The Experts below are selected from a list of 10404 Experts worldwide ranked by ideXlab platform
Byungdae Park - One of the best experts on this subject based on the ideXlab platform.
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modification of urea formaldehyde Resin adhesives with blocked isocyanates using sodium bisulfite
International Journal of Adhesion and Adhesives, 2017Co-Authors: Muhammad Adly Rahandi Lubis, Byungdae Park, Sangmin LeeAbstract:Abstract Polymeric 4-4 diphenyl methane diisocyanate (pMDI) was blocked with an aqueous sodium bisulfite solution to obtain water-dispersible blocked pMDI (B-pMDI) Resin with different HSO3/–NCO mole ratios for the modification of Urea-Formaldehyde (UF) Resin. Fourier transform infrared (FTIR) spectra of the B-pMDI Resin clearly showed that all isocyanate groups of the pMDI Resin were successfully blocked by sodium bisulfite. As the HSO3/–NCO mole ratio increased, the de-blocking temperature of the B-pMDI Resin also increased. Two addition levels (1% and 3%) of the B-pMDI Resin with different HSO3/–NCO mole ratios were mixed with UF Resins and used as an adhesive for plywood. The gel time of the UF/B-pMDI Resins decreased to a minimum at a mole ratio of 0.9 and then increased with the HSO3/–NCO mole ratio, and was consistent with the peak temperature (Tp). However, as the HSO3/–NCO mole ratio increased, the viscosity of the modified UF Resins by 1% B-pMDI Resin addition slightly increased, whereas those of modified Resins with 3% B-pMDI Resin addition rapidly increased. The adhesion strengths of plywood bonded with the hybrid Resins were greater for 1% B-pMDI Resin addition than for 3% B-pMDI Resin addition. Formaldehyde emission of plywood bonded with the UF/B-pMDI Resins significantly decreased up to 34% by the addition of B-pMDI Resin at a mole ratio of 1.8. These results suggest that the modification of UF Resins by mixing with water-dispersible B-pMDI Resin can be a method for improving the water resistance and formaldehyde emission of UF Resins for wood-based composites.
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crystallinity and domain size of cured urea formaldehyde Resin adhesives with different formaldehyde urea mole ratios
European Polymer Journal, 2013Co-Authors: Byungdae Park, Valerio CausinAbstract:Abstract As a part of understanding hydrolytic degradation of cured UF Resins responsible for formaldehyde emission, this study investigated the crystallinity and domain size of cured urea–formaldehyde (UF) Resins with different formaldehyde/urea (F/U) mole ratios using wide angle X-ray diffraction (WAXD) and small angle X-ray scattering (SAXS) techniques. Both techniques were employed to calculate the crystallinity and domain size of cured UF Resins as a function of F/U mole ratio. As the F/U mole ratio decreases, the crystallinity of cured UF Resins increases from 26% to 48%. The SAXS provided useful information on the spatial arrangement of the crystalline domains and of their average distance. As the F/U mole ratio decreased from 1.6 to 1.0, the average distance between domains in cured UF Resins decreased from 39 nm to 34 nm while the crystallite size increased from 1.3 nm to 5 nm. These results suggested that the crystallites were more closely packed with each other in cured UF Resins when the F/U mole ratio decreased and the ordered domains were more randomly dispersed in high F/U mole ratio than low F/U mole ratio of UF Resins. The greater amount of these ordered crystallites in cured UF Resins of low F/U mole ratio was found to be correlated to the improved hydrolytic stability of the cured Resins.
