Effects of Closure Phase on Vertical Density Profile of Fiberboard

摘要

Studying the vertical density profile (VDP) forming progress of fiberboard helps understand and improve the hot-pressing technology. The presented work aims to investigate the effects of coreline temperature and thickness curve on VDP by changing hot-pressing curve and moisture content of mat. In doing so, it was hoped to study the VDP forming progress and manufacture "Steep-Flat" VDP and "Flat" VDP fiberboard. The results indicated that Closure phase of traditional hot-pressing curve failed to alter shape of mat thickness curve which control the shape of VDP. The mat manufactured by traditional hot-pressing curve was "Steep" VDP and could not manufacture "Steep-Flat" VDP and "Flat" VDP; Closure phase of "high-low-high" hot-pressing curve could be separated into rapid compression stage, thickness expansion stage, and second compression stage. The density of surface layer formed at rapid compression stage and decided by first high-pressure. The density gradient between surface layer and core layer formed at thickness expansion stage and decided by expansion time. The density of surface layer formed at rapid compression stage and decided by second high-pressure. The "Steep-Flat" VDP and the "Flat" VDP could manufactured by modulated moisture content of mat, first high-pressure, expansion time, second high-pressure.