Weathering Stability and Durability of Birch Plywood Modified with Different Molecular Weight Phenol-Formaldehyde Oligomers

Abstract

This study investigated the effect of phenol-formaldehyde (PF) resin treatment on the weathering stability and biological durability of birch plywood. Silver birch (Betula pendula) veneers were vacuum-pressure impregnated with four different PF resins with average molecular weights (Mw) of 292 (resin A), 528 (resin B), 703 (resin C), and 884 g/mol (resin D). The aging properties of PF resin modified birch plywood were analyzed using artificial weathering with ultraviolet (UV) light, UV and water spray, and weathering under outdoor conditions. The same combinations of PF-treated plywood specimens were then tested in soil-bed tests to determine their resistance against soft-rot wood decay. It was not possible to compare weathering processes under artificial conditions to processes under outdoor conditions. However, the weathering stability of birch plywood treated with PF resins A, B, and C, scored better than plywood treated with commercial resin D (regardless of solid content concentration [%]). Results from unsterile soil bed tests showed improvements in resistance to soft-rot wood decay compared to untreated plywood and solid wood. Mass loss [%] was lowest for birch plywood specimens treated with resin of highest solid content concentration (resin D, 20%). Provisional durability ratings delivered durability class (DC) ratings of 2–3, considerably improved over untreated solid wood and untreated birch plywood (DC 5).

Incorporation of In Situ Synthesized Nano-Copper Modified Phenol-Formaldehyde Resin to Improve the Mechanical Properties of Chinese Fir: A Preliminary Study

“…To improve the surface hardness and stability of plantation wood, various modification methods have been developed, including chemical impregnation, densification, thermal treatment, and surface coating [2][3][4][5]. Chemical impregnation has been a powerful method to improve the mechanical properties of wood and promote its industrial utilization [6][7][8][9].…”

“…Low molecular weight phenolic resin as a common impregnation modifier has been widely used to improve wood properties [8,[10][11][12]. Among the modifiers, water-soluble low molecular weight phenol-formaldehyde (PF) resin is known for its low initial viscosity, low-cost, low-toxicity, and non-flammability; they can also easily diffuse into wood cell walls, and enhance the properties of wood [13].…”

New Challenges in Wood and Wood-Based Materials

“…This Special Issue of Polymers is a collection of 11 original high-quality scientific contributions on basic and applied research in the field of wood science and technology, and provides good examples of the recent challenges related to the production and application of wood and wood-based materials. Individual papers concerned with the enhancement of the performance and technological properties of wood composites, above all plywood [ 1 , 2 , 3 ], as well as with ignition and combustion of wood and wood composites in monitoring and evaluating these processes on state-of-the-art equipment [ 4 , 5 , 6 , 7 ], and monitoring chemical changes in wood and wood adhesives and composites [ 8 , 9 , 10 , 11 ], are included. The topic of the Special Issue has clearly resonated in the world’s scientific community and the traditional response has come from strong wood research centers in Europe and Asia.…”

“…This is also reflected in this Special Issue. The study [ 1 ] investigated the effect of phenol-formaldehyde resin treatment on the weathering stability and biological durability of birch plywood. Silver birch veneers were vacuum-pressure-impregnated with four different phenol-formaldehyde resins with average molecular weights.…”

New Challenges in Wood and Wood-Based Materials

“…This is also reflected in this Special Issue. The study [1] investigated the effect of phenolformaldehyde resin treatment on the weathering stability and biological durability of birch plywood. Silver birch veneers were vacuum-pressure-impregnated with four different phenol-formaldehyde resins with average molecular weights.…”