The effect of AlBr3 additive on the thermal degradation of PMMA A study using TG-DTA-DTG, IR and PY-GC-MS techniques

Article abstract of DOI:10.1007/s10973-009-0063-y

The thermal behavior of poly(methyl methacrylate) (PMMA) was studied in the presence of AlBr₃ using TG-DTA-DTG, IR and Py-GC-MS techniques. Degradation products were identified. It was found that PMMA started degrading at a lower temperature du

Full text of DOI:10.1007/s10973-009-0063-y

J Therm Anal Calorim (2009) 96:873–881
DOI 10.1007/s10973-009-0063-y
The effect of AlBr additive on the thermal degradation of PMMA
3
A study using TG-DTA-DTG, IR and PY-GC-MS techniques
M. Arshad Æ K. Masud Æ M. Arif Æ
S. Rehman Æ M. Arif Æ J. H. Zaidi Æ
Z. H. Chohan Æ A. Saeed Æ A. H. Qureshi
NATAS2008 Conference
Akad e´ miai Kiad o´ , Budapest, Hungary 2009
ꢀ
Abstract The thermal behavior of poly(methyl methac-
rylate) (PMMA) was studied in the presence of AlBr using
IR spectroscopy ꢀ Py-GC-MS ꢀ Flammability test ꢀ
Degradation mechanism
3
TG-DTA-DTG, IR and Py-GC-MS techniques. Degradation
products were identified. It was found that PMMA started
degrading at a lower temperature due to the generation of
Introduction
•
free radicals (Br ), being the product of decomposition of
AlBr . Despite early destabilization of the system, stabil-
3
For the last few decades, the thermal degradation behavior
and other related physical parameters of various homo-
polymers and copolymers have been studied extensively
[1–3] due to their commercial importance [4–6]. It has been
the interest of many researchers to extend these investiga-
tions to the examination of polymeric and copolymeric
systems especially in which various physical properties
[7, 8] and mechanisms of the degradation have already
been probed [9–12]. Since thermal properties of polymers/
copolymers provide valuable information regarding tough-
ness, stiffness, stability, compositions of intermediates and
types of residues formed, these have become topics of
several publications [13–15].
ization zone was also highlighted. Flammability test was
conducted to check the affectivity of AlBr . Degradation
3
mechanism has been proposed. Pyrolysis of the system
(
PMMA–AlBr ) was also monitored by heating it at dif-
3
ferent temperatures.
Keywords Thermal degradation ꢀ PMMA ꢀ
Aluminum tribromide ꢀ Thermoanalytical study ꢀ
M. Arshad (&) ꢀ M. Arif ꢀ J. H. Zaidi
Chemistry Division, PINSTECH, Nilore, Islamabad, Pakistan
e-mail: marshads53@yahoo.com.sg
Poly(methyl methacrylate) (PMMA), is a completely
amorphous vinyl polymer but it possesses high strength and
excellent dimensional stability due to its rigid polymer
chains. It shows exceptional optical clarity, very good
weatherability, and impact resistance. PMMA has many
applications like indoor and outdoor lighting, diffusers,
lenses and contact lenses [16]. The thermal as well as other
properties of poly (methyl methacrylate) alone [17–19] and
in the presence of a number of additives have been studied
by many workers [20–22].
K. Masud
NLP, PINSTECH, Nilore, Islamabad, Pakistan
M. Arif ꢀ Z. H. Chohan
Department of Chemistry, Bahauddin Zakariya University,
Multan, Pakistan
S. Rehman
Department of Chemistry, University of Peshawar, Peshawar,
Pakistan
In continuation of our previous investigations on
homopolymer and copolymer of PMMA with organome-
tallic additives [12, 23, 24], we have now decided to
concentrate more on purely inorganic additives to study the
mode of their (blends, additives and polymers/copolymers)
decomposition along with mechanistic pathways. This
A. Saeed
Department of Chemistry, Quaid-i-Azam University, Islamabad,
Pakistan
A. H. Qureshi
Materials Division, PINSTECH, Nilore, Islamabad, Pakistan
123

8
74
M. Arshad et al.
shifting in our interest was based on the exclusion of
flammable degradation products bound to arise from the
disintegration of organic part of the additive/s.
