Papers by Keyword: Uv LED

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Authors: Nur Farizah Ayub, Shahrir Hashim, Nadia Adrus
Abstract: Recent trends show that the UV LED light source can greatly reduce environmental effect without compromising performance as compared to conventional UV mercury-based lamp (UV Hg) system. In this study, the possibility of using UV LED technology for photopolymerization of polyacrylamide (PAAm) hydrogels is presented. This has strongly drives the needs for suitable water-soluble photoinitiator formulation. Specifically, the photoinitiator must possess characteristic wavelength within UV LED range as UV LED emits monochromatic light sources only (365 nm or 385 nm). Here, the commercially available photoinitiator Oligo [2-hydroxy-2-methyl-1-[4-(1-methylvinyl) phenyl] propanone] (Chivacure 300) was chosen. However, Chivacure 300 has limited solubility in water. Hence, addition of tetrahydrofuran (THF) at various ratios was required. The results demonstrated that 9.5:0.5 ratio of water/THF was the minimum ratio needed for the solubility of Chivacure 300. After the synthesis of PAAm hydrogels, almost complete conversion of hydrogels was achieved (> 80 %). The highest conversion was achieved with formulation of Chivacure 300 in 9.5:0.5 ratio of water/THF. At this ratio, the hydrogels obtained were transparent. With increasing ratio of THF in water, the appearance of hydrogels gradually changed to cloudy. Indeed, UV LED technology can be used to polymerize PAAm hydrogels with comparably high conversion to conventional UV Hg system.
Authors: Rui Hua Zhou, Xiu Yun Tian
Abstract: The effects of painting ink’s color on UV absorptivity and UV-light wavelength on curing depth in the process of rotating curing are analysed. Aiming at radial uneven curing, the scheme is proposed that using the UV LED with wavelengths of 365nm and 395nm to form a fan-shaped array on cylindrical surface. The curing system can achieve UV irradiance be enhanced gradually along the radial, and the technique problem of uneven curing is solved. The simulation result shows that the curing system meets design requirements on Tracepro.
Authors: Guo Gui Wang, Yi Qing Gao, Meng Chao Xiao
Abstract: We designed a lithographic system, which consists of an ultraviolet LED array as the source, a Compound Parabolic Collector (CPC) as the light collection and collimator, a double fly’s eye len and a convergent lens as light energy Homogenization unit. The second fly’s lens as a field lens is placed to the back focal plane of the first one to improve the light energy uniformity as the light rays output from the CPC are not strictly parallel. The simulation based on optical software indicated that the lithographic system is good at collecting and distributing uniformly light energy. It is a better solution as ultraviolet LED is good at space, price, Environmental Protection compared with Ultraviolet (UV) laser and high pressure mercury lamp.
Authors: Nur Farizah Ayub, Shahrir Hashim, Jamarosliza Jamaluddin, Roshafima Rasit Ali, Nadia Adrus
Abstract: Current studies showed that UV LED system is a green technology and highly efficient as compared to UV Mercury (UV Hg) system. In this study, the UV LED curing formulations of polyacrylamide (PAAm) hydrogels were developed. The formulations consisted of acrylamide (AAm) as a main monomer, N,N’-methylenebisacrylamide as a crosslinker and photoinitiator. UV LED emits monochromatic light sources only (365 nm or 385 nm). Thus, in order to developed formulation of UV LED curable hydrogels, a suitable water soluble photoinitiator (i.e. λ ~ 365 nm) has to be employed. A commercially available photoinitiator Oligo [2-hydroxy-2-methyl-1-[4-(1-methylvinyl) phenyl] propanone] under the trade name Chivacure 300 (λ ~ 330 nm) was chosen in the first formulations. However, due to limited solubility in water, addition of tetrahydrofuran (THF) at 9.5:0.5 ratio of water/THF was required for Chivacure 300. We also synthesized a photoinitiator based on 2,2-dimethoxy-2-phenyl acetophenone (DMPA) and methylated-β-cyclodextrin (MβCD) to be used in the second formulation. The complexation of DMPA and MβCD resulted in transparent and water-soluble supramolecular-structured photoinitiator (SSPI) (λ ~ 330 nm). Both formulations were irradiated using UV LED system (Hoenle AG, Germany, 365 nm) for 15 min. Synthesis of PAAm hydrogels with both photoinitiators has yielded almost complete conversion of hydrogels (> 80 %). Clearly, this study has revealed that enhanced formulation of UV LED curable hydrogels are due to appropriate choice of excellent water-solubility photoinitiators (Chivacure 300 and modified DMPA). We concluded that UV LED is an important tool for curing hydrogel formulations of various acrylate water-based monomers.
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