Particleboard is manufactured using a combination of wood or lignocellulosic materials, adhesives, and additives. Wood constitutes over 90% of the dry weight of the finished board. Raw wood materials typically come from forest thinnings, small-diameter logs (usually under 8 cm in diameter), logging leftovers, and waste from wood processing. These are transformed into flakes, strips, needles, granules, wood chips, and sawdust, collectively referred to as scrap. Non-wood materials, such as plant stems and seed hulls, can also be utilized to create panels, often named based on their source, like hemp boards or bagasse boards. Urea-formaldehyde resins and phenolic resins serve as the adhesives. The former has a light hue and a lower curing temperature, providing excellent bonding for various plant materials like wheat straw and rice husks. The pressing temperature typically ranges between 195 to 210°C. While widely employed due to its versatility, this resin can release free formaldehyde, contributing to environmental pollution.
The quality of particleboard hinges significantly on the shaving pattern, making the production of high-quality shavings crucial. Shavings left over from wood processing can be repurposed as the core layer for particleboard. Surface shavings are primarily sourced from premium residues obtained during harvesting or processing, such as trimmed or edge-cut pieces. The dimensions of the shavings—length, thickness, and width—are determined by the manufacturing method and whether they’re intended for the core or surface layers. Equipment for creating shavings includes chippers, crushers, sanders, and fiber separators, while cutting techniques range from slicing to grinding. To ensure superior quality, shavings undergo primary crushing, grinding, further crushing, and sieving.
Once processed, the wood shavings start with an initial moisture content of around 40 to 60%. According to the production specifications, the moisture content needs to be reduced to 2 to 4% overall, with the surface layer maintaining a slightly higher level at 5 to 9%. Consequently, shavings with varying initial moisture levels are dried in a dryer to achieve a consistent final moisture content. After drying, the shavings are blended with liquid glue and additives. Typically, 8 to 12 grams of sizing is applied per square meter of shavings. The mixture is sprayed through nozzles, forming particles roughly 8 to 35 microns in diameter, thereby creating a thin, even layer of glue across the shavings’ surface. These glued shavings are then layered into slabs, with the thickness usually being 10 to 20 times that of the final product. Pre-pressing and hot pressing follow. The pre-pressing pressure ranges from 0.2 to 2 MPa and can be executed using either a plate press or a roll press.
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