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

Abstract

The effect of acetic, maleic or succinic anhydride modi®-cations of wood ®ber on the mechanical properties and dimensional stability of differently bonded ®ber boards was studied. The binders for the ®ber boards used in this 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 modi®ed with succinic or phthalic anhydride were laminated with PP ®lms and the effect of the modi®cations on the interfacial bond between the two materials was studied. Signi®cant improvement in the mechanical properties of the PP-bonded boards was generally observed as a result of the anhydride modi®cations. Modi®cation of wood ®bers with maleic anhydride resulted in a reduction in the modulus of rupture of the PF-and PF/PPbonded boards, whereas acetylation and modi®cation with succinic anhydride did not cause any signi®cant changes in the modulus of rupture of the boards. The anhydride modi®cations improved the internal bond strength of the ®ber boards regardless of the binder type used. Dimensional stability of the ®ber boards was observed to increase signi®cantly as result of the modi®cations. Adhesion between the PP ®lms and wood veneer showed an increasing trend as function of the degree of modi®cation. In addition, SEM micrographs of the ®ber boards and PP-coated veneer revealed improved interaction between the two components due to the anhydride modi®cations. Einfluû chemischer Modifikation des Holzes auf die mechanischen und Hafteigen-schafton von Holz-und Polypropylen-Fascrplatten sowie Polypropylen/Furnier-Werkstoffe Der Ein¯uû der Modi®kation von Holzfasern mit Essig-, Malein-und Bernsteinsa Èureanhydrid auf die mechanischen Eigenschaften und die Dimensionsstabilita Èt von unterschiedlich gebundenen Faserplatten wurde untersucht. Als Bindemittel wurden verwendet: Phenol-Formaldehydharz (Pulver) vom Novolak-Typ (PF), Polypropylen (PP) sowie eine Kombiation der beiden. Weiterhin wurde Birkenfurnier mit Bernstein-und Phthalsa Èureanhydrid modi®ziert und mit PP-Filmen beschichtet. Der Ein¯uû der Modi®kation auf die Bindung zwischen den beiden Materialien wurde untersucht. Allgemein konnten signi®kante Verbesserungen der mechanischen Eigenschaften der PP-gebundenen Platten durch die Reaktion mit den Anhydriden erreicht werden. Die Modi®kation der Holzfasern mit Maleinanhydrid fu Èhrte zu einer Verringerung des MOR der PF-und PF/PP-gebundenen Platten. Dagegen blieb der MOR nach Acetylierung oder Modi®kation mit Bernsteinsa Èureanhydrid weitgehend unvera Èndert. Alle Modi®kationen mit den Anhydriden verbesserten die Querzugfestigkeit der Faserplatten unabha Èngig vom Bindemittel. Die Dimensionsstabilita Èt der Faserplatten stieg aufgrund der Modi®kation ebenfalls deutlich an. Die Haftung zwischen den PP-Schichten und dem Furnier verbesserte sich parallel zum Ausmaû der Modi®kation. Zusa Ètzlich konnte anhand von REM-Aufnahmen von Fascrplatten und PP-beschichtetem Furnier die verbesserte Wechselwirkung der beiden Kompon...

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Mechanical Properties and Dimensional Stabilities of Wood-Polypropylene Composites Prepared using Mechanochemically Acetylated Japanese Cedar (Cryptomeria japonica) Wood Meal

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