A simple method for determination of kinetics of radial, tangential and surface swelling of wood

The aim of this paper is to introduce an objective method for monitoring the swelling rates and the final values of swelling of hard and soft woods in the polar media. As can be concluded from the presented kinetic plots of sound and biodegraded beech wood and of mature and juvenile spruce wood, the method provides a possibility of recording the dimensional alterations of wood specimens from the first instant of their contact with polar media. The method provides the possibility of monitoring the swelling kinetics of wood within temperatures ranging between 20 and 60 oC. The data obtained by the presented method may be used for the assessment of wood behaviour in the environment with changing humidity and temperature, or in a direct contact with polar media

Selected properties of beech wood degraded by brown-rot fungus Coniophora puteana

U radu se objašnjavaju određene promjene fizikalnih i mehaničkih svojstava netenzijske, zdrave bukovine nastale kratkotrajnim i srednjetrajnim djelovanjem gljive Coniophora puteana, uzročnice smeđe truleži. Gljiva je tijekom svog razvoja i napredovanja prouzročila postupni gubitak mase i znatno smanjila gustoću bukovine. Biorazgradnjom se izrazito povećao sadržaj polarnih ekstraktiva, nestalo je celuloze i relativno se povećao sadržaj lignina u drvu. Navedene promjene bukovine očitovale su se izrazito povećanom interakcijom vode i drva, odnosno utjecale su na njegovu peremeabilnost i veličinu površinskog bubrenja. Boja drva postala je sme|a, a sjaj je nakon 60 dana izlaganja gljivi smanjen. VIS i FTIR spektralne kemijske analize potvrdile su znatne kemijske promjene bukovine.This paper reveals the alteration of selected physical and chemical properties of non-tension beech wood exposed to short- and medium-term degradation by the brown-rot fungus Coniophora puteana. The fungus caused a gradual mass loss and a significant decrease in wood density by the decay progression. Biodegradation increased the contents of polar extractives in wood markedly, it caused a substantial removal of cellulose and it relatively increased the contents of lignin in wood. The above mentioned alterations of beech wood were reflected in an expressively increased rate of wood/water interactions, influenced its permeability and the rate of surface swelling. Wood colour turned to brown, and its lightness was reduced after 60-day degradation. The chemical analyses, VIS and FTIR spectra confirmed significant chemical changes of beech wood

A simple method for determination of kinetics of radial, tangential and surface swelling of wood

The aim of this paper is to introduce an objective method for monitoring the swelling rates and the final values of swelling of hard and soft woods in the polar media. As can be concluded from the presented kinetic plots of sound and biodegraded beech wood and of mature and juvenile spruce wood, the method provides a possibility of recording the dimensional alterations of wood specimens from the first instant of their contact with polar media. The method provides the possibility of monitoring the swelling kinetics of wood within temperatures ranging between 20 and 60 oC. The data obtained by the presented method may be used for the assessment of wood behaviour in the environment with changing humidity and temperature, or in a direct contact with polar media

EFFECT OF BIOTIC AND ABIOTIC PRETREATMENTS OF HORN-BEAM WOOD ON ITS PROPERTIES INTERESTING FROM VIEWPOINT OF PULPING IN ALKALINE MEDIA.

A series of comparable specimens of hornbeam wood were submitted to pretreatments by white-rot fungi, by alkali alone, or by alkali and oxidizing agents. The pretreatments caused weight loss of wood and modified its physical properties and chemical composition. All pretreat-ments reduced markedly axial permeability of the test specimens in the wet state (w > FSP). The chemical pretreatments of the test specimens, however, increased the rate of diffusion in the direction parallel to the grain. All pretreatments made the kinetics of wood/water interactions in the initial phase much higher, especially when white-rot fungi were used. The chemical pretreatments caused extreme swelling of wood, and on the other hand, drying of the pretreated specimens to their initial moisture content resulted in extremely deep reduction of their dimen-sions. An increased rate of wood/water interactions, high uptake of water, and higher diffusion coefficients of wood pretreated by alkali may positively influence the pulping processes

EFFECT OF BIOTIC AND ABIOTIC PRETREATMENTS OF HORNBEAM WOOD ON ITS PROPERTIES INTERESTING FROM THE VIEWPOINT OF PULPING IN ALKALINE MEDIA.

A series of comparable specimens of hornbeam wood were submitted to fungal and chemical pretreatments. Two strains of erosive white-rot fungi (P. chrysosporium and T. versicolor) and a lignin-selective fungus C. subvermispora were used. Chemical pretreatments were carried out with diluted sodium hydroxide, or sodium hydroxide and then by hydrogen peroxide, or per-acetic acid. Both biotic and abiotic pre-treatments modified the chemical composition of wood and were accompanied by its weight loss. The applied fungi apparently delignified the specimens, however at the expense of cellulose, especially when the erosive strains of fungi were used. The chemical pretreatments caused deep deacetyl-ation, and milder delignification of wood and did not cause an apparent loss of cellulose. Biotic pretreatments of hornbeam wood, despite their marked delignification effect, led to unexpected increase in the contents of residual lignin in the resulting kraft pulps. On the other hand, pulping of the chemically pre-treated chips yielded pulps with low contents of residual lignin and much higher brightness