Evidence of dislocations in melt-crystallised and plastically deformed polypropylene

In view of the lack of other methods in the study of melt-crystallised polymers, this paper reports the application of a new kind of X-ray diffraction profile analysis to investigate dislocations in various plastically deformed α-phase isotactic polypropylene (α-PP). By means of a two-step evaluation it is shown that dislocations are present in α-PP and that their density increases with plastic deformation. Compared with metals, very high dislocation densities between 2×10 16 and 2.2×10 17 m −2 are evaluated which might result to some extent from the presence of uncorrelated lattice defects in the interface between crystalline and amorphous phase. It is shown, however, that the measured dislocation densities are consistent with the assumption that the mean free path of dislocations equals the lamella thickness.