Tw. Lee et al., INFLUENCE OF DIFFERENT CATALYST SYSTEMS ON THE HYDROLYTIC STABILITY OF PARTICLEBOARDS BONDED WITH UNMODIFIED AND MODIFIED UF-RESINS, Holzforschung, 48, 1994, pp. 101-106
After a storage time of one year, the influence of different catalyst
systems on the release of formaldehyde and volatile acids from particl
eboards bonded with unmodified and modified UF-resins was studied at 3
0 degrees C (only for formaldehyde), 40 degrees C and 50 degrees C and
100% relative humidity. The results reveal that modification of UF-re
sins with a melamine resin of molar ratio F:M 1.6:1 and resorcinol sig
nificantly increases the hydrolysis resistance of the UF-resin in the
boards. Resorcinol, especially at higher temperatures, was even more e
ffective than melamine resin. Measurable differences in the formaldehy
de release of particleboards were detected. The boards were separately
bonded with two low-emission UF-resins with subtle differences in the
chemical composition. The amount of hardener, varied between 0.8% and
3.2% (based on resin of 66% solids), had practically no influence on
the release of volatile acids from particleboards. In contrast to the
behaviour of solid wood, UF-particleboards made from pine chips releas
ed substantially more formic acid than acetic acid, especially at high
temperatures. Modification of the UF-resin with resorcinol and melami
ne resin had no effect on the release of acetic acids from the boards.
The release of formic acid decreased slightly on modifying the resin
with resorcinol and melamine resin. The results indicate that the infl
uence of modification and resin type on the hydrolytic resistance of t
he boards is still apparent even after a storage time of one year.