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acrylonitrile copolymers
Eur. Polym. J. Voi.26, No.10, Printed in Great Britain
pp.i149-I151,
SHORT
1990
0014-3057/90 $3.00+0.00 Pergamon Press plc
COMMUNICATIONS
MISCIBILITY OF BISPHENOL-A POLYCARBONATE ACRYLONITRILE COPOLYMERS
WITH~>-METHYLSTYRENE/ "
by S.H.GOH Department of Chemistry, National University 0511, Republic of Singapore.
of Singapore,
Singapore
(Received 7 May 1990)
ABSTRACT The miscibility of bisphenol-A polycarbonate (PC) with various ~>-methylstyrene/acrylonitrile copolymers (pM SAN) having acrylonitrile contents of 7.7-35.9 wt% has been studied by differential scanning calorimetry. Blends were prepared by solution casting from tetrahydrofuran (THF) and by precipitation of the THF solution in n..-hexane. Two glass transitions were observed for each of the blends, showing that PC is immiscible with pMSAN. INTRODUCTION The miscibility
of bisphenol-A
has been studied.
polycarbonate
(PC) with styrene/acrylonitrile
copolymers
Keitz et al. (I) reported that the two glass transition temperatures
(SAN) (Tg)
of PC/SAN blends prepared by melt mixing differed slightly from those of PC and SAN, indicating partial miscibility Recently,
in the blends. A later study by Mendelson concurred
Guest and Daly (3) showed that the shift in T
the plasticizing
effect of the oligomers
an "as received" SAN sample
g in the component
polymers. When PC was blended with
(24 wt% acrylonitrile),
those of PC and SAN. However, when the oligomers of dissolution
the T ' s of the blends deviated from g in the SAN sample were removed by a process
and precipitation,
the T ' s of the resulting g the same as those of the component polymers.
The miscibility
of PC with an ~-methylstyrene/acrylonitrile
wt% of AN was reported by Silvestri
PC/SAN blends were essentially
copolymer
(O(MSAN) containing
32
et al. (4). PC/~ M SAN blends prepared by freeze-drying
were found to be miscible and showed lower critical communication
(2).
values for PC/SAN blends arises from
reports on the miscibility
solution temperature
behaviour.
of PC with~)-methylstyrene/acrylonitrile
This
copolymers
(pMSAN) having AN contents ranging from 7.7 to 35.9 wt%. EXFERIF~NTAL PC (~w = 22,000) was obtained from BDH Chemicals. Various pMSAN samples were prepared by solution polymerization in 2-butanone at reflux temperature for 4 hr using 0.3 w~g of bis(azoisobutyronitril~as initiator. The copolymers were obtained by precipitation of the solutions in excess methanol. The ~$~ contents of p M S ~ samples were determined by elemental analysis for nitrogen. The molecular weights (polystyrene equivalent) of J{S~{ samples were determined by GPC (see Table !). Various PC/pMS~J~ (50/50) blends were prepared by solution casting from tetrahydrofuran (THF) at room temperature. Blends were also prepared by precipitation of THF solutions in n - h e x ane. All the blends were subsequently dried in vacuo at 110 ° for 72 hr. The Tg'S of samples were measured with a Perkin-Elmer DSC-4 differential scanning calorimeter. Each sample was scanned several times between 50 ° and 180 ° using a heating rate of 20 ° per min. The initial onset of the change of slope in the DSC curve was taken as Tg. RESULTS ~$D DISCUSSIO~ The DSC curves of various THF-cast blends are shown in Figure I. Two glass transitions observed for each blend. As shown in Table 2, the lower T those of the pI4S~{ samples but the upper T
were
values are generally close to
values are 7-~7 ° lower than the T of 147 ° for g g PC. The results show that PC is not completely miscible with any of the p M S ~ samples but that the PC phase contains £P; 2 6 , 1 ~
some ~dSAN. 1149
1150
Short Communications
T a b l e i. C h a r a c t e r i s t i c s of pMSAN samples.
