thermoplastic resins
Resins composed of separate linear non-reactive
macromolecules which, upon being heated, become
plastic due to the reduction of intermolecular
forces. Such resins can be made to flow under
pressure in this state; upon cooling they regain
their original physical properties. The
heating-cooling cycle can be repeated as long as
there is no thermal degradation of the polymer.
Most thermoplastic resins are produced by forcing
the heated material into a mold or through a die
under pressure, followed by cooling. The important
thermoplastic processing techniques include
injection molding, extrusion, and calendering.
Many such resins are also soluble in various
organic solvents, with the same intermolecular
cohesive forces being overcome in the process of
solution. The more important thermoplastic resins
include polyvinyl chloride, polyethylene,
polystyrene, and cellulose acetate. (233 )
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