The kinetics of anhydride modification reactions of wood. Experimental results and theoretical modelling

IRG/WP 98-40125

C A S Hill, J G Hillier

Although the chemical modification of wood remains a fertile area for research, there has been little work performed on the kinetics of the modification process. The reaction kinetics of a series of linear chain and cyclic anhydrides has been studied and activation energies of the reaction determined. The reaction kinetic profiles are determined by the relative rates of reaction of the reagent with the cell wall polymeric hydroxyl groups, and the rate of diffusion of the reagent within the bulk of the substrate. Thus initially, the rate of reaction is determined by the reaction of reagent with surface sites, but as reaction proceeds, diffusion processes begin to dominate. The relative contributions of the two processes depend upon a number of variables, which include size of reagent, reaction temperature, and ultrastructure of the substrate. This process has been modelled using percolation theory, which has previously had extensive application in describing the flow of liquids through complex porous media, yet has not been applied to wood. The modelling shows that the reaction profiles are determined by the relative rates of reaction and diffusion.


Keywords: CHEMICAL MODIFICATION; ACETYLATION; DIFFUSION; KINETICS; PERCOLATION THEORY

Conference: 98-06-14/19 Maastricht, The Low Countries


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