1. Laboratory for Characterization and Processing of Polymers, Institute of Textile Chemistry, Ecology and Colorimetry, Faculty of Mechanical Engineering, University of Maribor, Smetanova 17, SI 2000 Maribor, SloveniTel.: Fax:
2. Institute of Chemistry, Reology & Colloid Science, University of Graz, Heinrichstrasse 28 A-8010 Graz, Austria