• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.10
• /
• pp.339-345
• /
• 2018

We investigated the curing properties of cured coatings for a multi-focal UV-LED. The coatings are for LEDs that operate at multiple UV wavelengths, unlike conventional single-wavelength UV-LEDs. Using UV-LED light sources with wavelengths of 365, 395, 420, and 450 nm, we analyzed the optical characteristics such as the direction of light flux and light source. We also analyzed the curing characteristics at each UV-LED wavelength to optimize the LED for composite wavelengths. The curing performance state was predicted through computer simulation for when the multiple wavelengths of UV light sources are superimposed, and then actual LEDs were designed and fabricated. To improve the internal high-speed curing, a multi-spot module was fabricated, in which each LED is condensed, and multiple wavelengths are synthesized and condensed at the same position. The adhesive strength, surface hardness, and internal hardness of the curing agent were tested by varying the wavelength combination conditions. The surface hardening and internal hardening were compared and analyzed using a hardness tester and FT-IR analyzer. As a result, the characteristics of the surface and internal hardness were improved by a multi-spot method in which four wavelengths were overlapped in a UV-LED rather than a single wavelength.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.17 no.5
• /
• pp.8-15
• /
• 2018

Films with special properties (e.g., water-repellent films, optical films, anti-reflection films, and flexible films) are referred to as functional films. Recently, there has been interest in fine patterning methods for film fabrication. In particular there have been many studies that use a UV nanoimprint process involving a UV curing method. In this paper, a polymer film was fabricated by the UV nanoimprint process with a micro-pattern, and its durability was evaluated by a wear test and a nano-indentation test. The film mechanical properties (such as coefficient of friction, hardness, and modulus of elasticity) were measured. Moreover, the choice of PUA type resin used in the UV nanoimprint process was confirmed to impact the durability of the thin film. Despite making the polymer film samples using the same method and PUA type resin, different coefficient of friction, hardness, and modulus of elasticity values were obtained. PUA 4 resin had the most favorable coefficient of friction, hardness, and modulus of elasticity. This material is predicted to produce a high durability functional film.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2011.06a
• /
• pp.1059-1060
• /
• 2011

• Journal of the Korea Furniture Society
• /
• v.26 no.4
• /
• pp.428-434
• /
• 2015

In this study, we received each wood plastic composites (WPC) from three manufacturers. These WPCs were evaluated regarding their physical and mechanical properties of both before and after accelerated weathering by ultraviolet (UV) irradiation. The total time of exposure of the WPCs to UV irradiation was 1800 h. The water absorption, volumetric swelling and shrinkage of WPCs did not affected by UV irradiation. Among the mechanical properties, there was no significant differences in bending strength and screw withdrawal resistance of UV treated WPCs compared with those of reference WPCs. However, surface hardness of WPCs showed decrease under UV irradiation. Stereoscopic microscopy observation revealed deterioration of the surface layer polymer in all weathered WPCs by UV. Exposure of the WPCs to UV irradiation caused decomposition and disappearance of the polymer layer. From this result, we can estimate that damage of polymer by UV led to a decrease in the surface hardness of the WPCs. The wood flours retained original shape after accelerated weathering by UV irradiation.

• Korean Chemical Engineering Research
• /
• v.56 no.2
• /
• pp.162-168
• /
• 2018

UV-curable hard coating solutions were prepared by mixing organic or inorganic polysilazane with urethane acrylate. UV-cured hard coating films were also obtained by flow coating, subsequently UV-curing on polymethylmethacrylate (PMMA) sheets. The effect of types and amounts of polysilazane was investigated on properties of obtained coating films. As a result, the coatings obtained by using organic polysilazane showed a high hydrophobic property with water contact angle of $95^{\circ}$, pencil hardness of 7H and high transparency of 92% in the visible wavelength range. On the other hand, the PMMA sheets made by using inorganic polysilazane exhibited a pencil hardness of as high as 8H, good adhesion to the substrate and water contact angle of $82^{\circ}$.

• Journal of the Korean Wood Science and Technology
• /
• v.36 no.6
• /
• pp.121-129
• /
• 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
• /
• v.13 no.1
• /
• pp.38-44
• /
• 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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.06a
• /
• pp.551-552
• /
• 2007

Coating films were prepared from silane-terminated Colloidal silaca(CS) and UV-curable acrylate resin. The silane-terminated CSs were synthesized from CS and methyltrimethoxysilane(MTMS) and then treated with 3-methacryloxypropyltrimethoxysilane(MAPTMS)/3-glycidoxypropyltrimethoxysilane( GPTMS)/vinyltrimethoxysilane(VTMS) by sol-gel process, respectively. The silane-terminated CS and acrylate resin were hybridized using UV-curing system. Thin films of hybrid material were prepared using spin coater on the glass. Their hardness, contact angle and transmittance improved with the addition of silane-terminated CS.

• Applied Chemistry for Engineering
• /
• v.16 no.3
• /
• pp.449-455
• /
• 2005

Electron beam (EB) and ultraviolet (UV) curable monomers (AF-1 with mono functionality and AF-2 with tetra functionality) containing hydroxy and acrylate group for anti-fogging coating were synthesized and applied to EB and UV-curable coating systems. The synthesized reactive AF-1 and AF-2 monomers were first formulated into UV-curable system and the optimization of film properties for anti-fogging coating was investigated. The 5:17.5 ratio for AF-1 and AF-2 was found to be the best optimized formulation for anti-fogging coating without destroying the other essential properties such as hardness, solvent resistance, and adhesion. The optimized formulation was applied to the EB-curable system, and EB and UV-curable systems were compared. The results demonstrated that both EB and UV-cured films coated on PC sheet showed excellent anti-fogging properties; however, the EB-cured film exhibited better hardness, adhesion, and water repellent properties than the UV-cured film.

• Applied Chemistry for Engineering
• /
• v.28 no.6
• /
• pp.626-631
• /
• 2017

Transparent plastic substrates require an improvement in properties such as surface hardness and thermal stability for optical applications. In this study, UV-curable organic/inorganic hybrids were synthesized to improve those properties. In order to make the optimum dispersion of inorganic component into the organic matrix, an in situ synthetic method was applied based on sol-gel reaction. Dispersion of the inorganic component in the organic urethane acrylate matrix was improved by using a proper combination of sol-gel reaction and fast UV-curing resulting in the formation of the transparent coating layer. Various alkoxy silanes were employed to vary both the degree of curing and coating properties of UV-curable organic/inorganic hybrids. UV-cured organic/inorganic hybrid coatings showed an improved surface hardness and thermal resistance depending on the content of inorganic component.