Bakelite [key] [for its inventor, L. H. Baekeland], synthetic thermosetting resin. It has been widely used both alone, to form whole objects, and in combination with other materials, as a laminate or a surface coating. It was used as a substitute for hard rubber, amber, or celluloid; for insulating electrical apparatus (since it is a nonconductor); and for the manufacture of certain machinery gears, phonograph records, and many other articles useful and ornamental and as diverse in character as buttons, billiard balls, pipestems, and umbrella handles. Bakelite is a condensation polymer of formaldehyde and phenol. In practice, the phenol and formaldehyde are first polymerized to a small extent by using the proper choice of catalyst and temperature. The resulting prepolymer, called a resol, is a low-melting, soluble material, which can then be combined with a filler (usually cotton linters or wood fibers) and a pigment and heated under pressure in a mold to yield an object of the desired shape. The pure resin is colorless or amber-colored and very brittle; the various fillers and other additives give it the desired properties depending on its application. Heating of the prepolymer results in extensive cross-links between the polymer chains, resulting in a tightly bound three-dimensional network. A Bakelite-type resin can also be formed using furfural in place of the formaldehyde.
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