These are composed of wood chips carefully graded, mixed with synthetic resin glue and either pressed or extruded into rigid, self-supporting sheets of uniform thickness which are sanded down to close tolerances. Flax-sheaves are sometimes used instead of wood chips (flax boards) and have virtually the same properties, although they tend to be lighter in weight and not so strong for any given density. Considerable research has gone into the development of both types of board, and woodchip boards are marketed in several forms: flooring grade for general purpose in the building industry, low-density boards for door cores, partitioning, etc., standard all-purpose boards for built-in fitments, panelling, etc., and special furniture-boards (Weyroc 38) for carcass components. The last-mentioned boards are of graded density construction, with the finest chips near to the face, giving a high-
density, smooth, close-textured surface eminently suitable for veneering, as there is little tendency for the individual wood chips to show through under high polishes. They are invariably pressed, as distinct from extruded, boards in which the wood chips lie at right angles to the board surfaces, resulting in poor bending strength and lower stability.
Particle boards are heavier than most other wood materials (33 to 40 lb per cu. ft or 528.609 to 640.739kgpercu.m according to the density) as the glue content is relatively high; moreover they have no long fibres and thus have little bending strength and tend to crumble at the edges if roughly treated. Always provided that these boards are not treated merely as substitutes for solid timber and forced to conform to long-established constructional methods, but regarded as valid materials in their own right, well worthy of new methods and applications, there is no doubt whatever that their use will continue to expand, and indeed they will become the standard material for furniture-making. With their obvious advantages this is almost inevitable, for not only do they make use of what is virtually waste material (forest thinnings, bough wood, etc.) but the very fact that they are man-made materials means that there is always scope for research and development in the production of lighter, stronger, Stiffer and cheaper boards.
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