Instrumentations
The liquid chromatograph, Hitachi 655-A-11 with GPC
software and integrator (D-2200 GPC along with column
GLA-100 m (Gelko)) was employed for molecular mass
determination of polymer at room temperature. The ther-
moanalytical measurements were carried out with NET-
ZSCH Simultaneous Thermal Analyzer STA 429. The
measurements were made in an atmosphere of nitrogen, in
the temperature range of ambient to 800 ꢁC, at a heating rate
The purpose of the present work was to gain additional
evidence to propose a detailed mechanism of the degra-
dation of PMMA mixed film with aluminum tribromide
while getting insight into the behavior of polymeric system
in the presence of additive. The nature of degradation
products and the changes produced in PMMA–AlBr blend
3
during pyrolysis are studied using FTIR, TG-DTA-DTG
and Py-GC-MS techniques. Activation energy and order of
reaction were determined by Horowitz and Metzger
method [25], whereas the flammability test of polymer and
its blends were performed by using standard method [26].
-
1
of 10 ꢁC min using kaolin as reference material. The
infrared spectra of polymer, additives and those of residues
produced after heating the blends at different temperatures
were recorded with Nicolet 6700 FT-IR spectrometer in the
-
1
range 4000–400 cm . The GC-MS system was an Agilent
890 N type coupled with 5973 inert MSD, by Agilent
6
Experimental
Analytical Instruments, Agilent Technologies, USA. Anal-
ysis of the product in acetone was performed with a DB-5MS
Reagents, synthetic procedures and instrumentations
column. The activation energy (E ) and order of reaction (n)
o
of polymer and blends were calculated using Horowitz and
Metzger method [25] from TG curves.
All the chemicals obtained from standard source suppliers
were of analytical grade. Aluminum tribromide (Aldrich-
Sigma; 99% purity) was used without purification whereas
0
the monomer, methyl methacrylate (E. Merck), 2,2 -Az-
Results and discussion
obisisobutyronitrile (AIBN, E. Merck), absolute ethanol
(
E. Merck), acetone (E. Merck), diethyl ether (BDH) were
Thermoanalytical characterization
used with further purification.
The thermal curves (TG, DTA and DTG) of pure additive,
homopolymer and blends (polymer-additive), recorded
in inert (nitrogen) atmosphere from ambient to 800 ꢁC,
are produced in Figs. 1, 2, 3, and 4. The relevant data
and stages of pyrolysis regarding the thermal behavior
of additive, polymer and blends are presented in Table 1.
Preparation of poly (methyl methacrylate)
The homopolymer was prepared by the reported method
[
27]. The molecular mass was found as 120,000.
Method of preparing thin film for analysis
The thermal degradation study on AlBr has not been
3
The samples of polymer with additive for degradation were
prepared by the selection of common solvent, i.e., acetone.
The known amounts of both polymer and additive were
dissolved separately in a sufficient quantity of acetone and
both were left to stand overnight in closed Pyrex tubes.
Later on both the solutions were mixed and shaken thor-
oughly and poured into a well-cleaned transparent Pyrex
dish. Complete evaporation of the solvent was effected at
STP. The resultant mixed film was transparent in the dish
confirming the compatibility of the pair studied.
Method of preparing strip for horizontal burning test
For PMMA and blends the solid samples were added to
acetone and kept overnight to dissolve completely. The strips
were chipped off from aluminum mold according to the
reported procedure [26]. The dried strips were kept in des-
iccator for the required test. The results are shown in Fig. 8.
Fig. 1 Thermoanalytical curves (dynamic nitrogen, heating rate
10 ꢁC/min) for aluminum tribromide additive in nitrogen atmosphere
1
23

The effect of AlBr
3
additive
875
Fig. 2 TG curves (dynamic nitrogen, heating rate 10 ꢁC/min) for
PMMA–AlBr blends: 100% PMMA (a), 97.5% PMMA (b), 95%
PMMA (c), 92.5% PMMA (d), 90% PMMA (e) and 87.5% PMMA (f)
3
Fig. 4 DTA curves (dynamic nitrogen, heating rate 10 ꢁC/min) for
PMMA–AlBr blends: 100% PMMA (a), 97.5% PMMA (b), 95%
3
PMMA (c), 92.5% PMMA (d), 90% PMMA (e) and 87.5% PMMA (f)
in nascent or radical form). At 660 ꢁC, aluminum metal
starts melting and shows a mass-loss of 2.5% due to its
evaporation. The three DTA peaks at 95, 375 and 588 ꢁC
and one DTG peak at 215 ꢁC support the current degra-
dation behavior of metal halide. The residue is almost 9%
of the original mass and is pure aluminum metal. Thermal
degradation of PMMA is well-known both in air and under
nitrogen atmosphere. The degradation of PMMA proceeds
by combination of end-chain and main-chain scissions. It is
one-step degradation and yields monomeric methyl meth-
acrylate with no residue at the end [29, 30]. Our investi-
gation confirms the already known thermal degradation
pattern of PMMA (Fig. 2a) in the nitrogen atmosphere. It
begins to lose mass around 250 ꢁC with single stage
decomposition terminating around 440 ꢁC. Two DTA
peaks at 318 and 412 ꢁC and a DTG peak (for maximum
mass-loss in the only step of pyrolysis) at 396 ꢁC support
the well-established thermal degradation of PMMA. The
degradation is initiated near the chain ends (next to double
bonds—DTA peak at 318 ꢁC) and the monomers are fur-
nished by unzipping of chains. Random backbone scission
(DTA peak at 412 ꢁC) also contributes towards the pro-
duction of monomers at some later part of degradation.
