Binderless composites from pretreated residual softwood

Residual softwood was thermomechanically pretreated and used to produce com posites with no synthetic binders. The lignocellulosic material was steam e xploded with a thermomechanical aqueous vapor process in a continuous tubul ar reactor. The study attempts to use the intrinsic bonding capacity of the steamed fiber, which is due to the plastification of the lignin. Chemical and structural changes in the pretreated substrate were evaluated by analyt ical characterization and scanning electron micrographs (SEM). The effect o f the pressing conditions was evaluated in accordance with the physicomecha nical responses of the composites. The physical and mechanical properties o f the panels obtained were tested using UNE EN Spanish standard-European st andards. In order to get more information about the degree of adhesion betw een the lignin and the fibers, SEM micrographs were taken of the broken sur faces of the material tested by the internal bond method. The results show that the thermomechanical pretreatment, pressing temperature, and time have a great effect on the mechanical and physical properties of binderless com posites. The steam explosion aqueous vapor pretreatment is a good way for c onditioning softwood sawdust for production of composites. (C) 1999 John Wi ley & Sons, Inc.