Production of long rods by sequential extrusion of wood powders

Wood-based materials are environment-friendly resources as they eventually decompose into carbon dioxide and water after disposal. However, there are a number of productivity and workability related problems: it takes many years for a tree to grow to a useable size, and wood materials are more difficult to process than metal and plastic materials. To overcome these problems, sequential extrusion of cryptomeria powders mixed with Japanese cypress was performed in an attempt to make long wooden rods. In sequential extrusion, the powder replenishment and short-stroke extrusion steps are alternated until the desired rods are obtained. In this process, a strong extrusion seams were required between the new powder batch and the extruded portion of the rod. A steel container with a device for controlling replenishment temperature was used to increase the bonding strength of extruded rods. The results showed that there exist an optimal replenishment pressure and temperature, and that, under these optimal conditions, long rods with the strength of natural wood can be obtained. Finally, it is found that the presence of back-pressure is key in producing sound, high-strength rods.