Synthesis and thermal studies of bisphenol-A based bismaleimide: Effect of nanoclays

Article abstract of DOI:10.1007/s10973-010-1020-5

The compound 2,2-bis[4-(4-maleimidophenoxy phenyl)]propane was prepared by the imidization of bisamic acid of 2,2-bis(4-aminophenoxy phenyl)propane. Various nanoclays were blended with this bismaleimide and thermally cured. The structural characterization of the synthesized materials and the thermal properties of the bismaleimide and their blends were investigated through FTIR, ¹H and ¹³C NMR, differential scanning calorimetry and thermo gravimetric analysis. Among the various clays investigated, Cloisite 15A shows strong influence on the cure exotherm of bismaleimide. Introduction of clay mineral into bismaleimide shifts the onset of curing exotherm to higher temperature and is nearly 40 °C. The thermal stability of the clay loaded cured bismaleimide increases and the presence of clay particles in the cured bismaleimide matrix enhances the char formation.

Full text of DOI:10.1007/s10973-010-1020-5

J Therm Anal Calorim (2011) 103:693–699
DOI 10.1007/s10973-010-1020-5
Synthesis and thermal studies of bisphenol-A based bismaleimide
Effect of nanoclays
•
Chinnaswamy Thangavel Vijayakumar
•
Rajendran Surender Kumaraswamy Rajakumar
•
Sarfaraz Alam
Received: 17 April 2010 / Accepted: 24 August 2010 / Published online: 14 September 2010
´
´
Ó Akademiai Kiado, Budapest, Hungary 2010
Abstract The compound 2,2-bis[4-(4-maleimidophenoxy
phenyl)]propane was prepared by the imidization of bisa-
mic acid of 2,2-bis(4-aminophenoxy phenyl)propane.
Various nanoclays were blended with this bismaleimide
and thermally cured. The structural characterization of the
synthesized materials and the thermal properties of the
bismaleimide and their blends were investigated through
and aerospace sector because of their high thermal stability,
mechanical strength, and excellent chemical resistance. It is
classified into two types such as addition polyimides and
condensation polyimides. Addition polyimides generally
possess higher stiffness and dimensional stability than the
condensation polyimides due to their high crosslinking net-
work. These high performance polyimides are widely used as
matrices for many advanced composites [1, 2]. Polyimide
composites are very attractive for various applications due to
their high strength to mass ratio and excellent thermal sta-
bility [3].
1
FTIR, H and 13C NMR, differential scanning calorimetry
and thermo gravimetric analysis. Among the various clays
investigated, Cloisite 15A shows strong influence on the
cure exotherm of bismaleimide. Introduction of clay min-
eral into bismaleimide shifts the onset of curing exotherm
to higher temperature and is nearly 40 °C. The thermal
stability of the clay loaded cured bismaleimide increases
and the presence of clay particles in the cured bismalei-
mide matrix enhances the char formation.
Among the addition polyimides, bismaleimides are the
most important polyimide class because of their good
thermal stability, low water absorption, and high mechan-
ical properties at high temperature. Additionally, bisma-
leimides possess many desirable properties such as high
tensile strength, corrosion and excellent chemical resis-
tance and hot-wet performance [4]. The two maleimido
groups present at the end of the molecule will undergo
homo polymerization on heating without the addition of
any free radical initiators to result in highly crosslinked and
brittle thermosetting polyimides. Bismaleimides can be
cured without the evolution of volatiles. One drawback
arises from that unmodified bismaleimide resins suffer
from brittleness due to their high crosslinking density.
Micheal addition of primary or secondary diamines to
bismaleimides was used to effect chain extension through
thermal curing to reduce the high crosslinking density and
brittleness of the polymers [5, 6].
