Effect of chemical modification of wood on the mechanical and adhesion properties of wood fiber/polypropylene fiber and polypropylene/veneer composites

The effect of acetic, maleic or succinic anhydride modifications of wood fi ber on the mechanical properties and dimensional stability of differently b onded fiber boards was studied. The binders for the fiber boards used in th is work were: powdered phenol formaldehyde resin of the novolak type (PF), polypropylene (PP) and a combination of the two. In the second part of the research, birch veneers modified with succinic or phthalic anhydride were l aminated with PP films and the effect of the modifications on the interfaci al bond between the two materials was studied. Significant improvement in t he mechanical properties of the PP-bonded boards was generally observed as a result of the anhydride modifications. Modification of wood fibers with m aleic anhydride resulted in a reduction in the modulus of rupture of the PF - and PF/PP-bonded boards, whereas acetylation and modification with succin ic anhydride did not cause any significant changes in the modulus of ruptur e of the boards. The anhydride modifications improved the internal bond str ength of the fiber boards regardless of the binder type used. Dimensional s tability of the fiber boards was observed to increase significantly as resu lt of the modifications. Adhesion between the PP films and wood veneer show ed an increasing trend as function of the degree of modification. In additi on, SEM micrographs of the fiber boards and PP-coated veneer revealed impro ved interaction between the two components due to the anhydride modificatio ns.