Fire and Materials 1976, 1, 160 to 168

Toxicity of Thermal Degradation Products of Polyethylene

and Polypropylene
JAN MICHAL
Ore Research Institute, 147 13 Praha, Czechoslovakia

J16i MITERA
Institute of Chemical Technology, 166 28 Praha, Czechoslovakia

STANISLAV
TARDON
Coal Research Institute, 716 07 Ostrava-Radvanice,Czechoslovakia

(Received 23 February 1977; accepted 8 June 1977)

Abstract-Pyrolysis, thermo-oxidation and combustion of polyethylene and polypropylene were studied and
the products of these thermal degradation processes were identified by means of gas chromatographyand gas
chromatography-mass spectrometry. The individual products of thermal degradationwere evaluated for their
toxicity and a conclusion on presumed toxic effect of the combustion products of the polymers studied has
been drawn.

Introduction chain and random breakdown of common C-C bonds

under formation of free radicals.
POLYETHYLENE and polypropylene are among the most
In the propagation stage, a process which is the
extensively used plastics. Polyethylene is the second
reverse of polymerization proceeds
most important plastic following poly(viny1chloride). It
is widely used in the production of foils and plates in R'+R'+ CHz=CHz
packaging techniques (branched polyethylene) and for where intramolecular transfer of the radical with subse-
the production of injection-moulded and hollow
quent decomposition occurs
products (linear polyethylene). It is also widely used in
electrical engineering because of its high electro- R-+R-CH-CH~-R' R-+CH~=CH-CH~-R'
insulating and dielectric properties as well as in the R-CHzCHz + R'
building industry as insulating material, for production and intermolecular transfer of radicals with subsequent
of water distribution pipes, in chemical industry, etc. decomposition take place.
Production of polypropylene commenced in Italy in
1937. Because of its outstanding properties it is also R-CH~-R + R+R--~H-R + RH
applied, in addition to technically very intricate applica- R--CH-R+R-CH=CH~+R-
tions, to the production of consumer goods. It is used for An example of the reaction types characterizing
mouldings in the automotive industry, in electrical termination can be disproportionation
engineering,for sanitary goods as well as in the chemical
industry, for production of refrigerators, washing R + R +R-CH= C H+
~R'H
machines, in toy manufacture and in other fields. or combination
Thermal as well as thermo-oxidative degradations of R' + K~+R~-R~
polyethylene and polypropylene are complex reac-
tions.1-6 Their complexity is due to the degradation Formation of products containing oxygen in the
mechanism being influenced not only by the nature of molecule can be explained according to the following
degraded materials, but also, substantially, by external schemes.
conditions. The mechanism of polyethylene thermal Alcohols
degradation can be expressed generally by the following RO+HCHZ-R+R-CH~-OH+R
stages :
In the stage of initiation, breakdown of weak bonds Aldehydes
proceeds in the fashion ROO'+R-CH~OH+ROOH+ R--~HOH
2R--61HOH+RCH20H+R-CH=O
R-R+2R'
Ethers
The breakdown is due to irregularities in the polymer R'O + R' +R-0-R

160
0Heyden & Son Ltd 1976
 TOXICITY OF THERMAL DEGRADATION PRODUCTS OF POLYETHYLENE AND POLYPROPYLENE 161

Esters
RCH=O + 0~-+R--COOH+=RCOO' HO' +
RCOC+RCH=O+RCOOH+R~O
RCOOH + RCHzOH+ RCOOCHzR H20 +
With thermal degradation of polypropylene, initiation
due to random breakdown of the main chain proceeds
under formation of two main types of radicals : the very
reactive primary methylene radical (I) and the less I Air Nitrogen I
reactive secondary radical (11)

