Effect of surface treatment on bondability of birch veneer with PF resin

Abstract

The aim of this work was to study the bondability of birch (Betula verrucosa Ehrh.) veneer subjected to different surface treatments (chemical treatment, short term thermo-mechanical densification, and combination of these two processes) using phenol-formaldehyde (PF) resin with the aim of improving bonding during the production of plywood. Four chemical agents (hydrogen peroxide, aluminium potassium sulphate, potassium carbonate, and potassium permanganate) were used for chemical treatment of the veneer surface. The veneer samples were thermo-mechanically densified between heated plates of a laboratory press. The results revealed that short term thermo-mechanical densification and combined chemical and thermo-mechanical pre-treatment of the veneer surface prior to the resin application reduced the glue spread (a 33% reduction) and improved the bondability of the veneer. The obtained shear strength values for all of the studied treatments exceeded the standard requirements (1·0 MPa), and the properties of the plywood samples satisfied the European standard EN 314-2.

Keywords

Activating agents Birch veneer Phenol-formaldehyde resin Bondability Surface treatment Chemical treatment Short term thermo-mechanical densification

Get full access to this article

View all access options for this article.

References

Aydin

. 2004. Activation of wood surfaces for glue bonds by mechanical pretreatment and its effects on some properties of veneer surfaces and plywood panels. Appl Surf Sci, 233, pp. 268–74.

Back

. 1991. Oxidative activation of wood surfaces for glue bonding. Forest Products Journal, 41 (2), pp. 30–36.

Bekhta

. 2003. Method of the plywood production. Patent of Ukraine, no.62787A dated 15·12·03. Bulletin no.12.

Bekhta

, Hiziroglu

and Shepelyuk

. 2009. Properties of plywood manufactured from compressed veneer as building material. Mater Des, 30, pp. 947–53.

Bekhta

and Marutzky

. 2007. Reduction of glue consumption in the plywood production by using previously compressed veneer. Holz als Roh- und Werkstoff, 65, pp. 87–88.

Bekhta

, Niemz

and Sedliacik

. 2012. Effect of pre-pressing of veneer on the glueability and properties of veneer-based products. Eur J Wood Prod, 70, pp. 99–106.

Belfas

, Groves

and Evans

. 1993. Bonding surface-modified Karri and Jarrah with resorcinol formaldehyde. I. The effect of sanding on wettability and shear strength. Holz als Roh- und Werkstoff, 51, pp. 253–59.

Christiansen

. 1990. How overdrying wood reduces its bonding to phenol– formaldehyde adhesives: a critical review of the literature. Part I. Physical responses. Wood Fiber Sci, 22 (4), pp. 441–59.

Christiansen

. 1991. How overdrying wood reduces its bonding to phenol-formaldehyde adhesives. A critical review of the literature. Part II. Chemical reactions. Wood Fiber Sci, 23 (1), pp. 69–84.

10.

Croitorua

et al. 2011. Influence of ionic liquids on the surface properties of poplar veneers. Appl Surf Sci, 257, pp. 6220–25.

11.

Cruz

, Martins

and Carvalho

. 2007. Effect of surface treatment on the bondability of pine and eucalypt with UF resins. In: M. Sernek, ed. Proc. of the 5th COST E34 Int. Workshop on Bonding of Modified Wood, Bled, Slovenia, 6 September 2007; Ljubljana: Biotechnical Faculty, Department of Wood Science and Technology, 2007, pp. 95–105.

12.

EN 314-1 : 2005. Plywood. Bonding quality. Part 1: Test methods. Brussels: European Committee for Standardization.

13.

EN 314-2 : 1998. Plywood. Bonding quality. Part 2: Requirements. Brussels: European Committee for Standardization.

14.

Gardner

and Elder

. 1988. Surface activation treatment of wood and its effect on gel time of phenol-formaldehyde resin. Wood Fiber Sci, 20 (3), pp. 378–85.

15.

Loh

, Paridah

, Hoong

and Yoong

ACC

. 2011. Effects of treatment with low molecular weight phenol formaldehyde resin on the surface characteristics of oil palm (Elaeis quineensis) stem veneer. Mater Des, 32, pp. 2277–83.

16.

and Wu

. 2006. Surface characterization of chemically modified wood dynamic wettability. Wood Fiber Sci, 38 (3), pp. 497–511.

17.

Matuana

, Balatinecz

and Park

. 1998. Effect of surface properties on the adhesion between PVC and wood veneer laminates. Polym Eng Sci, 38 (5), pp. 765–73.

18.

Mirski

, Dziurka

and Łecka

. 2008. Properties of phenol-formaldehyde resin modified with organic acid esters. J Appl Polym Sci, 107 (5), pp. 3358–66.

19.

Mirski

, Dziurka

and Łecka

. 2011. Potential of shortening pressing time or reducing pressing temperature for plywood resinated with PF resin modified using alcohols and esters. Eur J Wood Wood Prod, 69 (2), pp. 317–23.

20.

Tinh

, Pollisco

and Casilla

. 1977. Effects of extraction on wettability and gluability of apitong (Dipterocarpus Grandiflorus Blanco). J Adhesion, 9, pp. 63–71.

21.

Wei

et al. 2012. Dynamic wettability of wood surface modified by acidic dyestuff and fixing agent. Appl Sur Sci, 258, pp. 1995–99.