Fig. 3 DTG curves (dynamic nitrogen, heating rate 10 ꢁC/min) for
PMMA–AlBr blends: 100% PMMA (a), 97.5% PMMA (b), 95%
PMMA (c), 92.5% PMMA (d), 90% PMMA (e) and 87.5% PMMA (f)
3
performed earlier to the best of our knowledge, though the
corresponding salt with chlorine was blended with poly-
styrene to investigate the catalytic effect [28]. TG trace of
AlBr exhibits a two-step degradation process starting to
3
decompose around 70 ꢁC (Fig. 1). The first mass-loss
(
about 5–6%) appears to be the result of elimination of
moisture. The major disintegration step commences at
08 ꢁC and ends at 223 ꢁC indicating an overall mass-loss
The TG traces obtained from blends of 2.5–12.5% AlBr
3
1
in PMMA compared to that of pure PMMA indicate the
of *76%. This part of decomposition is believed to be the
low-temperature degradation in the early stages (Fig. 2a–f).
The thermal degradation of blend (PMMA:AlBr , 90:
3
•
outcome of Br, Br2 and Br (free radical) production.
A DTG peak at 215.4 ꢁC marks the temperature of maxi-
mum mass-loss for this stage. The final stage of degrada-
tion shows a very slow rate of mass-loss over a temperature
range of 223–800 ꢁC. Up to 660 ꢁC, the mass-loss is only
10%—this is chosen from the whole percentage series as
representative sample for interpretation-sake; the other
members of this series behave in a similar fashion) begins
at low temperature (50 ꢁC) and occurs in two stages. In the
first temperature zone, 50–190 ꢁC, 21% of the blend
6
–7% which may be assigned to the loss of bromine (either
123

8
76
M. Arshad et al.
Table 1 Comparative TG, DTG and DTA data for PMMA–AlBr
3
blends
Blend composition
%) PMMA–AlBr
Temperature
range (ꢁC)
Stage
Weight
loss (%)
TG (ꢁC)
DTG (ꢁC)
DTA (ꢁC)
(
3
T
o
T
50
T
max
I
II
III
Peaks (Thermal effect)
1
9
00–00
250–440
50–170
I
100
10
250
50
390
384
440*
440
396
120
–
–
319 (Endo), 412 (Exo)
124 (Exo), 206 (Endo),
341 (Endo), 400 (Exo)
130 (Exo), 200 (Endo),
280 (Exo), 340 (Exo),
7.5–2.5
I
160
390
1
70–440
50–180
80–440
II
I
88.81
14
9
9
5–5
50
50
384
380
440
440
120
125
170
390
1
II
83.13
3
70 (Exo), 406 (Exo)
2.5–7.5
50–200
00–440
I
17
170
393
130 (Exo), 150 (Endo),
160 (Exo), 250 (Exo),
2
II
80.68
3
00 (Exo), 345 (Endo), 408 (Exo)
9
8
0–10
50–210
10–440
65–200
00–440
I
21
50
65
390
300
440
440
121
125
170
166
395
392
131 (Exo), 148 (Endo), 181 (Exo),
288 (Exo), 335 (Exo), 400 (Exo)
130 (Exo), 150 (Endo), 193 (Exo),
227 (Endo), 272 (Exo), 356 (Exo),
2
2
II
I
75.44
22
7.5–12.5
II
72.54
3
60 (Endo), 399 (Exo)
0
*
0–100
70–223
23–800
I
86
70
200
800
215
–
–
95 (Exo), 375 (Endo), 588 (Endo)
2
II
7.22
100% weight loss
volatilizes. This portion of pyrolysis is due to the degra-
dation of additive (AlBr ). It is noteworthy that AlBr
process ends at 440 ꢁC with the removal of a number of
products including those which were not found when the
components of the blend were pyrolyzed alone. For the
slower portion of degradation of the final step, two DTA
peaks (288 and 335.7 ꢁC) are observed which give the
energy changes occurring due to the chemical interaction
of blended components. For the faster portion of the final
degradation step, one DTA peak (400 ꢁC) and one DTG
peak (395 ꢁC) arise. The residue is only 4% of the original
mass of the blend and is identified as aluminum attached
with oxygen and carbon, aluminum metal and char [12,
31]. It has been noticed (Fig. 2b–f) that when the amount of
additive in the blend is increased to 12.5% from 2.5%,
sample volatilizes quickly from the temperature range of
50–360 ꢁC to 50–300 ꢁC. This may be attributed to the
3
3
commenced to decompose at 70 ꢁC when heated alone
Fig. 1). It is also observed that more mass-loss is found for
(
this stage of degradation than the overall percentage of
additive in the blend. It is believed that although additive
begins to disintegrate earlier than the temperature at which
it started to decompose alone, it causes polymer degrada-
tion at an early temperature. Similarly, in the presence of
polymer, the additive (due to interaction with polymer
