Drawn polypropylene fibres were produced from as-spun fibres with a pa
racrystalline structure of low orientation. Drawing was carried out at
60 degrees C in order to prevent the transformation of the paracrysta
lline form into the monoclinic structure. The internal texture of the
as-spun fibre and of a series of drawn fibres has been investigated by
electron microscopy following permanganic etching. At draw ratios of
7 and above a series of transverse bands can be observed along the fib
res. Homogeneous regions alternate with bands of defects which, after
etching, appear as longitudinal cavities. Defect bands become more reg
ular and increase in height with increasing draw ratio, lambda, occupy
ing almost all the sample at lambda = 8.3. The nature of the defects,
which are regions of reduced density, possibly voids, is discussed and
a simplified model for their formation is suggested.