Enhancing mechanical properties of aromatic polyamide fibers containing benzimidazole units via temporarily suppressing hydrogen bonding and crystallization

ABSTRACT The copolymerization modified poly(p‐phenylene terephthalamide) containing 2‐(4‐aminophenyl)−5‐aminobenzimidazole (PABZ) units in the main chain was synthesized and the corresponding poly‐p‐phenylene‐benzimidazole‐terephthalamide (PBIA) fibers were prepared by wet spinning. The HCl, the by‐...

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Bibliographic Details
Published in:Journal of applied polymer science 2015-09, Vol.132 (35), p.np-n/a
Main Authors: Li, Ke, Luo, Longbo, Huang, Jieyang, Wang, Huina, Feng, Yan, Liu, Xiangyang
Format: Article
Language:English
Subjects:
Aromatic polyamides
Byproducts
copolymers
Crystallization
Fibers
Formations
Hydrogen bonding
Materials science
polyamides
Polymers
Retarding
Tensile strength
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Summary:ABSTRACT The copolymerization modified poly(p‐phenylene terephthalamide) containing 2‐(4‐aminophenyl)−5‐aminobenzimidazole (PABZ) units in the main chain was synthesized and the corresponding poly‐p‐phenylene‐benzimidazole‐terephthalamide (PBIA) fibers were prepared by wet spinning. The HCl, the by‐product released during polymerization, can complex with PABZ units to prevent the formation of hydrogen bonding between PABZ units, resulting in amorphous PBIA fibers and a lower glass transition temperature (Tg). Therefore, for the purpose of gaining strong hydrogen bonding and high orientation degree at the same time in PBIA fibers, two‐step drawing–annealing processing was adopted. The as‐spun PBIA/HCl complex fibers were drawn first at 280°C, higher than the Tg of the PBIA/HCl complex fibers and lower than the decomplexed temperature of HCl, which temporarily suppresses the formation of hydrogen bonding and crystallization. Subsequently, the fibers were annealed to reform hydrogen bonding between PABZ units and crystallization via decomplexation of HCl at 400°C. However, when the drawing is above the decomplexed temperature of HCl, the decomplexation of HCl begins to occur which leads to the reform of hydrogen bonding and crystallization, and the tensile strength of the drawn‐annealed PBIA/HCl complex fibers decreases with a decrease in the HCl content of fibers. The tensile strength of two‐step drawn‐annealed fibers increased by approximately 15% compared to that of one‐step drawn PBIA/HCl complex fibers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42482.
ISSN:0021-8995
1097-4628
DOI:10.1002/app.42482