Role of additives on UV curable coatings on wood

An epoxy resin-coating formulation was prepared from diacrylated epoxy bisphenol-A-epichlorohydrin and a reactive monomer, tripropyleneglycol diacrylate. The additives, silane and fluorochemicals, were included in the formulation to evaluate their effects on the UV curing of the epoxy resin onto timber. Thin films coated on wood substrates were cured under UV radiation in the presence of the photoinitiator, benzoin ethyl ether. Adhesion of the cured films onto wood substrates was evaluated using the cross-cut and the pull-off tests. Film hardness was evaluated using the pencil hardness and the pendulum hardness tests. Water repellency of the films were measured from contact angles using a telegoniometer. Scanning electron microscopy (SEM) was used to investigate the interface between the films and the wood substrates. These studies showed that silane only enhanced the adhesion of the film onto the wood substrates but had no effect on the hardness of the films. The additives improved the water repellency of the films with the fluorochemicals, exhibiting dramatic improvement. SEM revealed that only the fluorochemical aided the penetration of the resin into the wood. © 1996 John Wiley & Sons, Inc.     

Mechanical properties study of photocured paperboard surface treated with aliphatic epoxy diacrylate

In order to improve the quality of paperboard (a well‐known packing material) surface by photocuring method, different formulations were developed with aliphatic epoxy diacrylate (EA‐1020) oligomer along with reactive monomers of various functionalities. The reactive monomers are tripropylene glycol diacrylate (TPGDA), a difunctional monomer, and trimethylol propane triacrylate (TMPTA), a trifunctional monomer. 2‐Benzyl‐2‐dimethylamino‐1(4morpholinophenyl) butanone‐1 (Irgacure 369), a photoinitiator (2%), was incorporated into the formulations to initiate photocuring reaction. The formulated solutions were coated on clean glass plate and irradiated under UV radiation of different intensities. Different physical properties like pendulum hardness and gel content of the cured films were studied. The formulation containing TMPTA showed better properties. After characterization of the films, these formulations were applied on paperboard surfaces and cured under the same UV radiation. Various physicomechanical properties such as pendulum hardness, tensile properties, surface gloss, adhesion, abrasion, and water uptake were studied. The best performance was obtained at 12 passes of radiation with 18% TMPTA‐containing formulation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1774–1780, 2003     

Effect of CaCO3 on the performance of Partex surface modification by ultraviolet radiation curing method

Several UV‐curable formulations containing epoxydiacrylate (EB‐600) oligomer with a tri‐functional monomer, trimethylol propane triacrylate (TMPTA), and photoinitiator Irgcure‐369 were developed to improve the surface of Partex. Filler or extender CaCO₃ was incorporated into the solution. Thin polymer films were prepared on glass plate with these formulated solutions and finally applied on polished Partex surface, and both were cured under UV‐radiation. The properties of UV‐cured thin films were studied as a function of CaCO₃ concentration. Pendulum hardness and gel content were found to decrease on glass plate with the increase of CaCO₃ concentration. Pendulum hardness, scratch hardness, and abrasion resistance of the cured Partex were found to be higher with the increase of CaCO₃ content up to 4%. Thus, the formulation containing 4% CaCO₃ showed the best performance over all formulations containing CaCO₃. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1858–1867, 2001     

Influence of Codiluent on the Properties of Radiation-Cured Films

A number of formulations were developed using urethane diacrylate oligomer in combination with a series of monofunctional and multifunctional reactive diluents possessing diverse glass transition temperatures from ?50°C to 250°C. Films prepared with these formulations were cured under ultraviolet (UV) radiation; their properties, such as hardness, gel content, tensile characteristics, etc., were determined and compared with those of the films cured by electron beam (EB) radiation. Effect of comonomer diluents was investigated in these cases. A good correlation was observed between these properties and the glass transition temperature (T _g) of the copolymer (cured film), prepared under radiation with urethane acrylate, monomer, and comonomer.     

Enhancement of Physico-mechanical Properties of Plywood Surface with Urethane Acrylate (M-1200) by UV Curing Method

Several UV-curable formulations containing urethane acrylate (M-1200) oligomer with a trifunctional monomer, trimethylol propane triacrylate (TMPTA), and photoinitiator Irgcure-369 were developed to improve the surface of plywood. Thin polymer films were prepared on glass plate with these formulated solutions and finally applied on polished plywood surface to modify the surface, and both were cured under UV-radiation. The properties of UV-cured thin films were studied as a function of UV-radiation intensities. Pendulum hardness (PH) and gel content were found to increase with the increase of TMPTA concentration up to a certain level and with further increase of monomer concentration the physical properties were decreased. The polymer-coated surface yielded enhanced physico-mechanical properties compared to that of unmodified surface.     