Keywords Bismaleimide ꢀ Nanoclay ꢀ FTIR ꢀ NMR ꢀ
DSC ꢀ TGA
Introduction
Recently, polyimides especially aromatic polyimides have
more and more applications in microelectronics, automotive,
C. T. Vijayakumar (&) ꢀ R. Surender ꢀ K. Rajakumar
Department of Polymer Technology,
Kamaraj College of Engineering and Technology,
S.P.G.C. Nagar, K. Vellakulam Post,
Virudhunagar 625701, India
Various processes have been made to improve the
properties of polyimides [1, 2, 6–8]. The dispersion of clay
particles is one of the method has been well established
since 1960s [8]. Nanocomposites are first commercially
focused on thermoplastics such as nylon 6 in Toyota R&D
labs. By the success of thermoplastic-clay nanocomposites
e-mail: ctvijay22@yahoo.com
S. Alam
Defence Materials and Stores Research and Development
Establishment (DMSRDE), G.T. Road, Kanpur 208013, India
123

694
C. T. Vijayakumar et al.
like polyethylene oxide/clay, polycaprolactone/clay, and
polymethylmethacrylate/clay it has been focused to
improve the properties of thermoset resins such as epoxy
and polyimide by converting them into clay nanocompos-
ites [9]. The polymer–clay nanocomposites can be formed
in one of the three ways, i.e., solution dispersion, in situ
polymerization, and intercalation method. In solution dis-
persion method the preformed polymer solution will mix
into the clay layers. Nanocomposites are formed by dis-
persion and distribution of clay layers into the monomer
followed by polymerization in in situ polymerization
method. The intercalation method involves mixing of clay
layers with polymer pellets while heating the mixture
above the softening point of the polymer [10]. Introduction
of small amount of nanoclay particles into the system will
enhance the properties like mechanical, thermal barrier,
optical, and flammable properties [11, 12]. The gas diffu-
sivity of polymer matrix can be reduced by the dispersion
of plate-like nanoparticles [8, 13]. The chemical substitu-
tion of the clay minerals will resolve the incompatibility
between the organophilic polymer matrix and hydrophilic-
layered silicates for an example the Na? montmorillonite
clay has been modified to convert the surface from
hydrophilic to organophilic [5, 14].
Lancaster Clariant Group Company, Chennai-600017.
Anhydrous potassium carbonate was obtained from
RanBaxy Laboratories Ltd., New Delhi-160055. Ethyl
alcohol and Hydrazine hydrate were purchased from Loba
Chemie Pvt. Ltd., Mumbai-400002. All the chemicals were
used as received.
Preparation of 2,2-bis(4-nitrophenoxy phenyl)propane
(DN-BPAPCNB)
Bisphenol-A (22.8 g), p-chloronitrobenzene (34.6 g), and
anhydrous potassium carbonate (30.4 g) were taken in a
round bottom flask containing 125 mL of N,N0-dimethyl-
formamide. After few minutes, the orange colored reaction
mixture changed its color to blood red and potassium
chloride gets precipitated. The resultant reaction mixture
was refluxed for 12 h. After this period, the precipitated
potassium chloride was filtered off. The filtrate was poured
into copious amount of crushed ice with effective stirring.
The separated yellow colored 2,2-bis(4-nitrophenoxy
phenyl)propane, DN-BPAPCNB, was filtered, washed with
ice cold water, and dried at 50 °C for 24 h in a hot air oven.
The yield was found to be 90%.
Hu et al. [8] studied the effect of organo silicate clay as
filler material on bismaleimide/diallyl bisphenol-A resin
system. They observed that when the clay concentration
increases, the gelation and rheological behavior of the
prepolymer differs. The fillers are also used as modifier to
toughen the BMI resin. Jana et al. [15] studied the exfoli-
ation of closite nanoclay in thermoset polyimide. The clay
particles increase the thermal and mechanical properties
compared to neat resin system.
