PERFORMANCE OF PHENOL-FORMALDEHYDE BASED WOOD ADHESIVES CONTAINING STEAM EXPLODED BEECH FLOUR

The effect of adding steam exploded beech flour (SE) to phenol-formald ehyde (PF) wood adhesive was examined. The viscosity of formulations p repared from SE and PF did not show significant time-dependent change, but showed a sharp decrease in response to an increase of rotatory sh ear speed. The tensile shear strength of a 3-ply veneer board bonded w ith a SE/PF formulation exceeded that of the PF-bonded sample with up to 60% replacement of PF by SE. A similar result was obtained in wood failure of the tensile test. Chemical analyses showed that little hemi cellulose remained in SE. As lignin extracted from SE was not an effec tive additive for PF, these results suggest that the improved performa nce of the SE/PF adhesives results from the physical, rather than the chemical nature of the additive.