cured thin films were screened using standard tests for coatings, including pencil hardness, impact resistance, and cross-hatch adhesion. Thiolactone-derived polymer films exhibited high transparency of 90%, pencil hardness in the range of 3B-HB, high impact resistance >2 kg m, and good adhesion to steel in dry conditions.

UV-cured polysulfone-based membranes: Effect of co-solvent addition and evaporation process on membrane morphology and SRNF performance

Membranes consisting of a semi-interpenetrating network of polysulfone (PSU) and cross-linked polyacrylate were synthesized via non-solvent induced phase inversion followed by UV-treatment. Tetrahydrofuran (THF) or 1,4-dioxane (DIO) was added as co-solvent to the N,N-dimethylformamide (DMF)-based polymer solutions and cast films were subjected to evaporation prior to coagulation. Effects of synthesis variables on the membrane morphology and solvent resistant nanofiltration (SRNF) performance were investigated by using a Rose Bengal solution in isopropanol. By increasing the evaporation time from 0 to 100s for the membranes prepared with THF and DIO as co-solvent respectively, rejections increased from 65.3% to 94.2% and 60.1–89.1%, while permeances decreased from 0.29 to 0.01l/m2 h bar and 0.41–0.08l/m2 h bar. A similar effect was observed when the co-solvent/solvent ratio was increased from 0/100 to 100/0: rejections increased from 63.1% to 94.9% and 59.2–90.6%, while permeances decreased from 0.43 to 0.01l/m2 h bar for THF-based membranes and to 0.07l/m2 h bar for DIO-based membranes respectively. A post-treatment was performed to increase the flux by immersing UV-cured PSU-based films in DMF for 48h. The resultant membranes showed higher permeances and lower rejections, making them especially useful as potential candidates for stable supports to apply selective layers upon, such as e.g. in thin film composite (TFC) membranes. As observed in scanning electron microscopy, higher evaporation times and lower initial co-solvent concentrations resulted in less or even no macrovoids.

Improvement of the water-vapor barrier properties of an uv-cured epoxy coating containing graphite oxide nanoplatelets

Abstract In this paper we investigated the improvement of water-vapor barrier properties of an UV-cured epoxy film containing graphite oxide nanoplatelets. Graphene platelets were successfully dispersed in the epoxy resin and cured by UV-irradiation. Good performances in increasing water vapor barrier properties at a very low filler loading are obtained: the permeability decreased of about 40% with a 0.5 wt.% of GOx and of about 60% with a 1.0 wt.% of GOx. These good results are attributed to a homogeneous filler dispersion, as clearly shown by TEM microscopy.

Modification and characterization of urethane acrylate oligomers used for UV-curable coatings

Nine modified urethane acrylate oligomers including polyether-modified polyurethane acrylate, epoxy-modified polyurethane acrylate and hyperbranched polyurethane acrylate have successfully been synthesized and characterized by Fourier transform infrared spectra. The properties of UV-cured films formed by these oligomers were also investigated. The effects of the molecular structure of the oligomers on the properties of cured film, including tack-free time, pencil hardness, impact resistance, adhesion and boiling water resistance, have been discussed. The results indicate that the UV-cured film with good performance can be designed by the modification of the molecular structure of the oligomer. Among the oligomers prepared in this paper, the cured film formed using HBPUA-50%OA as oligomer exhibits a relatively short tack-free time, high hardness, good impact resistance, great adhesion and boiling water resistance.

Oxygen concentration and conversion distributions in a layer-by-layer UV-cured film used as a simplified model of a 3D UV inkjet printing system

