Dynamic Mechanical Properties
5.1. Introduction
5.2. Results and Discussion
5.2.2.1. Uncompatibilised blends Figure 5.1: Variation of storage modulus (E’) of PA and PS with temperature.
Figure 5.2: Variation of tan δ of PA and (PS) with temperature
Figure 5.3: Variation of loss modulus (E”) of PA and polystyrene (PS) with temperature.
Figure 5.4: Variation of storage modulus (E’) of the uncompatibilised PA/ PS blends with temperature
Figure 5.5: Effect of blend composition on E’ values
Figure 5.6 (a): Variation of tan δ of the uncompatibilised (N80, N70 & N50) blends with temperature
Figure 5.6 (b): Variation of tan δ of the uncompatibilised blends (N30 & N20) with temperature
Table 5.1: Tg values for PA and PS from damping curves
Figure 5.6(c): Variation of tanδ max due to PA and PS in uncompatibilised blends with blend composition.
Figure 5.7: Variation of loss modulus (E”) of uncompatibilised (N80, N50 & N20) blends with temperature.
132 Chapter 5
Theoretical modelling of the dynamic mechanical properties Figure 5.8 (a): Experimental and theoretical curves of storage modulus of
uncompatibilised PA/PS blends as a function of wt % of PA at 70°C.
Figure 5.8 (b): Experimental and theoretical curves of storage modulus for N20 blends in the whole temperature range
Figure 5.8 (c): Experimental and theoretical curves of storage modulus for N80 blends in the whole temperature range
Viscoelastic properties of compatibilised blends Figure 5.9: Variation of storage modulus as a function of temperature for
N80 blends compatibilised with SMA8
Figure 5.10: Effect of compatibiliser (SMA8) concentration on the storage modulus of N80 blends
Figure 5.11: Effect of compatibilisation (SMA8) on the damping behaviour of N80 blends
Figure 5.12: Variation of storage modulus as a function of temperature for N20 blends compatibilised with SMA8
Figure 5.13: Effect of compatibiliser (SMA8) concentration on the storage modulus of N20 blends
Figure 5.14: Effect of compatibilisation (SMA8) on the damping behaviour of N20 blends
Figure 5.15: Loss modulus curves as a function of temperature for N80 and N20 blends compatibilised with SMA8 (1%)
Figure 5.16: Effect of compatibiliser (SEBS-g-MA) concentration on the storage modulus of N80 blends
Figure 5.17: Effect of compatibilisation (SEBS-g-MA) on the damping behaviour of N80 blends
Dynamic Mechanical Properties 133
Figure 5.18: Effect of compatibiliser (SMA28) concentration on the storage modulus of N80 blends
Figure 5.19: Effect of compatibilisation (SMA28) on the damping behaviour of N80 blends
Figure 5.20: Loss modulus curves as a function of temperature for N80 blends compatibilised with SEBS-g-MA (5%) and SMA28 (0.5%)
Figure 5.21: Storage modulus for uncompatibilised and
compatibilised 80 blends
Table 5.2: Damping properties of compatibilised N80 blends.
Figure 5.22: Storage modulus of compatibilised blends-Comparison with theory
Conclusion
References:
1
Chapter 5
Dynamic Mechanical Properties
5.1. Introduction Scientific interest in polymer blends has intensified in the recent years due to
their application in many technological products. However, the major
challenge in polymer blending is the heterogeneous nature of the blends, due
to the lack of miscibility in polymer blends. Therefore many attempts have
been made to enhance the miscibility in polymer blends and the incorporation
of compatibiliser was proved to be a successful approach [1-22].