EFFECT OF FILLERS ON THE PROPERTIES OF PHOTOCURED PARTEX SURFACE USING EPOXY ACRYLATE OLIGOMER

In order to improve the surface of partex by photocuring, various formulations of epoxydiacrylate (EB-600) oligomer, with a trifunctional monomer trimethylol propane triacrylate and a photoinitiator Irgacure 369 [2-benzyl 2-dimethylamine-1 (4-morpholinophenyl) butanone-1] were developed. Two fillers CaCO₃ and sand (SiO₂) were incorporated with base coat formulations to study their role in the properties of UV-cured partex surfaces. Thin polymer films were prepared on glass plate with these formulations and finally applied on polished partex surface and both were cured under UV radiation. Radiation intensities, expressed by number of passes were optimized to the extent of pendulum hardness (PH) and gel content. The properties of cured partex surface such as PH, gloss—both at 60 and 20° angles, macro and micro scratch hardness, adhesion strength of the coatings, and abrasion resistance were studied as a function of the concentration of fillers. The base coating containing 4% CaCO₃ and 3% SiO₂ showed the best performance amongst all of them. The effect of simulating weathering on the properties (PH, gloss, and adhesion) of the cured surface was also studied.     

Synthesis and characterization of palm‐based resin for UV coating

The production of UV curable acrylated polyol ester prepolymer from palm oil and its downstream products offer potential and promising materials for applications such as polymeric film preparation and coatings. In this study, palm olein polyol was reacted with acrylic acid in the presence of a catalyst and inhibitors via condensation esterification process. The reaction temperature of 80°C and the stirring rate of 400 rpm produce a homogeneous product. Based on iodine value result, the suitable amount of p‐toluene sulfonic acid monohydrate used as catalyst was 3.0% (w/w) of palm olein polyol. Different UV curable formulations have been investigated using the synthesized prepolymers with monomers and a small amount of photoinitiator. Monomers used were 1,6‐hexanediol diacrylate (HDDA) and trimethylolpropane triacrylate (TMPTA) while photoinitiator used was 1‐hydroxy cyclohexyl phenylketone (Irgacure 184). The mixtures were cured to make thin polymeric films under UV radiation with doses between 2 and 14 passes (energy per pass is 0.6 J/cm²). Coating and curing was carried out on glass for pendulum hardness and FTIR analysis. Pendulum hardness of the film prepared using monomer HDDA and the prepolymer previously synthesized using 3.0% catalyst was 24.5%. The radiation dose needed was 14 passes. The highest pendulum hardness of 49.4% was achieved using monomer TMPTA and the prepolymer synthesized using 2.0% catalyst. The radiation dose needed was 10 passes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Codiluent effect on the properties of UV-cured films

Different formulations were developed with an urethane oligomer combined with a number of reactive diluents with different functionalities such as N-vinylpyrrolidone (monofunctional), butanediol diacrylate (difunctional), tripropylene glycol diacrylate (difunctional), and trimethylolpropane triacrylate (trifunctional). The films were prepared with these formulations and cured under UV radiation in the presence of the photoinitiator Irgacura 184. Their properties were characterized. The effect of codiluents of low glass transition temperatures like ethyl hexyl acrylate and methoxyethyl acrylate on the properties of these films was studied. These formulations were then applied as thin coatings on the leather surface in order to study the improvement of the leather substrate. Both tensile strength and elongation of the treated leather increased. The gloss of the coated leather was also enhanced. Incorporation of a plasticizer into these systems substantially improved the rheological properties of the coated leather. © 1995 John Wiley & Sons, Inc.     