Three-dimensional (3D) ultraviolet (UV) inkjet printers represent a versatile technology for creating complex functional structures. During their operation, 3D objects are formed by repeating cycles of drawing a UV-curable resin with inkjet nozzles and then solidifying it with UV irradiation. In this study, the activity performed by a 3D UV inkjet printer was simulated by spin casting a 33µm thick layer of UV-curable resin (containing diurethanedimethacrylate and 1-hydroxycyclohexyl phenyl ketone compounds mixed at a weight ratio of 99:1) onto a Si wafer followed by photopolymerization for 2s at a UV irradiation of 10mWcm−2. Afterwards, the second resin layer with a thickness of 33µm was spun-cast onto the first layer and photopolymerized under the same conditions. The conversion distribution of C=C bonds in the UV-curable resin was investigated via confocal laser Raman microscopy and numerical calculations, which took into account the kinetics of photopolymerization and oxygen inhibition reactions. The confocal laser Raman microscopy technique provided a unique distribution of the C=C bond conversion across the film depth. Thus, the conversion magnitude at a depth of 0µm was zero and increased to 0.2 at 6µm. Afterwards, the slope of the conversion distribution plot became moderate until the conversion reached the value of 0.43 at a film depth of 28µm. Between the film depths of 28 and 38µm, the conversion remained constant with a variation not exceeding 0.03. After that, the conversion value increased again, reaching the magnitude of 0.48 at a depth of 50µm and remained constant in the region between 50 and 56µm (with a variation not exceeding 0.04). At higher depths, the graph slope became moderate again, and the conversion value increased gradually to 0.51 at 66µm, after which the silicon wafer was reached. As a result, two different plateaus were observed on the conversion distribution plot: between 28 and 38µm and between 50 and 56µm (the corresponding conversion variation in these regions was below 0.05). The obtained experimental data were in good agreement with the results of numerical calculations, which attributed the existence of the two plateaus on the plot of the C=C bond conversion distribution to the formation of an oxygen-lean point. In addition, the effects of the UV intensity, irradiation time, lamination time, photoinitiator concentration, and concentration of dissolved oxygen on the oxygen concentration and conversion distributions across the depth direction have been examined. The obtained results revealed that the increases in the UV intensity, irradiation time, and photoinitiator concentration as well as the decrease in the initial dissolved oxygen concentration effectively increased the conversion of C=C bonds in the resin film and decreased the thickness of an unpolymerized layer.

Synthesis of fluorinated polycarbonate-based polyurethane acrylate for UV-curable coatings

Fluorinated polycarbonate-based UV-curable polyurethane acrylate (F-PCUA) was synthesized by incorporating 1H, 1H, 2H, 2H-Perfluoro-1-octanol to the end of polycarbonate-based PUA chains. The structure of F-PCUA was determined by 1H-NMR, 19F-NMR, and FTIR analyses. The physical, surface, and thermal properties of F-PCUA were also examined. The F-PCUA was used as a hydrophobic additive in PUA coatings, and the water and oil wettability of the UV-cured film was investigated by contact angle measurements. The results showed that the coating system had great hydrophobicity. Furthermore, X-ray photoelectron spectroscopy research confirmed that a hydrophobic fluorine-enriched surface was obtained in the coating system. Moreover, the mechanical and chemical properties of the hydrophobic coatings did not show deterioration with the introduction of elemental F.

Physical Properties of UV-cured Epoxy Nanocomposite Films

Cationic UV-curing of a cycloaliphatic epoxy proceeds efficiently at room temperature, resulting in a highly crosslinked polymer network exhibiting the same excellent physical properties as obtained by thermal curing. However, the highly crosslinked rigid polymer network generally shows undesirable brittleness. Therefore, in this study, three kinds of reactive diluents, one epoxy and two polyols, were tested to prepare a cycloaliphatic epoxy film with reasonable physical properties by cationic UV-curing. Also, effects of nanosilica on the physical properties of the epoxy film were investigated. FTIR spectroscopy was used to investigate the UV-curing behaviour of the epoxy resin systems. Amongst the diluents enhanced UV-curing rate and final conversion levels, the epoxy diluent was the most effective. The tensile properties of the epoxy films were investigated by UTM. At a fixed diluent content of 30 phr, the film with the epoxy diluent showed best tensile strength. The film with the epoxy diluent 40 phr showed optimum tensile properties. The film with the epoxy diluent 40 phr showed further enhanced tensile properties at the nanosilica content 0.05 phr.

UV Cure Enabled Robust STI Oxide Gap Fill Solution for Thermally Limited Flow in Advanced Logic Devices