Preparation of 2,2-bis(4-aminophenoxy phenyl)propane
(DA-BPAPCNB)
Dinitro compound (DN-BPAPCNB) (28.2 g) and 0.15 g of
10% Pd/C dispersed in 180 mL of ethanol were taken in a
round bottom flask. About 60 mL of hydrazine hydrate was
added dropwise and the resultant reaction mixture was
refluxed at 85 °C for 12.5 h. The hot black colored solution
was filtered to remove palladized charcoal. The filtrate was
poured into large amount of ice cold water with efficient
stirring. A pale gray precipitate of 2,2-bis(4-aminophenoxy
phenyl)propane, DA-BPAPCNB, was filtered, washed with
ice cold water, and dried at room temperature. The yield of
the diamino compound was 85%.
The present investigation is focused on the synthesis of
bisphenol-A based bismaleimide and is blended with var-
ious nanoclays such as Cloisite 15A, Bentonite, Nanoclay
DK4, Nanoclay DK3, Micro Talc IT Extra, Calcined clay,
and Natural clay. The pure bismaleimide and the nano-
material blended materials are cured thermally. The ther-
mal properties of these materials are investigated using
DSC and TG technique and the results are discussed.
Preparation of bisamic acid (BAA)
Exactly 12.3 g of diamine (DA-BPAPCNB) was dissolved
in 155 mL of acetone with constant stirring at room tem-
perature. To this solution, 6.5 g of powdered maleic anhy-
dride was added in portions. Yellow precipitate was formed
and it was stirred continuously for half an hour. It was
filtered and washed with ice cold acetone to remove the
acetone soluble materials and dried. The yield was 86%.
Experimental
Materials
Bisphenol-A was purchased from SISCO Research Labo-
ratory Pvt. Ltd., Mumbai-400099. Maleic anhydride,
p-chloronitrobenzene, and anhydrous sodium acetate were
supplied by s.d. fine-chem Ltd., Mumbai-400025. The
solvents N,N0-dimethyl formamide and acetone were
purchased from MERCK Specialist Pvt. Ltd., Mumbai-
400018. Palladium 10% on carbon was supplied by
Preparation of bismaleimide (BMIX)
The yellow BAA was dispersed in a 500 mL round bottom
flask containing 160 mL of dry acetone. 3.44 g of
123

Synthesis and thermal studies of bisphenol-A based bismaleimide
695
anhydrous sodium acetate and 40 mL of acetic anhydride
were added into the reaction mixture and refluxed for
3 h. The brown color solution was poured into copious
amount of crushed ice and 2,2-bis[4-(4-maleimidophenoxy
phenyl)]propane (Scheme 1) was obtained as yellow pre-
cipitate. The material was filtered, washed with ice cold
water, and dried in vacuum. The yield was 90%.
made and ground repeatedly to effect intimate mixing. The
mixture was then dried in a vacuum oven and preserved for
the polymerization. The materials BMIX, BMIX ? 3%
Cloisite 15A, BMIX ? 3% Bentonite, BMIX ? 3%
Nanoclay DK4, BMIX ? 3% Nanoclay DK3, BMIX ?
3% Micro Talc IT Extra, BMIX ? 3% Calcined clay, and
BMIX?3% Natural clay were made.
Purification of natural clay
Thermal curing
About 100 g of natural clay was repeatedly treated with
4 N sodium hydroxide till the disappearance of red color.
All the acid soluble impurities were removed by dispersing
the clay in 1:1 hydrochloric acid–distilled water medium
several times till the disappearance of yellow color. Finally
washing with large amount of demineralised water gave
acid and alkali-free natural clay. This purified clay was
dried in an air oven at 130 °C for about 5 h and stored in a
desiccator for further use.
The pure bismaleimide and the nanoclay blended bisma-
leimides were taken in separate micro test tubes and flu-
shed with dry oxygen-free nitrogen and polymerized at
250 °C for 6 h. After the polymerization, the samples were
removed from the micro test tubes, ground to coarse
powder, packed, and stored for further analysis.
Methods
The FTIR spectra of the materials were recorded using
Fourier Transform Infrared Spectrophotometer-8400S,
Shimadzu, Japan by employing KBr disc technique. The 1H
and 13C NMR spectral analysis were performed in a Bruker
300 MHz NMR spectrometer with tetramethylsilane
(TMS) as the internal standard.
