The Influence of Sapwood-Heartwood Conversion of Bordered Pit Tori In Western Hemlock on Bisulfite Pulping

Authors

  • Richard L. Gray
  • Robert G. Rickey
  • Herbert L. Hergert

Keywords:

Western hemlock, bordered pits, bisulfite pulping, sapwood-heartwood tori

Abstract

In an effort to determine why heartwood of western Hemlock [Tsuga heterophylla (Raf.) Sarg.] is difficult to pulp by sulfite technology, ultraviolet (UV) and scanning electron microscopy were used to examine hemlock heartwood and sapwood before and after acid-bisulfite pulping. Resulting data showed that UV-absorbing material that is located in the intertracheid bordered-pit membranes and that is solvent-extractable in the sapwood is suggested to be low molecular weight procyanidins that polymerize into unextractable polymers during heartwood formation. Condensation of these polymers occurs under the strongly acidic conditions of acid bisulfite pulping, reducing wood permeability to cooking liquor.

References

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Published

2007-06-27

Issue

Number 3 / July 1983

Section

Research Contributions

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