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composition board,wood product produced in the form of a board or sheet, formed of cellulose fibers or particles derived from wood or other sources, and used principally as a building material. The oldest type of composition board is a relatively dense material known as hardboard, discovered accidentally in 1924 by the American scientist William Mason. After obtaining wood fibers by using high-pressure steam, Mason attempted to dry a matlike mass of them in a steam press. Because of a faulty valve, the press remained hot longer than had been planned and thus the first piece of hardboard was formed. In other forms of composition board the fibers are not as closely packed, and the density is correspondingly lower. Some of these boards find application as insulating and soundproofing materials. Other similar types are treated with waterproofing material, e.g., asphalt applied under pressure, and are usable as the sheathing of buildings. Such materials typically have a resistance to shearing forces exceeding that of plywood. Particle board, another form of composition board, is made by binding wood particles ranging in size from flakes to sawdust together with a suitable adhesive, such as a plastic resin, and pressing or extruding them to form sheets. Particle board is used as a cheaper substitute for plywood in some applications; but even though it has a higher density, it is less resistant to puncture and the effects of weather. When properly veneered it is suitable for making furniture. In its raw form it makes an excellent subflooring for dry locations.
composition board[‚käm·pə′zish·ən ‚bȯrd]
A wood product in which the grain structure of the original wood is drastically altered. Composition board may be divided into several types. When wood serves as the raw material for chemical processing, the resultant product may be insulation board, hardboard, or other pulp product. When the wood is broken down only by mechanical means, the resultant product is particle board. Because composition board can use waste products of established wood industries and because there is a need to find marketable uses for young trees, manufacture of composition board is one of the most rapidly developing portions of the wood industry. See Paper
Fiberboard is produced from wood chips. Synthetic resin may be added as a binder before the board is formed. After the board is formed, it may be impregnated with drying oils and heated in a kiln until the oils are completely polymerized to produce tempered board. If insulating board is required instead of hardboard, the material is less compacted, the degree of compaction being described by the specific gravity of the finished board.
When formed from wood particles that retain their woody structure, the product is termed particle board. Properties of such boards depend on the size and orientation of the particles, which may be dimensioned flakes, random-sized shavings, or splinters. After the particular type of particles are produced, they are screened to remove fines and to return oversizes for further reduction. Graded particles are dried, mixed with synthetic adhesive and other additives such as preservatives, and delivered to the board-forming machine.
Development of adhesives specifically for composition boards is extending their utilitarian value, and variety of textures is increasing their esthetic appeal. See Wood products