Ultraviolet Curable Coatings Research Articles

Preparation and photocuring performance of itaconic acid-derived hyperbranched macromers with internal and terminal C[dbnd]C bonds catalyzed by tetramethylguanidine

A series of hyperbranched polymers derived from biomass itaconic acid was prepared via aliphatic nucleophilic substitution polycondensation reaction under mild conditions by using bis(2-bromoethyl) itaconate and trimeric acid as A2 and B3 monomers, respectively, and tetramethylguanidine as catalyst. On this basis, the hyperbranched macromers that contained C = C double bonds in the internal skeleton and the periphery were obtained by further adding A1 monomer (2-bromoethyl acrylate) directly into the reaction system. The successful synthesis of these macromers were confirmed via proton nuclear magnetic resonance, Fourier transform infrared and gel permeation chromatography. The results of photo-differential scanning calorimetry and rheological experiments showed that these macromers exerted a positive effect on the ultraviolet (UV) curing of commercial resin. The properties of cured splines and coatings, such as mechanical properties, pencil hardness, and thermal stability, were considerably improved with the addition of hyperbranched macromers. They were significantly better than those of linear macromers and macromers that contained polymerizable groups only in the inner framework or their terminal units. The results show that both the inner and terminal C = C double bonds of hyperbranched macromers can participate in UV cross-linking. Thus, such macromers may be used as potential additives for high-performance UV curable coatings.

Study on Synthesis, Optical properties and Application of Benzophenone derivatives

AbstractIn this study, the mono‐substituted and di‐substituted benzophenone derivatives containing the ester group were synthesized by the reaction of dihydroxy benzophenone with acyl chloride. Their structures were characterized by 1H NMR and 13C NMR and their optical properties and application in ultraviolet curable coatings were studied. The mono‐substituted compounds can be used as UV absorbers and do not participate in the curing of the free radical system during UV‐curing, enhancing the light stability of coatings and cured coatings and facilitating the storage of UV‐curable coatings. The di‐substituted compounds can be used as photoinitiators for ultraviolet curable coatings and show good film morphology.

Synthesis and properties of polyurethane acrylate oligomer based on polycaprolactone diol

Abstract The polycaprolactone diol (PCL diol) was prepared by ring-opening polymerization method, with hydroquinone bis(2-hydroxyethyl) ether as the reactive initiator and ε-caprolactone as the monomer. The polyurethane acrylate (PUA) was prepared with the self-made PCL diol. Then, PUA was used to prepare the ultraviolet curable coatings. The structure and molecular weight of PCL diol was characterized by Fourier transform infrared spectroscopy, gel-permeation chromatography, and hydroxyl value titration. The performance of the cured coating film was characterized by thermogravimetric analysis and scanning electron microscope. The flexibility and hardness of the cured coating film were tested. The results showed that the narrow molecular weight PCL diol was successfully synthesized. The UV curing coating film had the optimal performance with a hardness of 3H, flexibility of 1.5 mm, abrasion resistance of 0.028 g−1, and adhesion of grade 1, all coating films showed good thermal properties.

Eugenol-Based Siloxane Acrylates for Ultraviolet-Curable Coatings and 3D Printing

Eugenol-Based Siloxane Acrylates for Ultraviolet-Curable Coatings and 3D Printing

Studying the Influence of Mica Particle Size on the Properties of Epoxy Acrylate/Mica Composite Coatings through Reducing Mica Particle Size by the Ball-Milled Method

In this work, a series of epoxy acrylate (EA)/mica composite coatings were synthesized through introducing mica powders of different particle size into epoxy acrylate coatings and using an ultraviolet (UV) curing technique to investigate the influence of mica particle size on the coatings. Mica powders of different particle sizes were obtained by ball-milling for 4, 8, 12, 16, and 20 h with a planetary high-energy ball mill. The particle size and morphologies of ball-milled mica powders were characterized by laser particle size analyzer and scanning electron microscopy (SEM). The results indicated that planetary ball-milling reduced the particle size of mica powders effectively. Mica powders that were un-ball-milled and ball-milled were added into the epoxy acrylate matrix by a blending method to synthesize the organic-inorganic UV curable coatings. The optical photographs of the coatings showed greater stability of liquid mixtures with smaller particle size fillers. The chemical structures of EA/mica composite coatings were investigated by Fourier transform infrared spectroscopy (FTIR), and the conversion rate of C=C bonds was calculated. The results indicated that the C=C conversion of coatings with mica powders of smaller particle sizes was higher. Tests of mechanical properties and tests using electrochemical impedance spectroscopy (EIS) showed that pencil hardness, impact resistance, and coating resistance were improved due to the reduction of mica powders particle size.