Blending of nanoclays with bismaleimide (BMIX)
All the nanoclays were dried at 105 °C for 24 h in a hot air
oven. The dry bismaleimide (BMIX) 97% and the mois-
ture-free dry nanoclay 3% were taken in an agate mortar
and with minimum quantities of dry acetone a paste was
The differential scanning calorimetric (DSC) curves for
pure BMIX and its blends with various nanoclays were
recorded in a TA Instruments DSC Q10. Nearly 5 to 6 mg
of the materials were taken in Tzero aluminum pan and
heated from ambient to 400 °C by 10 °C min-1. Dry
nitrogen gas was used to provide the inert atmosphere. The
thermogravimetric (TG) curve for all the thermally cured
materials were recorded in a Mettler STAR TG system.
The samples (nearly 6–7 mg) were taken in platinum pan
and heated from ambient to 850 °C at 10 °C min-1 in inert
(nitrogen) atmosphere.
CH
3
+
NO
Cl
OH
HO
2
CH
3
12 h
135 °C
10
CH
6
7
3
2
3
3
NO
O
O
O N
2
2
8
9
CH
1
4
5
Dinitro compound
.
2
Ethanol/H N–NH H O
10%
Pd/C
7
2
2
10
6
2
3
CH
3
Results and discussion
NH
O
O
H N
2
9
2
8
1
5
4
CH
3
Diamino compound
O
FTIR and NMR studies
2
O
The peak seen at 1344 and 1340 cm-1 in the dinitro and
diamino compound, respectively, is attributed to the C–H
deformation. The peak noted in the region 2970 cm-1 for
the dinitro, diamino, and bismaleimide is assigned to the
C–H stretching vibration. The peaks noted at 1344 and
1521 cm-1 in the FTIR spectrum of the dinitro compound
is due to the N–O stretching. In the diamino compound, the
N–H stretching was seen as doublet (3434 and 3406 cm-1).
The absence of N–O stretching peak in FTIR spectrum of
the diamino compound proves the complete reduction of
dinitro compound. The bismaleimide shows for the cyclic
O
O
O
O
O
CH
3
NH
HO
O
NH
OH
O
CH
3
Bisamic acid
–2 H O
2
O
N
O
N
10
CH
7
6
2
3
11
3
O
O
9
8
4
1
5
CH
3
O
O
Bismaleimide
Scheme 1 Preparation of bismaleimide (BMIX)
123

696
C. T. Vijayakumar et al.
Table 1 1H NMR and 13C NMR study for the dinitro, diamino, and bismaleimide materials
Code
1H NMR
13C NMR
DN-BPAPCNB
DA-BPAPCNB
BMIX
DN-BPAPCNB
DA-BPAPCNB
BMIX
1
–
–
–
147.5
125.9
120.0
163.3
152.5
117.0
128.6
142.5
30.9
42.5
–
156.6
116.1
116.4
144.3
148.6
121.0
127.7
142.5
41.8
31.0
–
130.5
128.4
117.0
152.8
153.4
117.5
128.0
135.8
41.7
2
8.17, 8.20
7.15, 7.12
7.26, 7.28
3
7.29, 7.31
6.89, 6.86
7.06, 7.09
4
–
–
–
5
–
–
–
6
7.25, 7.26
6.84, 9.81
6.95, 6.97
7
6.99, 7.02
6.68, 6.65
7.21, 7.24
8
–
–
–
9
–
–
–
10
11
NH2
1.73
–
3.57
–
1.69
6.84
–
31.1
136.4
–
–
1.64
–
–
For numbering refer Scheme 1
CO–NR–CO imide unit a strong absorption at 1744 cm-1
.
The absence of N–H stretching peak in the bismaleimide
proves the complete imidization of BAA.
The chemical shift values for the peaks noted in the
1H and 13C NMR spectra of 2,2-bis(4-nitrophenoxy phenyl)
propane, 2,2-bis(4-aminophenoxy phenyl)propane, and
2,2-bis[4-(4-maleimidophenoxy phenyl)]propane were pre-
sented in Table 1. The labeling of protons and carbons are
shown in Scheme 1. The peak assignments confirmed the
structure of dinitro, diamino, and bismaleimide.
