Morphological analysis of linear low density polyethylene films by atomic force microscopy

Abstract

Atomic force microscopy has been used to investigate the morphology of hexene linear low density polyethylene (LLDPE) blown film in the undrawn and drawn states. The morphology of the undrawn film, which is biaxially oriented due to the nature of the extrusion process, is composed of crystallites, which consist of aggregates of lamellae. Elongation of the film caused these crystallites to undergo deformation, resulting in the gradual formation of a fibrillar structure in the draw direction. The transformation of these crystallites into fibrils corresponded with an initial increase in the surface roughness, until 250% elongation. Further extension of the film to 450% caused the surface roughness to reach a plateau. The changes observed in the surface roughness and morphology indicate that drawing of the film caused the crystallites to tilt and slip, rupturing crystalline blocks, which then develop into a fibrillar structure. Further extension of these initial fibrillar structures resulted in a more oriented fibrillar morphology. Wide-angle x-ray scattering clearly showed the orientation of the crystals with respect to the draw direction throughout the film.

Phase structural analyses of polyethylene extrusion coatings on high‐density papers. I. Monoclinic crystallinity

“…Simply explained, the brighter yellow (light) regions represent stiffer structures at the surface and the darker regions represent softer structures. There are good reasons to believe that the stiffer regions have a higher crystalline content and that the softer regions are more amorphous 15, 16. The images were not easy to acquire for these samples because of residue particles (fiber residues) at the surfaces, and have to be interpreted with caution.…”

“…There are good reasons to believe that the stiffer regions have a higher crystalline content and that the softer regions are more amorphous. 15,16 The images were not easy to acquire for these samples because of residue particles (fiber residues) at the surfaces, and have to be interpreted with caution. A corresponding AFM picture without disturbing artefacts for sample 2 was not achieved due to these reasons.…”

Solid-state microcellular foaming of PE/PE composite systems, investigation on cellular structure and crystalline morphology

“…Classically, transformation from original spherulitic structure to fibrillar one, is a typical mechanism for cold drawing and yielding process in semi-crystalline polymers [16][17][18][19][20][21][22]. Peterlin in the 1960s proposed that drawing of polyethylene leads to permanent deformation of the lamellae causing the lamellae to tilt and slip, thereby rupturing into crystalline blocks.…”

“…Finally, the blocks of chains are incorporated into a fibrillar structure [15]. This model holds for a number of different forms of polyethylene, including crystals (on which the model was originally proposed) and melt drawn films [18]. The present phenomenon (tendency of dislocating from spherulitic to fibrillar morphology as a result of microcellular process) may be explained using the Peterlin's model [16,17] as follows.…”

Non-Fickian diffusion in systems with complex interfaces

“…High molecular symmetry and high cohesive energy between chains, require a fair degree of polymer crystallinity, which results in high tensile strength and high modulus of the fibers. Drummond et al 79 used atomic force microscopy (AFM) to study the structural changes due to external deformation. 76 Xiao et al 77 reported stress-enhancement of permeation rates in polyvinyl chloride geomembranes, but observed the opposite effect with highdensity polyethylene geomembranes (HDPE).…”