Improvement of polymer films in terms of barrier properties using nanotechnology
Polymer films are used in many ways as packaging materials. Especially in food packaging, they have to fulfill a variety of tasks. Here, UV protection and barrier properties against water, water vapor and other gases (eg CO2 and O2) are quality characteristics that - in order to save material - must be achieved at a low wall thickness. In some cases this can be obtained only by multilayer films of different polymers glued together using their specific intrinsic properties. By incorporation of nanoparticles further improvements in both the barrier properties as well as the processing properties can be achieved in particular in crystalline and semi-crystalline polymers. The investigations have shown that the improved barrier effect is not only based on a simple mechanical locking action, as this has been proposed for layer-silicates, but by using spherical SiO2 micro / nano-particles - in the example of PET - density and degree of crystallization can be increased. Further advantages are that exfoliation problems are eliminated and processing properties can be improved, so that film thickness of foils becomes more uniform.