Properties improvement of seven hardwood species by combination of thermal and chemical modifications

Most European hardwoods are nowadays under-utilized due to drawbacks such as low dimensional stability, durability and surface hardness. Seven hardwood species were thermally and/or chemically modified in order to improve these disadvantages. Heat treatment was carried out in air at atmospheric pressure at three temperatures, while two types of chemical modifications were tested, the first being based on furfuryl alcohol with tartaric acid, the second being based on succinic anhydride and glycerol. Then, modified woods were studied to determine weight loss due to thermal treatment, solution uptake, weight percent gain and swelling due to chemical modification processes. After that, main properties of chemically modified woods were characterized including density, equilibrium moisture content, dimensional stability and surface hardness. Effect of thermal pretreatment on subsequent chemical modification and on properties of modified woods obtained have also been evaluated. Combination of thermal modification with chemical modification had led to better improvements than each separately. Furfurylation treatment appeared to be more efficient than polyester modification. Most of the modified samples were denser, more stable and harder than native wood. These modified woods might compete with imported tropical wood for applications requiring high stability and hardness, such as joinery, decking or flooring, music instruments, handles for tools or kitchen utensils.