Wj. Okane et al., THE EFFECT OF ANNEALING ON THE STRUCTURE AND PROPERTIES OF ISOTACTIC POLYPROPYLENE FILMS, Journal of macromolecular science. Physics, B34(4), 1995, pp. 427-458
The effect of annealing on the structure and properties of two polypro
pylene (PP) films, one displaying the monoclinic or-structure and the
other the quenched structure, has been investigated using a combinatio
n of differential scanning calorimetry (DSC), small- and wide-angle x-
ray scattering (SAXS and WAXS), and uniaxial tensile testing. It has b
een established that upon heat treatment at temperatures >60 degrees C
there is an increase in the yield stress of both films, and that this
increase can be attributed to an increase in the size and perfection
of the crystalline regions. An attempt has been made to quantify the y
ield mechanisms occurring within these films. It has been found that a
good correlation could be obtained between the experimental results a
nd a crystal plasticity mechanism involving the thermal activation of
screw dislocations with their Burger vectors parallel to the chain dir
ection.