pendant groups and heat transfer) exhibited an early split-
ting. This shows destabilization of additive and polymer in
this part of heating. However, it certainly gives an indi-
cation of interaction (physical as well as chemical) between
the two components of the system. Formation of atomic
•
bromine (Br) and generation of bromine free radicals (Br )
higher content of AlBr which generates more bromine free
3
•
are believed to be the cause of destabilization of polymer.
radicals (Br ) hastening the decomposition of undegraded
Two DTG peaks (121 and 170 ꢁC) and two DTA peaks
part of the blends. The TG data indicate that aluminum
tribromide initiates the early degradation of PMMA at a
lower temperature. The degradation begins at a relatively
low temperature (50 ꢁC, except for the blend 87.5%
PMMA with 12.5% additive, which starts at 65 ꢁC) as
compared to that of pure PMMA (250 ꢁC). It has also been
observed that progressive percent mass-loss increases for
(
131 and 181 ꢁC) are found for this stage of pyrolysis. The
second stage starts soon after the completion of first stage
190 ꢁC) and gives a mass-loss of 76%. The slow rate of
decrease in mass of the degrading blend from 190 to
60 ꢁC suggests that the splitting is being hindered due to
(
3
the interaction of degrading species (formation of new
bonds which prevent quick mass-loss can not be excluded
in this zone). Alternatively, the degrading system seems
stabilized in this region. However, around 360 ꢁC the
energy content overcomes the holding forces (binding
forces) and the system degrades rapidly. The degradation
1st stage of degradation, when the amount of AlBr in the
3
blend is increased (i.e., from 2.5% additive to 12.5%
additive in the blend). This supports the observation made
earlier that both constituents of the system disintegrate in
the presence of each other at lower temperatures.
1
23

The effect of AlBr
3
additive
877
The plots (not shown) of T , T , T and Tmax of poly-
o
25
50
mer and its blends show a very clear trend of destabilization
when T is taken into account. It is the temperature corre-
o
sponding to the start of mass-loss. As the percentage of
additive in the blends is increased, a slight stabilization
of 20 ꢁC is noted which may be attributed to the number of
links which are developed between Al and pendent oxygens
of polymer per unit volume of additive. However, for T25
(
temperature at which 25% mass-loss occurs), the trend of
destabilization is more pronounced when mass% of additive
goes from 2.5 to 12.5. This seems to be due to the pro-
•
duction of Br which causes the accelerated degradation of
Fig. 5 Infrared spectra of PMMA (a), Additive, AlBr
PMMA (90%) ? AlBr (10%) (c)
3
(b) and blend,
3
polymer. At T50 (temperature at which 50% mass-loss is
observed), a very inappreciable stabilization is noted as
energy content is too great to be resisted by the different
types of interactions or bonds between additive and polymer
irrespective of the mass% of additive. Tmax (temperature for
maximum mass-loss) is same for polymer and blends which
is indicative of the region very close to the completion of
decomposition process. In this zone, almost all kinds of
bonds are prone to breakage. This graph, however, does not
shed any light as to how much residue is left at the termi-
nation of disintegration of the system.
Infrared spectroscopy and gas chromatography–mass
spectrometry
Fig. 6 Infrared spectra of blend PMMA (90%) ? AlBr
heated at 300 ꢁC (a), 400 ꢁC (b) and 500 ꢁC (c)
3
(10%) after
IR spectrum of the pure additive gives typical stretchings
for AlBr . As additive is hygroscopic so a broad band in the
3
-
region 3600–3000 cm hints at the presence of H O. The
1
500 ꢁC for a minute and the residue (in each case) was
dissolved in acetone. IR spectra of residues were taken as
KBr discs while the dissolved residues were subjected to
GC-MS. The IR spectra of residues coupled with GC-MS
helped in identifying the nature of residues at different
temperatures.
