Chemical modifications of Scots pine (Pinus sylvestris) wood flour were performed with vinyl acetate (VA) and acetic anhydride (AA) in the presence of potassium carbonate as a catalyst. Scots pine wood flour samples were successfully acetylated with VA (19 wt% gain) and AA (24 wt% gain). The effect of chemical modification of the Scots pine wood flour with AA and VA on the mechanical properties of wood high-density polyethylene composites (WPC) was determined. It was observed that acetylation of wood flour allowed a significant increase in both the mechanical properties and the thermal stability of the WPCs. It was concluded that acetylation of lignocellulosic fibers improves thermal stability, dispersion in the polymer matrix, and compatibility with the polymer matrix.
The potential of several tertiary amine catalysts (pyridine, 4-dimethyl-amino pyridine, N-methyl pyrrolidine and N-methyl pyrrolidinone) for the acetylation of Corsican pine sapwood, using acetic anhydride, has been investigated. Rates of reaction were compared with non-catalysed acetylation using acetic anhydride. The hypernucleophile 4-dimethylamino pyridine was found to be the most effective catalyst of those studied. At a concentration of only 1 % of the catalyst in acetic anhydride, a weight percent gain of 20 % was realised, compared with 7 % for the uncatalysed reaction, after 30 minutes system at 100°C. The influence of substrate swelling upon the rate of reaction with wood is discussed.
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