EFFECT OF STORAGE OF RESIDUES FROM SAW MI LL PROCESSING OF PINE AND SPRUCE ON ITS SUITABILITY AS A RAW-MATERIAL FOR PARTICLEBOARDS AND MEDIUM DENSITY FIBERBOARDS (MDF) .3. EFFECT OF STORAGE OF SAW MILL RESIDUES DERIVED FROM WOOD FELLED IN WINTER ON ADHESION RELEVANT PROPERTIES OF CHIPS AND FIBERS PREPARED THEREFROM

The residues of a saw mill with a profiling unit were stored in piles of about 40 m(3) for different time periods. From time to time wood ma terial was taken from the piles and disintegrated to chips using a rin g flaker or pulped using the thermomechanical process and defibrated. Both chips and fibres were analysed chemically to detect any change in adhesion relevant properties, especially in pH-value, buffering capac ity, amount of volatile acid content in the extractives. Moreover, the formaldehyde release and the emanation of volatile acids were assesse d using the flask-method technique. The results led to the following c onclusions: The pH-value of cold and hot water extractives of chips an d fibres derived from saw mill residues increased slightly on seasonin g of the residues. The hot extractives showed, however, lower pH-value s and higher alkaline buffering capacities than the cold water extract ives. The results of measuring the volatile acid content in extractive s are in harmony with those of pH-value and buffering capacity. The co ntent of volatile acids of fibres and flakes decreased on seasoning of saw mill residues as well as the release of volatile acids from flake s and fibres. Likewise, storage decreased the formaldehyde release fro m the chips on seasoning the saw mill residues. Pine flakes and fibres showed always lower pH-value, higher alkaline buffering capacity comp ared to Spruce chips and fibres. Moreover, the release of volatile aci ds from Pine flakes and fibres was much higher than from Spruce wood. The changes in adhesion related properties in saw mill residues of Pin e wood were much pregnant than in Spruce.