Urea-formaldehyde (UF) resin is a common binder in many fibre- and particleboards today. However, formaldehyde is a fairly reactive compound with many negative affects on health and environment. This paper describes a process to make thin high density fibreboards without use of conventional resin such as UF. Initially we found that wood particles such as ones used in particle board had, when activated with hydrogen peroxide and iron catalyst, self-bonding capability when hot-pressed into boards. Low swelling board, although at somewhat higher density than conventional glued ones, could be formed by pressing activated wood particles at 170 oC in a laboratory press. We found that the activation technique was applicable to dry or semi-dry board processes and was considered to be well suited for fibreboards from refined wood fibers especially as their specific (contact) area is high.
Activated wood fibres were produced at Metso Panelboards Pilot-refiner in Sundsvall and mats were also formed and pressed into boards 50×60 cm2 at fairly conventional pressing conditions. At a hydrogen peroxide charge of 4% boards made from birch fibres with good mechanical properties (in terms of bending strength and internal bonding) were produced. Thickness swelling in water was low (TS24h., 15-20%). At lower hydrogen peroxide charges (<2%) the swelling was higher. Development of the process to also include other wood species than birch is in our interest. Furthermore, properties of the boards were strongly dependent on the moisture content of fibres; at low moisture content (MC<8%) thickness swelling increased. We see a high potential in the process as the glue-free technique is estimated to reduce production cost of boards as well as give environmental advantages.
Keywords: Glue-free binderless fiberboard, Hydrogen peroxide activation, Environmentally friendly alternative
Authors
Olov Karlsson
LTU Skellefteå, Skellefteå
Ulla Westermark
LTU Skellefteå, Skellefteå
Ulrika Backlund
Metso Panelboard, Sundsvall
Sören Halvarsson
Metso Panelboard, Sundsvall
Mittuniversitetet, Sundsvall
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