Poly(phenylene sulfide) (PPS) is a high performance engineering
thermoplastic with outstanding chemical resistance and thermal stability
(1-3). PPS is generally known to be insoluble in any solvent below 200
[degrees] C. It has a high degree of crystallinity and good retention of
physical properties at elevated temperatures, so it is widely used for
applications including electrical and electronics.
There are several methods to overcome the marginal properties of PPS
including improving impact strength and high heat distortion
temperature. One approach is to manufacture the filled PPS resin as a
glass fiber or glass/mineral filled resin. Another approach is to
increase the glass transition temperature by increasing the molecular
weight of PPS resin. But this method is quite expensive compared with
blending or alloying resins.
Blending of PPS with thermoplastic polymers has been widely
investigated in various patents (4-11) and recently published in the
open literature (12-19). Yoon and White (13) have measured the
interfacial tension between PPS and various polymer melts. PPS and
polysulfone (PSF) blends are considered by Cheung (14-16) and Mai (17),
PPS-polyarylate (PAR) blends by Golovoy (18), PPS-polyetherimide (PEI)
blends by Scobbo (19), PPS - high density polyethylene (HDPE) blends by
Chen (20), and PPS-poly(ethylene terephthalate) (PET) blends by Nadkarni
(21). PPS-PC blends are considered in the patent by Bailey (4).
In our study, we characterize the thermal behavior and phase
morphology of blends containing PPS and PC using differential scanning
calorimeter (DSC) and dynamic mechanical thermal analyzer (DMTA).
Polycarbonate resin was chosen since this polymer shows high toughness
and has a high glass transition temperature. Thermal properties such as
melting temperature, crystallization temperature, heat of fusion, and
other properties were measured. Also we investigated the degradation of
polycarbonate in blends during processing.
The PPS polymer used in this investigation was Ryton E2480
manufactured by Phillips Petroleum Co. Shape of the PPS polymer was
white colored granular type. Glass transition temperature of PPS is
[approximately equal to] 90 [degrees] C and melting temperature is
around 285 [degrees] C. The Ryton E2480 PPS is a linear crystalline
polymer. The general properties of the PPS polymer are listed in Table
The polycarbonate resin used in this study was General Electric
Plastics' Lexan 141L, a medium-viscosity material most commonly
used for injection molding. The PC polymer has a glass transition
temperature of [approximately equal to] 150 [degrees] C. The general
properties of the polycarbonate are listed in Table 1.
Blending and Injection Molding
PPS and PC were dried at 150 [degrees] C under vacuum for 3 h and
then were dry blended. The weight ratios of PPS/PC blend were 80/20,
70/30, 60/40, 50/50, 40/60, 30/70, 20/80 and the dry blended materials
were melt blended using a ZSK-30 W & P co-rotating twin screw
extruder. This twin screw extruder is a modular intermeshing type and
has a screw diameter of 30.7 mm and a screw length of 880 mm. The
temperature was 280 [degrees] C for barrels and 300 [degrees] C near a
die. The screw rotation speed was 150 rpm.
The melt blended pellets were vacuum dried at 130 [degrees] C for 2 h
and injection molding was performed using a Mini-max molder (Custom
Scientific Instruments Inc., CS-183 MMX). The mold temperature was kept
at 70 [degrees] C and the shape of the mold was rectangular.
Measurement of Rheological Properties
Rheological properties of the pure resins and the blends were
measured using a rheodynamic spectrometer (RDS, Rheometrics Inc. 7700)
with a parallel plate type. The range of frequency was from 0.01 to 500
rad/s. The gap distance of the parallel plates was 1.2 mm and all
experiments were carried at 300 [degrees] C and in a nitrogen
Observation of Morphology
Scanning electron microscopy was used for morphological observation
of the PPS/PC blends. A Hitachi [TABULAR DATA FOR TABLE 1 OMITTED]
(Model S-2500) scanning electron microscope was used. The samples were
obtained by fracturing the extrudates in liquid nitrogen. The
magnification was 3000.
Differential scanning calorimetry (DSC, Model 8230) and dynamic
mechanical thermal analyzer (DMTA, Polymer Laboratories) were used in
order to characterize the thermal properties of the PPS/PC blend system.
For the DSC experiment, scanning rate was 10 [degrees] C/min, the weight
of samples was [approximately equal to]10 mg, and the scanning
temperature range was from room temperature to 320 [degrees] C. For
analyzing the crystallization behavior, the samples scanned to 320
[degrees] C were rapidly cooled using liquid nitrogen and re-scanned to
320 [degrees] C. DMTA analysis was performed to measure the bending
modulus and tan [Delta] of the PPS/PC blend.
Measurement of Solution Viscosity
Solution viscosity of polycarbonate in blends was measured in order
to calculate the molecular weight of polycarbonate in the blends.
