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

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. (C) 2002 John Wiley & Sons, Inc. J Appl Polym. Sci 83: 777-784, 2002.