UV coatings for wooden surfaces

Ultra violet (UV) radiation curing has emerged as a fast and environment friendly curing technique for coating on various surfaces (wood, metals, plastic & stone). Although, there are several UV curable coating formulations available in the international market, but these coatings have quite low viscosity and are not suitable for wooden surfaces as coatings tend to quickly get absorbed in to the porous structure of wood leading to slow curing. There is a need for designing coating formulations which are although sprayable, but have optimum viscosity so as to not get absorbed into the wooden surfaces. Besides, coatings have to have fast curing rate as well, so that while in process of curing they do not get absorbed in to the wood. Generally, UV curable coatings comprise of acrylate based oligomers (epoxy, polyurethane, and polyester), reactive diluents (mono-, di-, or polyfunctional glycidyl ether), photoinitiator (benzyl peroxide, phosphine oxide) and functional additives. These coating compositions are first applied on wooden surface and then exposed to UV radiation for curing. The photoinitiator dissociates on UV exposure to form free radicals, which initiate the polymerization of the oligomers and diluents, leading to the formation of a polymeric crosslinked network on the wooden surface. In the present study, sprayable coating compositions were designed based on epoxy acrylate that get cured within 10 s of UV exposure and exhibit excellent thermal and stain resistance properties.

Hectorite and bentonite effect on water-based polymer coating rheology

Increased interest in aesthetic, natural nail coatings has encouraged more in-depth studies, and particularly of ultraviolet curable coatings, their formation, processing, characteristics, and removal. This study investigated the impact of various thixotropic agents (organically modified hectorite and bentonite clays) on water-based oligomer system rheology. Ingredients were evaluated to determine their influence on unreacted composite characteristics (viscosity and pigment suspension stability) and reacted film characteristics (modulus of elasticity, elongation at break, and film adhesion force). It is concluded that clay-based thixotropic agents are suitable for use as a suspension agent in nail polish formulations and, depending on the concentration, can decrease the risk of pigment sedimentation and syneresis.

Functionalized multiwalled carbon nanotubes for UV coating

PurposeThis paper aims to investigate effects of acrylic functionalisation of multiwalled carbon nanotubes (MWCNTs) on properties of carbon nanotubes/epoxy nanocomposites.Design/methodology/approachA number of analytical techniques, including Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy, were used to assess the effects of acid treatment on MWCNTs. Ultraviolet-curable coatings were fabricated by sonication and cast moulding process. The mechanical properties of MWCNTs/epoxy composites at different weight fractions were evaluated by performing tensile tests and dynamic mechanical analysis tests. Also, gel contents were examined.FindingsIt was found that addition of nanotubes monomer to epoxy formulations had significant effect on the viscoelastic and mechanical properties.Practical implicationsImproving dispersion and alignment of MWCNTs in the composite matrix will contribute to the development of resin/MWCNTs nanocomposites and promote the applications.Originality/valueThe paper establishes a method to introduce MWCNTs into epoxy matrix as a monomer to enhance the photo curable and dispersion properties of the MWCNT/epoxy films.

Temperature dependence of the viscosity of epoxy acrylate-tripropylene glycol diacrylate binary mixtures

AbstractEpoxy acrylate (EA) and tripropylene glycol diacrylate (TPGDA) are two main components of ultraviolet-curable coatings. In this study, the viscosity of EA-TPGDA binary mixtures at various mass ratios was measured by a rotational viscometer at temperatures between 298.15 and 313.15 K. The temperature dependence of the viscosity of the mixtures is discussed. An empirical correlation between the viscosity and the temperature was obtained based on the Andrade equation. The results indicated that the calculated viscosity values show a good agreement with experimental data. This will contribute to the evaluation of the rheological properties and provide a theoretical basis for the industrial application of coatings.

Synthesis and characterization of dual-curable epoxyacrylates for polyester cord/rubber applications

In this study, bisphenol-A-based acrylated epoxy oligomers were prepared and utilized to improve the adhesion strength of polyester cords onto rubber. The structure of the oligomers was characterized by Fourier transform infrared spectroscopy and 1H-NMR spectroscopy. Ultraviolet-curable adhesive formulations were prepared by using acrylated epoxy oligomers and applied onto the polyester cord fabric by a dip-coating method and irradiated. Ultraviolet-cured coatings were characterized by thermal and scanning electron microscope analysis, contact angle measurements. In the second stage of the experiment, ultraviolet-cured polyester cords were adhered onto rubber under heat and pressure. The prepared adhesive formulation was expected to improve the adhesion strength. The adhesion strength of the coated material was evaluated by using peel test as a function of the carboxyl/epoxide ratio. The adhesion strength of 18.0 N/cm was obtained when the carboxyl/epoxide ratio was set as 1. It was observed that peel strength, contact angle, and surface energy values of acrylated epoxies strongly depend on the acrylic acid content of the oligomer.