Ultraviolet‐curable epoxidized sunflower oil/organoclay nanocomposite coatings

Hybrid nanocomposite coating films, prepared by the incorporation of epoxidized sunflower oil into organoclay, can be cured by ultraviolet radiation with either cationic or hybrid initiation. The organoclay used in this study was prepared by a cationic exchange process in which sodium ions were replaced by alkyl ammonium ions. The effects of types of photoinitiators on energy consumption in the curing process were studied. Formulations with a hybrid photoinitiator required less energy in the curing process than those with a cationic photoinitiator. Moreover, the physical properties of dried films were examined as a function of the organoclay incorporation, and it was found that the hardness of the films increased as the amount of organoclay in the formulation increased. The X‐ray diffraction patterns of an ultraviolet‐curable organoclay‐incorporated film showed an exfoliated structure of the organoclay in the ultraviolet‐curable coating film. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Comparison of mechanical and degradation properties of EG and EGDMA grafted gelatin films

Thin films of gelatin were prepared from gelatin granules in aqueous medium by casting and its mechanical properties like tensile strength (TS), tensile modulus (TM), and elongation at break (Eb %) were studied. Gelatin films were procured with two types of monomers such as 5% ethylene glycol (EG) and 5% ethylene glycol dimethacrylate (EGDMA) to increase the mechanical properties. Five percent of monomer solutions were prepared in MeOH along with 2% photoinitiator; Irgacure-651. Soaking time and UV radiation intensities were optimized with the extent of polymer loading (PL) and the mechanical properties of the cured films. Comparing the properties of EG and EGDMA treated gelatin film, EG showed the best performance. The EG-cured gelatin film with 5?min soaking time showed the highest tensile strength (58.6?MPa) and elongation at break (11.2%). The water uptake was determined for raw film (500.1%), EG grafted gelatin film (375.3%), and EGDMA grafted film (412.9%). The degradation properties in water and soil were determined for the raw and cured gelatin films. It was observed that the raw film degrades more than that of the treated films.     

Effect of fillers on curing of wood surfaces with polyester oligomers by ultraviolet radiation

A set of formulations was prepared with polyester acrylate (oligoester M‐9050) oligomers in combination with reactive diluents of different functionalities such as ethylhexyl acrylate, tripropylene glycol diacrylate , and trimethylol propane triacrylate (TMPTA). The thin films were prepared with these formulated solutions under UV radiation on a glass plate, and their physical properties such as pendulum hardness and gel content were studied. The formulation containing TMPTA showed the greatest pendulum hardness and gel content. The polished wood surfaces were cured with these formulated solutions. Physical properties such as pendulum hardness gloss at 20° and 60° angles, adhesion, abrasion resistance, and scratch hardness of UV‐cured surfaces of the wood were characterized. The formulation containing TMPTA had the best physical properties. Two types of filler, sand and talc, were used in the base coat to obtain these better properties. Both fillers improved the properties; however, the 1% sand– and 4% talc–containing formulations performed better. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3826–3834, 2003     

Morphologies and applied properties of free radical/cationic UV‐cured CPUA/TMPTMA/CER composite films

A UV‐cured composite film was prepared by free free‐radical photopolymerization from a blend containing oligomer cycloaliphatic polyurethane acrylate (CPUA) and reactive diluent trimethylolpropane trimethaacrylate (TMPTMA) with the same weight (coded as UT) in the presence of free free‐radical photoinitiator Irgacure 754. It was proved to be a homogeneous system featuring only one phase by means of scanning electron microscopy (SEM). Cycloaliphatic epoxy resin (CER) was introduced to enhance mechanical properties of the UV‐cured UT composite film in the presence of cationic photoinitiator Irgacure 250, and a series of UV‐cured CPUA/TMPTMA/CER composite films with different component ratios were prepared by free radical/cationic hybrid UV UV‐curing technique. Results of conversion curves, SEM, and Fourier‐ transform infrared spectroscopy illustrated that UT was cured faster than CER, leading to dynamically asymmetric photopolymerization‐induced phase ‐separation behaviors. The thermal and mechanical properties were evaluated via thermal degradation analysis, dynamic mechanical analysis, and stress–strain curves. Surface properties such as pencil hardness, pendulum hardness, shrinkage rate, contact angle, flexibility, and glossiness were also studied. All these measurements revealed that component ratios, intermolecular attractions, photopolymerization velocities, and viscosities had remarkably influenced on the morphologies and applied properties of UV‐cured composite films, and interpenetrating polymer network films had better comprehensive performances than other UV‐cured composite films with different microstructures. POLYM. COMPOS., 36:1177–1185, 2015. © 2014 Society of Plastics Engineers     

Curing of crust leather by ultraviolet radiation with urethane acrylate: Role of pigment

