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Polymer International
Polym Int 48:587±592 (1999)
Modification of two-component bismaleimide
resin by blending (meth)allyl compounds as
third components
Takao Iijima,* Noriyuki Yuasa and Masao Tomoi
Department of Applied Chemistry, Faculty of Engineering, Yokohama National University, Tokiwadai 79-5, Hodogaya-ku, Yokohama 240,
Japan
Abstract: A two-component bismaleimide resin composed of 4,4'-bismaleimidediphenyl methane
(BDM) and o,o'-diallyl bisphenol A (DBA) (Matrimid 5292 resin) was used as a parent bismaleimide
resin. Modi®cation of the parent bismaleimide resin was examined using several kinds of (meth)allyl
compounds as the third component. The (meth)allyl compounds include triallyl isocyanurate (TAIC),
o,o'-dimethallyl bisphenol A (DMBA) and trimethallyl isocyanurate (TMAIC). In the ternary BDM/
DBA/TAIC blends, the fracture toughness KIC and ¯exural strength for the cured resins decreased with
increasing TAIC content; thermal properties of the cured resins were not deteriorated. In the ternary
BDM/DBA/DMBA blends, KIC and ¯exural modulus for the cured resins increased and their glass
transition temperatures decreased with an increase in DMBA content. Flexural strength increased up
to DMBA 70 eq% blend and then decreased. In the ternary blend of BDM/DBA/TMAIC (1.0/0.5/0.5),
KIC for the blend increased 15%, with retention of ¯exural property and Tg. In the ternary BDM/
DMBA/TMAIC (1.0/0.5/0.5) blend, the cured resin had balanced properties and its KIC increased 50%
compared to the cured Matrimid resin.
# 1999 Society of Chemical Industry
Keywords: bismaleimide resin; modi®cation; (meth)allyl compounds; fracture toughness; ¯exural properties;
thermal properties
INTRODUCTION
Addition polyimide resins are one of the most
important thermosetting polymers. The drawback of
the polyimide resins is that they are brittle and dif®cult
to process. Bismaleimide resins are attractive because
of good processability and involatility. A two-component bismaleimide system (Matrimid 5292 A and B2),
composed of 4,4'-bismaleimidediphenyl methane
(BDM) and o,o'-diallyl bisphenol A (DBA), has been
developed by the Ciba Geigy Corporation to improve
mechanical properties and processability.1 During
curing, DBA copolymerizes with BDM via an enetype linear chain-extension reaction followed by the
Diels±Alder reaction. The brittleness of the cured
resin is improved, compared with the conventional
bismaleimide resins.
The toughness of these thermosetting resins has
been increased by blending with reactive liquid
rubbers such as carboxyl-terminated butadiene acrylonitrile rubbers (CTBN)2 or engineering thermoplastics, e.g. polysulphone (PSF) or poly(ether imide)
(PEI).3 Engineering thermoplastics are interesting
materials as modi®ers for bismaleimide resins from
the viewpoint of the maintenance of mechanical and
thermal properties for the matrix resins. The engineer-
ing thermoplastics used as the modi®ers for bismaleimide resins include PSF,4 PEI,4±6 polyhydantoin,4
poly(ether sulphone),6 poly(ether ketone)s,7,8 6F
polyimide9 and poly(arylene ether phosphine oxide).9
Modi®cation of a two-component bismaleimide
resin (the Matrimid 52922 system) has been carried
out on the basis of information on the toughening of
epoxies by thermoplastics in our laboratory.10±18 NPhenylmaleimide±styrene copolymers (PMS) are
effective modi®ers for both epoxy13,14 and bismaleimide resins,19 and toughening can be achieved
because of the co-continuous phase structure in every
case.
Furthermore, the effect of matrix composition on
toughening was examined by modi®cation of a
bismaleimide with PMS.20 The matrix structure was
controlled by changing the equivalent ratio of DBA
and triallyl isocyanurate (TAIC2), where the extent of
dispersion of the PMS-rich continuous phase increased with increasing TAIC content up to 30 eq%,
and the most suitable extent of dispersion of the cocontinuous phase was observed at TAIC 20 eq%
inclusion to improve the brittleness of the cured
bismaleimide resin. The result indicates that the
matrix composition is one of the important factors in
* Correspondence to: Takao Iijima, Department of Applied Chemistry, Faculty of Engineering, Yokohama National University, Tokiwadai 79-5,
Hodogaya-ku, Yokohama 240, Japan
(Received 4 January 1999; accepted 2 March 1999)
# 1999 Society of Chemical Industry. Polym Int 0959±8103/99/$17.50
587
T Iijima, N Yuasa, M Tomoi
Toagosei Corp (Nagoya, Japan). Other reagents were
used as received.