I -CH-CHz' I1 'CH-CHz-
I I
CH3 CH3

A large variety of compounds is formed due to stabiliza-

tion and a series of subsequent reactions. Tsuchyia and
Sumi7>8 studied the mechanism of polyethylene thermal FIG.1 . Thermal analysis of polyethylene in air and nitrogen.
degradation in vacuo and identified 30 compounds using
gas chromatography after condensation of the products
in liquid nitrogen. They came to the conclusion that DTG 1/10; heating time= 100 min; atmosphere=
intramolecular migration of radicals is apparently the nitrogen, air (Derivatograph).
predominating process in the formation of volatile Thermal degradation of both polymers takes place in
compounds. On the basis of kinetic studies Adams9 air as well as in inert nitrogen (Figs 1,2) at temperatures
proposed a complex scheme of thermal oxidation of c. 300 "C. During long-term heating, the initial thermal
polypropylene presenting a complete and relatively degradation can be observed already at temperatures
satisfactory picture of today's state of the knowledge in above 200 "C.
this field. Pyrolysis and thermo-oxidation of polyethylene and
In this paper, we have tried to look at the problem of polypropylene proceeded in a flow quartz microreactorlo
polyethylene and polypropylene combustion products at temperatures of 400 "C and 350 "C, in helium and air
from a somewhat broader point of view. We have per- flow respectively, at 100 ml min-1. The weighed amount
formed gas chromatographic and mass spectrometric of the sample was c. 1 mg. The degradation products
analysis of the pyrolysis as well as thermo-oxidation were adsorbed at 20°C in a small 10 cm column (i.d.
products ; moreover, we have analysed the products of 4 mm) filled with Chromosorb 101. Heating the column
air-combustion of polymers in a free space and assessed connected into the circuit of the carrier gas of the g.c.-
the toxicity of resulting gaseous combustion products. m.s. unit up to 200°C enabled the desorption of the
Special attention has been paid to solid combustion products, separation in an analytical column and
products. We observed especially the dependence of the identification by means of a mass spectrometer in a single
amount of solid products evolved on the burning condi- stage to be carried out.
tions; special attention has been paid to the character of A glass column of 5 m packed with 5 % Silicon Rubber
the resulting solid particles of smoke. These were studied
by means of electron microscopy. From the summarized
results, we have drawn conclusions as to the total danger
of the polyethylene and polypropylene combustion
products to the human organism.

Experimental
The following polymers were used for the study of
thermal degradation and toxicity of its products:
polyethykne (obtained from the National Enterprise
Slovnaft, Bratislava), type Bralen Z 1907-601 ;
polypropylene-isotactic (obtained from the Research
Institute of Macromolecular Chemistry, Brno), mol. wt
510 OOO.
Conditions of thermal analysis were as follows :
weighed amount 400 mg +400 mg A1203 as standard ;
200 400 600 800 "C 200 400 600 800 " C

t " = lo00 "C; sensitivity-TG 500 mg-DTA 1/5- FIG.2. Thermal analysis of polypropylene in air and nitrogen.
162 J. MICHAL, J. MITERA AND S. TARDON

TABLE1. Products of polyethylene pyrolysis, thermo-oxidation and combustion

Shockb
exposure
critical
Thermo- Com- Toxicological* concentration
Peak Product Pyrolysis oxidation bustion comparison (mg m-3> Danger

