Wood fibre anhydride modifications

The interface between plastic and wood fibres strongly influences the mechanical properties of a plastic/wood fibre composite. A means for evaluating the effectiveness of surface treatment on the wood fibres in the PVC/wood fibre composites is presented that investigated the adhesion between PVC and laminated wood veneers. Wood veneers were first treated with gamma-aminopropyltriethoxysilane, dichlorodiethylsilane, phthalic anhydride, and maleated PP for surface modification. The chemical modification made on the wood surfaces was then characterised by different complementary surface analytical techniques X-ray photoelectron spectroscopy and surface tension measurements. 63 refs. 

The effect of acetic, maleic or snccinic anhydride modifications of wood fibre on the mechanical properties and dimensional stability of differently bonded fibre boards was studied [33]. The binders for the fibreboards used in that work were powdered PF resin of the novolak type, PP and a combination of the two. Significant improvement in the mechanical properties was obtained as a result of the anhydride modifications. Thus, modification of wood fibres with maleic anhydride (MA) resulted in a reduction in the modulus of rupture of the PF and PF/PP-bonded boards, whereas acetylation and modification with succinic anhydride did not cause any significant changes in the modulus of rupture of the boards. The anhydride modifications improved the internal bond strength of the binder type used. Dimensional stability of the fibreboards was observed to increase significantly as result of the modifications [33]. 

Some authors used no catalysts or solvents to carry out the succinic anhydride (SA) and maleic anhydride (MA) modifications, which supports the assumption of the limited effect of the modifications on the fibre strength. It is not excluded that the improved interaction between the wood fibres and PP is related to more similar surface energies and even to chemical bond formation between the components. 

Thus, the mechanical tests of the fibreboards carried out by the same authors [60] showed that chemical modification of wood fibre by means of anhydrides was most beneficial for the fibre boards bonded with PP, i.e., significant improvement in the mechanical properties... 

The production of moisture resistant particleboard by treatment with a maleic anhydride -glycerol mixture and using phenol formaldehyde as the matrix material has been investigated (Fujimoto etal., 1987). Boards prepared from modified wood showed considerable improvements in modulus of elasticity and internal bond strength when compared to control boards. Composites made from aspen fibres modified with SA, MA or acetic anhydride using phenol-formaldehyde (PF) or polypropylene as binder have also been studied (Clemons etal., 1992 Rowell etal., 1993b). The reaction of wood with MA was found to proceed at a slower rate than with SA. The volume increase due to modification... 

Haque, M.N. and Hill, C.A.S. (1998). Chemical modification of wood flour and fibre with acetic anhydride. Journal of the Timber Development Association of India, 54(3), 25-33. 

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