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The effect of ethylenediamine pretreatment on the molecular structure of thermally stabilized polyacrylonitrile fibers before carbonization
Author(s) -
Karacan Ismail,
Erdŏgan Gulhan
Publication year - 2012
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.22104
Subject(s) - polyacrylonitrile , materials science , carbonization , ethylenediamine , chemical engineering , differential scanning calorimetry , fiber , polymer , polymer chemistry , composite material , organic chemistry , chemistry , scanning electron microscope , physics , engineering , thermodynamics
Aqueous ethylenediamine (EDA) pretreatment followed by thermal stabilization of polyacrylonitrile (PAN) fibers in an oxygen rich air environment was carried out prior to the carbonization stage. The results show that the EDA pretreatment is very effective and efficient in promoting the cyclization of nitrile groups by shortening the time necessary for the development of thermally stable structure needed to withstand the high carbonization temperatures. A direct relationship between the values of density and the oxygen content is found which is believed to be due to the positive role played by the oxygen containing functional groups in the formation of ladder frame structures. Analysis of the equatorial X‐ray diffraction traces shows the transformation of the original structure from a highly ordered phase to a totally disordered amorphous phase as indicated by the loss of the degree of order of the original PAN fiber. X‐ray, Differential Scanning Calorimetry (DSC), and infrared conversion indices show the rapid conversion from the original open structure to highly cyclized and crosslinked polymer structure. Utilization of EDA pretreatment prior to the thermal stabilization is expected to significantly reduce the cost of the final carbon fiber manufacturing by reducing the time necessary for the thermal stabilization stage. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers