Wood plastics and plates
In addition, on surfaces covered with a hydrophobizing oriented adsorption layer, the wetting hysteresis sharply increases, which even more reduces wetting such surfaces with water. This phenomenon underlines most processes of hydrophobi-pose of hydrophilic materials based on adsorption and chemical fixation on the surface of the latest surface-active hydrophobizing substances.
A point at which the hydrophilic surface, adsorbing the surface-active substance, becomes hydrophobic, t. e. the regional corner of 90 ° is called the inversion point moisten and I.
Wood plastics and plates have a fibrous or porous structure. This structure can be considered as a system of open capillaries (narrow channels) available to move water in them. If the end of such a capillary with the middle radius of G, the walls of which are completely moistened with liquid, is in contact with it, then the liquid, trying to moisten the internal walls of the capillary, forms inside his concave meniscus. This meniscus, created by the raised edges of the fluid level, leads to the appearance of capillary pressure
The absolute value of the anti-pyloric pressure negative in the sign expressed by the formula (57) can be considered a measure of hydrophobic and hydrophobized porous materials from 0>9o °.
Consider directly a drop (or large mass) of water on the surface of a porous solid. If the angle of wetting the surface of the material (including pore walls) exceeds 90 °, then areas of the lower surface of the drop (water layer) located above the surface of the open pores and not in contact with solid particles will be located above the surface of the solid.
To pass water through the burrows, a large pressure required to overcome significant curvature of the liquid surface will be required, the greater the dumb corner and the smaller the width of the pores. If the porous body is hydrophilic, t. e. 0<9o °, then wetting the walls of the pores will cause the penetration of liquid into them.