Premium
The Effect of Asymmetric Heterocyclic Units on the Microstructure and the Improvement of Mechanical Properties of Three Rigid‐Rod co‐PI Fibers
Author(s) -
Luo Longbo,
Wang Yazhe,
Zhang Jing,
Huang Jieyang,
Feng Yan,
Peng Chaorong,
Wang Xu,
Liu Xiangyang
Publication year - 2016
Publication title -
macromolecular materials and engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.913
H-Index - 96
eISSN - 1439-2054
pISSN - 1438-7492
DOI - 10.1002/mame.201600113
Subject(s) - materials science , bpda , ultimate tensile strength , fiber , composite material , toughness , microstructure , modulus , compressive strength , rod , layer (electronics) , polyimide , medicine , alternative medicine , pathology
Three kinds of rigid‐rod copolyimide (co‐PI) fibers are prepared by wet‐spinning of their precursor poly(amic acid)s, which are copolymerized from 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA), p‐phenylenediamine (PDA), and the third asymmetric heterocyclic diamines, including 2‐(4‐aminophenyl)‐5‐aminobenzoxazole (BOA), 2‐(4‐aminophenyl)‐5‐aminobenzimidazole (PABZ), and 2,5‐bis(4‐aminophenyl)‐pyrimidine (PRM), respectively. The asymmetry is increasing in the order PRM < BOA ≈ PABZ. The introduction of asymmetric heterocyclic units results in mesomorphic order structure and decreases the size of microvoid of PI fiber, which apparently improves the toughness of PI fiber and shows positive effects on mechanical properties. The tensile strength and initial modulus of co‐PI fibers are in the ranges of 2.6–3.2 GPa and 91.8–133.5 GPa, respectively. The lowest asymmetry leads to the highest lateral order, crystal orientation, and initial modulus of BPDA/PDA/PRM co‐PI. Moreover, the introduction of asymmetric heterocyclic units can effectively improve compressive properties. BPDA/PDA/PABZ co‐PI fiber shows the highest loop strength and recoil compressive strength due to hydrogen bonding interactions. The highest orientation leads to the lowest transverse strength of BPDA/PDA/PRM co‐PI fibers, reducing the recoil compressive strength.