for. 485: lignocellulosic composite materials lecture 1-5-1: consolidation behavior of...
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For. 485:Lignocellulosic Composite Materials
Lecture 1-5-1: Consolidation Behavior of Lignocellulosics in Thermal Processes, Part I
Consider a hot-pressing operation:
Platens heated to 150-225 oC (302-437 oF)
Pressure: 4-8 MPa (580-1160 psi)
Wood or lignocellulose “furnish” mat; 5-15% MC, 0-10+% resin solids Question: What effect
do these conditions have on the material placed between the platens?
Processes within…
Heat: Transferred from platens to wood (lignocellulose) furnish by conductive and convective mechanisms.
Wood surface (face) moisture is vaporized and driven toward center and edges of mat.
Mechanical (platen) and vapor pressure act together to increase total internal pressure on the furnish mat.
Consolidation
Transient (time- and location-dependent) conditions: Temperature Moisture content Pressure
Create conditions conducive to: Thermal softening of
cell wall polymers (Tg exceeded)
Viscoelastic deformation of furnish
Result is compression or compaction, otherwise known as consolidation.
FPL-GTR-149
Development of Vertical Density Profile (VDP)
Could you predict areas of high and low density, based on visual inspection?
What is the effect of particle size on localized density (with respect to Horizontal Density Distribution, HDD)?
Cover figure, FPL-GTR-149