Horizontal gas pressure and temperature distribution responses to OSB flake alignment during hot-pressing

Abstract

This study examines the effect of different flake alignments and densities on horizontal heat and gas flow from the mat centre to the edges. Robot-formed 660×660 mm single layer oriented-strandboard (OSB) mats, with various flake alignment distributions, were hot-pressed at 180°C to 10 mm thickness. Fine gauge thermocouple wire and steel capillary tubes were built into the mat to monitor core temperatures and gas pressures at ten locations across the board-plane. Results confirm the existence of lateral temperature and gas pressure gradients across the mat, with its edges having lower temperatures and pressures than its interior. Flake alignment was seen to skew the lateral gradients in the alignment directions, the extent being strongly influenced by interactions with mat density and the proximity to the edge. In highly aligned mats, lower temperatures and pressures were measured along the alignment direction than perpendicular to it, thus indicating greater heat and mass transfer along the flake alignment axis. These horizontal temperature and pressure distributions have practical implications on panel uniformity and quality as mat consolidation is dependent on internal conditions during hot-pressing.