Plywood QC Inspection Checklist : Part 10 hot pressing time
Hot pressing is an important process to manufacture the plywood manufacturing and plays a decisive role on the product quality and productivity.
Hot pressing refers to a process that the raw plywood under the combined function of temperature and pressure, is subjected to moisture evaporation, increase of density, glue solidification and water proof agent redistribution. The compositions in the raw materials are subjected to a series of physical and chemical change to form bonding force between the fibers and form the products confirming to quality requirements.
Hot pressing process involves the change in geometric shape, chemical change and physical change. There are
some factors which affect this method,i.e. temperature of the process, type of raw materials, separation mass of fiber, moisture content, resin type and performance, hot pressing method, and the temperature, pressure and time of hot pressing.
Hot pressing time affect the Water Absorption rate (Wt), Thickness Expansion rate (Ts), Modulus of Rupture (MOR) and Internal Bond (I.B) and density,plywood thickness can be accomplished on the basis of Pressure variation under fixed process conditions. Wt ,Ts and density arephysical properties of plywood while MOR and I.B are Mechanical properties of the formed plywood .
More longer hot pressing time affect the finished plywood quality ,especially the density and thickness of the plywood .The QC should have check it .