Measurements
Scheme 1. Structure of monomers.
enhancing the toughness of the cured resins by
blending modi®ers. Hence, it was decided to examine
the in¯uence of the matrix composition on the physical
properties of the cured bismaleimide resin to obtain
the most suitable resin composition for the modi®cation of bismaleimide resins by thermoplastics.
In this paper, modi®cation of the cured Matrimid
5292 A/B resin by using (meth)allyl compounds as the
third component is reported. The (meth)allyl compounds include TAIC, o,o'-dimethallyl bisphenol A
(DMBA) and trimethallyl isocyanurate (TMAIC).
The structures of the (meth)allyl compounds used
are shown in Scheme 1.
EXPERIMENTAL
Materials
The bismaleimide resin was a commercial product
composed of BDM and DBA (Ciba Geigy Corp,
Fribourg, Swtizerland, Matrimid 5292 A/B). The low
viscous liquid TAIC was supplied by Nippon Kasei
Chemical Ind Corp (Tokyo, Japan). DMBA (white
solid) and TMAIC (white solid) were gifts from
The mechanical properties of the cured resins were
determined with a Shimadzu autograph AGS-500B
universal testing machine (Shimadzu, Kyoto, Japan).
Flexural tests were carried out at a crosshead speed of
2mm minÿ1 (JIS K7203). The fracture toughness KIC
was measured in three-point bent geometry with a
crosshead speed of 1mm minÿ1 (ASTM E-399). The
glass transition temperatures (Tg values) of the polyesters and the cured resin were measured as the onset
temperatures by differential scanning calorimetry
(DSC) (Shimadzu DSC 41M type) at a heating speed
of 10 °C minÿ1 under nitrogen or by thermal mechanical analysis (TMA) (Shimadzu TMA 40 type) at a
heating speed of 5 °C minÿ1 under nitrogen.
Thermogravimetric analysis (TGA) was carried out
at a heating rate of 10 °C minÿ1 under nitrogen using
Shimadzu TGA 40 equipment.
Dynamic viscoelastic analysis was performed with a
Rheometrics RDS-II type (Rheometrics Co, Tokyo,
Japan) between ÿ50 and 400 °C at a heating speed of
5 °C minÿ1 at a frequency of 1 Hz.
Curing procedure
BDM and the (meth)allyl compounds were mixed at
130 °C without solvents. The resulting clean mixture
was degassed in vacuo at 130 °C. BDM and the
(meth)allyl components were used in an equivalent
ratio of 1:1. The mixture was poured into a mould,
preheated to 140 °C, to obtain 7 mm thick plaques.
The mould consisted of one pair of upright, metalclip-held, glass plates spaced by U-shaped silicon
rubber pieces. The curing cycle was 160 °C/
3 h ‡ 180 °C/1 h ‡ 200 °C/2 h ‡ 250 °C/6 h. After curing, the oven temperature was decreased from
250 °C to 50 °C at a cooling rate of 25 °C hÿ1.
RESULTS
Mechanical and thermal properties of cured
bismaleimide resins
The curing reactions of the bismaleimide resins were
examined by DSC as a function of matrix composiTcure ( °C)
Table 1. Curing behaviour of the bismaleimde
resins
588
Entry no.
Resin compositions (equivalent ratio)
1
2
3
4
5
6
7
8
BDM/DBA
BDM/DBA/TAIC
BDM/TAIC
BDM/DBA/DMBA
BDM/DMBA
BDM/DBA/TMAIC
BDM/TMAIC
BDM/DMBA/TMAIC
a
1.0/1.0
1.0/0.2/0.8
1.0/1.0
1.0/0.5/0.5
1.0/1.0
1.0/0.5/0.5
1.0/1.0
1.0/0.5/0.5
Tm a ( °C)
Onset
Peak
128
134
125
±
±
128
141
±
182
205
213
186
181
180
±
195
254
265
256
256
254
266
245
273
Melting point.
Polym Int 48:587±592 (1999)
Modi®cation of two-component bismaleimide
Table 2. Physical properties of cured bismaleimide resins
Resin compositions
Entry no.
