Formation of the density profile and its effects on the properties of fiberboard

Two main types of fiberboards were produced using lauan (Shorea spp.) fiber s with an isocyanate resin as the binder; fiberboard with a flat, homogeneo us (homoprofile), and typical U-shaped (conventional) density profile along the board thickness. The processing parameters included manipulation of ma t moisture content distribution, press closing speed, and hot pressing meth od. The results are summarized as follows: (1) A larger variation was obser ved in the peak density (PD) and core density (CD) of fiberboards at 0.5 g/ cm(3) mean density (MD) level than in those at 0.7 g/cm(3). Generally, PD s howed a greater variation than CD, irrespective of MD level. (2) Boards pro duced using two-step hot pressing recorded substantially higher PD with red uced CD. (3) Multiple regression analysis showed that CD and PD could be ca lculated based on the other profile defining factors, and a rough estimatio n for peak distance and gradient factor was possible. (4) Based on static b ending, conventional fiberboard had a higher modulus of rupture (MOR) than the home-profile board but a similar modulus of elasticity (MOE). (5) At 0. 5 g/cm(3) the MOR and dynamic MOE of fiberboard increased by up to 67% and 62%, respectively, when the PD increased from 0.5 to 1.07 g/cm(3). Similarl y, an increase of PD from 0.7 to 1.1 g/cm(3) resulted in corresponding incr eases of 55% and 34% in the MOR and dynamic MOE of 0.7 g/cm(3) boards. (6) The internal bond strength and screw withdrawal resistance were almost enti rely dependent on the CD and MD, respectively. (7) Home-profile fiberboards registered higher thickness swelling and water absorption than conventiona l fiberboards throughout the dry/wet conditioning cycle.