High mobility channel materials such as Si1-xGex (x = 0.1-0.5) are important to achieve performance targets for FinFET devices at dimensions scaled beyond 14nm. Previously, flowable (FCVD) SiO2 deposition processes have been developed to achieve adequate fill for Shallow Trench Isolation in FinFET structures. However, the thermal budget for curing FCVD oxide with SiGe fins must be limited to avoid out-diffusion of Ge. This restricts the processing options for achieving a robust material which is compatible with subsequent wets processing steps. FCVD oxide deposition employs an amine-based silicon precursor which, upon exposure to NH3 radicals, forms short chain -Si-N-Si- oligomers with terminal Si-H or N-H bonds. These oligomers flow into and fill deep isolation trenches. Once the trenches are filled, it is critical to stabilize the film and initiate cross linking for densification to SiO2. To this end, a cure while still under vacuum, such as O3 oxidation, is commonly used before a subsequent furnace steam anneal. This paper describes an alternate curing process using broadband UV light to densify FCVD oxide. Material properties were studied using cure by microwave-powered Hg lamps at 10 degC with broadband (200-450nm) spectrum and compared to the existing O3 cure. To achieve the desired FCVD film properties, it is beneficial to remove -OH terminations during the post-dep cure to promote a dense final -Si-O-Si- matrix. Fig. 1 shows high frequency FTIR spectra from UV-cured FCVD oxide films as a function of UV power post-steam anneal. Data from O3 cured FCVD oxide is plotted for comparison. The spectrum from the non-oxidizing UV cure process shows lower peak intensities for –OH and H-OH stretch peaks. For promoting densification, UV curing is also effective in breaking N-H bonds. The number of NH/NH2 bonds is reduced with increasing UV power and a corresponding increase in Si-H bonding is observed. Figure 2 shows FTIR spectra of cured FCVD films treated with a subsequent steam anneal. The film with O3cure show more residual silanols (Si-OH) relative to UV cured films. Also, the -Si-O-Si- bonding peak is higher in UV cured films, suggesting a denser -Si-O-Si- network. During the steam anneal process, we observed that UV cured films densify more rapidly than O3 cured films. For anneals at 500°C, a dense SiO2 surface layer is formed, blocking further O2diffusion and leaving a less dense film below which has a higher wet etch rate (Fig. 3). This effect is evident in Fig. 4a where FCVD oxide has been recessed using an etching technique. The oxide between fins is weaker and has recessed more than the oxide in the field region outside of the array (see reference lines). A two-step steam anneal was then developed to achieve uniform properties through film depth: 400°C for 1 hour followed by 500°C for 2 hours. Fig 4b shows a structure with oxide annealed in this way and then recessed through etching; it was observed that the recess is now equivalent in the field and between fins. The impact of UV power on the cure process was also explored. Fig. 5 shows the WERR as a function of thickness for blanket O3 cured FCVD films and UV cured films after steam anneal. The UV cure again shows significantly lower WERR compared to O3 cure, with more densification and improved film uniformity through depth with increased power. Fig. 6 compares cumulative electrical breakdown behavior for O3 cured and UV cured films after steam anneal obtained using MIS structures. The UV cured films show a higher breakdown voltage (Vbd ~10MV/cm) relative to O3 cured films (~9MV/cm). Fig. 7 is a comparison of WERR between O3 cured film and UV cured film inside the narrow STI Trench Features. The films were steam annealed followed by 2x900°C-1min soak RTA in N2. Data shows 30% lower in-trench WERR for UV cure compared to O3cure. In conclusion, UV cure has been demonstrated as a means to provide improved FCVD quality over O3cure as measured by wet etch rate ratio, in blanket films and within trenches for STI applications. This work was performed by the Research Alliance Teams at various IBM Research and Development Facilities. Figure 1

UV-cured polymeric films containing ZnO and silver nanoparticles with UV–vis light-assisted photocatalytic activity

Hybrid polymer composites incorporating preformed ZnO alone or its mixture with Ag nanoparticles created during UV irradiation of some urethane acrylic monomers including trietoxysilylpropyl carbamoyloxyethyl methacrylate were synthesized and characterized by spectroscopic (1H (13C) NMR, FTIR, UV–vis, fluorescence, X-ray diffraction) and microscopic (AFM, ESEM/EDX, TEM) techniques. The results confirmed that the double bond conversion measured through FTIR spectroscopy varied in the range of 57–90% (after 60s of irradiation), exhibiting formulation composition dependence. In the crosslinked polymer networks the existence of individual nanoparticles with primarily spherical shape and sizes between 5 and 15nm for ZnO, and around 3nm for in situ photogenerated silver nanoparticles was evidenced. Additionally, the photocatalytic effect of the photopolymerized hybrid films was investigated by determining the decomposition rate of the methylene blue (MB) in ethanol (over 90%) under UV (2.7×10−2s−1) and visible irradiation (2.9×10−2min−1). It was found that the composite films containing a higher amount of ZnO-Ag nanoparticles placed in water induced the photodecomposition of MB (∼87% after 100min of visible irradiation; k=2.1×10−2min−1). The good efficiency of the NPs from these polymer films make them attractive for applications in photocatalysis of organic dye molecules.

