The raw materials used to make particleboard include wood or wood fiber materials, adhesives and additives, the former accounting for more than 90% of the dry weight of the board. Timber raw materials are mostly harvested from forest timber, small diameter timber (usually less than 8 cm in diameter), harvesting residues and wood processing residues. Processed into sheets, strips, needles, granular wood chips, wood shavings, wood silk, sawdust, etc., called scraps. In addition, non-wood materials such as plant stalks, seed husks can also be made into boards, and their names are often named after the materials used, such as hemp stalk (shaving) board, bagasse (shaving) board, etc. The adhesive mostly uses urea-formaldehyde resin glue and phenolic resin glue. The former has light fat color, low curing temperature, and has a good gluing effect on the particleboard of various plant raw materials such as wheat straw and rice husk, and the hot pressing temperature is 195~210 °C. It is widely used in production, but it has the disadvantage of releasing free formaldehyde to pollute the environment. The shape of the shavings is a decisive factor in the quality of the particleboard, so it is first necessary to manufacture a good shaving. The shavings of the leftovers from wood processing can be reprocessed to be used as the core layer of the particleboard. Surface shavings are mainly produced from high-grade residues (timber truncation, board edges, etc.) that are harvested or processed. The length, thickness, and width of shavings vary depending on the production method and the core or surface layer used. The processing equipment for the preparation of shavings includes chippers, reshredders, grinders and fiber separators, and the cutting methods include cutting, cutting and crushing. In order to obtain high-quality shavings, they go through the processes of primary crushing, grinding, re-crushing and screening. The initial moisture content of the processed shavings is roughly 40~60%, the moisture content of the core layer that meets the process requirements is 2~4%, and the surface layer is 5~9%. Therefore, it is necessary to use a dryer to dry the shavings with different initial moisture content to achieve a uniform final moisture content. The dried shavings are then mixed with liquid glue and additives. Usually on the surface area of each square meter of shavings, 8~12 grams of sizing is applied. After the rubber is sprayed from the nozzle, it becomes particles with a diameter of 8~35 microns, forming an extremely thin and uniform continuous adhesive layer on the surface of the shavings. Then the sizing shavings are paved into a slab, and its thickness is generally 10~20 times the thickness of the finished product. It can be pre-pressed and hot-pressed. The pre-pressing pressure is 0.2~2 MPa, which is carried out with a flat press or roller press.
