1. School of Chemical Engineering, College of Engineering, University of Tehran Tehran 11155‐4563 Iran
2. Department of Polymer ProcessingIran Polymer and Petrochemical Institute Tehran 14965‐115 Iran
3. Leibniz Institute of Polymer Research Dresden Hohe Straße 6 Dresden D‐01069 Germany
4. Polymer Engineering Department, Faculty of EngineeringGolestan University Gorgan 49138‐15739 Iran