VARIATIONS IN HARDNESS AND SCREW WITHDRAWAL RESISTANCE OF HEAT-TREATED MEDIUM DENSITY FIBERBOARDS

A series of MDF panels were exposed to a post-manufacture heat-treatment at various temperatures and durations using a hot press and just enough pressure to ensure firm contact between the panel and the press platens. Screw withdrawal resistance (SWR) and Janka hardness (JH) of the MDF panels were significantly decreasing with increasing post-treatment press temperature. The panels treated at 225 C for 30 min had the lowest SWR and JH values among the treatment groups, while the highest performance was found for the panels treated at 175 degrees C for 15 min. The highest JH value was of 672.3 kg for the control and the lowest was of 561.3 kg for the panels treated 225 degrees C for 30 min. The lowest SWR value with 158.4 kg was found for 225 C at 30 min, while the control group had the highest SWR value with 196.1 kg. Although JH and SWR values of the treated MDF panels decreased with increasing post-treatment temperature, the values met minimum SWR and JH requirements specified in ANSI-A208 Standard.