AN
Wt%
* M,, ~
~."
Tg
Tg
7.7
21,000
34 000
107 °
108 °
13.6
21,000
42,000
105
ii0
21.3
28,000
52,000
105
114
26.5
27,000
44 000
105
114
29.1
34,000
56 000
105
114
32.3
38,000
62 000
104
116
35.9
31,000
50 000
104
114
and T 2 for p M S A N as prepared.
Tg for p M S A N s u b j e c t e d to a d i s s o l u t i o n
in T H F / p r e c i p i t a t i o n
in a - h e x a n e process.
g H
e
d I
cL
~
b 0 O
- -
f
--
I 60
I
I
I00
I
;
140
]80
Temp. (°C) Fig.
i. DSC curves of T H F - c a s t pMSAN:
(a) 7.7,
(f) 32.3 and
P C / p M S A N blends.
(b) 13.6,
(g) 35.9.
(c) 21.3,
Wt% AN of
(d) 26.5,
(e) 29.1,
Short Communications
Table
2.
Wt%
Tg v a l u e s
AN
of various
THF-cast
1151
blends
blend
Precipitated
blend
7.7
105,
130 °
107,
140 °
13.6
103,
130
108,
137
21.3
105,
138
113,
143
26.5
105,
134
115,
143
29.1
106,
140
115,
142
32.3
106,
128
115,
140
35.9
105,
128
113,
138
The miscibility of a blend depends also on the method of preparation. One recent example is found with blends of PC with poly(methyl methacrylate)
(PMMA) (5-7). PC/PMMA blends cast from
THF are immiscible but those prepared by the precipitation method are miscible. The immiscibility of solution-cast blends has been attributed to the presence of a two-phase loop in the ternary polymer-polymer-solvent system (8). To determine whether the immiscibility of THF-cast PC/pMSAN blends arises from "the solvent effect", the glass transition behaviour of blends prepared by the precipitation method was examined; the T ' s are shown g blend. The lower T ' s of the g The shift in T may indicate g blends had been subjected to
in Table 2. Again, two glass transitions were observed for each precipitated blends are higher than those for THF-cast blends. the presence of PC in the pMSAN phase. However, the precipitated a dissolution/precipitation
process which might have removed the
low molecular weight species of the pMSAN samples. The various pMSAN samples were then subjected to a similar dissolution/precipitation process and the T ' s of the precipitated g samples were found to be higher (see Table 1). Evidently, the lower Tg'S of the precipitated blends are close to those of the reprecipitated pMSAN samples. In other words, the pMSAN phase in the blend is essentially free of PC, indicating the presence of a small amount of pMSAN in the PC phase. In summary, PC is not completely miscible with pMS~4 having AN contents ranging from 7.7 to 35.9 wt%. One of the phases is essentially pure pMSAN and the other is a PC-rich phase containing a small amount of ~4S~4. The author thanks Miss C.S.Lee for determining the molecular weights of ~ S A N
samples.
REFERENCES (1). J.D.Keitz, J.W.Barlow & D.R.Paul, J. A ~ I . Pol~m. Sci., 2~9, 3131 (%984). (2). R.A.Mendelson, J. Pol[m. Sci.! Pol~m. Ph~s.Ed., 2~3, 1975 (1985). (3) M.J.Guest & J.H.Daly, Eur. Pol[m. J., 2.5, 985 (1989). (4). R.Silvestri, M.Rink & A.Pavan, Macromolecules, 2~2, 1402 (1989). (5). J.S.Chiou, J.W.Barlow & D.R,Paul, J. Pol~m. Sci. T Part B t Pol[m. Phys., 2~5, 1459 (1987). (6). J.M.Saldanha & T.Kyu, Macromolecules, 2~0, 2840 (1987). (7). T.Kyu & J.M.Saldanha, J. Pol[m. Sci.! Part C~ Pol~m. Lett., 26, 33 (1988). (8). D.Patterson, Pol~m. En~n@. Scio, 2~2, 64 (1982).
