The effect of tannin ratio and pH on the physical properties of Eucalyptus tannin phenol formaldehyde (ETPF)

The current increase oil prices has intensified the efforts to seek for renewable resources to be converted into biopolymers .Tannin can alternatively replace phenol (partial or full substitution) in adhesive. Because of their polyphenolic structure tannins have a range of actual and potential uses. This study evaluates the properties of tannin from Eucalyptus tree bark for adhesive application. The results show that Eucalyptus tannin has suitable properties for adhesive: pH 13.2; gel time 23.3 min ; and viscosity 45.6 cP. The effect of the tannin content on the bonding properties of the Eucalyptus tannin phenol formaldehyde (ETPF). Subsequently for the bonding properties, phenol formaldehyde (PF) and ETPF 3-layer plywood boards were fabricated from mixed light hardwood (MLHW) veneers. The veneers were spread with the adhesive at 200 g/m2 single glue line. Veneers with tannin phenol formaldehyde resin were assembled and hot pressed at 130 for 7 min. The controls PF resin assembled were pressed at 140 ̊C for 6 min. The testing procedure based on BS EN 314 in order to proof the bonding quality by means of shear strength. The results of the shear test showed that the plywood bonded with ETPF met the requirement the EN 314 standard higher than 1.0 Mpa. It was conclude that Eucalyptus tannin can be used as partial replacement for PF adhesive.

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