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Crystal structure and drawing‐induced polymorphism in poly(aryl ether ether ketone). IV
Author(s) -
Liu Tianxi,
Wang Shanger,
Mo Zhishen,
Zhang Hongfang
Publication year - 1999
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/(sici)1097-4628(19990711)73:2<237::aid-app10>3.0.co;2-l
Subject(s) - ether , peek , orthorhombic crystal system , ketone , crystallization , crystal structure , polymorphism (computer science) , crystallography , polymer chemistry , aryl , materials science , polymer , chemistry , organic chemistry , composite material , biochemistry , alkyl , genotype , gene
A new crystal modification induced by strain and denoted as form II exists alongside the dominant form I structure in the uniaxially oriented poly(ether ether ketone) (PEEK) and the related polymers. The crystal structure of form II for PEEK is also found to possess a two‐chain orthorhombic packing with unit cell parameters of a equal to 0.475 nm, b equal to 1.060 nm, and c equal to 1.086 nm. More extended and flattened chain conformation of form II relative to that of form I is expected to account for an 8% increase in c ‐axis dimension, which is attributed to the extensional deformation fixed in situ through strain‐induced crystallization during uniaxial drawing. Annealing experiments suggest that form II is thermodynamically metastable and can be transformed into more stable form I by chain relaxation and reorganization at elevated temperature without external tension. This strain‐induced polymorphism exists universally in the poly(aryl ether ketone) family. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 237–243, 1999