Keywords: superplasticity, hierarchical composites, cell slippage, superplastic deformation, solid wood, slipping cells, intercellular layers, nanotechnology, phenol formaldehyde resin, wood cells, flow behaviour, free compression test, wood flow forming, backward extrusion
Superplastic deformation of solid wood by slipping cells at sub–micrometer intercellular layers
In order to facilitate the generation of a flow phenomenon due to the slipping of wood cells under a specific temperature condition, a phenol formaldehyde resin of low molecular weight was introduced into wood cells. The effects of the existence of phenol formaldehyde molecules in wood cells on the flow behaviour of solid wood were investigated experimentally by means of a free compression test. The effectiveness of using phenol formaldehyde resin as an adsorbent to act as both binding and plasticising agents in the proposed wood flow forming shaping technique was examined, and an application to wood flow forming was demonstrated. The results revealed that the flow phenomenon of solid wood occurred at a certain resin content, even under compression at less than 25 MPa. An increase in the moisture content led to further improvement of the flowability of solid wood, which resulted from weakened facial strength among wood cells and intercellular layers due to a local increase in the volume of nano–level pores. Finally, the effectiveness of introducing phenol resin into wood for wood flow forming through backward extrusion was confirmed.