The Path of Penetration of Pulping Media into Wood

Abstract

In Giertz’ paper, it has been pointed out that the papermaking properties of fibres depend in part on the pulping processes used in their production. The purpose of this contribution is to outline some recent investigations on how morphological factors, especially those that affect the path of penetration of the pulping medium into wood, are of influence on the composition and structure of the fibres ultimately used in sheet formation. The composition of the fibres is especially influenced by the manner of their separation during the pulping process . As background to this discussion, it will be recalled that the basic organisation of a typical fibre or tracheid is as shown in Fig. 1 . The layers corresponding to those in Fig. 1 can be seen in the electron micrographs Fig. 2 and 3. Furthermore, as shown by Lange,⁽¹⁾ most of the lignin of the cell wall is concentrated in the region external to the layer S2 and, for Eucalyptus regnans and Pinus radiata (the species here under discussion), similar values were obtained by Wardrop, Dadswell and Davies.⁽²⁾ It was shown further in this investigation that the lignin concentration in the middle lamella is greatest at the cell corners and somewhat greater between radial walls than that between tangential walls.