X-ray diffraction, Fourier Transform infra-red (FTi.r.) spectroscopic
and refractive index measurements have been utilized to characterize t
he state of molecular orientation in one-way and two-way (biaxially) d
rawn isotactic polypropylene (iPP) films. It is shown that the use of
all three techniques leads to much greater confidence in the orientati
on averages deduced than can be obtained by using any two of the techn
iques. Orientation parameters in terms of <cos2 theta> values in machi
ne, transverse and normal directions have been evaluated and compared
quantitatively for the different techniques. The results indicate that
with one-way drawing the chain axes of both crystalline and amorphous
regions orient towards the direction of drawing. The crystalline chai
ns are more highly oriented than the amorphous chains and tend to orie
nt towards the plane of the film, whereas the amorphous chains tend to
be more uniaxially oriented towards the draw direction. In balanced,
simultaneously two-way drawn films the crystalline chains are more hig
hly oriented towards the plane of the film than the non-crystalline ch
ains. For a sequentially, equibiaxially drawn iPP film, the orientatio
ns of the chain axes of both the crystalline and amorphous regions wer
e found to be higher in the second draw (i.e. transverse) direction th
an in the first draw direction. The orientation of the crystalline cha
ins was very close to the plane of the film, whereas the amorphous cha
ins were almost uniaxially oriented with respect to the second draw di
rection. In all the films there is a strong tendency for the b-axes of
the crystallites to align normal to the plane of the film.