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Scudla, J. ; Eichhorn, K.-J. ; Raab, M. ; Schmidt, P. ; Jehnichen, D. ; Häußler, L.
The Effect of Specific Nucleation on Molecular and Supermolecular Orientation in Isotactic Polypropylene

The molecular and supermolecular orientation, morphology and structural changes observed during cold drawing of injection moulded isotactic polypropylene modified by specific , and nucleating agents were studied by polarised photoacoustic FTIR spectroscopy, wide-angle X-ray diffraction and differential scanning calorimetry. Significantly lower molecular orientation was found in the core of the -nucleated injection moulded specimens as compared to unmodified and -nucleated materials. This has been ascribed to the fast growth of the -crystallites which inevitably dislocates the flow-induced orientation within the crystalline regions and in their vicinity. Moreover, it was found that the presence of the developed -crystallites distinctly diminishes the efficiency of the orientational solid-state drawing assessed on both levels of the hierarchical structure (molecular and crystalline). This structural observation is directly connected with macroscopic softening effect of the -phase: lowering the yield stress and flattening the neck shoulder. Thus, the interrelation between the microstructural and macroscopic effects of the -phase could be described as a feedback process.

Macromolecular Symposia 184, 371-387


August 2002