8
7
5
–0.2
6
4
3
–0.4
–0.6
–0.8
1
2
–1.0
Thermal studies
50
150
250
350
DSC studies
Temperature/°C
Fig. 1 DSC curves for pure BMIX and its blends with 3% of various
nanoclays. 1 BMIX, 2 BMIX ? 3% Cloisite 15A, 3 BMIX ? 3%
Bentonite, 4 BMIX ? 3% Nanoclay DK4, 5 BMIX ? 3% Nanoclay
DK3, 6 BMIX ? 3% Micro Talc IT Extra, 7 BMIX ? 3% Calcined
clay, 8 BMIX ? 3% Natural clay
The DSC curves for pure BMIX and its blends with dif-
ferent nanoclays are shown in Fig. 1. For clarity, the curves
are shifted in the ordinate by using a common factor for
each curve. The pure BMIX shows the melting point at
74 °C and the cure exotherm starts at 227 °C, reaches the
maximum at 305 °C and ends at 378 °C. Pure BMIX
undergoes thermal curing with in a temperature region of
151 °C. The melting characteristic of the bismaleimide is
not much altered by the incorporation of 3% of different
nanoclays. But the Bentonite incorporated BMIX increases
the melting point to 77 °C. Priya and Jog [16] studied the
organically modified Bentonite clay interaction in the
poly(vinylidene fluoride) (PVDF). They observed that the
clay particle increases the melting point of the virgin
polymer. This is attributed to the presence of b-form of
PVDF. In our studies also, Bentonite clay increases the
melting point of BMIX and this may be due to the inter-
action of the bentonite clay with the crystal structure of
BMIX (Table 2).
The Micro Talc IT Extra incorporated BMIX shows
much broader curing exotherm region covering 160 °C
than the virgin BMIX (Table 2). Incorporation of Cloisite
15A and nanoclay DK4 in BMIX reduce the cure exotherm
temperature region to 59 and 98 °C, respectively. There is
no tremendous change in the curing exotherm region for all
other nanoclays incorporated BMIX. Except Cloisite 15A
and nanoclay DK4, all the other nanoclay incorporated
BMIX showed very little influence on the DHc value. Both
Cloisite 15A and nanoclay DK4 particles are having
interaction with the intermediates formed during the ther-
mal curing of BMIX and this interaction causes reduction
in the DHc value.
123

Synthesis and thermal studies of bisphenol-A based bismaleimide
697
Table 2 DSC studies: melting and curing characteristics of BMIX and its blends with different clay materials
Sample
Tm/°C
TS/°C
T
max/°C
TE/°C
TE - TS/°C
DHc/J g-1
BMIX
74
74
77
71
71
71
72
71
227
226
236
215
206
214
234
226
305
252
312
256
275
301
309
303
378
286
366
313
319
374
376
377
151
59
186
67
BMIX ? 3% Cloisite 15A
BMIX ? 3% Bentonite
BMIX ? 3% Nanoclay DK4
BMIX ? 3% Nanoclay DK3
BMIX ? 3% Micro Talc IT Extra
BMIX ? 3% Calcined clay
BMIX ? 3% Natural clay
130
98
108
111
103
186
174
178
112
160
141
152
The possibility of clay exfoliation in thermoset matrix
can be predicted from the thermodynamic point of view.
The free energy changes for the polymer or monomer
matrix and clay blended polymer matrix are given below:
8
100
7
6
5
4
3
DGp ¼ DHp ꢁ TDSp
for polymer or monomer matrix
DGc ¼ DHc ꢁ TDSc
for clay blended polymer matrix
2
50
0
1
À
Á
À
Á
DGt ¼ DHt ꢁ TDSt ¼ DHp þ DHc ꢁ T DSp þ DSc
for the total free energy change.