1 Carbon dioxide 0.1 0.4

2 Propylene 0.1 0.35 0.5 2 max. 0 . 4 % 15 %-Narcotic after 30 min
3 C ~ H (Butylene)
S 1.5 3.7 2.1 2 max. 0.1 mg 1-1 Irritating, pungent odour
4 Butane 1.5 2.3 1 1 %-Sleepiness after 10 min
5 1,3 Butadiene 0.75 4.1 1.1 2 500/2500 lO%-Deep narcosis,
2 %-Light narcosis
6 Pentene + F'ropanal 6.5 7.5 6.7 3 max. 1000 pprn Irritating, pungent odour
7.4 3 from 6 mg m-3 upwards
7 n-Pentane 6.2 3.9 2 max. 1000 ppm
8 C5Hs 0.5 3.7 2.4
9 C5H10 0.5
10 Butyraldehyde 14.5 5.8 3 0.55 mg 1-1 unbearable
irritation
11 Cyclohexane 4.5 3.3 1 80 mg m-3
max. 400 ppm
12 Hexene-1 9.9 10.8 3 Irritating and narcotic effect
13 n-Hexane 4.8 4.9 2
14 C6H14 0.9 1.3
15 C6HlO 0.7 0.3
16 Cyclohexene 0.27 2.2 1 max. 400 ppm Irritation, lethal dose-
15 000 ppm
17 Benzene 2.6 0.65 5.9 2 501250 20 000 ppm-Heavy
poisoning after 5-10 min
18 Methylcyclopentene 2.5 0.8
19 Varelaldehyde 11.5 5.6
20 Heptene-1 5.6 1.4 3.0 3 Irritating effect, spasms
21 n-Heptane 6.2 1.3 1.6 2 5000 ppm-Intoxication
after 15 min
22 C7H14 1 .o 0.4 0.3 3 Irritation
23 Toluene 0.8 0.9 3.3 2 200/1000
24 Ethylcyclopentene 0.5
25 Methyl isobutyl ketone 2.2 1.7
(or ally1 acetate)
26 Hexanal 5.6 2.7 2 3.5 mg 1-'-Heavy irritation
27 Octen-1 5.7 3.9
28 n-Octane 4.6 2.0 2 see 21
29 CSHIS 0.89 0.7
30 Acrylic acid 0.9 0.8 4 Heavy irritation
31 Ethyl benzene 1.3 0.89 2.5 2 max. 200 ppm 5000 ppm-Unbearable
irritation
32 C9Hl0 1.4 1.8
33 Heptanal 3.1 3.1
34 Nonene-1 5.4 0.7 2.7
35 n-Nonane 3.5 1.4 1.2 2
36 C9HI6 0.1
37 CsHis 0.7 0.6
38 Epoxide 0.3 0.2
39 C9H16 0.4
40 Keto-aldehyde 0.6 0.3
41 Octanal 2.5 0.2
42 Decene-1 5.8 0.7
43 -
n D ecane 3.0 0.6 0.3 2
44 CioHis 0.1
45 CioH2o 0.3 0.3 0.2
46 CiiH2z 0.2 0.07
47 Undecene-1 4.3 0.9
48 n-Undecane 3.0 0.3
49 Nonanal 1.9
50 CllH24 0.2
51 CiiH2o 0.2
52 Dodecene-1 2.7 0.5
53 n-Dodecane 2.2 0.4
54 Decanal 0.8 2 Irritation
 TOXOCITY OF THERMAL DEGRADATION PRODUCTS OF POLYETHYLENE AND POLYPROPYLENE 163

TABLE1 (continued)

Shockb
exposure
critical
Thermo- Com- Toxicologicala concentration
Peak Product Pyrolysis oxidation bustion comparison (mg m-3) Danger

55 Tridecene-1 1. 9 0.2
56 n-Tridecane 1. 5 0.4
57 Undecanal 0.4 2 Slight irritation
58 C13H26 0.6
59 Silicone 0.1
60 Tetradecene-1 2.0 0.15
61 n-Tetradecane 1.2 0.2
62 Dodecanal 0.2
63 Pentadecene-1 1.8 0.15
64 n-Pentadecane 0.7 0.15
65 Tridecanal 0.1
66 Hexadecene-1 1.3 0.07
67 n-Hexadecane 0.9 0.07
68 Tetradecanal 0.1
69 Heptadecene-1 0.5 0.15
+
n-Heptadecane 0.4
70 Pentadecanal 0.1
71 Octadecenel 0.6 0.15
+
n-Octadecane 0.5

a Degree of actual danger according to Marhold. Comparison scale: 9-hydrogen cyanide, hydrogen sulphide; 8-carbon monoxide;
7-phosgene; 5-chlorine; 4-ethylene oxide, carbon disulphide; 3-sulphur dioxide ; 2-ammonia; 1-methane.
The concentration should be atmospheric concentration. It is not related to the concentration data in columns 1, 2 and 3 of Table 1.