Development of palm oil‐based alkyds as UV curable coatings

PurposeThe purpose of this paper is to develop palm oil‐based alkyds as ultraviolet (UV) curable coatings and investigate the parameters that affect the coating performances.Design/methodology/approachAlkyds were formulated from palm stearin, glycerol, phthalic anhydride and maleic acid. Keeping the total molar amount of dicarboxylic acids constant, the proportions of maleic acid and phthalic anhydride were varied in order to produce polymer chains with different content of unsaturation, which is crucial for UV curability. Characterisations were carried out by FTIR and 1HNMR. The alkyds were then mixed with methyl methacrylate (MMA) monomer as active diluents and cured by exposure to UV light. Performances of the cured coatings were tested in terms of film hardness, adhesion, water and alkali resistance, and thermal stability.FindingsUpon introducing sufficient C=C, the alkyd in combination with MMA is able to UV‐cure within short time and produce film of satisfactory quality. There are several other factors, which influence the coating properties; these include thickness of coating, ratio of alkyd to active diluents, and duration of UV exposure.Social implicationsThe product is a form of green technology that could benefit the environment as it involves very low or near zero emission of volatile organic compounds (VOC).Originality/valueThe novelty of this work lies in the formulation of new products from palm stearin, leading to new developments in the surface coating and palm oil industries.

Application of a UV curable hard coating containing κ-aluminum oxide particles on poly (vinyl chloride) plastic tiles

In this study, ultraviolet (UV) curable hard coatings, containing various κ-aluminum oxide (κ-Al2O3) contents, have been used to improve the abrasion resistance of poly (vinyl chloride) (PVC) plastic tiles. This developed UV curable hard coating can form a protection film on the surface of the PVC plastic tile. Thus, the abrasion resistance of the PVC plastic tile can be improved. After coated by the UV curable hard coating containing 10wt% κ-Al2O3, the abrasion resistance of the PVC plastic tile can be improved up to 16.6%. Besides, the transparent UV curable hard coatings showed excellent adhesion on the PVC plastic tiles. Scanning electron microscopy (SEM) images showed that most of κ-Al2O3 particles were well dispersed in the UV curable hard coating film.

Preparation of ultraviolet-cured nanocomposite coatings for protecting against corrosion of metal substrates

A cycloaliphatic di-epoxy monomer was used to prepare ultraviolet-cured coatings, in the presence of montmorillonites, either commercially available, or modified on purpose (Cloisite Na +, Cloisite 30B), dispersed at two different concentrations (5% and 10% w/w). The corrosion resistance of the ultraviolet-cured films coated on a metal substrate was investigated with electrochemical techniques and compared to the behaviour of the neat ultraviolet-cured epoxy resin films. The coatings showed different stability as revealed by the measurements of the barrier properties depending on the type of nanoclay used. Changing the modifier employed the coatings exhibited intercalated or exfoliated morphologies, as assessed by electron microscopy analysis and confirmed by X-ray diffraction results; the prevention of corrosion was proved dependent on the morphology.

Tetrafunctional acrylates based on β-hydroxy alkyl amides as crosslinkers for UV curable coatings

Ultraviolet (UV) curable coating formulations were prepared from novel crosslinking acrylates synthesized from β-hydroxy alkyl amides. Variations were done with respect to the nature of the monomer backbone by introducing aliphatic, aromatic and cycloaliphatic structures in between the amide groups. The synthesized multifunctional alcohols and acrylates were subjected to IR and NMR analysis for structure confirmation. The acrylates were dissolved in chloroform and the UV–vis spectrum was recorded to substantiate the presence of carbonyl group conjugated to the vinyl group. The new acrylates were added to basic formulation and exposed to UV radiation to get transparent films. The dynamic mechanical properties of the films cast from the formulations were assessed and studies on the effect of the synthesized crosslinking acrylate content and their nature on the viscoelastic properties of the films were carried out. Improvements in glass transition temperature ( T g) were observed with increasing percentage of crosslinker. Acrylates based on aromatic acid amides showed higher T g than aliphatic acid amides. The storage modulus ( E′) increased up to 10% and further increases in the crosslinker percentage led to a decrease in the modulus. The rubbery modulus depended on percentage of crosslinker and not on crosslinker structure.