50
200
400
600
800
Temperature/°C
From the above expression the possibility of clay ex-
foliation can be determined by the total free energy change,
DGt. The most favorable case should be DHt is negative
and DSt is positive. When the clay is blended with the
monomer and polymerized, the blended system experi-
ences a strain due to the penetration of the monomer
molecules into the gallery resulting in an entropy loss, i.e.,
DSp is negative. This causes the entropy gain in clay gal-
lery, i.e., DSc is positive and this will compensate the
entropy loss experienced by the monomer matrix. So, the
total enthalpy change will determine whether the clay ex-
foliation is possible or not. That means the larger the value
of heat released, DHp (negative) by intragallery polymeri-
zation, compared to the van der Waals attractive energy
DHc, the higher the possibility of clay exfoliation [7].
Pure BMIX has the cure enthalpy as 186 J g-1. The
enthalpy of curing for the Micro Talc IT Extra, Calcined
clay, and Natural clay blended BMIX matrix are more or less
same as the pure BMIX. So, there is no possibility of rea-
sonable interaction between the above said three clays and
BMIX. Even though the heat release for other clays blended
BMIX differ from pure BMIX, significant difference is noted
in the case of Cloisite 15A blended BMIX (Table 2). So out
of the different clays investigated, Cloisite 15A is having
strong interaction with the molten BMIX matrix and influ-
ences the total heat release during polymerization reaction.
Fig. 2 TG curves for thermally cured BMIX and its blends with 3%
of various Nanoclays. 1 BMIX, 2 BMIX ? 3% Cloisite 15A, 3
BMIX ? 3% Nanoclay DK4,
BMIX ? 3% Nanoclay DK3, 6 BMIX ? 3% Micro Talc IT Extra,
7 BMIX ? 3% Calcined clay, 8 BMIX ? 3% Natural clay
BMIX ? 3% Bentonite,
4
5
8
7
6
5
4
3
2
0.000
1
–0.002
–0.004
–0.006
–0.008
100 200
400
600
800
Temperature/°C
Fig. 3 DTG curves for thermally cured BMIX and its blends with 3%
of various Nanoclays. 1 BMIX, 2 BMIX ? 3% Cloisite 15A, 3
BMIX ? 3% Nanoclay DK4,
BMIX ? 3% Nanoclay DK3, 6 BMIX ? 3% Micro Talc IT Extra,
7 BMIX ? 3% Calcined clay, 8 BMIX ? 3% Natural clay
BMIX ? 3% Bentonite,
4
5
123

698
C. T. Vijayakumar et al.
100
80
Table 3 TG studies: the degradation parameters for the thermally
cured BMIX and different clay loaded BMIX cured thermally
Sample
TS/°C
Tmax/°C TE/°C Char residue
at 700 °C
60
40
20
0
BMIX
404
445
446
445
469
467
474
472
465
552
543
546
552
562
549
42
46
47
46
47
48
BMIX ? 3% Cloisite 15A
BMIX ? 3% Bentonite
BMIX ? 3% Nanoclay DK4 452
BMIX ? 3% Nanoclay DK3 451
BMI
Cloisite 15A
BMI + 3% Cloisite 15A
BMIX ? 3% Micro Talc IT 444
Extra
50
200
400
600
800
Temperature/°C
BMIX ? 3% Calcined clay 449
468
465
553
544
50
52
BMIX ? 3% Natural clay
441
Fig. 4 TG curves for cured BMIX, pure Cloisite 15A, and the cured
blend of 3% Cloisite 15A with BMIX
TG studies
nanoclay in BMIX system increases the thermal stability of
the system and is reflected in the char residue value
(Table 3).