(Merck) on Chromosorb WAV was used for the separa- The polyethylene and polypropylene samples were
tion. Carrier gas (helium) flow was 40mlmin-1, analysed using gas chromatography in direct connection
temperature was linearly programmed from 50-280 "C with mass spectrometry. The individual compounds in
at a rate of 5 "C min-l. Gas chromatograms (FID) were the products of pyrolysis, thermo-oxidation and com-
recorded on a Hewlett Packard 7634A Chromatograph bustion were identified by comparing their mass spectra
equipped with 3380A integrator. Mass spectra were with the published ones.12 The toxic effect was assessed
recorded on the LKB Gas Chromatograph-Mass for the individual compounds13,l4 and the total pre-
Spectrometer (energies of electrons 70 eV, temperature sumed toxicity of gaseous products of the pyrolysis and
of ion source 250 "C, pressure Pa). combustion of polymers was evaluated on the basis of
The analysis of the combustion products of polymers polyethylene and polypropylene. Compounds identified
proceeded so that the polymer (c. 50 mg) was ignited in in the products of pyrolysis, thermo-oxidation and
air with a gas flame and inserted, burning, into the space combustion of polyethylene are summarized in Table 1;
under a glass funnel. A small pre-column (i.d. 4 mm), those identified in the products of pyrolysis, thermo-
filled with 5 mm layer of Chromosorb 102, was attached oxidation and combustion of polypropylene are sum-
to the glass funnel and to a vacuum pump which marized in Table 2. The toxic effect of the products is
removed the combustion products from the funnel space shown in Tables 1 and 2.
through the pre-column which was cooled with dry ice. Gas chromatograms of the products of pyrolysis,
The samples obtained in this way were analysed by thermooxidation and combustion of polyethylene at low
means of gas chromatography as well as g.c.m.s. as in as well as high temperatures are illustrated in Fig. 3;
previous cases.10111 those of the products of pyrolysis, thermo-oxidation and
The smoke was studied by means of a device for combustion of polypropylene are illustrated in Fig. 4.
controlling the thermal' degradation of polymers, The polyethylene and polypropylene samples for the
enabling their combustion in a gas mixture stream with smoke study were combusted in a device for controlled
an oxygen concentration of 0-30% and nitrogen con- thermal degradation. The smoke products were retained
centration of 70-100% to take place. The smoke pro- on a fibreglass filter and the dependence of the amount
ducts retained in a tube of a fiberglass surface filter of smoke on oxygen concentration at various tempera-
Schleicher Schiill No. 8 were analysed for quantity, tures (Fig. 5), size distribution of the smoke particles at
percentage of particles and their dispersion rate. Mor- two various temperatures (440 and 800°C) (Table 3)
phology of the smoke particles was studied by means of and the dependence of the mean diameter of aerosol
electron microscope Tesla BS-232 (operating voltage particles on the oxygen percentage (Fig. 6) were
60 kV, maximum current 100 A, tungsten wire cathode). observed. The morphology of the smoke particles was
164 J. MICHAL, J. MITERA AND S. TARDON

studied using electron microscopy (Figs 7-9). Conclu- temperatures above 600 "C-are summarized in Tables 1
sions about the dangerous effect of the smoke evolved and 2. Various degradation conditions were chosen
during combustion of polyethylene and polypropylene purposely for the approximation of 'real life' combustion
have been drawn from the results. of polymers, at least up to a certain degree. As expected,
saturated as well as unsaturated hydrocarbons are
important products of thermal degradation. Analysis of
Results and Discussion
the resulting hydrocarbons is characteristicfor the given
The results of identification of polyethylene and poly- polymer.
propylene thermal degradation products12 under mark- The main products of polyethylene thermo-oxidation
edly different conditions-pyrolysis at 400 "C, thermo- under the above-mentioned conditions are C3-cl5
oxidation at 350°C and combustion in air at polymer aldehydes representing 48.2 % of the chromatogram area

TABLE2. Products of polypropylene pyrolysis, thermo-oxidation and combustion

~

Shock"
exposure
critical
Thermo- Com- Toxicologicala concentration
Peak Product Pyrolysis oxidation bustion comparison (mg m-3) Danger

