LIGNIN FROM STEAM-EXPLODED WOOD AS BINDER IN WOOD COMPOSITES

A study demonstrating the approach of zero-waste technologies, a component of the Zero Emissions concept, and using lignin extracted from steam-exploded wood as adhesive in hot-pressed fibre boards and plywood to substitute phenol-formaldehyde resins is reported. Properties of sample boards containing different amount of lignin adhesive are compared between themselves and with the EU standards for fibre boards. A strong correlation of density and form stability under humid conditions with the lignin content is found. Results of testing mechanical properties of the boards suggest that effect of lignin on mechanical strength depends on the size of particles and hot-pressing temperature. Steam explosion and hot-pressing technologies tested in the study are shown to have potential of utilizing low-quality wood and waste from forest industry to make value-added products. Complementing a saw mill they represent a model of integrated technologies cluster in accordance with the concept of Zero Emissions facilitating environmental protection by reducing pollution and eliminating waste. Mixtures of commercial phenol-formaldehyde resins containing 10% lignin by weight, tested as plywood binders under conditions of factory production, show satisfactory cohesion.