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hydrolytic stability and crystallinity of cured urea formaldehyde Resin adhesives with different formaldehyde urea mole ratios
International Journal of Adhesion and Adhesives, 2011Co-Authors: Byungdae Park, Howon JeongAbstract:Abstract This study investigated the relationship between the hydrolytic stability and the crystalline regions of cured UF Resins with different formaldehyde/urea (F/U) mole ratios to better understand the hydrolysis of cured urea–formaldehyde (UF) Resin adhesives responsible for its formaldehyde emission in service. As the F/U mole ratio decreased, the hydrolytic stability of cured UF Resins improved, but decreased when the particle size of the Resin was reduced. To further understand the improved hydrolytic stability of cured UF Resin with lower F/U mole ratios, X-ray diffraction (XRD) was extensively used to examine the crystalline part of cured UF Resins, depending on F/U mole ratios, cure temperature and time, hardener type and level. Cured UF Resins with higher F/U mole ratios (1.6 and 1.4) showed amorphous structure, while those with lower F/U mole ratios (1.2 and 1.0) showed crystalline regions, which could partially explain the improved hydrolytic stability of the cured UF Resin. The crystalline part intensity increased as cure temperature, cure time and hardener content increased. But the 2θ angles of these crystalline regions did not change, depending on cure temperature and time, hardener type and level, suggesting that the crystalline regions of the cured UF Resin were inherent. This study indicates that the crystalline regions of cured UF Resins with lower F/U mole ratio contribute partially to the improved hydrolytic stability of the cured Resin.
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dynamic mechanical analysis of urea formaldehyde Resin adhesives with different formaldehyde to urea molar ratios
Journal of Applied Polymer Science, 2008Co-Authors: Byungdae Park, Jaewoo KimAbstract:As a part of abating formaldehyde emissions of urea–formaldehyde (UF) Resin adhesives, using dynamic mechanical analysis (DMA), we attempted to investigate the influence of the formaldehyde to urea (F/U) molar ratio on the thermomechanical curing of UF Resin adhesives with different F/U molar ratios. The thermomechanical curing of these UF Resin adhesives was characterized with DMA parameters such as the gel temperature, maximum storage modulus, peak temperatures of the storage and loss moduli, and maximum tan δ. As the F/U molar ratio decreased, the gel temperature of UF Resin adhesives increased, whereas the maximum storage modulus, an indicator of the rigidity of UF Resin adhesives, decreased. The maximum tan δ increased with the F/U molar ratio decreasing, and this indicated that the UF Resin adhesive with a low F/U molar ratio had greater damping than the one with a high F/U molar ratio. A decrease in the rigidity of the UF Resin with a lower F/U molar ratio was explained by the calculated crosslinking density, which decreased with the F/U molar ratio decreasing. These results partially explained why UF Resin adhesives with lower F/U molar ratios showed relatively poor adhesion performance when they were applied to the manufacture of wood panels. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
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13 c nmr spectroscopy of urea formaldehyde Resin adhesives with different formaldehyde urea mole ratios
Journal of the Korean wood science and technology, 2008Co-Authors: Byungdae Park, Sang M Lee, Jongyoung ParkAbstract:As a part of abating formaldehyde emission of Urea-Formaldehyde (UF) Resin adhesive, this study wasconducted to investigate chemical structures of UF Resin adhesives with different formaldehyde/urea (F/U)mole ratios, using carbon-lS nuclear magnetic resonance ("C-NMR) spectroscopy. UF Resin adhesives weresynthesized at four different F/U mole ratios such as 1.6, 1.4, 1.2, and 1.0 for the analysis. The analysisof 'UC-NMR spectroscopy showed that UF Resin adhesives with higher F/U mole ratios (i.e., 1.6 and 1.4)had two distinctive peaks, indicating the presence of dimethylene ether linkages and methylene glycols,a dissolved form of free formaldehyde. But, these peaks were not detected at the UF Resins with lowerF/U mole ratios (i.e., 1.2 and 1.0). These chemical structures present at the UF Resins with higher F/Umole ratios indicated that UF Resin adhesive with higher F/U mole ratio had a greater contribution to theformaldehyde emission than that of lower FAJ mole ratio. Uronic species were detected for all UF Resinsregardless of F/U mole ratios.
Y Yan - One of the best experts on this subject based on the ideXlab platform.
