On the Differences in Micro-deformation Mechanism Between Isotactic Polypropylene and β-Nucleated Isotactic Polypropylene as Revealed by the Confocal Laser Scanning Microscopy

摘要

To understand the toughness enhancement of p-nucleated isotactic polypropylene (iPP) in comparison with iPP, the differences in the micro-deformation mechanisms between the neat iPP and β-nucleated iPP were visualized using the confocal laser scanning microscopy (CLSM). Structure of the α- and β-spherulites situated close to the tip of the sharp starter crack has been investigated during tensile deformation in the viewing field of the CLSM. In the a-spherulite of the neat iPP, highly localized inter- and intra-spherulitic micro-shear bands have been observed. In the β-nucleated iPP, relatively uniform distribution of diffuse shear bands has been observed in the β-phase, while the α-phase remained relatively undeformed exhibiting only narrow intra-spherulitic shear bands in the direction perpendicular to the loading direction. Derealization of plastic deformation into diffuse shear bands inβ-nucleated iPP can explain its enhanced crack resistance compared with the neat iPP exhibiting highly localized shear banding.