2
-
other peaks at 1603, 1089, 676, 580, 478 cm arise due to
1
Al–Br bond.
-
1
The bands in the region 1725–1735 cm evidence the
presence of ester linkages for PMMA. The absence of
-
1
peaks in the region 1630–1640 cm clearly indicates the
conversion to polymeric form of the compound and
absence of monomeric C=C double bonds. The saturated
The IR spectrum (Fig. 5c) of the blend (90% PMMA:10%
AlBr ) and residue of this blend after heated at 300 ꢁC
3
-
1
C–H stretchings appear around 3000 cm [31]. The IR
spectrum of the blends—films were produced with differ-
(Fig. 6a) are not showing much difference thereby revealing
that after the initial low-temperature decomposition of
•
ent percentage ratios of PMMA to AlBr —gives charac-
3
additive (it is believed that Br (free radical), Br, Br , HBr,
2
teristic peaks for PMMA with displaced positions. This
may be due to the presence of additive and the physical
interactions the additive may have developed with the
polymer. For instance, the peaks for ester linkages of
PMMA appear now at lower frequencies, i.e., around
CH , CO, CO , CH Br, CH OH and certain other smaller
3
4
2
3
molecules evolve as the temperature rises to 300 ꢁC) which
also causes a minor degradation of polymer, the system is
intact with aluminum forming bonds with ester oxygen of
several chains, thus, stabilizing the blend in this temperature
zone. The amount of moisture appears to have diminished
which may be attributed to its complete elimination by
-
1
1
716 cm . On the other hand, Al-Br stretchings either
seem suppressed or appear at higher frequencies. Peaks at
-
616, 686, 593 cm are ample proof for the interaction
1
1
300 ꢁC and then reabsorbance by the undegraded AlBr in
3
between PMMA and AlBr . The film cast by common
3
the residue. TG curve is in agreement with IR findings as rate
of mass-loss is slow around 300 ꢁC. GC-MS results (gas
chromatograms combined with mass spectra) confirm the
observations made on the basis of IR spectra. No peaks
(chromatograms) are present for smaller molecules as these
solvent was transparent which confirmed the compatibility
of the components and mixing at molecular level.
For gaining conclusive evidence regarding the products
identification, the blends were heated at 300, 400 and
123

8
78
M. Arshad et al.
CH
C
3
CH3
Other products
including CO or Al bonded to carbonyl oxygen
C
Br
C
O
C.
O
Br
Al
OCH
3
3
Al
Br
Br
Br
Br
.
OCH
.
H abstraction
3
H COH
Scheme 1
CH
3
.
C
C
O
H
3
C
Br
+
C
C
O
O
O
Br
Al
CH
3
CH3
Br
Br
.
Br
CH
3
C
C
O
Br
O
C
C
O
O
3
H C
CH
3
Scheme 2
Table 2 GC-MS results of blend (PMMA 90% ? AlBr
heating at 300 ꢁC and 400 ꢁC
3
10%) after
Fig. 7 GC-MS results of blends: a heated at 300 ꢁC, b heated at
00 ꢁC
Blend heated at 300 ꢁC
Blend heated at 400 ꢁC
4
Peak no.
Product identified
Peak no.
Product identified
1
2
3
4
C
C
C
C
4
H
H
6
O
2
1
2
3
4
C
C
C
C
3
H
3
O
6
Al
have already left the scene. The products are either fractions
of degraded polymer, i.e., methacrylic acid, cyclic products
having few carbons, more than trace MMA units forming
compounds which are cyclic in nature involving unsaturation
etc. or oligomers bonded [32] to aluminum through ester
oxygen or oligomers with bromine that replaces the –CH3
group other than ester –CH3 (Fig. 7a). The production
of methanol (its identification was made possible through
Py-GC-MS) clearly shows the involvement of another
interaction, i.e., Al…O=C\(Schemes 1, 2).
6
10
O
2
H
8 14
O
4
AlBr
10
H
12
O
2
4
14
H
25
O
6
Al
Al
10
H
16
O
Br
23
H
41
O
5
2
Br
–CH
and –CH – can still be observed (3749, 3675,
3 2
-
1
3648 cm ). The bromine content has almost vanished. Few
bromine atoms are believed to be still bonded to aluminum
which, in turn, appears to have developed true bonds with
oxygen of ester linkages [33, 34].
