The Simultaneous Drying and Densification of Sapwood

Abstract

A process for densifying wood while simultaneously drying it in a platen press is described. The effect of various pressure-time functions on the density distribution of the final product is discussed as is the effect of these functions on the dimensional stability characteristics of the product. Low density wood of high permeability, generally sapwood, is applicable to this process. A product with the most uniform density distribution and the best stability characteristics is obtained by rapidly compressing the material after the center has reached 212 F. Springback of such material after soaking for three weeks amounts to 10 to 15%. More stable material can be produced by steeping green wood in phenol formaldehyde impregnating resin prior to drying and densification. Springback after soaking can then be reduced to 1 to 2%. The bending strength properties of the densified material was found to be proportional to the density in a range from 0.60 to 1.00 gm per cm 3 . Some estimates of cost of the process are presented.