UV curable coatings with mesogenic side groups

Copolymers having liquid crystalline (LC) side groups were prepared by ultraviolet (UV) photo-polymerization of acrylic monomers with mesogenic groups, acrylic monomers, and acrylic oligomers. These copolymers were evaluated as coatings on metal substrates in view of enhancement of film hardness and flexibility. A non-LC copolymer, i.e., a copolymer without mesogenic units, was used as control. Extraordinary balances of elongation and hardness have been obtained from the coatings consisting of copolymers with an LC side group.

Stress Buildup in Ultraviolet-Cured Coatings: Sample Thickness Dependence

Stress buildup in ultraviolet radiation-induced coating can vary significantly as a function of processing conditions. Depending on radiation intensity and photoinitiator concentration, the average stress in the film may either increase or decrease with film thickness. On the basis of the current study on trimethylolpropane triacrylate (TMPTA) together with data reported previously, we conclude that the two main factors affecting stress in radiation curable coatings are (i) degree and distribution of cross-linking and (ii) temperature at solidification point. In certain experimental conditions, an uneven distribution of the conversion within the film may occur, leading to a decrease of the average film stress with increasing film thickness. In contrast, the temperature jump in the sample when irradiated may lead to an increase of the ultimate stress with film thickness.

Cationic ultraviolet curable coatings from castor oil

Coatings formulated from castor oil glycidyl ether (COGE), epoxy resin UVR 6100, and photoinitiator UVI 6990 produced smooth coatings with excellent gloss and good flexibility, adhesion, gloss retention, and water resistance. Formulations containing up to 50% COGE afforded promising coating performance attributes. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 8–13, 2000

Polymeric photoinitiators having benzoin methylether moieties connected to the main chain through the benzyl aromatic ring and their activity for ultraviolet-curable coatings

New polymeric UV photoinitiators, bearing the benzoin methyl ether moiety linked to the side chain through the 4′ position, were synthetized by radical homopolymerization of the corresponding monomers, 4′-methacryloyloxy benzoin methyl ether and 4′-methacryloyloxy α-methyl benzoin methyl ether, prepared in turn after a thorough investigation of synthetic methods. For comparison, low molecular weight structural models of the repeating co-units of the polymers having the pivaloyloxy group linked to the 4′ position of the benzoin methyl ether moiety were also prepared. All polymeric and model compounds were fully characterized and employed in the photoinitiated polymerization and crosslinking of a standard acrylic formulation for clear UV curable coatings. The photoinitiating activity of these systems, measured by microwave dielectrometry, indicates a higher cure fastness for the model compounds with respect to the corresponding polymeric derivatives, and such a behaviour is tentatively interpreted in terms of the fragmentation mechanism of the benzyl methyl ether radicals formed on α-photocleavage of the benzoin moiety.

Outdoor applications of UV curable clearcoats - a real alternative to thermally cured clearcoats

In addition to other technologies, i.e. high-solids, waterborne and powder coatings, UV curable coatings are also certain to play an important role in the coating industry's future, especially as a means of overcoming solvent emission limitations and energy savings. In principle, ultraviolet curable coatings can be used in all applications as long as the performance requirements are fulfilled. One of the most important requirements for a broad use of UV curable coatings in the coating industry is that coatings are stable against degradation caused by atmospheric influences. This weathering leads to a degradation of the polymeric binder. With novel photoinitiators based on bis-acylphoshinoxides (BAPO) it is possible to cure clearcoats containing a combined UV-absorber/HALS light stabilizer package. These clearcoats show both a very good curing behaviour and an improved weather-fastness over a long period of time.

Investigation of the effects of formulation on selected properties of UV curable IPN coatings

Ultraviolet curable coatings based on urethaneacrylic resins were prepared by free radical polymerization. The effects of photoinitiators on the curing reaction and the influence of polyol types and dimethylopropionic acid (DMPA) amounts on the properties of UV curable coatings prepared by free radical polymerization (UVF) were investigated. The effects of polymerization (UVC) and the consequences of postcuring conditions on the properties of UVC were evaluated. The interpenetrating polymer network (IPN) containing UV curable coatings (UVIPN), which were composed of UVF and UVC at different ratios (by weight), were prepared. The properties of UVIPN with varied UVF/UVC ratios were studied.