Nanostructure of metallic coating on plastic films

Abstract

Packaging is the largest application of polymers in all countries, at all levels of development. It is about 30-40% of total plastic consumption (1). The development of packaging materials based on plastic commodities is a very dynamic research area (1-3). Polypropylene (PP) has demonstrated a very strong growth over the past several years all around the world. In general, this growth has exceeded that of other high volume commodity polymers and it is projected to continue over the next years (4). PP is an extremely versatile material in the packaging industry. It has low density, excellent heat and chemical resistance, good mechanical properties, and a modest cost (5). However, it has a high gas permeability to be used in some applications. Vacuum vapor deposition of metals on the surface of PP films is used to improve the barrier properties. This processing technique would provide nanocrystalline materials (6). The microstructure of the metallic layer will have a strong effect on the final properties. An adequate knowledge of it would help to ameliorate these properties.In this work we characterized the crystalline microstructure of the aluminum layer vacuum deposited on PP films. The studies included transmission electron microscopy (TEM) and wide angle x-ray diffraction (WAXS). A methodology to analyze the size of Al crystals was applied.