A high degree of dimensional stability was obtained by epoxy treatment of Corsican pine (Pinus nigra) wood. It was found that the degree of dimensional stability was strongly and positively correlated with the level of substitution obtained. The dimensional stability obtained was of permanent nature and was practically unaffected by quite severe simulated weathering. The introduced material was in the cell wall and probably covalently bonded to the same.

The wood specimens, chemically modified by propylene oxide under 10 bar Na pressure and 130°C temperature for 90 minutes, were tested for sorption at various relative humidities. Typical isotherms for normal pine wood were also found with controls, whereas, a noticeable change in the isotherms was observed with modified specimens. At low values of RH the treated specimens absorbed and retained less moisture than the controls. Above about 55 % RH the modified wood started to absorb increasing quantities ofmoisture and in the 95-100% RH region the EMC of treated wood was slightly greater than that of controls.

Reduction, in the degree of swelling of treated specimens compared to that of controls was reasonably constant throughout the sorption range. High moisture sorption at high levels of RH was not accompanied by a corresponding increase in dimensional change. Large water uptake was probably due to the rigid bulky propane chains retaining the cell walls in a swollen but relatively porous state. Treatment with propylene oxide, thus, led to significant improvement in dimensional stability throughout the hygroscopic range.