Properties of compression densified wood. Part I: bond performance.

Bond performance of hygro-thermally compression densified wood was studied using hygro-thermally treated and control yellow-poplar wood (Liriodendron tulipifera). Opening mode double cantilever beam fracture testing and cyclic boiling were used to evaluate bond performance. Phenol–formaldehyde (PF) film and polymeric diphenylmethane diisocyanate (pMDI) adhesives were used to bond specimens for fracture testing. Fracture toughness of hygro-thermal samples bonded with PF film was significantly higher than control samples, while no difference was found for densified samples. Fracture toughness of densified samples bonded with pMDI was significantly higher than control samples, however no change was seen for hygro-thermal samples. Cyclic boiling reduced the fracture toughness of hygro-thermal fracture samples only, irrespective of adhesive type. [ABSTRACT FROM AUTHOR]