Tuomas Hänninen

A study by X-ray photoelectron spectroscopy (XPS) of the chemistry of the surface of Scots pine (Pinus sylvestris L.) modified by friction

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Viscoelastic Properties of Core–Shell-Structured, Hemicellulose-Rich Nanofibrillated Cellulose in Dispersion and Wet-Film States

We report the viscoelastic properties of core-shell-structured, hemicellulose-rich nanofibrillated cellulose (NFC) in dispersion and wet-film states. The hemicellulose-rich NFC (hemicellulose neutral sugars 23%, carboxylate 0.2 mmol g(-1)), prepared from Japanese persimmons, had a core crystallite thickness of 2.3 nm and unit fibril thickness of 4.2 nm. A carboxylate-rich NFC (hemicellulose neutral sugars 7%, carboxylate 0.9 mmol g(-1)) with crystallite and fibril widths of 2.5 and 3.3 nm, respectively, was used as a reference. The solid-concentration dependencies of the storage moduli of gel-like water dispersions of the hemicellulose-rich NFC were weaker than those of carboxylate-rich NFC, and the dispersions were loosely flocculated even at high salt concentrations and low pH values. The viscoelastic properties of wet NFC films were similar to those of their dispersions; the hemicellulose-rich NFC films were significantly less sensitive to salt concentration and pH and were soft and swollen at high salt concentrations and low pH values.

Antioxidant activity of Scots pine heartwood and knot extractives and implications for resistance to brown rot

Abstract Brown rot (BR) fungi are highly destructive wood decaying organisms that utilise free radicals in the initial stages of decay. Although many wood extractives have been shown to have antioxidant (AO) activity, their ability to protect wood from radical-based degradation has received little attention. The present paper reports on the ability of Scots pine heartwood (hW) and knotwood (knW) extractives to inhibit radical-based degradation, with a focus on the Fenton reaction. AO assays showed that extract solutions and pure pinosylvins had good radical scavenging activity and weak to moderate ferrous iron binding and ferric iron reducing activities. AO assays were repeated with wood powders and showed that extractives were also active in wood: hW and knW had significantly higher activities than their extracted counterparts or sapwood. However, when wood powders were subjected to degradation by Fenton reagent, only knW showed reduced mass loss. Based on the activity profiles of knW and hW, it appears that the radical scavenging activity of pine extractives is more important than their interaction with iron. The results suggest that the AO activity of extractives may play a role in inhibiting BR, but its importance relative to the other biological activities of extractives is unknown.

Chemical, water vapour sorption and ultrastructural analysis of Scots pine wood thermally modified in high-pressure reactor under saturated steam

AbstractThermal modification of wood results in improved dimensional stability and increases the end-use possibilities of wood. Modification under saturated steam is reported to result in higher performance when compared to more traditional thermal modification methods.n This study analyses the chemical and ultrastructural changes, as well as water vapour sorption properties of Scots pine modified thermally in a high-pressure reactor under saturated steam. The aim is to reveal important chemical and sorption-related changes in wood modified under saturated steam. Chemical composition, water vapour sorption properties, accessibility and concentration of cellulosic hydroxyl groups, as well as evolution of cell wall are discussed. At a temperature of 180xa0°C, clear cell wall delamination and distortion were observed. In nanoscale, the results indicated opening of microfibril bundles, which leads to higher surface area and theoretically, a higher accessibility. However, a decrease in the equilibrium moisture content and accessibility of both extracted and unextracted samples were observed, but the decrease was less obvious in extracted samples.Hence, it was concluded that extractives and degradation products play an important role during thermal modification by blocking porosity and therefore decreasing accessibility and reducing sorption of thermally modified samples. The changes in hysteresis behaviour after extraction also support this outcome.

Effect of volatile organic compounds from Pinus sylvestris and Picea abies on Staphylococcus aureus, Escherichia coli, Streptococcus pneumoniae and Salmonella enterica serovar Typhimurium

Abstract Pine and spruce heartwood and sapwood were milled to wood particles and the volatile organic compounds (VOCs) of the wood particles were tested against four bacterial strains. To study the influence of relative humidity on the antibacterial effect, both dry and wet wood particles were tested. Twenty microliters of the bacterial dilution with a concentration of 1.5×107 CFU ml−1 was cultured on glass surfaces in the presence of VOCs and the amount of viable bacteria was studied after 2, 4, and 24 h. The volatile emissions were evaluated by GC/MS and the results were compared with the results from the bacterial trial. VOCs had an antibacterial effect on Escherichia coli, Streptococcus pneumoniae and slightly on Salmonella enterica serovar Typhimurium. But the effect on Staphylococcus aureus was minute even after 3 days’ incubation. The dry wood particles generally had a stronger antibacterial effect, though the amount of VOCs from the wet wood was higher. Pine heartwood had the strongest antibacterial effect and also the highest emissions of VOCs. However, the interaction between different bacterial strains and wood species shows some variations.