The effect of pH on surface activation of wood polymer composites (WPCs) with hydrogen peroxide for improved adhesion

The best results were achieved with a mild alkaline hydrogen peroxide treatment at a pH of 7.5 (37% improvement); however a mild acidic hydrogen peroxide treatment also showed a suitable level of adhesion improvement (29%, pH 6). In the alkaline medium it was found that the hydroperoxy anion was efficient in altering both the lignin and the hemicellulose component of the wood flour. It was necessary to limit the extent of wood particle degradation by the hydroperoxy anion, explaining the poor adhesion for treatments with pH 9 peroxide solution. This study indicates that mild (pH 7.5) alkaline treatment solution could be employed. In the acidic medium, the free radical based reaction processes dominated, and were likely to have altered the polypropylene matrix of the WPC material.