R. Lelis et E. Roffael, ON THE REACTIVITY OF SAPWOOD AND HEARTWOO D OF DOUGLAS-FIR AS WELL ASTHEIR WATER EXTRACTIVES TOWARDS FORMALDEHYDE, Holz als Roh- und Werkstoff, 53(1), 1995, pp. 12-16
Sap- and heartwood of Douglas fir were fumigated with formaldehyde at
103 degrees C for different time intervals. Thereafter, the extract co
ntent and the reactivity of extractives towards formaldehyde, as measu
red by the stiasny (Wissing 1955) and UV-method (Roffael 1976), were e
valuated. In further investigations, the reactivity of extractives fro
m sap- and heartwood of Douglas fir of different ages from different s
ites were assessed using the above mentioned methods. The results reve
al, that heartwood extractives are much more reactive towards formalde
hyde compared with sapwood extractives. The UV-method is more sensitiv
e than the stiasny-method in detecting changes in wood extractives due
to reactions with formaldehyde. This may be due to the fact, that onl
y those reactions leading to precepitation are detectable by the stias
ny-method. The results show no pronounced influence of age or site on
the reactivity of extractives towards formaldehyde.