Control
BDM
1.0
DBA
TAIC
DMBA
(equivalent ratio)
Flexural properties
TMAIC
KIC a
(MPa m1/2)
n
b
Strength a
(MPa)
Modulus a
(GPa)
nb
Tg c ( °C)
1.0
±
±
±
0.62 0.03
8
200 6
4.02 0.11
6
299
0.7
0.5
0.3
0.3
0.5
0.7
±
±
±
±
±
±
0.67 0.01
0.59 0.02
0.47 0.02
9
6
5
162 6
134 10
100 16
3.97 0.04
4.08 0.12
4.00 0.07
9
6
5
286
±d
±d
BDM/DBA/DMBA series
11
1.0
0.5
12
1.0
0.2
±
±
0.5
0.8
±
±
0.73 0.04
1.02 0.06
6
6
202 6
208 10
4.12 0.18
4.29 0.15
5
6
226
181
BDM/DBA/TMAIC series
16
1.0
0.7
15
1.0
0.5
±
±
±
±
0.3
0.5
0.64 0.06
0.71 0.04
6
5
196 3
185 17
3.79 0.11
3.99 0.07
6
5
290
299
BDM/DMBA/TMAIC series
19
1.0
±
20
1.0
±
±
±
0.5
0.3
0.5
0.7
0.97 0.07
0.90 0.06
6
5
206 8
189 11
3.83 0.06
3.89 0.10
4
6
190
210
BDM/DBA/TAIC series
05
1.0
04
1.0
03
1.0
a
The x values show standard deviation.
Number of specimens tested.
c
By DSC.
d
Not obtained by DSC.
b
tions to obtain the optimum curing conditions. Table
1 collects the results of the DSC examination. In the
binary BDM/TMAIC blend, the onset temperature of
curing could not be obtained because of overlapping
with the endothermic peak corresponding to the
melting of TMAIC. The exothermic behaviour between 180 and 300 °C was rather similar, independent
of the resin composition. Curing of the bismaleimide
resins was then carried out under the same curing
conditions.
Table 2 shows representative results for the modi®cation of the bismaleimide resin. The cured bismaleimide resin was transparent in every case. Figure 1
shows the effect of the resin composition on the
mechanical and thermal properties of the cured resins
as a function of TAIC content in the ternary BDM/
DBA/TAIC blend system. The KIC values for the
cured resins were comparable to that for cured
Matrimid resin with blending TAIC up to 50 eq%.
Flexural strength for the cured resins decreased
linearly with increasing TAIC content. Flexural
moduli for the cured resins were equal to that for the
parent Matrimid materials, independent of TAIC
content. The Tg values for the cured resins decreased
slightly on blending with TAIC; when using TAIC
over 30 eq%, the Tg for the cured resins could not be
obtained by DSC or TMA. Dynamic viscoelastic
analysis was examined for the ternary BDM/DBA/
TAIC (1.0/0.2/0.8) blend, but no a-relaxation peak
was observed in the tand curve, and the storage
modulus G' decreased monotonously with increasing
temperature up to 380 °C (the G' values (dyne cmÿ2)
at 25 and 380 °C are 1.46 1010 and 0.875 1010,
respectively): in the previous study, dynamic viscoPolym Int 48:587±592 (1999)
elastic analysis for the cured resin of the ternary BDM/
DBA/TAIC (1.0/0.8/0.2) blend was examined; an
a-relaxation peak (322 °C) in the tand curve was
Figure 1. Effect of the resin compositions on physical properties of the
modified resins as function of TAIC content in the BDM/DBA/TAIC system.
589
T Iijima, N Yuasa, M Tomoi
Figure 2. TGA of the cured resin in the BDM/DBA/TAIC system: (——)
BDM/DBA 1.0/1.0; (- - - -) BDM/DBA/TAIC 1.0/0.5/0.5; (– - –) BDM/TAIC
1.0/1.0 equivalent ratios.
Table 3. Thermal properties of cured bismaleimide resins
Resin compositions
Entry
no.
BMI DBA TAIC TMAIC
(equivalent ratio)
Control 1.0
1.0
±
Td5 a Td10 b Td50 c Tg d
( °C) ( °C) ( °C) ( °C)
±
433
450
505
299
BDM/DBA/TAIC series
04
1.0 0.5
0.5
03
1.0 0
1.0
±
±
440
452
450
461
505
538
±
±
BDM/DBA/TMAIC series
15
1.0 0.5
±
18
1.0 0.3
±
17
1.0 0
±
0.5
0.7
1.0
436
437
441
446
448
450
495
506
502
299
±
±
Figure 3. Effect of the resin compositions on physical properties of the
modified resins in the BDM/DBA/DMBA system.
a
By TGA; 5% weight loss temperature.