Several experimental techniques are being used to characterise polymer
blends. Polymer glass transition temperature (Tg) has been accepted as a
diagnostic aid for determining the miscibility of polymer blends. Dynamic
Mechanical Analysis (DMTA) has the advantages of a thousand-fold
greater sensitivity when studying glass transition phenomena and the ability
to detect all secondary motional transitions at low temperatures which
influence the impact strength characteristics [23-25]. DMA measures the
stiffness and mechanical damping or internal friction/thermal dissipation of
a dynamically deformed material as a function of temperature. Literature
shows that DMA has been accepted as a powerful tool in characterising
polymer blends [7-22].
Very recently Kong and Al-Malaika studied the viscoelastic properties of
PET/EPR blends and found that the peak position of tanδ varies with blend
composition [22]. The dependence of tanδ peak on weight ratios of individual
polymer components of the blends based on different polymer combinations has
2
been reported previously and has been related to the differences in blend
morphology [26-28]. Thomas and co workers reported the effect of
compatibilisation on the viscoelastic properties of various blends [16-21].
The present chapter deals with the viscoelastic properties of nylon
copolymer (PA)/polystyrene (PS) blends. The effect of blend composition
and compatibilisation on the viscoelastic properties has been analysed.
SMA8, SMA28 and SEBS-g-MA are used as compatibilisers. We have
made an attempt to correlate the viscoelastic properties with the phase
morphology of the blends in which the morphology of both the
compatibilised as well as the uncompatibilised blends are accounted. The
experimentally obtained results have been compared with certain
theoretical models.Their correlation has been discussed.
5.2. Results and Discussion
5.2.2.1. Uncompatibilised blends The dynamic mechanical properties such as storage modulus, loss modulus
and damping behaviour of the hompolymers were analysed over a
temperature range of -100 to 150°C at a frequency of 1Hz.The storage
moduli and tanδ for the neat polymers has been plotted in Figures 5.1 and
5.2 respectively.
3
-100 -50 0 50 100 150
0
1
2
3
4
Log
E' (
MP
a)
Temperature°C
N100 N0
Figure 5.1: Variation of storage modulus (E’) of PA and PS with temperature.
The value of E′ signifies the stiffness of the material. At any fixed rate of
deformation, the temperature at which E′ starts to decrease rapidly corresponds
to the glass transition temperature (Tg). PS exhibits higher modulus than PA up
to its Tg. At the transition zone there is drastic decrease in modulus with
temperature. This is because at the transition zone segmental mobility sets in
followed by a corresponding decrease in the E′ values. Thus the storage modulus
drops drastically at about 100°C for PS and for PA the drop is at about 40°C. In
the case of PS there is a drastic fall around Tg, whereas the modulus drop for PA
is less due to its crystalline nature. For crystalline materials only the amorphous
part undergoes segmental motion at Tg while the crystalline regions remain
unaffected till the melting temperature. Thus in the case of PA a rubbery plateau
is observed after Tg
4
-100 -50 0 50 100 150
0
1
2
3
-100 -50 0 50 100 1500.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
tanδ
Temperature °C
Temperature (°C)
N100 N0
tanδ
Figure 5.2: Variation of tan δ of PA and (PS) with temperature
The tanδ curve for PA consists of two peaks. The transition occurring
around high temperature (around 48°C) is the α relaxation and this
corresponds to the glass transition of the amorphous phase. The transition
at the lower temperature (around -50°C) corresponds to the β relaxation
which has been related to movements involving carbonyl groups which
have formed hydrogen bonds with absorbed water [30, 31]. The tan δ curve
for PS shows maxima at 114°C which corresponds to the Tg of PS. The
damping curves indicate that PS has high damping than PA up to it’s Tg
(114°C). The loss modulus curve for PA and PS are presented in Figure
5.3, which shows a loss maximum at 42°C for PA and 104°C for PS. PA
shows a β relaxation peak around -50°C.
5
-100 -50 0 50 100 150-100
0
100
200
300
400
500
600
700
E" (
MPa
)
Temperature °C
N100 N0
Figure 5.3: Variation of loss modulus (E”) of PA and polystyrene (PS) with temperature.