The IR and GC-MS (Figs. 6b, 7b, respectively) of residue
(
when the blend was heated at 400 ꢁC) were markedly dif-
The heating of blend to 500 ꢁC was carried out to study
the nature of residue only. The degradation of the blend
completed around 440 ꢁC (Fig. 2). The IR spectrum of the
residue (Fig. 6c) gives evidence for Al–O–C linkages
ferent from those which were recorded for the residue when
the blend was heated at 300 ꢁC (Table 2). As the major and
quick (sharp fall in TG traces, Fig. 2) mass-loss is observed
in this region (300–400 ꢁC), the products seem to be those
which are expected prior to completion of degradation
process, i.e., undegraded portion of polymer end chains,
Al–O linked with smaller carbon moieties, absence of ester
linkages, branched hydrocarbons with limited chain length,
etc. (Schemes 3, 4). However, some C–H stretchings of
-
1
-1
(900–1200 cm ), C–C bonds (1300–800 cm which may
-
1
be ascribed to char) and Al–C linkages (400–900 cm that
may be attributed to Al ). The presence of aluminum
C
4 3
metal cannot be excluded on visual inspection-basis. The
GC-MS studies only confirm the Al–O–C bonds in the
form of Al(HCOO) [33].
3
1
23

The effect of AlBr
3
additive
879
CH3
C
C
O
O
CO2
+
CH4
+
Br
CH3
C
CH3
CH3
C
Al
H3C
CH2
CH2
C
.
Br
Br
H3C
Br
Branched alkane with limited chain length
+
Al(HCOO)3
Scheme 3
CH3
C
CH3
.
C
+
Br
C
O
Br
Br
.C
O
Br
Br
Fig. 8 Horizontal burning rate of mixes A–F
Table 3 Formulation of the mixes
Al
Al
OCH3
OCH3
Br
Ingredients
Blend mix number
H3COH
+
compounds which may involve
Al bonds
O
C
A
B
C
D
E
F
Scheme 4
PMMA (%)
100
–
92.5
2.5
95
5
92.5
7.5
90
10
87.5
12.5
The IR and GC-MS investigations of residues at 300, 400
and 500 ꢁC helped monitor the progress of degradation.
These studies provided enough insight which suggests that
apart from earlier low-temperature degradation, the blend is
stable around 300 ꢁC (the nature of products found around
this temperature is a convincing clue). In the region around
AlBr (%)
3
Table 4 Activation energies and order of reaction for PMMA,
additive and PMMA-additive blends
Blend composition
(%) PMMA–AlBr
E
(KCal/mol)
o
Order of
reaction (n)
4
00 ꢁC, the energy content is so high that the links between
3
Al and O (both ester as well as carbonyl) cannot block the
unzipping of main chain. The presence of Al–O and Al–C
linkages in residue at 500 ꢁC indicates the role played by
aluminum of the additive in modifying the overall degra-
dation mechanism of polymer. Bromine (free radicals) was
thought to initiate the early decomposition of the PMMA. In
later part of the degradation, it is Al which interacts with
disintegrating polymer, thus, modifying the pattern of
pyrolysis and mode of formation of degradation products.
1
9
9
9
9
8
0
00–0
138.9
3/2
3/2
1
7.5–2.5
5–5
39.105
37.278
39.470
41.423
40.567
11.114*
2.5–7.5
0–10
1
1/2
1
7.5–12.5
–100
0
* overall activation energy
Flammability of polymer and blends
Activation energy and order of reaction
of polymer and blends
Figure 8 depicts the burning rate of PMMA–AlBr blends
3
(
Table 3) determined by horizontal burning test. The
Activation energy and order of reaction are tabulated in
Table 4 for polymer, additive and blends. The trend confirms
the findings from TG curves. PMMA is more stable than the
blends of all compositions. As the percentage of additive
burning rate of blend with 12.5% of additive (Mix F)
decreases to 5 times when compared with that of neat
polymer whereas the effectivity, in this connection, is very
pronounced even for the lowest proportion (Mix B). This
(AlBr ) is enhanced, a slight increase in activation energy is
3
attributes to the retarding effect caused by AlBr additive
3
noticed. This not only points out the early destabilization of
the system but also indicates the interaction associated
with the additive’s degradation (concentration-based) for
the promotion of polymer’s disintegration at lower
temperatures.
to PMMA. The trend is clearly linear one, i.e., higher the
concentration of additive, lower is the rate of burning and
vice versa. This also confirms the uniform distribution of
additive in the polymer.
