EFFECTS OF PRETREATMENT WITH SHORT PRESSURE PULSES ON THE PROPERTIES OF WOOD

In the reported experiments, the influence of short pressure pulses on the chemical and physical properties of spruce wood was studied on a laboratory scale. The pressure pulses were generated by rapidly raising the pressure from a low value to atmospheric pressure, or by reducing excess pressure to atmospheric pressure. In the former case it was possible to keep the wood temperature below 100 degree C, while in the latter case the temperature was always higher than 100 degree C. It was found that both kinds of treatment resulted in partial fiber separation. When the high-pressure pulses were effected by means of saturated steam, the temperature had a significant influence on both the chemical and physical properties of the wood. Groundwood pulp made from the treated wood exhibited superior strength properties but inferior optical properties compared with those of a conventional mechanical pulp.