Bonding strength of benuang and duabanga glulams using their barks as phenol formaldehyde-filler

In line with environmental issues and forest sustainability, tree bark of two species from tropical rain forests i.e. benuang (Octomeles sumatrana/BN) and duabanga (Duabanga moluccana/DB) was used as filler for phenol formaldehyde resin (PF-filler). The main objective of the research was to analyze effect of tree barks as PF-filler on bonding strength of BN and DB glulams produced. Four glue mixture compositions with ratio PF, technical filler, and tree bark filler, respectively are 10: 0: 0 (A); 10: 1.5: 0.5 (B); 10: 1.25: 0.75 (C); and 10: 1: 1 (D) were prepared. Characteristics of tree bark and glue mixtures were also investigated. Glulam parameters i.e. moisture content, density, delamination, bonding strength, wood failure, and formaldehyde emission were determined following JAS 1152. Results showed bonding strength was influenced by wood species and glue mixture composition. The B composition—the lowest ratio of tree bark filler—is the best for BN glulam, while for DB glulam D composition—the highest ratio of tree bark filler—was the best. Generally, tree bark filler improved the bonding strength, however, without bark as PF-filler, the failure occurred on the glue line. Furthermore, DB bark is more potential to be utilized as PF-filler.