The phase structures of uniplanar-drawn isotactic polypropylene (iPP) have been investigated. Three phases (or-crystal, smectic and amorphous) are found to coexist in the uniaxially compressed samples. From thermal analyses and density measurements, the fractions and densities of these phases have been evaluated. At a compression draw temperature of 50°C < T~ (the upper smectic phase stability limit), the amount of or-crystal decreased significantly and the smectic phase increased on developing a compression ratio up to ~ 10. The transition energy for smectic to crystal phase was found to be ~ 5.5 cal g- 1. At a draw temperature > T~, decrystallization without smectic phase stability proceeded during the deformation. No draw-induced crystallization was observed. At all deformation temperatures, the density of the amorphous phase increased in the initial stage of deformation reaching a limit on further draw.
Посилання на статтю:
Uniplanar deformation of isotactic polypropylene: 2. Phase structure / Satoshi Osawa and Roger S. Porter // Polymer. – 1994. – Vol 35. – P. 545-550.