Eight different formulations were developed with four diacrylate reactive monomers such as tripropylene glycol diacrylate (TPGDA), 1,4‐butanediol diacrylate (BDDA), 1,6‐hexanediol diacrylate (HDDA), and 2‐ethylene glycol dimethacrylate (EGDMA) and aromatic urethane diacrylate (M1100) in order to modify the crust leather surface. To study the effect of pigment on the performance of ultraviolet (UV)‐cured leather surface, 1% pigment (congored) was incorporated in the formulations. Irgacure 369 (2%) was also used in the formulation as photoinitiator. The gel content, tensile strength, elongation at break, and pendulum hardness of UV‐cured thin films with and without pigment was studied. The films without pigment produced better properties. Among all the diluents, BDDA‐containing films showed the best performance. Different properties of UV‐coated leather surface such as pendulum hardness, tensile strength, elongation, gloss (at 20° and 60°), adhesion, and abrasion were studied. Effect of gloss on simulating weathering was also performed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 692–697, 2002     

Preparation and properties of UV-autocurable BTDA-based epoxy-multiacrylate resins. Effects of the degree of polymerization and the epoxy type

A series of UV-autocurable epoxy-multiacrylate resins was synthesized, and the effects of degree of polymerization (DP) and epoxy type on their properties were investigated. These autocurable multiacrylate resins possess good pot life and are cured rapidly when exposed to ultraviolet (UV) without the addition of photoinitiator or photosensitizer. The curing rate of the autocurable resins was probably dependent on the number of abstractable hydrogen in epoxy resins. Stress-strain, differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA) were used to characterize the properties of cured multiacrylate resins. Increased crosslinking density of cured films improved tensile properties. Increasing the molar ratio of epoxy resin in the multiacrylate resins was found to decrease the effective acrylate concentration of resins and to depress crosslinking density of cured resins, which also resulted in an increased elongation at break but a decreased Young's modulus and breaking strength. Furthermore, the different structures of epoxy resins were used to give wide range properties of cured epoxy-multiacrylate resins with a glass transition temperature (T_g range from 74 to 102°C. The film properties of the multiacrylate resins coated on steel plates were also investigated.     

Effect of Adhesion,Film Thickness,and Substrate Hardness on the Scratch Behavior of Poly(carbonate) Films

The effect of adhesion, film thickness, and substrate hardness on the scratch behavior of poly(carbonate) (PC) films was investigated. Films of various thickness were prepared by spin-coating solutions of PC in chloroform onto glass, ferroplate, Al 1100, Al 6022, and Al 6111 substrates. Adhesion between the films and the substrates was controlled by pretreatment of the substrates and the thickness of the films was controlled by the concentration of the PC solutions. Adhesion of the films to the glass substrates was measured by a blister test. Scratch tests were performed using a custom-built, progressive-load scratch tester with interchangeable diamond indenters; the resulting scratches were observed by optical microscopy, atomic force microscopy (AFM), and environmental scanning electron microscopy (ESEM). The critical normal load (i.e., the smallest applied normal load for which delamination of the film from the substrate was observed) was used as a criterion to determine the scratch resistance of the films. It was found that better film/substrate adhesion resulted in a higher critical load for delamination. As film thickness increased, the critical load and, thus, scratch resistance also increased. Substrate hardness had a strong influence on the scratch behavior of the PC films. For a low-hardness substrate (i.e., Al 1100), the work from scratching was mainly consumed by deforming the substrate. In the case of substrates with intermediate hardness (i.e., Al 6022, Al 6111, and ferroplate), the substrates were more resistant to the stresses that were generated in the films; hence, the deformation of the substrates was less severe. A high-hardness substrate (i.e., glass) resisted the applied load and resulted in higher stress concentrations in the films and at the interface. Consequently, a rougher surface inside the scratch track was observed.     

Comparative study of electron-beam- and ultraviolet-cured films of urethane acrylate

A urethane diacrylate oligomer was used to develop 40 different formulations in combination with eight different reactive diluents in the presence of five different coadditives. Thin films were prepared with these formulated solutions under ionizing radiation using either electron beam (EB) or ultraviolet (UV) rays. In the latter case, a photoinitiator was incorporated into the formulation. Physical, mechanical, and thermal properties of the cured films were studied. Tensile properties (strength and elongation) were almost double with the UV-cured films than those of the EB-cured films. Thermal behavior was also observed to be different in these two systems. These properties were correlated with the glass transition temperatures of the homopolymer of codiluents used. © 1996 John Wiley & Sons, Inc.     

