Macromol. Chem. Phys. 201, 349–354 (2000)
349
Full Paper: Besides the monomer some minor but char-
acteristic volatile thermal decomposition products are
observed pyrolysing polyamide-6 in the presence of PVC.
It was proven that hydrogen chloride thermally eliminated
from PVC gives rise to facilitated depolymerization of
PA-6, partial hydrolysis of the amide groups, evolution of
6-chlorohexanenitrile, and promoted nitrile and vinyl end
group formation. A mechanism is proposed for the
advance of these reactions by hydrogen chloride. Depoly-
merization and hydrolysis are initiated at a considerably
lower temperature in the presence of PVC, at the tempera-
ture of the hydrogen chloride elimination from the latter.
Studying the aspect of high temperature decomposition it
was observed that the presence of PVC severely increased
the hydrogen cyanide evolution from PA-6 at 9008C.
Thermal decomposition of polyamide-6 in the presence
of PVC
Ferenc Kubatovics, Marianne Blazso´*
Research Laboratory for Materials and Environmental Chemistry, Chemical Research Center, Hungarian Academy of
Sciences, PO Box 17, 1525 Budapest, Hungary
(Received: June 21, 1999; revised: September 10, 1999)
ied the effect of HCl eliminated from PVC on the decom-
position of other polymers and found that PA-6 decom-
poses at a lower temperature in the presence of PVC.
Pyrolysis-MS performed in the direct inlet probe is a
fast and relatively inexpensive method for monitoring the
changes in the volatile product formation under pyrolysis
of polymers13). This method was used also for studying
thermal decomposition of polyamides1, 3, 4, 6, 7) and that of
PVC in the presence of plasticisers14), metals and metallic
Introduction
Thermal decomposition of polymers may rise problems
not only during processing and utilization, but after con-
sumption as well. Waste generally contains various poly-
mers leading to unwanted products when incinerated or
pyrolyzed. In this work the thermal decomposition pro-
cesses of polyamide-6 (PA-6 or Nylon-6) are investigated
in the presence of poly(vinyl chloride) (PVC), because
these polymers are often found together (e.g. in automo-
tive shredder waste).
compounds15, 16)
.
Pyrolysis-gas chromatography/mass
spectrometry supplies detailed information on the volatile
thermal decomposition products, and could serve as a
basis of understanding primary thermolysis reactions in
macromolecules17).
The aim of this study was to investigate the changes in
the thermal decomposition of PA-6 in the presence of
PVC.
The main thermal decomposition process in PA-6 is the
depolymerization leading to e-caprolactame1–5). Forma-
tion of cyclic oligomers was observed as well3, 4)
.
Moreover, above 5008C hydrocarbon gases, 5-hexene-
nitrile and hexanenitrile were also identified as volatile
pyrolysis products2). Montaudo and Puglisi4) rationalized
the production of oligomers of PA-6 as the result of intra-
molecular rearrangement of a pair of amide groups. A
cis-elimination mechanism proposed by Lu¨derwald6, 7) for
the macromolecular chain scission in other aliphatic poly-
amides explains adequately the formation of nitrile and
vinyl end groups in PA-6 as well, hence that of 5-hexene-
nitrile.
PVC thermal decomposition starts with dehydrochlori-
nation8–11) below 2008C, at the same time benzene is also
formed during this first step. The majority of the polyenic
carbon chains left behind after HCl elimination decom-
pose at around 4508C to alkylaromatic volatile products
Experimental part
PA-6 (Ultramid B2) and PVC (Vinoflex) were unstabilised
polymers from BASF (Ludwigshafen, Germany).
Direct inlet pyrolysis-mass spectrometry was performed in
the Direct Inlet Probe of a Hewlett-Packard 5985 B gas chro-
matograph-mass spectrometer (GC/MS), using in EI mode at
15 eV ionization energy. The formation of volatile products
was continuously monitored by repetitive scanning the mass
range from 10 to 600 Dalton while heating the sample of
some micrograms from room temperature to 6508C at a rate
and some percent of char. Knu¨mann and Bockhorn12) stud- of 308C/min.
Macromol. Chem. Phys. 201, No. 3
i WILEY-VCH Verlag GmbH, D-69451 Weinheim 2000
1022-1352/2000/0302–0349$17.50+.50/0