Structure of drawn fibres: 1. Neutron scattering studies of necking in melt-crystallized polyethylene

Tensile yield of isotactic polypropylene in terms of a lamellar-cluster model

“…They emphasized that the piles of lamellae containing 3-10 lamellae act as one unit and do not separate into single lamellae during deformation. A similar structural unit was proposed by Peterlin 9,21 to describe the necking process. Accordingly, these results imply that the lamellar clusters play a central role in tensile-yield processes in semicrystalline polymers.…”

The use of etching techniques to investigate the morphology of mechanically induced transformations in an aliphatic polyketone

“…This is also evident in that at 140°C, the polymer does not whiten as much as was observed at lower temperatures. The spherulites were observed to elongate and become highly disordered as the polymer lamellae are reorganized possibly due to local melting 8 as shown in Figure 4(b). It is indeed surprising to see any remnants of the original spherulitic structure in samples deformed at such high temperatures.…”

“…Further deformation from a lamellae/deformed spherulitic structure to a fibrillar structure can, at high temperatures, occur through local melting, but at lower temperatures other explanations must be sought. 8 Peterlin argued that the fibrillar structure is formed at lower temperatures by the breakup and rotation of lamellae toward the draw direction. 9,10 Sadler and Barham later added to this theory that the thinnest lamellae are able to rotate without being broken up and that where local melting occurs, lamellar thickening follows due to annealing.…”

“…9,10 Sadler and Barham later added to this theory that the thinnest lamellae are able to rotate without being broken up and that where local melting occurs, lamellar thickening follows due to annealing. 8 The micromechanics of crack growth in many polymers is associated with the accumulation of damage around the crack tip, commonly called a process zone. 11 High stress intensity around the crack tip induces a series of microvoids near the crack tip that either coalesce to form microcracks or crazes, or initiate shear bands.…”

Plasticity of semi-crystalline polymers: crystal slip versus melting-recrystallization

“…A few years before, Sadler and Barham [89] reported more contrasted findings depending on sample preparation and drawing conditions : at a draw temperature above 90 °C, the appearance on an isotropic segregation signal in the SANS patterns of melt-crystallized HDPE was attributed to a local melting during necking. But no evidence of local melting was observed at lower temperature, the deformation being nearly affine at a molecular scale.…”