Meg. Mosquera et al., THERMAL TRANSFORMATIONS OF KEVLAR ARAMID FIBERS DURING PYROLYSIS - INFRARED AND THERMAL-ANALYSIS STUDIES, Chemistry of materials, 6(11), 1994, pp. 1918-1924
The main objective of this work was to get some further insight into t
he chemistry involved in the carbonization of aramid fibers. For this,
the pyrolysis behavior of Kevlar [poly(p-phenylene terephthalamide)]
fibers under argon was studied using thermoanalytical and FT-IR spectr
oscopic methods to get direct information on the progressive changes u
ndergone by the solid material and its carbon fiber residues. Variatio
ns in concentration of major elements (C, H, N, S, and O) were also mo
nitored as a function of pyrolysis temperature. Below 500-degrees-C on
ly minor changes associated with loss of hydrogen bonds occur. Above 5
00-degrees-C the weight loss becomes significant. However, no noticeab
le framework changes take place until about 545-degrees-C. Kevlar appe
ars to be chemically stable up to this temperature. The main pyrolytic
transformation occurs over a narrow temperature interval (550-575-deg
rees-C) leading to the collapse of the initial framework, which procee
ds mainly through the progressive decomposition of amide groups by C=O
and C-N bond cleavage. Intermediate aryl nitrile products are formed
during this process. Above 600-degrees-C depolymerization gives way to
progressive aromatization/condensation reactions leading to polynucle
ar aromatic compounds, the degree of condensation of the network incre
asing with treatment temperature.