BONDING FLAKEBOARDS WITH COPOLYMER RESINS MADE OF TREE FOLIAGE EXTRACTS, PHENOL, AND FORMALDEHYDE

Foliage of southern pine (Pinus taeda), Douglas-fir (Pseudotsuga menziesii), and western hemlock (Tsuga heterophylla) were ectracted with a 10% solution of sodium hydroxide at 40-degrees-C. Copolymer resins of the foliage extracts, phenol, and formaldehyde were synthesized having 40% by weight of chemical phenol replaced with the foliage extracts. The gluability of the copolymer resins in bonding flakeboards were evaluated with white oak (Quercus alba), sweetgum (Liquidambar styraciflua), and southern pine flakes. The hot press time requirements of the copolymer resins in bonding these flakeboards were also investigated. A resorcinol catalyzed commercial phenol formaldehyde resin was used as the control. The experimental copolymer resins proved to require shorter hot press time than the resorcinol catalyzed commercial control resin. The copolymer resins containing tree foliage extracts also exhibited superior bond quality than the commercial control resin. The experimental copolymer resins of foliage extracts provided internal bond of more than 6.3 kg/cm2 in bonding southern pine flakeboards, 3.5 kg/cm2 in sweetgum flakeboards, and 2.8 kg/cm2 in oak flakeboards with as little as 5 minutes press time at 177-degrees-C, whereas the resorcinol catalyzed commercial resin needed 6 minutes or longer press time to achieve similar quality. The commercial resin provided a better dimensional stability for the longer press time of 7 minutes flakeboards than the copolymer resins, however, the copolymer resins provided a better dimensional stability than the control resin for the flakeboards with shorter press time of 5 minutes.