123

8
80
M. Arshad et al.
Conclusions
2. Szocik H, Jantas R. Multimonomer and cross-linked polymers
formed by its copolymerization—thermal studies. J Therm Anal
Calorim. 2004;76(1):307–12.
Based on the preceding results the following conclusions
can be drawn:
3
. Majumdar J, Cser F, Jollands MC, Shanks RA. Thermal prop-
erties of polypropylene post-consumer waste (PP PCW). J Therm
Anal Calorim. 2004;78(3):849–64.
I. The system—PMMA/AlBr —showed interaction between
3
4. Prolongo MG, Arribas C, Salom C, Masegosa RM. Mechanical
properties and morphology of epoxy/poly (vinyl acetate)/poly (4-
vinyl phenol) brominated system. J Therm Anal Calorim. 2007;
both components, when polymer and additive are mixed
at molecular level.
8
7(1):33–40.
II. IR results shed convincing light on chemical interac-
tion between the components of blend.
5
6
. Prolongo SG, Prolongo MG. Epoxy/poly(4-vinylphenol) blends
Cross linked by imidazole initiation. J Therm Anal Calorim.
2007;87(1):259–68.
. Prolonga SG, Buron M, Salazar A, Urena A, Rodriguez J. Mor-
phology and dynamic mechanical properties of epoxy/poly (sty-
rene-co-allyl alcohol) blend-influence of hardener nature. J
Therm Anal Calorim. 2007;87(1):269–76.
III. In the early stages of degradation of blends, desta-
bilization dominates which is attributed to the
decomposition/partial sublimation of the additive.
However, as the pyrolysis progresses and the inter-
action binds the degrading members of the systems,
the stabilization can be observed in different temper-
ature zones.
7. Vyazovkin S, Stone J, Sbirrazzuoli N. Hoffman–Lauritzen,
parameters for non-isothermal crystallization of poly (ethylene
terephthalate) and poly(ethylene, oxide) melts. J Therm Anal
Calorim. 2005;80(1):177–80.
IV. Aluminum may also act as heat sink, hence, provid-
ing evidence for physical interaction.
8
. Zuoyun H, Xingzhou H, Gang S. Study of the mechanism of
thermal degradation of poly (vinyl chloride). Polym Degrad Stab.
1
989;24:127–35.
V. Activation energies also substantiate the destabiliza-
tion factor for blends in the initial stages of degrada-
tion when compared to the degradation of neat
PMMA.
9
. McNeill IC, Liggat JJ. The effect of metal acetlyacetonates on the
thermal degradation of poly (methyl methacrylate): part II-manga-
nese (III) acetylacetonate. Polym Degrad Stab. 1992;37(1):25–32.
10. Wochnowski C, Shams Eldin MA, Metev S. UV-Laser—assisted
degradation of poly (methyl methacrylate). Polym Degrad Stab.
VI. Emergence of new degradation products can be
ascribed to the chemical interaction between the
components of blend. The path of decomposition of
polymer has certainly been changed in the presence
of additive.
2
005;89(2):252–64.
1
1. McNeill IC, Neil D. Degradation of polymer mixtures—III:
poly(vinyl chloride)/poly(methyl methacrylate) mixtures, studied
by thermal volatilization analysis and other techniques. The
nature of the reaction products and the mechanism of interaction
of the polymers. Eur Polym J. 1970;6(4):569–83.
2. Zulfiqar S, Masud K, Ameer Q. Thermal degradation behavior of
blends of phenyl methacrylate-styrene copolymers with alumi-
num isopropoxide. J Therm Anal Calorim. 2003;73(3):877–86.
3. Turi EA, editor. Thermal characterizations of polymeric materi-
als. New York: Academic Press; 1972.
4. Mothe CG, Tavares MIB. Study of phenolic resin/EVA blends by
thermal analysis. J Therm Anal. 1997;49:477–81.
15. Amin MB, Maadhah AG, Halim SH, editors. Handbook of
polymer degradation. New York: Marcel Dekker; 1992.
6. Nemec JW, Bauer WI Jr. In: Mark HF, Bikales NM, Overberger
CG, Marges G, editors. Encyclopedia of polymer science and
engineering, vol. 1. New York: Wiley Interscience; 1985. p. 211.
VII. Pure PMMA is the most stable of the polymer-blend
1
systems when T is taken into account, however, as
o
the concentration of additive is increased, T shifts to
o
1
1
higher temperatures for blends. T25 shows a desta-
bilization effect for higher additive concentration in
the blends whereas T50 follows the trend observed for
To. Tmax exhibits identical behavior for PMMA and
blends. By and large, stability prevails and interac-
tions strengthen.