Polycarbonate was extracted from the blends using a soxhlet equipment
for 24 h and dichloromethane was used as a solvent. Solution viscosity
was obtained from a one-point method (22) using an Ostwald viscometer at
25 [degrees] C with the concentration of polycarbonate solution of 0.005
RESULTS AND DISCUSSION
Melt viscosity of pure polymers and blends was measured as a function
of shear rate using a RDS. Figure 1 shows the viscosity change for
various ratios of PPS/PC blends. Melt viscosity of pure PPS and PC was
[approximately equal to]220 and 420 Pa [center dot] s at 300 [degrees] C
and a range of melt viscosity of PPS/PC blend was from 10 to 50 Pa
[center dot] s. Melt viscosity of PPS / PC blends severely decreased as
a small amount of PPS was added to the PC polymer. This is a very
interesting phenomenon, which implies the better processibility of the
PPS/PC blends due to the reduced viscosity. Actually, this blend can be
processed at 250 [degrees] C using a twin screw extruder. Melt viscosity
of the blends gradually increased as the content of PPS was increased in
A morphological study was carried out using a scanning electron
microscopy (SEM). The fracture of the blend shown in Fig. 2 represents
the incompatibility of the PPS/PC blend. When the content of PC is up to
40 wt%, the PC domain has the spherical shape. The domain shape changes
from sphere to rod between 60/40 and 50/50 of PPS/PC blends, which shows
that the phase is converted from PC domain to PPS domain. This
phenomenon was confirmed in the experiment of dynamic mechanical thermal
analysis [ILLUSTRATION FOR FIGURES 2 AND 4 OMITTED].
The dynamic mechanical thermal analysis for PPS/PC blend as molded
was performed to investigate the glass transition temperature of each
component. The DMTA results of all blends were represented In one figure
to compare the transition temperature, where 1 Hz was chosen. Figure 3
shows the storage bending modulus and Fig. 4 shows the tan [Delta] of
PPS/PC blends. These Figures demonstrate that the glass transition
temperature of the PPS did not change regardless of the composition of
the blends but the glass transition temperature of the polycarbonate was
decreased from 150 to 120 [degrees] C as the PPS was added. This is due
to the degradation of the polycarbonate during blending in the twin
screw extruder. The molecular weight of the PC in the blends were
measured using an Ostwald viscometer, which is listed in Table 2. The
molecular weight was severely decreased from 30,400 to 4,900 as the PPS
was added. The molecular weight-glass transition temperature relations
were confirmed from Cowie's work where he studied the relationship
between MW and [T.sub.g] (23). Also, we can see that the bending modulus
of the blends shows a different trend at high temperature range
[ILLUSTRATION FOR FIGURE 3 OMITTED]. For the low content of PC (less
than 40%), the modulus of the blends changes very slowly at the high
temperature range but for the high content of the PC (more than 50%),
the modulus rapidly decreased. This phenomenon is related to the
property of the matrix in the blends. The blends with PPS matrix show
little change in modulus above the glass transition temperature due to
the crystalline region but the blends with the PC matrix show a rapid
change in modulus above the glass transition temperature. So we can
expect that the phases are inverted between 60/40 and 50/50 of PPS/PC
blends. For the low content of PC (less than 40%), the modulus is
slightly increased around 110 [degrees] C, which is due to the
crystallization of the PPS. This phenomenon is also observed in Fig. 4,
where the tan [Delta] of the pure PPS shows a peak near 110 [degrees] C.
The pure PPS (100/0) shows a large drop of the modulus above the glass
transition temperature comparing with the PPS/PC blends. This is due to
the lower crystallinity of the pure PPS than the PPS/PC blends since the
molecular motion of the blends is easier than that of pure PPS due to
the reduced viscosity of the blends.
[TABULAR DATA FOR TABLE 3 OMITTED]
Differential scanning calorimeter was used to measure the
crystallinity of the PPS in the blends. The samples were scanned up to
320 [degrees] C at the rate of 10 [degrees] C/min after quenching from
320 [degrees] C. Figure 5 shows the DSC thermograms of the PPS/PC
blends. The glass transition temperature of the PPS was observed near 90
[degrees] C but it's difficult to observe the [T.sub.g] of PC in
the blends by DSC. We can see that the [T.sub.g] of the PPS,
crystallization temperature of the PPS, and Tm of the PPS do not change
regardless of composition. The results of the DSC thermogram are
summarized in Table 3. The heat of fusion obtained experimentally was
normalized with respect to PPS content in the blends. The crystallinity
of the blends becomes a little bit higher than the pure PPS due to the
reduced viscosity of the blends and the nucleating ability of PC in the
interface between PPS and PC.
[TABULAR DATA FOR TABLE 4 OMITTED]
A transition temperature change of PPS after annealing was reported
by Cheung (14). This transition is attributed to the glass transition of
the amorphous phase of crystallized PPS. This phenomenon is common to
many semicrystalline polymers and has been reviewed by Struik (24).
Figures 6 and 7 show the results of dynamic mechanical thermal analysis
for the annealed PPS/PC blends. Since the [T.sub.g] of PC in the blends
occurs at temperatures between 120 and 150 [degrees] C, the annealing
condition should be carefully chosen. After annealing at 130 [degrees] C
and 2h, a surface of the blends bulged out and many voids were formed
inside the specimens. The annealing condition of 110 [degrees] C and 4 h
was chosen for annealing the PPS/PC blends from several annealing
experiments. The storage bending modulus of the annealed PPS/PC blends
is represented in Fig. 6 and the tan [Delta] is represented in Fig. 7.
