The Biological Durability of Thermally- and Chemically-Modified Black Pine and Poplar Wood Against Basidiomycetes and Mold Action

Vasiliki Kamperidou

doi:10.3390/f10121111

Abstract

Wood of black pine and poplar species were subjected to thermal modification under variant conditions, while subsequently, a number of the thermally-modified black pine specimens were subjected to surface modification with organosilane solutions, and the biological resistances of the different materials were examined using laboratory agar block tests against the action of basidiomycetes and microfungi. Thermally-modified pine specimens were exposed to the brown rot fungi Coniophora puteana and Oligoporus placenta, whereas poplar wood was exposed to the white rot fungus Trametes versicolor and O. placenta. Regarding the biological durability of thermally-chemically-treated pine wood with organosilanes, it was tested against the action of C. puteana. Additionally, both of the thermally-treated wood species, as well as thermally-chemically-treated pine wood were exposed to a microfungi mixture, so that the wood treatments efficacy would be evaluated through a visual assessment of fungal growth on the specimen’s surface The thermal treatments seem to increase the biological resistance of black pine against C. puteana by 9.65–36.73% compared to unmodified wood. The most significant increase in biological durability among all the thermally-treated wood categories was recorded by O. placenta, with 28.75–68.46% lower mass losses in treated pine specimens and 31.98–64.72% in thermally-treated poplar, respectively, compared to unmodified wood. The resistance of treated poplar against T. versicolor was also found increased (13.25–46.08%), compared to control. Thermal modification affected positively the biological resistance of both species, though it did not manage to protect effectively pine and poplar wood from the microfungi action. The combination of thermal and organosilanes treatment revealed a significant improvement of the durability of pine wood compared to? control (45.68–87.83% lower mass losses against C. puteana), as well as against the microfungi action, with the presence of benzin to have a positive effect on the silanes solutions performance and protective action.

Highlights

The resistance of wood to rot is often considered to be synonymous with its duration
The combination of thermal and organosilanes treatment revealed a significant improvement of the durability of pine wood compared to? control (45.68–87.83% lower mass losses against C. puteana), as well as against the microfungi action, with the presence of benzin to have a positive effect on the silanes solutions performance and protective action
The aim of this research is to examine the biological resistance of black pine (Pinus nigra L.) and poplar (Populus sp.) wood after short-term thermal modification for three different durations at two temperature levels, as well as, for the first time, the combination of the described thermal modification with a subsequent chemical surface modification with water-borne and benzin-borne organosilane systems of different ratios on black pine wood, against the action of some of the common European basidiomycetes species and a mixture of commonly found microfungi species

Summary

Introduction

The resistance of wood to rot is often considered to be synonymous with its duration. Apart from chemical protection measures, one of the most effective ways to prevent or limit the action of microorganisms in wood is to keep the moisture content low enough or to prevent at least one of the necessary growth requirements of the microorganisms to be fulfilled, such as the presence of oxygen in wood, proper pH (3–8), appropriate temperature (15 ◦ C–40 ◦ C), absence of toxic extracts, presence of other growth factors such as vitamins, nitrogen etc. Despite the fact that thermal treatment decreases the density and most of the times the mechanical strength of wood, since it increases its brittleness, it seems to limit the hygroscopic nature and enhance the natural durability of wood, providing the chance, (especially to species characterized by low water resistance, dimensional stability and susceptibility to bio-degradation factors), to be adequately utilized, participating in a much wider range of applications [3,4,5,6]

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