1 Carbon dioxide 0.4 0.01 0.24

2 Propylene 1.1 0.025 0.08 2 max. 0 . 4 % Narcotic effect o n heart
15 %-Narcosis after 30 min
35 %-Deep narcosis
3 Acetone 10.5 5.4 2 0 . 2 mg 1-1 Irritating, narcotic effect
1000 ppm 22 mg I-'-Unbearable after
I5 rnin
4 n-Pentane 18.7 2 1000 ppm Narcotic
5 Cyclopentadiene+ acrolein 2.25 3.4 2 Narcotic, effect on heart,
8 irritating
0.35 mg 1- l-Lethal dose after
15 min
6 Hexene 0.45 0.16 3 Narcotic effect
7 Crotonaldehyde 6.0 5.7 7 Strongly irritating
0.05 mg 1-1-Iris itching
after 10 s
8 Dimethylpentadiene 1.3 1.25 0.88
9 2-Methyl-1-pentene 8.8 3.8 11.0 Slightly toxic
10 Acetic acid 1.1 0.96 2 max. lOpprn Irritating, dangerous to eyes
I 1 C8H16 0.2
12 2-Butylene-1-01 2.9 1.1 Irritating
13 1-Butanol 2.15 0.6 3 100-200 mg m-3 Very dangerous to eyes
14 C8Hl8 1.3
15 Diacetyl 4.2 4.8
16 C8H14 2.6 1.4
17 4-Methyl-2-pentanone 4.5 3.3
18 C ~ H I Z C O
Ketone 3.8 4.2
19 Toluene 0.45 0.6 2 200/1000 Narcotic effect
20 C9H18 0.4
21 C9Hl8 2.6 1.9
22 Acetyl acetone 3.7 2.8 3 Slightly toxic
23 C ~ H I ~ CKetone
O 1.25 1.5
24 2-Heptanone 1.35 1.04 3 Slightly toxic
25 CgHi8 0.2 0.72
26 2,6-Dimethyl-3-heptene 49.0 2.0 12.4
27 C9Hl8 2.0
28 CgHi8 1.2 0.8
29 C9H16 1.1
30 Epoxide 1.8 2.0
31 C9H16 0.9
32 CioHzo 1.5
33 CioHzo 1.4 1.6
34 C10H18 0.2
35 ClOHlS 1.6 0.96
36 4-Methyl-Zheptanone 3.7 3.5
37 Ketone or epoxide 0.4 1.8 1.5
38 C9H160 Ketone 11.66 3.6
 TOXICITY OF THERMAL DEGRADATION PRODUCTS OF POLYETHYLENE AND POLYPROPYLENE 165

TABLE2 (continued)
~~ ~

Shockh
exposure
critical
Thermo- Com- Toxicologicala concentration
Peak Product Pyrolysis oxidation bustion comparison (mg m-3) Danger
~

39 CiiHzz 0.7 0.96

40 4,dDimethyl nonane 0.9 0.5 0.24
41 C12H24 0.2
42 CgHleO Ketone 3.0 I .76
43 C12H24 mixture 5.7 2.9 7.4
44 C13H26 0.4
45 C13H24 3.5 1.4
46 Ci4Hz8 0.4
47 C14HZ8 0.3
48 C14Hz6 0.2
49 ClzHzzO Ketone 2.6 2.32
50 C15H30 1.5 3.1
51 C15H30 3.4 1.3
52 Ci5H28 0.25 0.6
53 C14H2.50 Ketone 0.35 0.4
54 C15H280 Ketone 1.7 1.12
55 C18H36 0.35 0.4

The numbers denote contents by volume (related to total chromatogram area).

Degree of actual danger according to Marhold. Comparison scale: 9-hydrogen cyanide, hydrogen sulphide; 8-carbon monoxide;
a
7-phosgene; S-chlorine; 4-ethylene oxide, carbon disulphide; 3-sulphur dioxide; 2-ammonia; 1-methane.
b The concentration should be atmospheric concentration. It is not related to the concentration data in columns 1, 2 and 3 of Table 2.

(TIM). Other oxygen-containing products of poly-

ethylene thermo-oxidation are ketones (2.8 %). We
presume that the ketones identified in the products
resulted from the oxidation of the polyethylene chain at
branching points (see oxidation of polypropylene).
Epoxides probably also result from thermo-oxidation in
small quantities. Ethanol was identified as well. In
addition to oxygen-containing compounds, olefins i
(25.05 %) and paraffins (1 1.89 %) are present in the
thermo-oxidation products. The paraffin-to-olefin ratio
in the thermo-oxidation products is lower than that of
the pyrolysis products where the sum of paraffins is
35.00 % and that of olefins 59.25 %.

