Das Fibrillierungsverhalten von monoaxial verstreckten und unter Spannung getemperten Folien aus isotaktischem Polypropylen

Abstract

Uniaxial stretched polypropylene filmtapes were annealed under stretching tension during 20 seconds up to an annealing temperature of 210 ~ The splittabitity and the fibrillability were investigated as function of the annealing temperature. The splittability, measured as tearing force in transverse direction, remains constant up to 196 ~ and there upon drops abruptly as a result of a transformation of the fibrillar texture into a bimodal lamellatexture, which was visualised by TEM. At this annealing temperature the crystalline orientationfunction, the crystallinity, and the long identity period pass through a distinct maximum. Compared with this the fibrillability, measured as the number of fibrilruptureends, decreases constantly away from an annealing temperature of 165 ~ down to a complete disappearance. This phenomenon is explained by the diffusion of the originally irregularly in the microfibrils distributed defects to the crystallite boundaries, where they accumulate in lateral direction. For this reason the single microfibrils do not rupture anymore under tensile tension at the points of defect concentration but along the regular pattern of the uncrystallized regions. The decrease of the fibrillability correlates well with the drop of the tenacity as result of the weaker linkage of the crystallites in the longitudinal axis.