Preparation and properties of UV-autocurable BTDA-based polyurethane methacrylates

Syntheses of several UV-autocurable methacrylourethanes and the effects of polyol type on their properties are investigated. Autocurable benzophenone tetracarboxylic dianhydride (BTDA)-based polyurethane methacrylates are prepared by addition reaction from benzophenone tetracarboxylic dianhydride (BTDA), 2,4-toluene diisocyanate (TDI), 2-hydroxyethyl methacrylate (HEMA), and polyol (polyethylene glycol, polydiethylene succinate, polydiethylene maleate, or polydiethylene hexamethylene-dicarbamate). Autocurable oligomers possess good pot life and are cured rapidly when exposed to ultraviolet (UV) radiation without the addition of photoinitiator. The different polyols are used to obtain wide range properties of cured films with a glass transition temperature (T_g) range of -10.5-5.5°C. Increasing the T_g of polyol shifts the dynamic mechanical storage modulus and loss factor of the cured film to high temperature. For practical application, oligomer is mixed with reactive monomers to bring the systems to a workable viscosity at room temperature. Among the monomers, the higher the composition of hydroxyethyl acrylate in the oligomer-monomer system, the higher the curing rate of the system as compared with neat oligomer. Moreover, increasing the chain length of dimethacrylate monomers results in a decrease in breaking strength from 160 to 140 kg/cm², in Young's modulus from 771 to 400 kg/cm², and in glass transition temperature from 18 to 6.5°C, while the elongation at breaking increases from 70 to 130%.     

Ultraviolet curing of epoxy coating on wood surface

Different formulations were developed with EB-600 (Ebcryl-600), an epoxy acrylate oligomer in the presence of N-vinylpyrrolidone and trimethylol propane triacrylate. Thin films were prepared with these formulated solutions under ultraviolet (UV) radiation. These solutions were coated on a low-grade wood substrate (simul) and cured under UV light. Both UV-cured thin films and surface coatings were characterized, and the best formulations for coating wood surface were evaluated. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1997–2004, 1997     

Development of coating materials from liquid wax esters for wood top-based coating

Of late, UV-curable products are gaining attention in the wood industry because of the effectiveness and efficiency of this method. UV-curable surface coatings are widely used because of their excellent properties and because they are environmentally friendly products. In this study, immobilized Candida antarctica lipase B was used to catalyze formation of liquid wax esters, such as adipate esters, via a solvent-free process. The adipate esters formed were then used as UV-curable reactants in the wood coating formulations, consisting of epoxy acrylate, additives, and a photoinitiator. The performance of the products was evaluated by coating them onto glass tiles (using gel content, hardness, and scratch resistance tests) and wood panels (using adhesion, impact, and heat resistance tests). The coated film from this formulation performed well during the evaluation tests. The gel content exhibited more than 90% polymerization, while the pendulum hardness gave a value of 55.25%. Both analyses were significant in determining the effect of irradiation cycles. A scratch test was also carried out to verify the resistance of the coating. The maximum weight load which can be resisted by the wax esters formulation is 4.5 N.     

Effects of the electron‐beam absorption dose on the glass transition,thermal expansion,dynamic mechanical properties,and water uptake of polycardanol containing epoxy groups cured by an electron beam

In this study, the glass transition, thermal expansion, dynamic mechanical properties, and water‐uptake behaviors of diepoxidized polycardanol (DEPC) cured by electron‐beam radiation in the presence of cationic photoinitiators were investigated. How the type and concentration of cationic photoinitiators and the electron‐beam absorption dose influenced the properties of the cured DEPC was also studied. Two types of cationic photoinitiators, triarylsulfonium hexafluorophosphate (simply referred to as phosphate type or P‐type) and triarylsulfonium hexafluoroantimonate (simply referred to as antimonate type or Sb‐type), were used. Electron‐beam absorption doses of 200, 300, 400, and 600 kGy were applied to the uncured diepoxidized cardanol (DEC) samples, respectively. It was revealed that the Sb‐type photoinitiator was preferable to the electron‐beam curing of DEC; this led to a lower photoinitiator concentration and/or a lower electron‐beam absorption dose compared to that in the phosphate‐type photoinitiator. As a result, the variations in the glass‐transition temperature, coefficient of thermal expansion, storage modulus, and water uptake of the cured DEPC were quite consistent with each other. We found that the optimal conditions for the enhanced properties of DEPC by electron‐beam curing were an Sb‐type photoinitiator at 2 wt % and an electron‐beam absorption dose of 600 kGy. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42570.