Effect of oil impregnation on water repellency, dimensional stability and mold susceptibility of thermally modified European aspen and downy birch wood

Tom Morén,Margot Sehlstedt-Persson,Åsa Blom,Sheikh Ali Ahmed

doi:10.1007/s10086-016-1595-y

Tom Morén, Margot Sehlstedt-Persson + Show 2 more

Open Access

https://doi.org/10.1007/s10086-016-1595-y

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Abstract

Conventional chemical wood preservatives have been banned or restricted in some applications due to human and animal toxicity and their adverse impact on the surrounding environment. New, low-environmental-impact wood treatments that still provide effective protection systems are needed to protect wood. Thermal modification of wood could reduce hygroscopicity, improve dimensional stability and enhance resistance to mold attack. The aim of this study was to investigate if these properties enhanced in thermally modified (TM) wood through treatments with oils. In this study, TM European aspen (Populus tremula) and downy birch (Betula pubescens) wood were impregnated with three different types of oil: water-miscible commercial Elit Träskydd (Beckers oil with propiconazole and 3-iodo-2-propynyl butylcarbamate, IPBC), a pine tar formulation and 100% tung oil. The properties of oil-impregnated wood investigated were water repellency, dimensional stability and mold susceptibility. The treated wood, especially with pine tar and tung oil, showed an increase in water repellency and dimensional stability. However, Beckers oil which contains biocides like propiconazole and IPBC showed better protection against mold compared with pine tar and tung oil. To enhance the dimensional stability of the wood, pine tar and tung oil can be used, but these oil treatments did not significantly improve mold resistance rather sometimes enhanced the mold growth, whereas a significant anti-mold effect was observed on Beckers oil treated samples.

Highlights

In the past several decades, a number of methods to thermally modified wood have been successfully developed
thermally modified (TM) European aspen (Populus tremula) and downy birch (Betula pubescens) wood were impregnated with three different types of oil: water-miscible commercial Elit Traskydd (Beckers oil with propiconazole and 3-iodo-2-propynyl butylcarbamate, IPBC), a pine tar formulation and 100% tung oil
This study provides a significant amount of information regarding the effects of thermal modification and oil impregnation on the moisture properties and mold susceptibility of these two important Swedish hardwood species

Summary

Introduction

In the past several decades, a number of methods to thermally modified wood have been successfully developed. In Europe, five processes are currently available at the industrial scale, including ThermoWoodÒ (or Premium wood) using steam in Finland; the Perdure process (BOIS PERDURE), which is conducted in a steam atmosphere in France; the Retification process using nitrogen (Retiwood) in France; the Plato process (PlatoÒWOOD) in an aqueous environment at super-atmospheric pressures in the Netherlands; and an oilheat treatment (Menz HolzÒ) in Germany All these processes are used to improve wood properties by reducing hygroscopicity, improving dimensional stability and enhancing resistance against biological attack by modifying the chemical structure of the wood at temperatures ranging from 160 to 260 °C [1,2,3,4]. The extent to which the wood properties are modified after the thermal treatment depends on the method, the wood species, inherent wood properties, the type and condition of the heating gas and the treatment schedules. The available –OH groups in the hemicellulose have the most significant effect on the hygroscopicity of wood

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