Preparation of High Performance Copolyimide Fibers via Increasing Draw Ratios. Issue 11 (13th June 2015)

• Record Type: Journal Article
• Authors: Zhang, Mengying; Niu, Hongqing; Lin, Zhiwei; Qi, Shengli; Chang, Jingjing; Ge, Qiyan; Wu, Dezhen
• Is Part Of: Macromolecular materials and engineering. Volume 300:Issue 11(2015:Nov.)
• Page Start: 1096
• Page End: 1107
• Publication Date: 2015-06-13
• Subjects: copolyimide fibers -- draw ratio -- mechanical properties -- molecular orientation; Plastics -- Periodicals; Polymers -- Periodicals; Polymerization -- Periodicals; 547.705
• DOI: 10.1002/mame.201500126
• Languages: English
• ISSNs: 1438-7492

Abstract

Abstract : High performance fibers based on copolyimide (co‐PI) containing benzimidazole and ether moieties were prepared via a two‐step wet spinning method. The effects of draw ratio on the structures and properties of the fibers are investigated. The mechanical properties of the co‐PI fibers are improved greatly by increasing draw ratio at temperatures above 400 °C, reaching the optimum tensile strength of 2.8 GPa and modulus of 136 GPa, which is due to the development of the molecular orientation along the fiber direction. The hot drawing process roughens the fiber surface and stretches the molecules in the fibers. Moreover, the fiber structure evolutions during the drawing process were also discussed and a "smectic A liquid crystal‐like" model was proposed. Abstract : Two‐dimensional wide‐angle X‐ray diffraction (2D WAXD) results show that the molecular orientation of the co‐PI fibers along the fiber direction is developed as the draw ratio increased. When the fibers are treated at high draw ratios, the molecule chain is stretched and aligned closely, just as the "smectic A liquid crystal‐like" structure, which is orientationally and positionally ordered.