Synthesis and characterization of novel UV-curable fluorinated polyurethane-acrylate copolymer

A series of UV-curable fluorinated polyurethane-acrylate(PUA) has been developed by incorporating octafluoropentyl alcohol into the segment of UV-curable polyurethane-acrylate to improve the thermal property and surface property of the copolymer material. The structures of the synthesized polymers were characterized by Fourier transform infrared(FTIR) spectrometry. In order to find out the effect of incorporated fluorine on the UV-cured films, the properties of the UV-cured films were tested through contact angle, water absorption, and thermogravimetric analysis (TGA). The fractured-surface morphologies of the UV-cured coatings were investigated by scanning electron microscopy(SEM). With increasing the content of fluorine segments, the contact angle of the UV-cured films increased and the water absorption decreased, suggesting the fluorine segments migrated and formed a fluorine-covered surface to avoid water penetration. The observation of the fractured-surface morphology through SEM test showed that the fluorinated UV-cured films gained rough fractured-surface compared with the pure UV-cured polyacrylate film, demonstrating the migrating of the fluorine segments. The TGA curves show that the fluorinated UV-cured films gained higher thermal degradation temperature than the virgin UV-cured polyacrylate film. And as increasing the fluorine content, the thermal degradation temperature increased. These phenomena could be reasonably explained by the enrichment of fluorinecontained segment on the surface of the film and the high thermal property due to fluorine atom.

Preparation and properties of UV-curable waterborne comb-like (meth)acrylate copolymers with long fluorinated side chains

Abstract A novel waterborne UV-curable comb-like (meth)acrylate graft copolymer containing long fluorinated side chains (UVWCAC) was synthesized by conventional radical copolymerization of a novel mono-methacryloyloxy terminated fluorinated macromonomer (PHFBMA-GMA) and (meth)acrylate monomers. GPC, FTIR and 1 H NMR were employed to characterize the structure of the polymers. The influence of both the molecular weight and concentration of PHFBMA-GMA on the properties of UV-cured films was investigated. Hydrophobic surface could be obtained with just small amount of PHFBMA-GMA copolymerized into the polymer. The surface energy of UV-cured films decreased as both the concentration and the molecular weight of PHFBMA-GMA increased. The surface composition of the graft copolymer was characterized by XPS. XPS results confirmed the enrichment of the fluorine atoms on the surface quantitatively. In addition, the physical properties of UVWCAC UV-cured films, such as gel content, water absorption, pencil hardness, adhesion, chemical resistance, mechanical properties, optical transmittance and thermal properties were also investigated in detail. The novel UVWCAC prepared via conventional radical polymerization not only had excellent properties but also had the prominent potential application in large scale industrialization.

Studies of optical properties of UV-cured acrylate films modified with spherical silica nanoparticles

This study presents the optical properties of UV-cured acrylate films modified with spherical silica nanoparticles. The nanoparticles together with the UV-acrylate monomer solution were first prepared by an ultrasonic method to produce a suspension of silica–acrylate. The UV-cured acrylate films modified with the nanoparticles were fabricated by coating the suspension on cleaned glass substrates, then exposed to UV light for 10min at ambient temperature. The effect of the silica nanoparticle content on the optical properties of the modified films was determined by a UV–Vis spectrophotometer and an apparatus equipped with a laser. Based on the visible absorption data, the transmittance of all the modified film coated substrates is lower than that of the unmodified film. The transmittance of the modified films decreases with the increasing silica content. The increasing silica content also improves the haze and light diffusing ability of the modified films. The highest haze of about 0.26 and the largest range of scattered light were achieved using the film modified with 30vol% particles. These nanoparticles show a good potential to improve the optical properties of the UV-cured acrylate film, especially the light diffusing property that may be utilized in electronic display technologies.

