Michael Altgen
Forsker
Sammendrag
Heat treatment increases the decay resistance of wood by decreasing its hygroscopicity, but the wood material remains degradable by fungi. This study investigated the degradation of heat-treated wood by brown rot fungi, with the aim of identifying fungal-induced hygroscopicity changes that facilitate degradation. Scots pine sapwood samples were modified under superheated steam at 200 and 230 °C and then exposed to Coniophora puteana and Rhodonia placenta in a stacked-sample decay test to produce samples in different stages of decay. Sorption isotherms were measured starting in desorption from the undried, decaying state to investigate their hygroscopic properties. Although there were substantial differences in degradative ability between the two fungi, the results revealed that decay by both species increased the hygroscopicity of wood in the decaying state, particularly at high relative humidity. The effect was stronger in the heat-treated samples, which showed a steep increase in moisture content at low decay mass losses. The reference samples showed decreased hygroscopicity in absorption from the dry state, while the heat-treated samples still showed an increase at low mass losses. Near infrared spectroscopy showed that the early stages of decay were characterised by the degradation of hemicellulose and chemical changes to cellulose and lignin, which may explain the increase in hygroscopicity. The results provide a new perspective on brown rot decay and offer insight into the degradation of heat-treated wood.
Forfattere
Samuel L. Zelinka Samuel V. Glass Eleanor Q. D. Lazarcik Emil E. Thybring Michael Altgen Lauri Rautkari Simon Curling Jinzhen Cao Yujiao Wang Tina Künninger Gustav Nyström Christopher Huber Dreimol Ingo Burgert Mohd Khairun Anwar Uyup Tumirah Khadiran Mark G. Roper Darren P. Broom Matthew Schwarzkopf Arief Yudhanto Mohammad Subah Gilles Lubineau Maria Fredriksson Marcin Strojecki Wiesław Olek Jerzy Majka Nanna Bjerregaard Pedersen Daniel J. Burnett Armando R. Garcia Els Verdonck Frieder Dreisbach Louis Waguespack Jennifer Schott Luis G. Esteban Alberto Garcia-Iruela Thibaut Colinart Romain Rémond Brahim Mazian Patrick Perre Lukas Emmerich Ling LiSammendrag
Automated sorption balances are widely used for characterizing the interaction of water vapor with hygroscopic materials. These instruments provide an efficient way to collect sorption isotherm data and kinetic data. A typical method for defining equilibrium after a step change in relative humidity (RH) is using a particular threshold value for the rate of change in mass with time. Recent studies indicate that commonly used threshold values yield substantial errors and that further measurements are needed at extended hold times as a basis to assess the accuracy of abbreviated equilibration criteria. However, the mass measurement accuracy at extended times depends on the operational stability of the instrument. Published data on the stability of automated sorption balances are rare. An interlaboratory study was undertaken to investigate equilibration criteria for automated sorption balances. This paper focuses on the mass, temperature, and RH stability and includes data from 25 laboratories throughout the world. An initial target for instrument mass stability was met on the first attempt in many cases, but several instruments were found to have unexpectedly large instabilities. The sources of these instabilities were investigated and greatly reduced. This paper highlights the importance of verifying operational mass stability of automated sorption balances, gives a method to perform stability checks, and provides guidance on identifying and correcting common sources of mass instability.
Sammendrag
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