1. Industrial Research Institute of Nonwovens and Technical Textiles, College of Textiles & Clothing Qingdao University Qingdao 266071 P. R. China
2. Shandong Center for Engineering Nonwovens Qingdao 266071 P. R. China
3. State Key Laboratory of Bio‐Fibers and Eco‐Textiles Qingdao University Qingdao 266071 P. R. China