pp.i149-I151,
SHORT
1990
0014-3057/90 $3.00+0.00 Pergamon Press plc
COMMUNICATIONS
MISCIBILITY OF BISPHENOL-A POLYCARBONATE ACRYLONITRILE COPOLYMERS
WITH~>-METHYLSTYRENE/ "
by S.H.GOH Department of Chemistry, National University 0511, Republic of Singapore.
of Singapore,
Singapore
(Received 7 May 1990)
ABSTRACT The miscibility of bisphenol-A polycarbonate (PC) with various ~>-methylstyrene/acrylonitrile copolymers (pM SAN) having acrylonitrile contents of 7.7-35.9 wt% has been studied by differential scanning calorimetry. Blends were prepared by solution casting from tetrahydrofuran (THF) and by precipitation of the THF solution in n..-hexane. Two glass transitions were observed for each of the blends, showing that PC is immiscible with pMSAN. INTRODUCTION The miscibility
of bisphenol-A
has been studied.
polycarbonate
(PC) with styrene/acrylonitrile
copolymers
Keitz et al. (I) reported that the two glass transition temperatures
(SAN) (Tg)
of PC/SAN blends prepared by melt mixing differed slightly from those of PC and SAN, indicating partial miscibility Recently,
in the blends. A later study by Mendelson concurred
Guest and Daly (3) showed that the shift in T
the plasticizing
effect of the oligomers
an "as received" SAN sample
g in the component
polymers. When PC was blended with
(24 wt% acrylonitrile),
those of PC and SAN. However, when the oligomers of dissolution
the T ' s of the blends deviated from g in the SAN sample were removed by a process
and precipitation,
the T ' s of the resulting g the same as those of the component polymers.
The miscibility
of PC with an ~-methylstyrene/acrylonitrile
wt% of AN was reported by Silvestri
PC/SAN blends were essentially
copolymer
(O(MSAN) containing
32
et al. (4). PC/~ M SAN blends prepared by freeze-drying
were found to be miscible and showed lower critical communication
(2).
values for PC/SAN blends arises from
reports on the miscibility
solution temperature
behaviour.
of PC with~)-methylstyrene/acrylonitrile
This
copolymers
(pMSAN) having AN contents ranging from 7.7 to 35.9 wt%. EXFERIF~NTAL PC (~w = 22,000) was obtained from BDH Chemicals. Various pMSAN samples were prepared by solution polymerization in 2-butanone at reflux temperature for 4 hr using 0.3 w~g of bis(azoisobutyronitril~as initiator. The copolymers were obtained by precipitation of the solutions in excess methanol. The ~$~ contents of p M S ~ samples were determined by elemental analysis for nitrogen. The molecular weights (polystyrene equivalent) of J{S~{ samples were determined by GPC (see Table !). Various PC/pMS~J~ (50/50) blends were prepared by solution casting from tetrahydrofuran (THF) at room temperature. Blends were also prepared by precipitation of THF solutions in n - h e x ane. All the blends were subsequently dried in vacuo at 110 ° for 72 hr. The Tg'S of samples were measured with a Perkin-Elmer DSC-4 differential scanning calorimeter. Each sample was scanned several times between 50 ° and 180 ° using a heating rate of 20 ° per min. The initial onset of the change of slope in the DSC curve was taken as Tg. RESULTS ~$D DISCUSSIO~ The DSC curves of various THF-cast blends are shown in Figure I. Two glass transitions observed for each blend. As shown in Table 2, the lower T those of the pI4S~{ samples but the upper T
were
values are generally close to
values are 7-~7 ° lower than the T of 147 ° for g g PC. The results show that PC is not completely miscible with any of the p M S ~ samples but that the PC phase contains £P; 2 6 , 1 ~
some ~dSAN. 1149
1150
Short Communications
T a b l e i. C h a r a c t e r i s t i c s of pMSAN samples.
AN
Wt%
* M,, ~
~."
