Particleboard is made from a combination of wood or lignocellulosic materials, adhesives, and various additives. Wood-based materials typically make up over 90% of the dry weight of the board. These raw materials are often sourced from forest residues, small-diameter logs (usually under 8 cm in diameter), and by-products from logging and wood processing. They are then processed into different forms such as flakes, shavings, strands, and sawdust—collectively referred to as "wood chips" or "scrap."
In addition to wood, non-wood materials like plant stems, straw, and seed husks can also be used to produce particleboard. These products are usually named after their primary material, such as hemp boards, bagasse boards, or rice husk boards. The most common adhesives used are urea-formaldehyde resin and phenolic resin. Urea-formaldehyde is preferred for its light color and low curing temperature, making it suitable for bonding materials like wheat straw and rice husk. It requires hot pressing at temperatures between 195°C and 210°C. While widely used due to its effectiveness, it has the drawback of releasing free formaldehyde, which can harm the environment.
The quality of particleboard largely depends on the shavings used. Producing high-quality shavings is therefore crucial. Shavings from wood processing waste can serve as the core layer, while surface shavings are typically made from higher-grade wood remnants like trimmed or edged pieces from harvesting or cutting operations.
The size of the shavings—length, thickness, and width—varies depending on the production method and whether they are intended for the core or surface layer. To prepare these shavings, equipment such as chippers, crushers, sanders, and fiber separators are used. Common cutting techniques include slicing, chopping, and crushing. For optimal quality, the shavings go through several stages, including initial crushing, grinding, further crushing, and sieving.
Once processed, the shavings have an initial moisture content ranging from 40% to 60%. Depending on the process, the moisture level is reduced to about 2–4% for the core layer and 5–9% for the surface layer. This means that shavings with different moisture levels must be dried in a dryer to ensure uniform final moisture content. After drying, the shavings are mixed with liquid adhesive and other additives. Typically, 8 to 12 grams of sizing agent is applied per square meter of shavings.
The mixture is then sprayed through nozzles to form particles with diameters ranging from 8 to 35 microns, creating a thin and even layer of glue on the shavings' surfaces. These sized shavings are then laid out 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 is carried out using either a plate press or a roll press.
Stop Valves are closed by screwing a rubber gasket down onto a seat in the middle of the valve. Pros only use small versions that act as shutoff valves for fixtures such as sinks and toilets and outdoor sillcocks. Flow is inefficient because of the circuitous route the fluid (water, in most cases) has to follow. It's important to orient the valve in the right direction with the arrow (cast into the side of the valve) aligned with flow direction. That way, water flows against the bottom of the rubber gasket. If the valve is put in backward, the flow will force the gasket away from the top of the valve.
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