polyester fibers
Synthetic paper fibers prepared and spun by
procedures similar to those used in producing
nylon. The long polymer chains in the filaments
are arranged randomly and have very little
orientation in line with the longitudinal axis of
the filament; consequently the filaments have
relatively little strength. Strength is added by
drawing or stretching the filaments approximately
two to five times their original length. The
polymer chains become oriented in this stretching,
with an accompanying decrease in filament diameter
along the major axis of the filament. In addition,
it is possible to develop a relatively high degree
of lateral order (crystallinity) of the polymer
chains by means of heat or solvent treatment. The
filaments assume the cross-sectional configuration
of the spinneret hole, which is usually circular,
although non-circular cross sections are also
used. The drawing process leaves the circular
cross-sectional configuration unchanged; however,
it does reduce the sharpness of the non-round
cross section. (42 )
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