By TGA; 10% weight loss temperature.
c
By TGA; 50% weight loss temperature.
d
By DSC.
b
observed and compared to that (309 °C) for the cured
Matrimid resin.20 Then TGA was carried out to
examine the thermal stability of the cured resins (Fig
2). Thermal stability of the cured resin in the ternary
BDM/DBA/TAIC (1.0/0.5/0.5) blend was comparable to that of the cured Matrimid material, and the
cured resin composed of BMI and TAIC had slightly
greater thermal stability than the control (Table 3).
Figure 3 shows the effect of the resin composition on
the mechanical and thermal properties of the cured
resins in the ternary BDM/DBA/DMBA blend system.
The KIC for the cured resins increased with increasing
DMBA. Flexural strength for the cured resins increased gradually with increasing DMBA up to 70 eq%
and then decreased. Flexural moduli increased, and
the Tg value for the cured resins decreased linearly
with increasing DMBA content.
Figure 4 shows the mechanical and thermal properties of the cured resins as a function of TMAIC
content in the ternary BDM/DBA/TMAIC blend
system. KIC for the cured resins increased slightly at
590
Figure 4. Dependence of physical properties of the cured resins on the
resin compositions in the BDM/DBA/TMAIC system.
Polym Int 48:587±592 (1999)
Modi®cation of two-component bismaleimide
depend considerably on the resin compositions in the
present resin systems. The modi®cation behaviour
could be explained by the difference in reactivity
between allyl and methallyl groups, and the presence
or absence of hydroxyl groups in the (meth)allyl
components.
The cure reaction of the Matrimid 5292 system has
been examined by Zahir et al 21: an ene addition
reaction of BDM and DBA occurs to give a 1:1
adduct, followed by a Diels±Alder addition reaction of
other maleimide groups to the ene adduct to give a
densely crosslinked polymer. Furthermore, the curing
was investigated in detail as a function of temperature±
time cure conditions by Fourier transform infrared
spectroscopy and DSC, and the reaction mechanism
was concluded to be22,23
Figure 5. Effect of the resin compositions on physical properties of the
modified resins in the BDM/DMBA/TMAIC system.
the 50 eq% blend. Flexural strength for the cured
resins decreased with increasing TMAIC content.
Flexural moduli for the cured resins were independent
of TMAIC content. The Tg values for the cured resins
were equal to that for the parent resin with blending
TMAIC up to 50 eq%; when using more TMAIC, the
Tg was not observed by DSC and TMA. TGA
indicates that the cured resins in the ternary BDM/
DBA/TMAIC (1.0/0.3/0.7) and binary BDM/TMAIC
(1.0/1.0) blends have similar thermal stability to the
cured Matrimid resin (Table 3).
Figure 5 shows the mechanical and thermal properties of the cured resins in the ternary BDM/DMBA/
TMAIC blend. The KIC values for the cured resins
were larger than the KIC (0.62 MPa mÿ1/2) for the
parent resin except for the binary BDM/TMAIC blend
resin. Flexural strength for the cured resins was
159 MPa and 123 MPa, respectively, in both binary
BDM/DMBA and BDM/TMAIC blends, lower than
that (200 MPa) for the cured Matrimid resin, whereas
the ¯exural strength (206 MPa) of the cured resin was
restored in the ternary BDM/DMBA/TMAIC
(1.0/0.5/0.5) blend and its ¯exural modulus
(3.83 GPa) was comparable to that (4.02 GPa) of the
cured Matrimid resin.
DISCUSSION
Mechanical and thermal properties of the cured resins
Polym Int 48:587±592 (1999)
(1) In the 100±200 °C range the BDM and DBA
monomers react slowly via the ene reaction to form
the ene adduct.
(2) The principal cure reactions occur in the 200±
300 °C range. The ene reaction occurs rapidly.
BDM homopolymerization also occurs. At higher
temperatures homopolymerization of the ene
adduct and crosslinking by the Diels±Alder reaction of the ene adduct and maleimide groups
occur. Above 240 °C, dehydration of the phenolic
hydroxyl groups of DBA occurs to form ether
bonds.
(3) Cure was incomplete due to glassy-state diffusion
restrictions at 250 °C and further cure at 300 °C for
1 or 2 h produced a constant Tg near 350 °C.
However, the resin can undergo further cure at
300 °C via dehydration with associated Tg increase and
mechanical property deteriorations. Hence, it is
essential to control the curing conditions in order to
obtain balanced properties of the cured resins.
