Waterproof agent in wood-based panel production

Waterproof agent in wood-based panel production

In the production of wood-based panels, the purpose of applying waterproofing agent is to improve the water resistance, dimensional stability, reduce or eliminate warping deformation caused by wet swelling and drying shrinkage, and to prevent moulding and conductivity enhancement caused by moisture absorption. It is one of the simplest, cheaper and most effective measures. It is widely used in the production of particleboard and fiberboard.

The essence of applying waterproofing agent is to apply hydrophobic substances on particles or fibers. After adsorbing hydrophobic substances on the surface of particles or fibers, it can produce the following effects: hydrophobic substances partly block the voids between particles or fibers, cut off the channel of water transmission; increase the contact angle between water and particles or fibers, and reduce it. The contact area is partly covered by polar functional groups (such as hydroxyl groups) on the surface of the material, which reduces the adsorption.

There are many kinds of waterproofing agents, such as paraffin, rosin, asphalt, synthetic resin, dry oil, silicone resin, etc. Paraffin wax is the most widely used waterproofing agent at home and abroad because of its good waterproofing performance, abundant sources and low price. Paraffin is a by-product of petroleum industry. Its main component is straight chain or branched alkanes containing 19 – 35 carbon atoms. The general chemical formula is CnH2n + 2. Paraffin is hydrophobic, soft, meltable, white and yellow in color. The melting point of paraffin used in wood-based panel industry is 42 – 75 C. The melting point of paraffin is 52 – 58 C. The density of paraffin is related to its melting point and temperature. Paraffin has stable chemical properties and can not be saponified, but can be dissolved in gasoline, benzene, trichloromethane and many other organic solvents. Under the action of emulsifier, paraffin wax is easily emulsified into emulsion. Paraffin can be applied by spraying molten liquid on slabs, particles and fibers, or by emulsifying emulsion dispersion. Practice has proved that good waterproofing effect can be obtained as long as the application process is reasonable and uniformly distributed. Different wood-based panels have slightly different amount of application. Excessive application of paraffin, as a hydrophobic substance, will hinder the combination of fiber materials and reduce the strength of products.

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