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thermal degradation and flame retardancy of epoxy Resins containing intumescent flame retardant
Journal of Thermal Analysis and Calorimetry, 2009Co-Authors: Ming Gao, Y YanAbstract:Abstract Pentaerythritol diphosphonate melamine-Urea-Formaldehyde Resin salt, a novel cheap macromolecular intumescent flame retardants (IFR), was synthesized, and its structure was a caged bicyclic macromolecule containing phosphorus characterized by IR. Epoxy Resins (EP) were modified with IFR to get the flame retardant EP, whose flammability and burning behavior were characterized by UL 94 and limiting oxygen index (LOI). 25 mass% of IFR were doped into EP to get 27.2 of LOI and UL 94 V-0. The thermal properties of epoxy Resins containing IFR were investigated with thermogravimetry (TG) and differential thermogravimetry (DTG). Activation energy for the decomposition of samples was obtained using Kissinger equation. The resultant data show that for EP containing IFR, compared with EP, IFR decreased mass loss, thermal stability and R max, increased the char yield. The activation energy for the decomposition of EP is 230.4 kJ mol−1 while it becomes 193.8 kJ mol−1 for EP containing IFR, decreased by 36.6 ...
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thermal degradation and flame retardancy of epoxy Resins containing intumescent flame retardant
Journal of Thermal Analysis and Calorimetry, 2009Co-Authors: Ming Gao, W Wu, Y YanAbstract:Pentaerythritol diphosphonate melamine-Urea-Formaldehyde Resin salt, a novel cheap macromolecular intumescent flame retardants (IFR), was synthesized, and its structure was a caged bicyclic macromolecule containing phosphorus characterized by IR. Epoxy Resins (EP) were modified with IFR to get the flame retardant EP, whose flammability and burning behavior were characterized by UL 94 and limiting oxygen index (LOI). 25 mass% of IFR were doped into EP to get 27.2 of LOI and UL 94 V-0.
Bernard Riedl - One of the best experts on this subject based on the ideXlab platform.
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a study on the curing and viscoelastic characteristics of melamine urea formaldehyde Resin in the presence of aluminium silicate nanoclays
Composites Part A-applied Science and Manufacturing, 2010Co-Authors: Bernard Riedl, S Y Zhang, Xiangming WangAbstract:Abstract Low viscosity melamine–urea–formaldehyde (MUF) Resin for wood impregnation was synthesized and mixed with layered silicate nanoclays. Ball-milling of the nanoclays was performed to have a better dispersion of the nanoclays into the MUF Resin. The effect of nanofillers both milled and unmilled, on the curing and viscoelastic properties of the MUF was investigated, using differential scanning calorimetry and dynamical mechanical thermal analysis methods. Two exotherms were observed during the MUF curing process. The apparent activation energy was lowered for the first exotherm at lower temperature, while increased for the second exotherm, with the addition of nanoclays into the MUF. Ball-milling of nanofillers resulted in an increased apparent activation energy and longer gel time for the milled organophilic nanoclay/MUF, but shorter gel time and better dynamic mechanical properties of the milled hydrophilic nanofiller/MUF, as compared to the correspondingly unmilled nanofiller/MUF systems. The storage modulus of all the nanofiller/MUF Resins was considerably increased as compared to the neat MUF Resin. This improvement is, however, more obvious for the surface modified layered silicate/MUF system, due to more compatible functional-groups grafted onto the nanoclays, and stronger layered silicate/MUF matrix adhesion, thus better performances were observed for the resulting nanoclay/MUF composites.
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effects of nanofillers on water resistance and dimensional stability of solid wood modified by melamine urea formaldehyde Resin
Wood and Fiber Science, 2007Co-Authors: Xiaolin Cai, Bernard Riedl, S Y Zhang, Hui WanAbstract:The water absorption and dimensional stability of wood impregnated with melamine-ureaformaldehyde (MUF) and wood impregnated with different nanofiller/MUF formulations were investigated. Three kinds of nanoparticles, Cloisite® 30B, Claytone® APA, and Cloisite® Na + , were selected and mixed with MUF Resin, and subsequently impregnated into solid aspen wood through a vacuum and pressure process. The wood polymer nanocomposites were prepared by in situ condensation polymerization of the impregnated wood under specific conditions. Significant improvements in water repellency and better dimensional stabilities were obtained for the nanofiller/MUF-treated wood. The untreated wood absorbed around 63% of moisture after 24 h soaking in water, while water uptake was about 125% after 1 week immersion in water. The MUF Resin-impregnated wood absorbed about 8.3% and 38.5% of moisture after 24 h and 1 week immersion in water, respectively. For the organophilic nanoclay/MUF Resin-impregnated wood, much lower water absorption in the amounts of around 5% water uptake in 24 h and 22% after 1 week was observed. The antiswelling efficiency (ASE) was also improved from 63.3% to 125.6% for the nanofiller/MUF-treated wood. The significant improvement in water resistance and dimensional stability of the resulting wood polymer nanocomposites can be attributed to the introduction of MUF and nanofillers into the wood. X-ray fluorescence shows that some nanoparticles have migrated into the wood cell wall. Wood treatments with MUF and nanofiller/MUF showed no significant influence on the color of the wood, which is important for practical application of the treated wood in some specific areas such as flooring.