I I I I I
45 36 27 18 9 0
12
min
I 1 I 1 I I I
275 230 185 140 95 5.
"C

275 230 185 140 95 50

"C 45 36 27 18 9 0

FIG. 3. Gas chromatography analysis of products of pyrolysis,

thermo-oxidation and combustion of polyethylene.
166 J. MICHAL, J. MITERA AND S. TARDON

((1 1 50

40

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$ 30
0)
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20

43
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I I
45 36 27 I€
min
I1 I I I I L 0 5 10 15 20
275 230 185 140 95 5( %02
"C
FIG. 5. Dependence of smoke amount on oxygen concentration.
1. Standard 440°C; 2. polyethylene 440°C; 3. polypropylene
440°C; 4. standard 800°C; 5. polyethylene 800°C; 6. poly-
propylene 800°C. Red oak was used as standard.

19 Ii0 No reference mass spectra have been found in litera-

ture for some of the epoxides summarized in Table l and,
therefore, the identification cannot be definitive. For
instance, branched aldehydes can have similar mass
spectra.
The main oxygen-containing products of poly-
propylene thermo-oxidation are methyl alkyl ketones
(CH3COR) occupying 57.36 % of the chromatogram
5
3 area. Compounds having the number of C atoms a
multiple of three-from C3 up to Cis-prevail among the
resulting ketones.
Under the condition of polyethylene and polypropyl-
ene combustion in air, degradation proceeds primarily
on a base heated to a temperature of about 600°C and
the products of this degradation burn with flame. Stable
aromatic compounds (Tables 1 and 2) were found in the
I I I I I I products. Compounds which oxidize easily are com-
275 230 185 140 95 50
"C

(C)
I

Y 3
-1
4
I

I
Y
43
I 0
t i 3
7
18 15 2
4
5
I 2 6

5
I
36
I
27
min
I
18
I
9 0
0 4 10
% 0,
15 20
I I I I I
'5 230 185 140 95 5? FIG.6. Dependence of the mean radius of aerosol particles &O on
OC
oxygen concentration. 1. Standard 440°C; 2. polyethylene
FIG. 4. Gas chromatography analysis of products of pyrolysis, 440°C; 3. polypropylene 440°C; 4. standard 800°C; 5. poly-
thermo-oxidation and combustion of polypropylene. ethylene 800°C; 6. polypropylene 800°C.
 TOXICITY OF THERMAL DEGRADATION PRODUCTS OF POLYETHYLENE AND POLYPROPYLENE 161

FIG. 9. Polypropylene, isometric particles with typical ray

structure, average particle size 4.2 pm, magnification x 7000
(8 mm=l pm).
FIG. 7. Polyethylene, magnification x 7000 (8 mm= 1 pm),
aggregates of polyethylene particles with size up to 4.3 pm.
tive determination of the particular products, can be
busted under these conditions to COZ and water. used only as guides to the possible toxic effect of the
Permanent gases (CO, COZ)and water were not analysed products of polyethylene and polypropylene combustion
in any of these cases, as the method for retention of and they cannot be considered, in any case, to be
products (adsorption on an organic co-polymer) does equivalent to toxicological tests on animals. Neverthe-
not permit their quantitative determination. less, we will try to correlate these values with those tests
These data, together with the results of the quantita- in the next stage of the research.
During the study of smoke, the amount of smoke
resulting was observed, especially in its dependence on
the thermal degradation, temperature and on the oxygen
percentage in the surrounding atmosphere. The results
are plotted in Fig. 5 from which the essential effect of
temperature as well as oxygen content in air on the
amount of the smoke is seen. Practically no smoke arises
at 440°C and zero content of oxygen. However, the
amount of smoke rises steeply with increasing oxygen
content attaining c. 45 % in the case of polypropylene and
c. 20% in the case of polyethylene at 10% oxygen. At
higher temperatures (800 "C), the dependence of the
amount of smoke on the oxygen content is diverse: the
amount of smoke decreases more (polyethylene) or less
(polypropylene)with the increasing oxygen content. The
effort to avoid or reduce the formation of smoke during
combustion of polyethylene or polypropylene can be suc-
cessful on the presumption only that the burning temp-
erature drops to c. 400-450 "C.In that case, it would be
necessary to stop the access of fresh air to the burning
material so that the oxygen percentage on the site of
burning drops to under 1 vol. %.
FIG. 8. Polypropylene, magnification x 7000 (9 mm= 1 pm),
The particle size distribution was also observed under
spherical particles with fibrillar component. Average particle size the same temperatures at oxygen concentrations of 0,
0.7 pm,length of fibres up to 2.8 pm. 10.9 and 21 % (Table 3). These data are useful for
168 J. MICHAL, J. MITERA AND S. TARDON