Tg
Tg
7.7
21,000
34 000
107 °
108 °
13.6
21,000
42,000
105
ii0
21.3
28,000
52,000
105
114
26.5
27,000
44 000
105
114
29.1
34,000
56 000
105
114
32.3
38,000
62 000
104
116
35.9
31,000
50 000
104
114
and T 2 for p M S A N as prepared.
Tg for p M S A N s u b j e c t e d to a d i s s o l u t i o n
in T H F / p r e c i p i t a t i o n
in a - h e x a n e process.
g H
e
d I
cL
~
b 0 O
- -
f
--
I 60
I
I
I00
I
;
140
]80
Temp. (°C) Fig.
i. DSC curves of T H F - c a s t pMSAN:
(a) 7.7,
(f) 32.3 and
P C / p M S A N blends.
(b) 13.6,
(g) 35.9.
(c) 21.3,
Wt% AN of
(d) 26.5,
(e) 29.1,
Short Communications
Table
2.
Wt%
Tg v a l u e s
AN
of various
THF-cast
1151
blends
blend
Precipitated
blend
7.7
105,
130 °
107,
140 °
13.6
103,
130
108,
137
21.3
105,
138
113,
143
26.5
105,
134
115,
143
29.1
106,
140
115,
142
32.3
106,
128
115,
140
35.9
105,
128
113,
138
The miscibility of a blend depends also on the method of preparation. One recent example is found with blends of PC with poly(methyl methacrylate)
(PMMA) (5-7). PC/PMMA blends cast from
THF are immiscible but those prepared by the precipitation method are miscible. The immiscibility of solution-cast blends has been attributed to the presence of a two-phase loop in the ternary polymer-polymer-solvent system (8). To determine whether the immiscibility of THF-cast PC/pMSAN blends arises from "the solvent effect", the glass transition behaviour of blends prepared by the precipitation method was examined; the T ' s are shown g blend. The lower T ' s of the g The shift in T may indicate g blends had been subjected to
in Table 2. Again, two glass transitions were observed for each precipitated blends are higher than those for THF-cast blends. the presence of PC in the pMSAN phase. However, the precipitated a dissolution/precipitation
process which might have removed the
low molecular weight species of the pMSAN samples. The various pMSAN samples were then subjected to a similar dissolution/precipitation process and the T ' s of the precipitated g samples were found to be higher (see Table 1). Evidently, the lower Tg'S of the precipitated blends are close to those of the reprecipitated pMSAN samples. In other words, the pMSAN phase in the blend is essentially free of PC, indicating the presence of a small amount of pMSAN in the PC phase. In summary, PC is not completely miscible with pMS~4 having AN contents ranging from 7.7 to 35.9 wt%. One of the phases is essentially pure pMSAN and the other is a PC-rich phase containing a small amount of ~4S~4. The author thanks Miss C.S.Lee for determining the molecular weights of ~ S A N
samples.
REFERENCES (1). J.D.Keitz, J.W.Barlow & D.R.Paul, J. A ~ I . Pol~m. Sci., 2~9, 3131 (%984). (2). R.A.Mendelson, J. Pol[m. Sci.! Pol~m. Ph~s.Ed., 2~3, 1975 (1985). (3) M.J.Guest & J.H.Daly, Eur. Pol[m. J., 2.5, 985 (1989). (4). R.Silvestri, M.Rink & A.Pavan, Macromolecules, 2~2, 1402 (1989). (5). J.S.Chiou, J.W.Barlow & D.R,Paul, J. Pol~m. Sci. T Part B t Pol[m. Phys., 2~5, 1459 (1987). (6). J.M.Saldanha & T.Kyu, Macromolecules, 2~0, 2840 (1987). (7). T.Kyu & J.M.Saldanha, J. Pol[m. Sci.! Part C~ Pol~m. Lett., 26, 33 (1988). (8). D.Patterson, Pol~m. En~n@. Scio, 2~2, 64 (1982).