Radial Penetration of Urea-Formaldehyde Adhesive Resins into Beech (Fagus Moesiaca)

Penetration of adhesives plays an important role in wood adhesion, since wood is a porous material. Objectives of this work were (i) the evaluation of the influence of the degree of condensation of urea-formaldehyde (UF) resins on their penetration into beech, showing the distribution of the adhesive in the cell layers close to the bondline using microscopic detection, and (ii) the comparison of data for beech with results for fir obtained earlier. The degree of penetration mostly depends on the permeability and porosity of the wood surface as well as on the resin type and the size of the resin molecules. The process parameters, which also can affect penetration, were kept constant throughout all tests performed. The results show a significant correlation between the penetration behavior and the degree of condensation (molecular size, viscosity) of the resins and adhesive mixes based on these resins. The higher the degree of condensation, the lower the possibility for penetration, expressed as “Average penetration depth” (AP). AP into beech is higher than into fir. The portion of filled tracheids and vessels on the whole cross section of the interphase (“Filled interphase region” FIR) increases slightly with the degree of condensation, but this increase is not statistically significant. FIR in fir is higher than in beech.

[1]  M. Dunky,et al.  Softwareunterstützte statische und dynamische Kontaktwinkelmeßmethoden bei der Benetzung von Holz , 1996, Holz als Roh- und Werkstoff.

[2]  Frederick A. Kamke,et al.  Characteristics of Phenol-Formaldehyde Adhesive Bonds in Steam Injection Pressed Flakeboard , 2007 .

[3]  J. Kennedy,et al.  Handbook of Wood Chemistry and Wood Composites, Roger M. Rowell (Ed.), CRC Press, Boca Raton, FL (2005), (487 pp., $179.95/£99.00, ISBN 0-8493-1588-3) , 2006 .

[4]  Jun Zheng,et al.  Rheological, wood penetration, and fracture performance studies of PF/pMDI hybrid resins , 2004 .

[5]  Y. Imamura,et al.  The modification of wood by treatment with low molecular weight phenol-formaldehyde resin: a properties enhancement with neutralized phenolic-resin and resin penetration into wood cell walls , 2004, Wood Science and Technology.

[6]  A. Pizzi,et al.  Chapter 23 – Wood adhesives , 2002 .

[7]  W. Gindl.  SEM and UV-microscopic investigation of glue lines in Parallam® PSL , 2001, Holz als Roh- und Werkstoff.

[8]  Moon G. Kim.  Examination of selected synthesis parameters for typical wood adhesive‐type urea–formaldehyde resins by 13C NMR spectroscopy. I , 1999 .

[9]  A. Pizzi.  On the correlation equations of liquid and solid 13C‐NMR, thermomechanical analysis, Tg, and network strength in polycondensation resins , 1999 .

[10]  M. Dunky,et al.  Urea–formaldehyde (UF) adhesive resins for wood , 1998 .

[11]  M. Dunky,et al.  Measurement of Dynamic and Staue Contact Angles on Wood for the Determination of its Surface Tension and the Penetration of Liquids into the Wood Surface , 1998 .

[12]  F. Kamke,et al.  Quantitative Analysis of Gross Adhesive Penetration in Wood Using Fluorescence Microscopy , 1992 .

[13]  Alan A. Marra,et al.  Technology of Wood Bonding : Principles in Practice , 1992 .

[14]  M. Dunky,et al.  Untersuchung der molmassenverteilung von harnstoff‐formaldehyd‐leimharzen durch GPC gekoppelt mit lichtstreuung , 1990 .

[15]  D. E. Brady,et al.  Effects of hot-pressing parameters on resin penetration , 1988 .

[16]  M. Dunky,et al.  Untersuchungen der Molgewichtsverteilung von Harnstoff‐Formaldehyd‐Leimharzen , 1982 .