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유선화,김창근 한국고분자학회 2010 Macromolecular Research Vol.18 No.10
Dental restorative composites containing spiro orthocarbonates (SOCs) have been studied extensively to minimize the volumetric shrinkage that occurs during polymerization. Previous reports suggested that dental composites with low volumetric shrinkage could be obtained by mixing SOC with conventional resins. However,its inclusion had adverse effects on the mechanical properties of dental composites. A novel SOC (2,2-bis-4,4'-(7-phenyl-1,4,6,9-tetraoxaspiro[4.4]nona-2-ylmethoxyphenyl)propane), SOC-N, was synthesized to overcome these adverse effects resulting from the previously developed SOCs. The mechanical strength and volumetric shrinkage of the dental composites composed of 70 wt% inorganic fillers and resin matrices containing SOC-N,2,2-bis-[4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane (Bis-GMA), and triethylene glycol dimethacrylate (TEGDMA) were explored. When compared to a control resin-containing composite (Bis-GMA/TEGDMA=70/30), the volumetric shrinkage of the composite containing new resin matrix, obtained through the addition of SOC-N to the Bis-GMA/TEGDMA=70/30 mixture, was reduced gradually by increasing the SOC-N content. Furthermore, the latter sample showed better mechanical strength than the former when the resin matrix contained 30 wt% SOC-N.
Changes in the Moisture Stability of CaS:Eu2+ Phosphors with Surface Coating Methods
유선화,김창근 한국고분자학회 2009 Macromolecular Research Vol.17 No.11
To improve the moisture stability of the CaS:Eu2+ red phosphor, surface coatings with silica nanoparticles were performed using five different methods, i.e., P1, P2, P3, P4, and P5. The phosphors were coated with silica nanoparticles using a dip coating method (P1) and sol-gel method (P2). The phosphors were coated using a solution containing silica nanoparticles and poly(1-vinyl-2-pyrrolidone), PVP, (P3). The phosphors were also coated with silica nanoparticles by reacting with the 1-vinyl-2-pyrrolidone (VP) monomer (P4) or by reacting with mixtures containing VP and tetraethylorthosilicate (P5). A decrease in the photoluminescence (PL) intensity was observed regardless of the coating methods. However, the moisture stability of the phosphors was enhanced by the coating when aged in a temperature-controlled humidity chamber. Among these methods, the P4 (or P5) method exhibited the greatest increase in moisture stability of the phosphors. The coated phosphors showed a relatively constant intensity with aging time, whereas the uncoated phosphor showed a decrease.
유선화,박광용,김주헌,김창근 한국고분자학회 2011 Macromolecular Research Vol.19 No.1
The characteristics of resin matrices containing 2,2-bis[4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl]propane (Bis-GMA) alternatives and spiro orthocarbonate (SOC) were examined to produce dental restorative composites exhibiting lower curing shrinkage and better mechanical strength than the commercially available dental composites. Bis-GMA alternatives were prepared by replacing the hydroxyl groups in Bis-GMA with alkoxy groups. Various SOCs that showed the expected volume expansion during the curing reaction caused by the ring opening reaction were added to Bis-GMA alternatives for a further decrease in curing shrinkage. The curing shrinkage of the dental composites containing Bis-GMA alternative and SOC was always lower than that of the dental composite used as the control, which contained 70 wt% Bis-GMA and 30 wt% triethylene glycol dimethacrylate (TEGDMA) as the resin matrix. Furthermore, the mechanical strength of the dental composites prepared from the 2,2-bis[4-(2-methoxy-3-methacryloyloxy propoxy)phenyl]propane (Bis-M-GMA) mixture containing approximately 10 wt% SOC was higher than that of the dental composite used as the control.