The TG and DTG curves for thermally cured BMIX and
the nanoclay incorporated BMIX are shown in Figs. 2 and
3, respectively. For clarity, the TG curves were shifted in
the mass axis uniformly. In the DTG curves (Fig. 3), the
curves are shifted both in the X and Y axis direction uni-
formly. The thermally cured BMIX starts degrade around
404 °C and the degradation reaches maximum at 444 °C
and the process is over at 553 °C. The incorporation of
nanoclay shifts the degradation temperature to nearly
440 °C, i.e., 40 °C higher than the pure cured BMIX and
the degradation is over approximately 10 °C earlier. The
major degradation covering the temperature region
404–553 °C amounts to a weight loss of 46% in the case of
thermally cured pure BMIX. The nanoclay incorporated
systems show decreased mass loss in the degradation
region and the amount of weight loss noted is around 38%.
Among these nanoclays, the incorporated Natural clay
reduces the mass loss of the pure BMIX to 36%. From this,
it is evident that the interaction existing between the net-
work structure of the thermally cured BMIX and the dis-
persed natural clay is maximum compared to other
nanoclays. It is interesting to note that the amount of char
value noted at 700 °C is roughly 10% higher than the cured
pure BMIX in the case of natural clay and calcined clay
loaded systems. The DTG curves (Fig. 3) shows that the
Tmax value of the initial degradation shifts to higher tem-
peratures roughly by 25 °C owing to the incorporation of
the clay particles when compared to the thermally cured
pure BMIX (444 °C). The DTG curve recorded for the
thermally cured BMIX shows two major degradations,
overlapping with one another. It shows that the initiation of
the second degradation reaction is effected before the ter-
mination of the initial degradation process. Nearly in all the
nanoclay incorporated thermally cured BMIX a single
degradation is noted. Thus, the incorporation of the
Using Cloisite 15A clay system, the interaction between
the clay and the thermally cured BMIX matrix may be
explained. The char residue at 800 °C for the pure ther-
mally cured BMIX and pure Cloisite 15A clay are 30 and
57%, respectively (Fig. 4). For the thermally cured BMIX
matrix (97%) and Cloisite 15A (3%) the theoretically
expected char residue value at 800 °C is 31%. But the
experimentally found value is 39%. Thus, the presence of
3% of Cloisite 15A in cured BMIX matrix enhances the
char value by 8%. It is very clear from this fact clay like a
Cloisite 15A is able to influence the primary degradation of
the thermally cured BMIX and hence results in a com-
paratively higher char yield.
Conclusions
From bisphenol-A and p-chloronitrobenzene, the aromatic
dinitro compound was prepared and it was reduced to yield
aromatic diamine using hydrazine hydrate. The imidization
of bisamicacid prepared from aromatic diamine gives
bismaleimide. Different types of nanoclays were incorpo-
rated into the bismaleimide and thermally cured. The
complete reduction of nitro compound was confirmed by
using FTIR. The DSC studies illustrate that the Cloisite
15A clay reduces the cure exotherm window and also the
amount of heat liberated during the curing process. So, the
physical blending of Cloisite 15A with BMIX matrix is
efficient. The thermal stability and the char residue value
are generally increased and this is certainly due to the
incorporation of clay particles in the bismaleimide matrix.
Among the different clays investigated using BMIX, the
bentonite clay increases the melting point of pure BMIX
whereas the Cloisite 15A and nanoclay DK4 reduces the
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699
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thermally cured BMIX increases the char residue indicat-
ing its strong influence over the primary thermal degrada-
tion of the thermally cure BMIX. Further investigation is
under progress.
Acknowledgements The authors would like to acknowledge the
Directorate of Extramural Research & Intellectual Property Rights
(ER & IPR), Defence Research & Development Organization, Min-
istry of Defence, Government of India, New Delhi-110105 for
financially supporting this work under the Grant ERIP/ER/0704359/
M/01/1101 dated 12-12-2008. The authors wish to express sincere
thanks to Dr. W. Selvamurthy for his keen interest in this research
work. Sincere thanks to the Management and the Principal of Kamaraj
College of Engineering and Technology, S.P.G.C. Nagar, K. Vel-
lakulam Post-625701, India for providing all the facilities to do this
work. Thanks to R. Nagarajan, K. Ponprabhakaran, and N. Than-
gakameshwaran for their participation in this work.
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