TECH 20002 Chapter Notes - Chapter 31: Acetic Anhydride, Polyethylene, Fireproofing
13 Dec 2016
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Anisotropic material- different strength along different planes: wood is stronger when force is applied against the grain, wood is weaker when force is applied with the grain. Wood will only heat in a microwave if it contains moisture. Over heating will burn the wood: forms carbon. Dried woods are stronger than wet woods. Infuse with methacrylate in a vacuum: heat with gamma rays. Impreg: soak wood in water soluble phenol-formaldehyde resin, dry to improve strength, resists decay, rot, and insects. Stabilized wood- colors and chemicals applied by: coating. Compreg- impreg done under pressure: very strong, must cut with metal cutting saws. Acetylated- infusing acetic anhydride in a pressure chamber: good acoustic properties. Immerse wood in liquid (-31 f) or gaseous ammonia: softens wood structure, becomes pliable. Compress and heat wood without adding resin. Empty cell process: air pressure forces oil based preservatives into wood. Full cell process- infuse preservatives into wood in a vacuum. Chromated copper arsenate: most popular preservative.