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characterization of urea formaldehyde Resin penetration into medium density fiberboard fibers
Wood Science and Technology, 2005Co-Authors: Cheng Xing, Bernard Riedl, Alain Cloutier, Stephen M. ShalerAbstract:The amount of UF Resin penetration into fibers, used for the production of medium density fiberboard (MDF), is unknown. To evaluate the relationship between Resin viscosity and Resin penetration depth, an experimental procedure involving confocal laser scanning microscopy (CLSM) and a Toluidine Blue O staining system was performed. The results indicate that CLSM in combination with a Toluidine Blue O staining system is a good way to characterize UF Resin penetration into wood fibers. The main penetration direction is toward the fiber lumen. For wet fibers, whose moisture content is about 88%, the effect of Resin viscosity with a range of 80 cps – 340 cps on penetration is very similar, with all adhesives reaching or almost reaching the fiber lumen after 60 min at room temperature. For MDF industrial samples, the highest depth of penetration of the adhesive was attained in the second dryer stage. After the second dryer stage, the Resin penetration into the fiber did not increase.
Stephen M. Shaler - One of the best experts on this subject based on the ideXlab platform.
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characterization of urea formaldehyde Resin penetration into medium density fiberboard fibers
Wood Science and Technology, 2005Co-Authors: Cheng Xing, Bernard Riedl, Alain Cloutier, Stephen M. ShalerAbstract:The amount of UF Resin penetration into fibers, used for the production of medium density fiberboard (MDF), is unknown. To evaluate the relationship between Resin viscosity and Resin penetration depth, an experimental procedure involving confocal laser scanning microscopy (CLSM) and a Toluidine Blue O staining system was performed. The results indicate that CLSM in combination with a Toluidine Blue O staining system is a good way to characterize UF Resin penetration into wood fibers. The main penetration direction is toward the fiber lumen. For wet fibers, whose moisture content is about 88%, the effect of Resin viscosity with a range of 80 cps – 340 cps on penetration is very similar, with all adhesives reaching or almost reaching the fiber lumen after 60 min at room temperature. For MDF industrial samples, the highest depth of penetration of the adhesive was attained in the second dryer stage. After the second dryer stage, the Resin penetration into the fiber did not increase.
Valerio Causin - One of the best experts on this subject based on the ideXlab platform.
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crystallinity and domain size of cured urea formaldehyde Resin adhesives with different formaldehyde urea mole ratios
European Polymer Journal, 2013Co-Authors: Byungdae Park, Valerio CausinAbstract:Abstract As a part of understanding hydrolytic degradation of cured UF Resins responsible for formaldehyde emission, this study investigated the crystallinity and domain size of cured urea–formaldehyde (UF) Resins with different formaldehyde/urea (F/U) mole ratios using wide angle X-ray diffraction (WAXD) and small angle X-ray scattering (SAXS) techniques. Both techniques were employed to calculate the crystallinity and domain size of cured UF Resins as a function of F/U mole ratio. As the F/U mole ratio decreases, the crystallinity of cured UF Resins increases from 26% to 48%. The SAXS provided useful information on the spatial arrangement of the crystalline domains and of their average distance. As the F/U mole ratio decreased from 1.6 to 1.0, the average distance between domains in cured UF Resins decreased from 39 nm to 34 nm while the crystallite size increased from 1.3 nm to 5 nm. These results suggested that the crystallites were more closely packed with each other in cured UF Resins when the F/U mole ratio decreased and the ordered domains were more randomly dispersed in high F/U mole ratio than low F/U mole ratio of UF Resins. The greater amount of these ordered crystallites in cured UF Resins of low F/U mole ratio was found to be correlated to the improved hydrolytic stability of the cured Resins.
