Kraft lignin wood fiberboards -: The effect of kraft lignin addition to wood chips or board pulp prior to fiberboard production

Kraft lignin is a by-product of kraft pulping with great potential as an additive for wood composites. Kraft lignin was added to wood chips prior to defibration and alternatively to fibers to improve the properties of fiberboards. Lignin-wood fiberboards were produced on both laboratory and semi-industrial scale using different methods of adding the lignin and fixing it with metal salt solutions. Both wet-formed (hardboards) and dry-formed (MDF) boards were produced. The properties of lignin hardboards without a post-heat-treatment were slightly better than heat-treated control hardboards. This indicates that addition of kraft lignin in combination with a di- or trivalent metal salt can be an economic alternative to heat-treatment of boards. Results for MDFs indicate that boards with improved dimensional stability could be produced at relatively low cost without need of major investments in equipment.