Step-closing pressing of medium density fiberboard - Part 2. Influences onpanel performance and layer characteristics

The previous paper in this series discussed the step-closure pressing sched ule to change the density profile of lab-made MDF panels. The purpose of th is research was to investigate the effect of the step-closure schedule on t he end-product performance, especially on the layer thickness swell and its relationship with layer density. The results of this work showed that step -closure schedules resulted in improved internal bond strength of the teste d specimens. The step closing schedule significantly increased the core den sity and decreased the face density, resulting in lower bending properties. The results showed that greater core density did not result in higher inte rnal bond strength. The more unsteady phase in a mat resulted in the poorer quality of the bond formation. The layer thickness swell after three water exposure times is significantly and positively related to layer density in all panels studied. The correlation coefficient between the actual layer t hickness swell and layer density increased with increasing water exposure t ime. The greater thickness swell in the surface layers of MDF suggests that efforts to improve dimensional stability of MDF should be focused on stabi lizing the high-density surface layers.