The glass transition temperature of the pure PPS was increased from 94
to 119 [degrees] C after the PPS was annealed. For the annealed blends
it was difficult to observe the glass transition temperature of the PPS
in the blends because of the high crystallinity of the PPS after
annealing. The glass transition temperature of the PC in the blends was
decreased from 152 to 116 [degrees] C after annealing the blends. This
is the same trend as the unannealed blends. We can clearly observe the
different shape of the modulus change above the glass transition
temperature of the PC in the blends from Fig. 6, which represents the
phase inversion between 50/50 and 60/40 of the PPS/PC blends. The glass
transition temperature of the PPS and the PC is summarized in Table 4
from the results of the dynamic mechanical thermal analyzer.
[T.sub.[g.sub.1]] represents the glass transition temperature of the PPS
in the blends and [T.sub.[g.sub.2]] represents the glass transition
temperature of the PC in the blends. The glass transition temperature of
the PPS in the blends shows almost the same temperature regardless of
composition but after annealing the [T.sub.g] of the PPS was increased
to around 118 [degrees] C. The glass transition temperature of the PC in
the annealed blends shows a large decrease when the PPS was added to the
PC, which represents the degradation of the PC in the blends during
processing. This severe degradation of PC occurred when the PC was
blended with PPS, which means the PC molecules are easily broken down by
the PPS molecules in the molten state. This phenomenon is more severe
for the crosslinking type PPS which has a lower molecular weight than
the linear type PPS.
The melt viscosity of the PPS/PC blends was largely decreased as the
PC was added to the PPS polymer. This seems to be due to the degradation
of the PC during blending in the twin screw extruder. The phenomenon was
confirmed by measuring the molecular weight of the PC in the blends. The
molecular weight of the PC was severely decreased from 30,400 to 4900 as
the PPS was added. The phases are inverted between 60/40 and 50/50 of
the PPS/PC blends, which was observed from the SEM pictures and the
results of the dynamic mechanical thermal analysis. The glass transition
temperature of the PPS in the blends did not change regardless of
composition but the [T.sub.g] of the PC in the blends decreased from 150
to 120 [degrees] C, which is due to the degradation of the PC in the
blends. The degradation of the PC becomes severe when the PC is blended
with PPS. The blends with a high content of PPS have a little higher
crystallinity than the pure PPS because of the reduced viscosity of the
blends and the nucleating ability of PC in the interface between PPS and
1. H. W. Hill, Jr., and D. G. Brady, Polym. Eng. Sci., 16, 832
2. L. C. Lopez and G. L. Wilkes, JMS-Rev. Macromol. Chem. Phy., 29,
3. C. C. Martin, J. E. O'Connor, and A. Y. Lou, SAMPE Q., 12
4. F. W. Bailey, U.S. patent 4,021,596 (1977).
5. R. T. Alvarez, U.S. patent 4,017,555 (1977).
6. S. Adelmann, D. Margotte, J. Merten, and H. Vernaleken, U.S.
patent 4,046,836 (1977).
7. G. Salee, U.S. patent 4,211,687 (1980).
8. H. F. Giles, U.S. patent 4,455,410 (1984).
9. R. A. Garcia and R. J. Martinovich, U.S. patent 4,451,607 (1984).
10. B. D. Dean, U.S. patent 4,497,928 (1985).
11. Y. F. Liang, U.S. patent 4,708,983 (1987).
12. C. J. T. Landry and D. M. Teegarden, J. Polym. Sci. (B), 32, 1285
13. P. J. Yoon and J. L. White, J. Appl. Polym. Sci., 51, 1515
14. M. F. Cheung, A. Golovoy, H. K. Plummer, and H. van Oene,
Polymer, 31, 2299 (1990).
15. M. F. Cheung, A. Golovoy, and H. van Oene, Polymer, 31, 2307
16. M. F. Cheung, A. Golovoy, V. E. Mindroiu, H. K. Plummer, Jr., and
H. van Oene, Polymer, 34, 3809 (1993).
17. K. Mai, M. Zhang, H. Zeng, and S. Qi, J. Appl. Polym. Sci., 51,
18. A. Golovoy, M. F. Cheung, and M. Zinbo, Polym. Commun., 30, 322
19. J. J. Scobbo, Jr., SPE ANTEC Tech. Papers, 38, 605 (1992).
20. T. H. Chen and A. C. Su, Polymer, 34, 4826 (1993).
21. V. L. Shingankuli, J. P. Jog. and V. M. Nadkarni, J. Appl. Polym.
Sci., 51, 1463 (1994).
22. O. F. Solomon and I. Z. Ciuta, J. Appl. Polym. Sci., 6, 683
23. J. M. G. Cowie, Eur. Polym. J., 11, 297 (1975).
24. L. C. E. Struik, Polymer, 28, 1521 (1987).
Table 2. Solution Viscosity of PC Extracted From the PPS/PC Blends.
PPS/PC (by wt%) [M.sub.v]