Long-term deformation of MDF panels under alternating humidity conditions

Creep tests were carried out on 19 mm thick commercial MDF panels, raw and overlaid with melamin resin-impregnated 80 g/m2 paper. The tests were carried out under cyclic environmental conditions with relative humidity levels of 30%-90%, a steady temperature of 20 degrees C, 3 different stress levels, 20%, 30% and 40%, and using mid-span loading. The relative creep of the MDP panels was considerably higher than that in particleboards with similar characteristics. Creep behaviour of the raw panels seems to be strongly influenced by melamin coating of the boards' surfaces but not by the edge coating, except when both were combined. This study debates the convenience of comparing the rheological behaviour of MDF and particleboards by means of the relative creep.