Mobility and relaxation of amorphous chains in drawn polypropylene: 2 H-NMR study

Investigation of the large plastic deformation of iPP induced by plane strain compression: Stress–strain behavior and thermo-mechanical properties

“…Another important feature of plastically deformed iPP is the enhancement of the Ta (Rault, 1997;Botev et al, 1999) transition with compression ratio, thermally observable by non-reversible MDSC curves in Fig. 13.…”

“…The second order polymer transitions have been extendedly discussed in the literature in the last thirty years. Specially Rault (Rault, 1997) and Botev (Botev et al, 1999) discussed the iPP and showed that the maximum of Ta is located at about 60°C. These transitions are related to relaxation phenomena due to mobility activation processes of non crystalline local order regions, macromolecular backbone, specific macromolecular parts or macromolecular chain terminal groups.…”

Study of stretched polypropylene fibres by pulsed and CW NMR spectroscopy

“…The fibrillar structure is characterized by a higher degree of ordering of the crystalline and non-crystalline regions, e.g. it can be observed by the increasing of the optical birefringence value Dn for the stretched fibres (Table 1) [22,23].…”

Large Strain Tensile Deformation and Failure in Oriented Isotactic Polypropylene/Clay Nanocomposite: Role of Voiding and Molecular Orientation

“…4). We note that the calculated crystallinity On the other hand, local relaxation in the constrained samples, which begins at around 80 • C (as evidenced by NMR [29] ), will reduce the molecular orientation in the amorphous phase due to entropy driven segmental motions, which in turn results in decreasing of recovery ratio. Figure 5 shows the recovery ratio of oriented samples after complete melting of crystallites at 180 • C. As expected, local relaxation occurred in all oriented samples prepared at either 140 or 160 • C, since the initial unextruded length l 0 could not be achieved (complete recovery giving a recovery ratio of unity).…”