Abstract
The orientation behavior of the polypropylene film stretched mono- or biaxially as previously-described in I and II was further investigated by means of X-ray diffraction method and the following results were obtained:
A. Monoaxial stretching:
(1) The original film is paracrystalline but it converts into monoclinic after stretching at 110°C or higher temperature.
(2) fx, the orientation degree of the crystalline region increases with stretching degree λ at 130°C and amounts to 0.99 at λ=800%, while fa, orientation degree of the amorphous region always falls behind fx and goes through a small negative value in the early stage of the stretching.
(3) In the 160°C stretching the orientation is lower than that at 130°C and fa is nearly zero or slightly negative.
(4) Crystallinity decreases from 0.59 to 0.54 after the 130°C stretching, while it increases from 0.59 to 0.66 after the 160°C stretching.
(5) The orientation of the crystaline region is cylindrical symmetry with respect to the stre-tching axis and no selective planar orientation is observed.
B. Biaxial stretching
Restretching the monoaxially oriented film perpendicularly to the first stretiching direction, three arcs, (110), (040) and (130) diffractions, do not change monotonously the positions from the equator to the meridian through rings. At the intermediate state two orientation axes appear which incline ± θ symmetrically against the first orientation axis and θ grows larger up to 90° with increase in the restretching. This phenomenon is more remarkable at the lower temperature: restretching and it appears faintly at the 160°C restretching.
