• Journal of the Korean Wood Science and Technology
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• v.34 no.2
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• pp.58-67
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• 2006

The relationship between acoustic property and coating hardness of musical instruments was investigated using a sound level meter and a pendulum hardness tester. Urethane topcoat, oil stain, natural oil varnish, and UV-curable epoxy acrylate coatings were applied on four different substrates: Paulownia coreana, Pinus koraiensis, Castanea crenata var. dulcis and Pinus densiflora. The influence of the coating type on the acoustic properties was stronger than that of the substrate. In the case of an oil stain formed with tacky coating layer, the sound pressure level (SPL) and surface hardness decreased with increasing of coating thickness. In the other coatings, SPL decreased and hardness increased as the coating layer thickened. However, SPL began to increase again at coating thickness above $100{\mu}m$.

• Journal of Adhesion and Interface
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• v.9 no.2
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• pp.32-37
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• 2008

A series of UV-curable powder coatings with different contents of photoinitiator (0.5 wt%, 1 wt%, 2 wt%) were formulated and measured gel content, tensile strength of cured film. Heat-sensitive substrates such as MDF, plywood and PVC were coated UV-curable powder and cured coatings were measured physical properties by pendulum hardness tester, glossmeter, pull-off adhesion tester. With increasing photoinitiator content, adhesion force between coating and substrate decreased because of crosslinking density increasing. The results of pendulum hardness was not significantly changed but gloss was changed according to different substrates. Adhesion of UV-curable coatings was enough to apply for heat-sensitive substrates. From these results, we concluded that contents of photoinitiator was a effective factor in UV-curable powder coatings. UV-curable coatings was a portential candidate for heat-sensitive substrates.

• Journal of the Korean Wood Science and Technology
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• v.36 no.6
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• pp.121-129
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• 2008

Environmental friendly UV-curable coatings, having excellent hardness, gloss, mar and chemical resistance, are commonly used for the wooden flooring coatings. Especially epoxy acrylate oligomers are chosen for the wooden flooring coatings, due to their thermal stability and fast curing. In this study, we investigated the effect of the acrylate functionality on the thermal stability and surface hardness. The thermal degradations of monomers, oligomer, photoinitiator and formulated coatings with different acrylate functionality were measured using a thermogravimetric analysis (TGA). And the surface hardness was also measured with a pendulum hardness tester to compare relationship between the thermal stability and the physical property. The cured coatings became thermally stable by crosslinking during UV-curing. Both the thermal stability and surface hardness of cured coatings were improved with increasing acrylate functionality.

• Journal of Adhesion and Interface
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• v.13 no.1
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• pp.38-44
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• 2012

Surface properties and curing behavior of UV-initiated photopolymerization with and without wax have been investigated by pendulum hardness, pencil hardness, gloss, photo-differential scanning calorimetry (photo-DSC) and SEM. In addition, the influence of wax type (paraffin wax, PE wax) on the various properties of UV cured films was studied. The results showed that the wax type was the significant factor affecting gloss and surface hardness of UV cured films. Specially, the photo-DSC results showed that ${\Delta}H$ for the UV cured films containing paraffin wax was higher than the corresponding values for the formulation without wax and with PE wax. The observed results clearly demonstrate that the photopolymerization of UV curing with paraffin wax in an air atmosphere is less inhibited by the oxygen compared to UV curing without wax and with PE wax.

• Journal of the Korean Applied Science and Technology
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• v.25 no.3
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• pp.322-331
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• 2008

In order to synthesize high-solid coatings, acrylic resins (HSAs) containing 90% solid content were first synthesized, then the synthesized HSAs were cured with a curing agent, isocyanate, at room temperature to obtain high-solid coatings. In the HSAs synthesis, conversion was in a range of $82{\sim}87%$, and viscosities and number-averaged molecular weight ($M_n$) of the HSAs were in a range of $4380{\sim}8010$ cP and $1540{\sim}1660$, respectively. From the correlation between $T_g$ value, viscosity and $M_n$, it was found that, with increasing $T_g$ value, viscosity increases rapidly and molecular weight increases slowly. From the visco-elasity measured by the pendulum method, it was found that the curing time decreased with increasing $T_g$ values. From the tests of physical properties of the coatings' film, $60^{\circ}$ specular gloss, impact resistance and heat resistance were proved to be good and pencil hardness, drying time and pot-life were proved to be poor.

