FAIR-CT98-5023 Biological aspects of chemical wood modification

Contacts




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Crops for Solid Wood Products : FAIR Area 1.3 - Forestry-Wood Chain : FAIR Marie Curie Research Training Grants

Objectives:

Acetylation of solid wood to enhance anti-shrink-efficiency and resistance against fungal decay is a fairly new approach in wood technology. In the near future acetylation of solid wood will be carried out on an industrial scale. Nevertheless some questions concerning the effects of acetylation on wood structure and biological degradation remain unanswered and formed the basis for this project.

Activities and Results:

Samples wood from Scots pine, Norway spruce and beech treated using various acetylation processes were investigated using a range of techniques. These included: light microscopy, electron microscopy, confocal laser scanning microscopy together with image analysis, UV-spectroscopy and fluorescence spectroscopy. In addition decay patterns in non-treated and acetylated wood under soil exposure were studied using different microscope techniques. It was found that the optimised processes designed for industrial acetylation do not cause any damages to wood structure. Thin walled parenchyma tissue as well as pit membranes were unaffected. A bulking effect due to acetylation led to a higher cell wall/lumen relation in the early-wood of spruce: The wood became denser. It was found that only sub-optimised processes, with uncontrolled temperature, might cause damage such as fibre detachment and dissolution of pit membranes.

Acetylated spruce had a lower permeability for waterborne solutions. The impregnation deepness was measured using image analysis and revealed significantly lower impregnation depth in the axial direction. UV-spectroscopy of acetylated spruce showed that even a high degree of acetylation does not affect the aromatic structures of lignin, implicating a possible side chain reaction. A change in the fluorescence characteristic of lignin was found using fluorescence spectroscopy. Intensity of lignin fluorescence in softwoods was significantly correlated with the degree of acetylation.

Conclusions:

The work was not finished by the end of the project. Preliminary results, however, showed that a high degree of acetylation did not suppress colonisation of wood by fungi, but biological degradation was severely reduced or completely prevented.

Keywords: Wood acetylation

Contacts

Scientific Supervisor

• Stichting Hout Research (SHR) Foundation for Timber Research / NETHERLANDS