1
VIII. The effective flame retardance of AlBr is proven
3
beyond all doubts. As the concentration of additive
goes up in the blends, the rate of burning goes down.
17. Dakka SM. TG/DTA/MS OF poly(methyl methacrylate)—the
effect of particle size. J Therm Anal Calorim. 2003;74(1):729–34.
1
8. Dakka SM. TG/MS of poly (methyl methacrylate)—the effect of
heating rate on the rate of production of evolved gases. J Therm
Anal Calorim. 2004;75(3):765–72.
Acknowledgements The authors are indebted to PINSTECH,
Islamabad, for providing the facility of thermoanalytical techniques.
Thanks are due to Nehad Ali, Senior Tech., IAD, PINSTECH for
drawing the figures. We are obliged to Nadeem Ahmad and Gulzar
Ali (MD, PT) for their technical assistance.
19. Dakka SM. The role of the oxidative environment. J Therm Anal
Calorim. 2003;73(1):17–24.
20. Etienne S, Becher C, Ruch D, Grignard B, Cartigny G, Det-
renbleur C, et al. Effects of incorporation of modified silica
nanoparticles on the mechanical and thermal properties of
PMMA. J Therm Anal Calorim. 2007;87(1):101–4.
2
1. Cardelli C, Conti G, Giann P, Porta R. Blend formation between
homo and co-polymers at 289.15 K.PMMA.SAN bends. J Therm
Anal Calorim. 2003;71(2):353–65.
References
2
2. McNeill IC, McGuiness RC. The effect of zinc bromide on the
thermal degradation of poly (methyl methacrylate) part-I, thermal
analysis studies and general nature of the interaction. Polym
Degrad Stab. 1984;9(3):167–83.
1
. Osowiecka B, Bukowski A, Zielinski J, Ciesinska W, Zielinski T.
Investigations on nucleated polyproplyne with using thermal
analysis method. J Therm Anal Calorim. 2003;74(2):673–79.
1
23

The effect of AlBr
3
additive
881
2
2
3. Zulfiqar S, Masud K. Thermal degradation of blends of allyl
methacrylate-methyl methacrylate copolymers with aluminum
ethoxide. Polym Degrad Stab. 2000;70:229–39.
4. Zulfiqar S, Masud K, Ameer Q. Thermal degradation of blends of
phenyl methacrylate–styrene copolymers with aluminium ethox-
ide. Polym Degrad Stab. 2002;77:457–64 (references therein).
5. Horowitz HH, Metzger G. A new analysis of thermogravimetric
traces. Anal Chem. 1963;35:1464–68.
6. Sain M, Park SH, Suhara F, Law S. Flame retardant and
mechanical properties of natural fibre-PP composite containing
magnesium hydroxide. Polym Degrad Stab. 2004;83:363–7.
7. Grassie N, McNeill IC, Cooke I. Thermal degradation of polymer
mixtures. (I) Degradation of polystyrene- poly methyl methac-
rylate mixture and a comparison with the degradation of styrene-
methyl methacrylate copolymers. J Appl Polym Sci. 1968;12:
29. Manring LE. Thermal degradation of poly(methyl methacrylate):
4. Random side-group scission. Macromolecules. 1991;24(11):
3304–9.
30. Chang TC, Chen YC, Chiu YS, Ho SY. The effect of silicon and
phosphorus on the degradation of PMMA. Polymer. 1996;37(14):
2963–68.
31. The Sadtler Standard Spectra, Sadtler Research Laboratories,
Philadelphia, PA 5;1974.
32. Ebdon JR, Hunt BJ, Joseph P. Thermal degradation and flamma-
bility characteristics of some polystyrenes and poly(methyl meth-
acrylate)s chemically modified with silicon-containing groups.
Polym Degrad Stab. 2004;83(1):181–5.
2
2
2
2
33. Robinson JW, editor. CRC handbook of spectroscopy, vol. II.
USA: CRC Press Inc.; 1974.
34. Szymanski HA, Erikson RE, editors. Infrared band handbook,
vol. 1 and 2. 2nd ed. New York: IFI/Plenum; 1970.
8
31–7.
8. Nanbu H, Sakuma Y, Ishihara Y, Takesue T, Ikemura T. Cata-
lytic degradation of polystyrene in the presence of aluminium
chloride catalyst. Polym Degrad Stab. 1987;19(1):61–76.
123