The curing reactivities of the (meth)allyl compounds were examined by the model reactions of Nphenyl maleimide (PM) and monomeric (meth)allyl
compounds (2-allyl-4-tert-butylphenol and 2-methallyl-4-tert-butylphenol).24 In the 120±200 °C range
PM and the (meth)allyl compounds react via the ene
reaction regardless of allylic or methallylic groups.
Further, the reactions of PM and the model reaction
products of the ene adducts (2-methyl-1-phenyl
propene (MPP) and trans-1-phenyl propene (PP))
were carried out, where the hydroxylic groups of the
ene adduct were not considered. The Diels±Alder
reaction occurred at 160 °C in the PM/PP reaction
system, but the reaction of PM with MPP was not
observed in the 120±180 °C range. The result indicates
that the Diels±Alder reactivity of methallyl group in
the latter system is suppressed because of steric
hindrance, compared to that of allyl group in the
former system.
The above information is interesting and instructive
when considering the effect of the matrix structure on
the mechanical and thermal properties of the present
cured resins.
591
T Iijima, N Yuasa, M Tomoi
The exothermic behaviour in DSC indicates that the
ene reactivities of allyl groups in TAIC are similar to
those in DBA (Table 1). In the ternary (BDM/DBA/
TAIC) blends, TAIC was incorporated into the
network only by the ene reaction, and the ¯exural
moduli of the cured resins were maintained because of
its trifunctional rigid isocyanurate ring structure (Fig
1). However the ¯exural strength decreased with
increasing TAIC content, perhaps because of weaker
intermolecular bonding: the Diels±Alder reaction and
the etheri®cation of phenolic groups are absent in the
reaction of BDM with TAIC. KIC for the cured resin
was comparable to the cured Matrimid resin with
increasing TAIC content up to 50 eq%. Thermal
properties for the cured resins were not deteriorated
on TAIC inclusion.
In the ternary (BDM/DBA/DMBA) blends, the Tg
values for the cured resins decrease with increasing
DMBA content (Fig 3). This indicates that the
crosslink density of the network decreases because of
lower Diels±Alder reactivities of methallylic groups in
DMBA than those of allylic groups in DBA. In
general, a decrease in the crosslink density leads to
enhancement in toughness of the cured resin. Despite
the decrease in Tg, the ¯exural moduli of the cured
resins were equal to or larger than the value of the
cured Matrimid resin. Flexural strength was also
maintained except for the binary (BDM/DMBA)
blends.
In the ternary (BDM/DBA/TMAIC) blends,
TMAIC was also incorporated into the network only
by the ene reaction. Flexural strength for the cured
resin decreased gradually with increasing TMAIC
content. However, the cured resins have balanced
properties compared to the cured materials in the
ternary (BDM/DBA/TAIC) blends. Especially, in the
ternary BDM/DBA/TMAIC (1.0/0.5/0.5) blend, KIC
for the cured resin increases with no deterioration of
¯exural properties and Tg (Fig 4). This resin composition is interesting as the matrix resin for modi®cation
with various kinds of thermoplastic polymers.
The modi®cation of the ternary (BDM/DMBA/
TMAIC) blends is interesting. When using the ternary
BDM/DMBA/TMAIC (1.0/0.5/0.5) blend, the cured
resin has balanced properties: KIC increased 50%, and
¯exural strength and modulus for the cured resin were
comparable to those for the cured Matrimid resin, but
Tg decreased slightly (Fig 5). This resin composition
may be also suitable to enhance the toughness by
blending with thermoplastics.
CONCLUSIONS
A bismaleimide resin composed of 4,4'-bismaleimidediphenyl methane (BDM) and o,o'-diallyl bisphenol A
(DBA) (Matrimid 5292 resin) was used as the twocomponent bismaleimide resin. Modi®cation of the
parent bismaleimide resin was examined by using
592
several kinds of (meth)allyl compounds as the third
component. In the ternary BDM/DBA/TAIC blends,
the fracture toughness KIC, and ¯exural strength for
the cured resins decreased with increasing TAIC
content. In the BDM/DBA/DMBA blends, KIC and
¯exural modulus for the cured resins increased and Tg
decreased with increase in DMBA content. In the
ternary blends of BDM/DBA/TMAIC (1.0/0.5/0.5),
KIC increased 15% with retention of ¯exural property
and Tg. In the ternary BDM/DMBA/TMAIC (1.0/0.5/
0.5) blend, the cured resin had balanced properties
and KIC increased 50% compared to the cured
Matrimid resin. The results indicate that mechanical
and thermal properties of the parent Matrimid resin
can be modi®ed by blending the (meth)allyl substances as the third components.
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Polym Int 48:587±592 (1999)
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