1. National Engineering Research Center for Advanced Polymer Processing Technology Key Laboratory of Material Processing and Mold of Ministry of Education Zhengzhou University Wenhua Road 97‐1 Zhengzhou 450002 P. R. China
2. Institute of Polymer Materials Friedrich‐Alexander‐University Erlangen‐Nuremberg Martensstr. 7 Erlangen 91058 Germany
3. Bavarian Polymer Institute Dr. Mack‐Strasse 77 Fürth 90762 Germany