What are the requirements of particle board hot pressing process

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Hot pressing is a key process of chipboard production. The function is to solidify the rubber in the slab, and the loose slab is pressed and consolidated into a plate of a specified thickness. Particleboard hot pressing process requirements are:

1, the appropriate moisture content. Surface water content of 18 ~ 20% is conducive to the improvement of bending strength, tensile strength and surface finish, reducing the possibility of slab delamination during pressure relief. The moisture content of the core layer should be appropriately lower than the surface layer in order to maintain proper planar tensile strength.

2, appropriate hot pressure. Pressure can affect the contact area between shavings, the thickness deviation of the sheet, and the degree of transfer of the glue between shavings. According to the different density requirements of products, the hot pressing pressure is generally 1.2-1.4 MPa.

3, the appropriate temperature. Excessive temperature not only decomposes the urea-formaldehyde resin, but also causes partial hardening of the slab at the time of temperature rise, resulting in waste products.

4, the appropriate pressure time. If the time is too short, the intermediate resin cannot be sufficiently cured, the elastic recovery of the finished product in the thickness direction is increased, and the planar tensile strength is significantly reduced. The hot pressed particle board should be subjected to a period of humidity treatment to bring the moisture content to equilibrium, then sawn the sanding and inspect the package. However, it cannot be stacked in hot state after pressure relief, otherwise it will increase the brittleness of the sheet.

Molding technology refers to the technique of forming a product in one operation. There are three kinds of mature crafts. The hot-mold method can be used with little or no compound, and the lignin activates the flow in the closed hot mold and acts as a glue, but it needs to be cooled and demoulded. The heat consumption is large and the productivity is low, and it has been gradually eliminated. The box forming method uses a special press to pressurize and pressurize the product once to make the box. The hot press forming method mainly manufactures furniture fittings, interior fittings and pallets, etc. The adhesive is mainly based on urea-formaldehyde resin, and the surface of the product is affixed with veneer or resin-impregnated paper and molded once. In addition, there are also surface molding methods such as forming a relief pattern on a surface of a finished particle board or forming slabs that have not been hot pressed.

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