CREEP-BEHAVIOR OF UF BONDED MDF

The object of investigation were MDF of 19 mm thickness bonded with UF-resin originating from different manufacturers. The boards distinctly differred from each other in their short-term properties as well as in their formaldehyde emission potential and their density profiles. The tests regarding the long-term behaviour were carried out according to the FESYP method. Despite the high short-term property values MDF proved to be very sensitive towards storage in changing climate. This phenomenon is likely to be caused by insufficient or wanting repartition of glue. Thus, after only 5 cycles one series showed a decrease of the internal bond to only 1/3 of the initial strength. Also the bending strength values incurred a greater reduction than those of comparable particleboards. This is documented by the pronounced creep tendency of the tested MDF. It was varying to a large extent but was always clearly higher than the creep tendency of comparable particleboards.