Effects of UV Intensity, Line-speed, and Light Distribution on Conversion and Surface Elastic Modulus of Roll-to-roll UV-cured Film

Effects of UV Intensity, Line-speed, and Light Distribution on Conversion and Surface Elastic Modulus of Roll-to-roll UV-cured Film

Anisotropic charge-carrier mobilities of liquid crystalline conjugated polymers on photo-aligned PVCN dielectric insulators

We fabricated organic thin-film transistors (OTFTs) with photo-reactive poly(vinylcinnamate) (PVCN) as a dielectric layer and liquid crystalline poly(2,5-bis(3-dodecylthiophene-2-yl)thieno[3,2-b]thiophene) (PBTTT) as a semiconducting layer. The PVCN layer plays an important role in the fabrication of OTFTs with solution processable PBTTT, because it provides orientation of the liquid crystalline polymer chains as well as gate insulating characteristics. The electrical properties of PBTTT-OTFTs with the UV-cured PVCN film were investigated for the films prepared with linearly polarized ultraviolet light irradiation along parallel and perpendicular to the electrode channel direction.

Tetra-functional epoxy-acrylate as crosslinker for UV curable resins: Synthesis, spectral, and thermo-mechanical studies

Abstract UV-curable tetra-functional epoxy acrylate (EA4) was newly synthesized using 4,4′-methylenebis(N,N-diglycidylaniline). Effects of reaction temperature and epoxy/acrylic acid molar ratios on the reaction conversion were investigated. The conversion of epoxy to ester group was monitored by FTIR spectroscopy and the relative concentration of epoxy value and conversion of the reactions were calculated from FTIR data, in different intervals of the reaction time. EA4 curing under UV irradiation was studied, and the physicochemical characteristic of the cured resin was determined. DMTA, TGA and mechanical properties of the casted films were evaluated. Moreover, studies on effect of the synthesized EA4 content on properties of conventional epoxy acrylate (EA2) were carried out. According to TGA and DMTA studies, the UV-cured blend films of EA2 containing ≤9% EA4 presented film homogeneity, and improved thermal and mechanical properties. Thus, it can be used as a crosslinking agent in UV-curable formulations.

Preparation and properties of UV-curable multi-arms cardanol-based acrylates

Abstract A series of multi-arms cardanol-based acrylates (CGHA, CDHA, CTHA) were synthesized using renewable cardanols and bio-based polyols (glycerol, diglycerol, tripilyglycerol) as precursors. The structures and molecular weights of the cardanol-based acrylates were characterized by FT-IR, 1H NMR and GPC, respectively. The synthesized multi-arms cardanol-based acrylates were used to produce UV-curable films and coatings. High mechanical strength as well as good biodegradability of the UV-cured films was obtained. The important coating film properties, such as hardness, gloss and adhesion were also investigated. The results showed that the coatings with high bio-based content exhibit good adhesion, gloss and acid-resistance, which is comparable to the soybean oil (AESO)-based and polyester acrylate.

Hydrophobic Scratch Resistant UV-Cured Epoxy Coating

A selective modification of the surface properties of UV-cured epoxy films was achieved, with an important enhancement of hydrophobicity and scratch resistance, by dispersion on the UV-curable formulations of fluorinated functionalized silica particles. The photopolymerization process was investigated and the films were fully characterized. Contact angle measurements with water on UV-cured films showed a linear increase of the contact angle of cross-linked films by increasing the functionalized SiO2 content in the photocurable formulation. Also, a consistent and linear improvement of penetration resistance was noted in terms of penetration depth by increasing the fluorinated functionalized silica content.

Synthesis and properties of photopolymerizable bifunctional polyether-modified polysiloxane polyurethane acrylate prepolymer

A UV-curable polyether-modified polysiloxane polyurethane acrylate prepolymer PESiUA that can be used for polyvinyl chloride leather finishing agents has been synthesized and characterized by nuclear magnetic resonance, Fourier transform infrared spectroscopy, and gel permeation chromatography. The prepolymer exhibited excellent compatibility with acrylate monomers, satisfying photopolymerization efficiency and good yellowing resistance. The influences of the monomers on the properties of the UV-cured film were systematically studied. The results showed that the increase in the functionality of monomers can increase the thermostability, glass transition temperature, tensile strength, tensile modulus, dispersion surface energy, and decrease the contact angle and elongation at break. More significantly, the PVC leather finishing agent designed based on the photopolymerizable polyether-modified polysiloxane polyurethane acrylate prepolymer PESiUA possessed excellent performances and had great application potential, due to the combination of advantages of polysiloxane segment and polypropylene glycol segment as well as photopolymerization technique.