L. Guadagno et al., Structural organization of syndiotactic polypropylene films quenched at different temperatures, J MACR S PH, B39(4), 2000, pp. 425-439
Films of highly syndiotactic polypropylene (sPP) were quenched at different
temperatures between 0 degrees C and 100 degrees C and analyzed as soon as
prepared and after 1 month of aging at room temperature. Wide-angle X-ray
diffractograms (WAXDs) showed that all the samples crystallized in the diso
rdered helical form I, with the crystallinity increasing both on increasing
the quenching temperature and on aging, although to a lower extent. The an
alysis of sorption and diffusion of dichloromethane vapor at low activity s
hows that, in some samples, the fraction of impermeable phase is consistent
ly higher than the crystalline fraction. This induced us to hypothesize the
presence of an intermediate phase, or mesophase, not crystalline, yet impe
rmeable to the vapors. The fraction of mesophase decreases on increasing th
e quenching temperature, and it is a very small quantity at 100 degrees C.
The dynamic-mechanical analysis showed two transitions in the aged samples,
which could correspond to the lower and upper glass transitions, already s
uggested for aged films of isotactic polypropylene (IPP).