1070-4272/05/7810-1720 + 2005 Pleiades Publishing, Inc.
Russian Journal of Applied Chemistry, Vol. 78, No. 10, 2005, pp. 1720!1722. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 10, 2005,
Original Russian Text Copyright + 2005 by Gankov, Nenov, Radenkov.
Influence of the Caprolactam Quality on the Characteristics
of Polycaproamide Thereof
N. P. Gankov, D. P. Nenov, and F. D. Radenkov
Ekomedbio EAD Business-Innovation Center, Sofia, Bulgaria
Technical University, Sofia, Bulgaria
Received March 2, 2005
Abstract-The influence of the caprolactam quality on the characteristics of polycaproamide thereof was
Among the main factors governing the quality of
polycaproamide (PCA) is the quality of the raw ma-
terial, caprolactam (CL) .
We have found earlier  that caprolactam under-
goes major changes during preparation for polymeri-
zation. Accumulation of the oxidation products begins
even during transportation of liquid CL, as well as
during melting of crystalline CL and storage of CL in
the liquid state .
It was of interest to elucidate how the quality of
satisfying the requirements imposed
by the appropriate standard affects the characteristics
of PCA thereof, using high-sensitive instrumental
methods of analysis along with the conventional tech-
First, we examined samples of commercial crys-
talline caprolactam, CL-1, prepared using phenol
reference CL-2 sample prepared by recrystallization
of CL-1 from dilute aqueous solution at room tem-
perature; and sample of preoxidized caprolactam,
CL-3, prepared by heat treatment of CL-1 in air at
90oC for 24 h.
The CL samples were polymerized at 260 + 1oCin
sealed glass ampules heated in an aluminum unit for
24 h. This time is sufficient equilibrium in molecular
weight to be attained. Before being sealed the ampules
containing CL were purged with nitrogen for a long
time. The AG salt (3%) was added to the samples
as a polymerization activator. No H
O was introduced
as activator and no acid, as chain-terminating agent,
Bulgarian State Standard BDS 10780!88.
Agrobiokhim Company, EAD, Stara Zagora.
since they create superpressure and cause ampules
to break. After polymerization was the complete, the
ampules were cooled, and the polymer was crushed
The CL samples under study were characterized by
such parameters as compliance with the BDS 107803
88 requirements, content of carbonyl compounds
(CCs) , and fluorescence intensity. The PCA sam-
ples werecharacterized by relative viscosity, Huggins
 characterizing the content of branched
and cross-linked PCA structures, content of the ab-
normal acylation product (1,11-diamino-6-ketoundec-
ane, DAKU)  and of carbonyl compounds, optical
density , fluorescence intensity, and content of
terminal carboxy groups.
We measured the relative viscosity of a 1% (by
weight) PCA solution in H
(95.6 wt %) at 25oC
using an Ubbelohde viscometer at the solvent outflow
time of over 100 s. The CC and DAKU content in
CL and PCA was determined polarographically .
The optical density of the solutions was measured
on an SF-16 spectrophotometer (according to BDS
10780388), and the fluorescence intensity, on a KFL-
2-1 instrument. The optical density of the sulfuric acid
solutions of PCA was measured by the modified
Sbrolli technique  (300 mg PCA per 25 ml of
60 wt % H
, wavelength 245 nm, rectangular cell
with the absorbing layer thickness of 10 mm). The re-
sults obtained are listed in the table.
The table shows that the samples of commercial
and additionally crystallized CL contain no carbonyl
compounds. The freshly prepared CL should not con-
tain oxidation products . If these compounds are