Table 3. Size distribution of smoke particles at degradation temperatures440 "Cand 800 "Cand oxygen concentrations 0.0,10.9 and 21 .O %

Particle size, pm

Degradation Mean 0.88 1.25 1.77 2.50 3.55 5.0 7.1 10

temperature, 02, radius, -- -
Polymer "C % Pm Percentage

Polyethylene 440 0.0 1.58 10.6 44.4 29.5 13.4 2.0 - - -

10.9 2.27 2.3 20.4 33.2 20.9 18.9 4.3 - -
21.0 1.29 26.8 49.3 21.8 2.1 - - - -
800 0.0 1.76 5.1 36.7 36.8 15.4 5.5 0.5 - -
10.9 2.36 12.4 30.0 38.8 30.0 12.4 - - -
21.0 1.63 4.9 37.0 48.7 8.8 1.2 - - -
Polypropylene 440 0.0 1.45 11.7 57.4 22.6 6.6 1.7 - - -
10.9 2.28 - 17.9 51.2 17.2 4.9 5.4 2.1 1.3
21.0 2.80 2.0 28.5 27.6 13.6 9.6 8.3 6.8 3.6
800 0.0 1.50 10.5 54.9 25.5 6.7 1.1 1.3 - -
10.9 1.32 20.9 55.8 20.7 2.3 0.3 - - -

21.0 1.52 7.0 43.3 45.5 3.5 0.7 - - -

characterizing smoke and studying its macrophysical ducts must be appreciated. The smoke arising during
properties. The results show that the smoke aerosol combustion of both polymers is rich in solids, its optical
resulting from the combustion of both polymers is density being relatively high. Acrylic acid is, apparently,
typically polydisperse in the range of sizes. Particle size the most toxic component of polyethylene combustion
distribution does not vary substantially either with rising products. No amount of carbon monoxide content
temperature or with oxygen amount. was taken in this paper, as the applied conditions of
Because many aerosol properties such as surface, the chromatographic separation did not permit its
diffusion coefficient and mass depend on the mean determination. At present, the possibility of specific
diameter of the particles, we have made relevant mea- chromatographic determination of carbon monoxide
surements and used the mean arithmetic radius FIO for is being considered and the results will be dealt with
evaluation of the average particle size. This is in the in a subsequent contribution. The products do not
range c. 1-2 pm and its variation with temperature and contain a markedly toxic component. Strongly irritating
oxygen content in air is negligible. Condensation pro- and corrosive crotonaldehyde, the toxicity of which
cesses, where smaller spherical particles condense and is comparable with that of phosgene according to the
react in the gaseous state, usually forming various Marhold's scale, is the most toxic component of the
amounts of aggregates, and also plastic spherical polypropylene combustion products. The products of
particles in a broader size range, arising in some ways polypropylene thermal degradation can therefore entail
like dispersed particles from the breakdown of the basic certain danger.
structure of the plastics, both have a marked effect on REFERENCES
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shapes-from microcrystallinic to huge aggregates of (1971).
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aerosol of plastics. Electron microscopy studies of Dev. 11, 36 (1972).
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smoke aerosols have shown that polyethylene produces
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combustion products are characteristic isometric par- 7. Y. Tsuchyia and K. Sumi, J. Polym. Sci. Part A, 6,415 (1968).
ticles of spherical shape with ray structure. There are 8. Y. Tsuchyia and K. Sumi, J. Polym. Sci. Part A, 7,1599 (1969).
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of markedly toxic compounds, the dangers of these pro- Poisons in Industry, in Czech), Prague (1959).