Wood As a Polyblend-Composite

In many ways, wood, one of man s oldest and most widely used materials, resembles the polyblends or composites discussed elsewhere (Hearmon, 1953). Since wood is a mixture of two polymers, it is a polyblend. Its behavior, however, more closely resembles that of oriented fiber composites. Since many synthetic materials are competitive with wood in commerce and resemble the structure of wood, it is of interest to understand the original natural product. 

Wood may then be pictured as an assembly of oriented fibers in an amorphous matrix. The fibers are hollow, lowering the density and altering the mechanical behavior in a manner analogous to high-density foams. 

Acetylation Hydroxyl groups reacted to form esters Acetic anhydride with pyridine catalyst and swelling agent in gas phase capillaries empty ASE about 70% (acetyl 25 %) Thin veneers to 2 X 6 X 48 in. stock 

Ammonia Vapor and liquid Wood pumped down, exposed to anhydrous ammonia vapor or liquid at ISOpsi treatment time depends upon thickness and moisture content, ranges from minutes to hours loblolly pine requires longer exposure than hardwoods bends in -in, stock up to 90 treated wood darker in color and sometimes streaked Experimental products made snowshoes, picture frames, chair backs, lamps, room dividers 

Compreg Compressed wood- phenolic-formaldehyde composite Wood soaked in water or alcohol solution of P-F, dried, heated, and compressed during polymerization cell structure collapsed, density 1.3-1.4, ASE about 95 % resistant to decay strength, hardness, and abrasion increased Cutlery handles, electrical insulators, thin veneers 

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