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Properties of Tannin Extract from Tree Bark as Adhesive for Plywood and Particleboard
Dissertation Abstract:
Four experiments were conducted to determine the properties of tangal [Ceriops tagal (Perr.) C. B. Rob.] tanbark extract for use as adhesive for plywood and particleboard. The predominant compounds identified in both monomeric and polymeric polyphenols with the amount of 63 percent and 58 percent, respectively, were flavonol with resorcinol A nucleus and polygallol B nucleus. Chemical analysis of tangal bark showed 40.5 percent solubility in hot water (unleached).
The yield of tangal bark extract under six-stage counter current process was 232.4 kg/ton of air dried bark with efficiency of 85.5 percent (based on total solid of raw and spent materials). The tannin content of bark was 26.1 percent; tannin formaldehyde precipitate from the bark, 47.2 percent; and the tannin to non-tannin ratio of the bark was 1.6:1.0.
The three-ply white lauan [Pentacme contorta (Vid.) Merr. & Rolfe] plywood was glued with unfortified tangal tannin formaldehyde with 5 percent paraformaldehyde, 10 percent tangal bark flour, and 1 percent phenol solution (based on total dry weight of tannin powder) with a final pH of 5.7. The final glue bond quality passed the Type 2 bond (PHILSA, R1975). The unfortified tangal tannin formaldehyde was developed by adding 20-40 percent phenol formaldehyde adhesive resin or 10-30 percent resorcinol phenol formaldehyde adhesive resin. The glue bond quality of three-ply white lauan plywood met with the Type 2 bond. Plywood glued with 30-40 percent phenol formaldehyde in glue-mix improved the glue line quality of Type 1 bond (PHILSA, R1975).
The properties of kaatoan bangkal Anthocephalus chinensi (Lamk.) Rich ex. Walp. particleboard bonded with tangal tannin formaldehyde at 6, 8, and 10 percent resin content (based on oven dry weight of wood chips) met with the Type 100 standard (JIS A-5908, 1997). Bond quality of unfortified tangal tannin formaldehyde adhesive was improved by adding 2, 4, 6, and 8 percent phenol formaldehyde adhesive (based on total glue-mix at 10% resin content). Board properties at 8 percent phenol formaldehyde in glue-mix met the Type 150 standard.
In general, tangal bark extract combined with phenol formaldehyde alone or fortified by resorcinol-phenol formaldehyde met the standards of commercial adhesive for plywood and particleboard.