Isotactic polypropylene (iPP) (Mw = 2.9 x 105) has been deformed in uniaxial compression by forging at several constant temperatures from 20 to 140°C. A relation between draw efficiency and the formation of the smectic phase during deformation has been examined over a wide range of compression draw ratios (~ 50). At a forging temperature below the smectic-phase stability limit temperature (T~), the efficiency of draw, parallel to the uniplanar direction, was high (~97%) and independent of the compression ratio, pressure and draw temperature (T0). The relation between the compression yield energy (Er) and T d has also been examined. E r, the area under the compressive stress-strain curve up to the yield point, as a function of Ta was found to consist of two linear components of different slope. These two linear relations arose from the glassy and crystalline phases. The intercept temperature (T~) at zero yield energy for the glassy phase has been evaluated to understand compression drawability. Above T~, the achievable compression ratio (CR) increased steadily with Td. At a given Ta, the CR increased with increasing applied pressure, and this tendency was more prominent above T~. The T~ moved higher as the compression rate was increased.
Посилання на статтю:
Uniplanar deformation of isotactic polypropylene: 1. Draw characteristics / Satoshi Osawa and Roger S. Porter // Polymer. – 1994. – Vol 35. – P. 540-544.