• Journal of the Korean Applied Science and Technology
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• v.20 no.3
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• pp.237-242
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• 2003

The high-solid coatings were prepared by blending the synthesized acrylic resin in the previous paper and hexamethylene diisocyanate-trimer and curing it at room temperature. The characterization of the films of the prepared coatings was performed. The impact resistance, $60^{\circ}C$ specular gloss, cross-hatch adhension, and heat resistance of the films proved to be good, and the pencil hardness and drying time proved to be slightly poor. Especially, there was a remarkable improvement in the heat resistance. This improvement may stem from the regular arrangement of ethyl groups introduced into the acrylic resin. From a viscoelastic measurement using a rigid-body pendulum, curing was accelerated with the $T_g$ value. With the increase in $T_g$, log damp value was lowered and dynamic viscoelasic $T_g$ of a cured film was increased.

• Journal of the Korean Applied Science and Technology
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• v.23 no.2
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• pp.110-114
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• 2006

The high-solid coatings were prepared by blending the synthesized acrylic resin in the previous paper, and hexamethylene diisocyanate-trimer and curing it at room temperature. The characterization of the films of the prepared coatings was performed. The $60^{\circ}$ specular gloss, impact resistance, cross-hatch adhesion, and heat resistance of the films proved to be good, and the pencil hardness, drying time, and pot-life proved to be slightly poor. From a viscoelastic measurement using a rigid-body pendulum, curing was accelerated with the Tg value.

• Journal of the Korean Applied Science and Technology
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• v.21 no.4
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• pp.300-305
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• 2004

High-solid coatings were prepared by blending of previosly synthesized acrylic resins and hexamethylene diisocyanate-trimer and curing it at room temperature. The characterization of the films of the prepared coatings was performed. The impact resistance, cross-hatch adhesion, $60^{\circ}$specular gloss, and heat resistance of the films proved to be good, and the pencil hardness and drying time proved to be slightly poor. Especially, there was a remarkable improvement in the heat resistance. This improvement may stem from the regular arrangement of ethyl groups introduced into the acrylic resin. As a result of Rigid-body pendulum visco-elasticity measurement, dynamic $T_g$ values of cured films increased with dynamic $T_g$ values.

• Journal of Adhesion and Interface
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• v.15 no.1
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• pp.22-30
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• 2014

Self-photoinitiating acrylate (SPIA) which can undergo self-initiation under UV irradiation was synthesized by a Michael addition in the presence of a base catalyst. The SPIA polymerizations were investigated by photo-differential scanning calorimeter (photo-DSC) and surface physical properties such as pendulum hardness and pencil hardness. The results showed that the SPIA can cure upon UV irradiation by itself without a photoinitiator. But we found out that both the curing rate and the conversion were too low for the self-curing reaction of SPIA. In order to improve the SPIA curing properties, we introduced the SPIA/cationic hybrid system and observed the effects of the addition of commercial free radical type monomer and photoinitiator on the curing behaviors. SPIA/cationic hybrid system was the best suitable to improve the SPIA curing properties. The kinetic analysis indicated that the cationic monomer and photoinitiator apparently accelerated the cure reaction and rate of the hybrid SPIA system, mostly due to the synergistic effect of cationic monomer and photoinitiator increasing the mobility of active species and the generation of reactive species (free radical, cation) during the photopolymerization process. The physical properties showed that, unlike typical free radical system, the hybrid systems did not show oxygen inhibition effect because of cationic reaction on the coating surface.

• Journal of Adhesion and Interface
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• v.12 no.2
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• pp.47-55
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• 2011

UV-curable coatings have been used in various industries due to their advantages such as high mechanical property, good solvent resistance, fast curing process and low volatile organic compounds. However, a lack of flexibility of UV-cured films is a weak point for the pre-coated system of roll-to-roll process. In this study, UV-curable polycarbonate-based methacrylates were synthesized with polycarbonate diol, isophorone diisocyanate and 2-hydroxyethylmethacrylate to improve flexibility of the UC-cured films. The effects of polyol molecular weight, content of photoinitiator and monomers on the UV-curing behavior, flexibility and properties were investigated. The UV-curing behavior was measured by a photo-DSC, the pendulum hardness, tensile strength, viscoelastic properties were also evaluated.