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KOVERZANOVA et al.
glass column; stationary phase OV-17 phenylmethyl-
.
.
HOO + H = H O + H ,
2
2
2
silicone; column and injector temperatures 230 C;
detector temperature 290 C; carrier gas nitrogen, flow
rate 16 ml min ; sample volume 2 l).
.
H O = 2HO ,
2
2
1
.
.
HO + RH = R + H O,
2
Analysis of the most representative samples by gas
chromatography mass spectrometry was performed on
a laboratory complex consisting of a Varian 3300 gas
chromatograph, a Finnigan MAT ITD 800 mass spec-
trometric detector of the ion trap type, and a computer
system for data processing. Separation was performed
on a quartz capillary column (30 m long, 0.32 mm
i.d.) coated with a 0.25- m film of DB-5 phenylmeth1-
ylsilicone. The column was heated at a 10 deg min
rate from 50 to 270 C; the injector temperature was
.
.
HO + H = H + H O,
2
2
and chain branching:
.
.
.
H + O
HO + O ,
2
.
.
.
O + H
HO + H ,
2
.
.
ROOH
RO + HO .
2
0
00 C. The carrier gas was helium (inlet pressure
.1 MPa). Samples (1 l) were injected without flow
It is generally accepted that fire retardants can
actively participate in pyrolytic reactions and inhibit
radical generation in the combustion zone or directly
before it. Jha et al. [8] subdivided fire retardants with
respect to the mechanism of their effect into two
groups: (1) additives acting in the gas phase (terminat-
ing generation of free radicals in the preliminary flash
and combustion front zones); (2) additives acting in
the solid phase (decelerating common pyrolysis by
increasing the amount of coke, thus insulating the
polymer melt from the intense high-temperature flame
flow or ignition source, or altering the pyrolysis
course so as to prevent dropping of the polymer melt).
division; the time before the start of purging of the
sample inlet unit was 30 s. The mass spectra were
taken with the electron impact (70 eV) ionization
mode at a scanned rate of 1 mass spectrum per min-
ute; the scanning range was 40 650 amu.
At 300 and 500 C, the major reaction products
are alkenes, alkanes, dienes, and also alcohols and
ketones. The composition and percent content of com-
ponents in pyrolysis products of PP and its composite
with Mg(OH) are given in the table. The strongest
2
peaks in the chromatograms correspond to 2,4-dimeth-
yl-1-heptene, 4-methyl-2-heptanone, 2,6-dimethyl-4-
heptanone, isomers of dimethyloctanol, and some
other hydrocarbon derivatives. At low pyrolysis tem-
It is commonly believed that magnesium hydroxide
belongs to the first group.
In this work we studied how magnesium hydroxide
affects solid-phase coke formation enhancing the fire
resistance of polypropylene.
peratures, Mg(OH) exerts no noticeable effect on the
2
composition of pyrolysis products, whereas at higher
temperatures this effect becomes significant. Benzene
derivatives appear at 500 C. At this temperature, we
identified allylbenzene. Its content in the pyrolysis
products of the composite (1.5%) was lower compared
to pure PP (2.8%). At 700 C, the number and content
of aromatic compounds grow. We identified toluene,
ethylbenzene, xylenes, and isomeric ethyltoluenes and
methylstyrenes. As seen from the table, their content
in pyrolysis of the composite is considerably higher
compared to pure PP. As for compounds with fused
benzene rings, the pyrolysis products of pure PP con-
tain no methylnaphthalene and dihydronaphthalene
isomers detected in pyrolysis of the composite. The
content of naphthalene in the pyrolysis products of the
composite was two times higher compared to pure PP.
In pyrolysis products of the composite, we also identi-
EXPERIMENTAL
Polypropylene was of BE677MO brand (Bore-
alis), and its composite with magnesium hydroxide
(FD905-U brand, Borealis) contained 40% Mg(OH)2.
Pyrolysis of pure polypropylene and its composite
with Mg(OH) was performed at 300, 500, and 700 C
2
in a tubular flow-through pyrolytic cell in air (flow
1
rate 40 ml min ). The outflowing gases were passed
through a bubbler filled with 4 ml of hexane and
cooled on an ice bath, to trap the pyrolysis products.
The thermal gravimetric analysis of PP and its
composite with Mg(OH) was performed on a 950Q
2
1
derivatograph in air at a heating rate of 10 deg min .
fied biphenyl. Thus, in the presence of Mg(OH) for-
mation of aromatic compounds (mononuclear com-
pounds, naphthalenes, biphenyls) is more intense.
2
The screening analysis of the pyrolysis products
was performed on a Tsvet 500 M gas chromatograph
(electron capture detector, ECD; 4000 3-mm packed
The TG analysis of the composite revealed forma-
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 77 No. 3 2004