Performance of Urea-Formaldehyde Resins Synthesized at Two Different Low Molar Ratios with Different Numbers of Urea Addition

1) This study reports the performance of urea-formaldehyde (UF) resins prepared at two different low formaldehyde/urea (F/U) mole ratios with different numbers of urea addition during synthesis. The second or third urea was added during the synthesis of UF resins to obtain two different low molar ratios of 0.7 and 1.0, respectively. The molecular weights, cure kinetics, and adhesion performance of these resins were characterized by the gel permeation chromatography, differential scanning calorimetry, and tensile shear strength of plywood, respectively. When the number of urea additions and F/U molar ratio increased, the gelation time decreased, whereas the viscosity and molecular weight increased. Further, the UF resins prepared with the second urea and 1.0 molar ratio resulted in greater activation energy than those with third urea and 0.7 molar ratio. Tensile shear strength and formaldehyde emission (FE) of the plywood that bonded with these resins increased when the number of urea additions and molar ratio increased. These results suggest that the UF resins prepared with 0.7 molar ratio and third urea addition provide lower adhesion performance and FE than those resins with 1.0 mole ratio and the second urea addition.

[1]  Byung‐Dae Park,et al.  Effect of Analytical Parameters of Gel Permeation Chromatography on Molecular Weight Measurements of Urea-Formaldehyde Resins , 2017 .

[2]  S. M. Lee,et al.  Formaldehyde Emission of Wood-Based Composite Panels with Different Surface Lamination Materials Using Desiccator Method , 2016 .

[3]  Byung‐Dae Park,et al.  Hydrolytic Stability of Cured Urea-Melamine-Formaldehyde Resins Depending on Hydrolysis Conditions and Hardener Types , 2015 .

[4]  V. Causin,et al.  Crystallinity and domain size of cured urea–formaldehyde resin adhesives with different formaldehyde/urea mole ratios , 2013 .

[5]  G. Marković,et al.  Thermal behavior of modified urea–formaldehyde resins , 2011 .

[6]  J. D. Jonge,et al.  The reaction of urea with formaldehyde , 2010 .

[7]  Byung‐Dae Park,et al.  Dynamic mechanical analysis of urea–formaldehyde resin adhesives with different formaldehyde‐to‐urea molar ratios , 2008 .

[8]  Byung‐Dae Park,et al.  Effects of formaldehyde to urea mole ratio on thermal curing behavior of urea–formaldehyde resin and properties of particleboard , 2006 .

[9]  S. Vyazovkin.  Model-free kinetics , 2006 .

[10]  M. Schäfer,et al.  On the formaldehyde release of wood , 2000, Holz als Roh- und Werkstoff.

[11]  光夫 樋口,et al.  Synthetic Conditions and Chemical Structures of Urea-Formaldehyde Resins IV. Curing behavior of the resins , 1996 .

[12]  C. Hse,et al.  Properties of the resins synthesized by three different procedures , 1995 .

[13]  J. Valenzuela,et al.  Theory and Practice of the Preparation of Low Formaldehyde Emission UF Adhesives , 1994 .

[14]  C. Hse,et al.  Effects of Reaction pH on Properties and Performance of Urea-Formaldehyde Resins , 1994 .

[15]  G. E. Myers,et al.  Procedure for measuring formaldehyde liberation from formaldehyde-based resins , 1987 .

[16]  R. Reinhardt,et al.  Formaldehyde Release from Wood Products , 1986 .

[17]  G. E. Myers.  How mole ratio of UF resin affects formaldehyde emission and other properties: a literature critique , 1984 .

[18]  G. E. Myers.  Formaldehyde emission from particleboard and plywood paneling : measurement, mechanism, and product standards , 1983 .

[19]  W. Johns,et al.  Formaldehyde release from sulfur-modified urea-formaldehyde resin systems. , 1980 .

[20]  B. Meyer.  Urea-Formaldehyde Resins , 1979 .