The storage modulus value for the different blend compositions is shown in
Figure 5.4. All the blends show a modulus value in between the component
polymers of which the PS rich blends exhibit moderately large values at room
temperature. The variation of storage modulus as a function of PA concentration
in the blends at 25°C is shown in Figure 5.5. from which it can be observed that
with the increase in PA concentration the storage modulus decreases. The curve
exhibits a negative deviation from the additivity line indicating the immiscibility
of the system. This negative deviation can be attributed to the lack of interfacial
interaction and adhesion between the polar PA phase and the non polar PS
phase. It can also be seen that N50 blends have the lowest storage modulus. This
behaviour can be explained on the basis of the morphology of the system. Phase
morphology analysis of uncompatibilised blends suggest that N50 blends exhibit
a co-continuous morphology whereas in all the other cases the system shows
dispersed phase morphology (chapter 3). The morphological observation
through SEM analysis was further supported by the co-continuity index
6
measurement via solvent extraction technique and is presented in chapter 3.
Hence the tendency of the N50 blends to exhibit the minimum storage modulus
can be attributed to the co-continuous nature of the system at that particular
composition. Castro et al. [32] while anlaysing the low frequency
viscoelastic behaviour in immiscible polymer blends reported that the
decrease in the G’ coincides with the creation of continuous phases in the
blend. The variation of slope in the storage modulus-composition curve at the
phase inversion region is reported by George et al. [21].
-100 -50 0 50 100 1500.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
g(
)
Temperature °C
N80 N70 N50 N30 N20
Figure 5.4: Variation of storage modulus (E’) of the uncompatibilised PA/ PS blends with temperature
7
0 20 40 60 80 1001000
1500
2000
2500
3000
3500
E' (
MP
a)
Wt % of PA
Figure 5.5: Effect of blend composition on E’ values.
The effect of blend compositions on the damping behaviour of blends are shown
in Figure 5.6 (a & b). All the blends show two peaks indicating the
immiscibility between the phases. In the case of PA rich blends (N80 and
N70), the β relaxation peak is also visible. The Tg values for PA and PS from
the damping curves is shown in Table 5.1.The polystyrene Tg remains almost
unaffected on blending. The PA Tg shifts slightly towards the high
temperature range with PS content which may be due to the low moisture
absorption of the blends compared to pure PA. PA rich blends show a β
relaxation peak around -50°C which is due to the absorbed moisture as
discussed earlier [19,20].
8
-100 -50 0 50 100 150
0.0
0.1
0.2
0.3
0.4
0.5
Temperature°C
N80 N70 N50
Figure 5.6 (a): Variation of tan δ of the uncompatibilised (N80, N70 & N50) blends with temperature
-100 -50 0 50 100 150
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
Temperature°C
N30 N20
Figure 5.6 (b): Variation of tan δ of the uncompatibilised blends (N30 & N20) with temperature
9
Table 5.1: Tg values for PA and PS from damping curves
Tg (°C) Sample
PA PS
N100 47.7
N80 47.7 112.2
N70 51.8 111.1
N50 52.6 112.2
N30 53.3 111.1
N20 53.2 112.2
N0 113
The effect of blend composition on the damping properties is shown in
Figure 5.6©. It is evident from the figure that tan δ maximum due to the PA and
PS increases with the concentration of the respective phases. It is known that the
height of the dynamic transition of a component of a composite apparently
reflects the relative quantity of the component itself [33-35]. PS is showing high
damping compared to PA in whole range of compositions studied. Even though
brittle, the high damping values shown by PS may be due to its amorphous
nature, while PA which is semi crystalline exhibits poor damping.
10
0 20 40 60 80 100
0.06
0.08
0.10
0.12
0.14
0.16
0.18due to PA due to PS
Wt. farction of PA
tan δ
max
due
to P
A
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
tan δ max due to PS
Figure 5.6©: Variation of tanδ max due to PA and PS in uncompatibilised
blends with blend composition.
Variation of loss modulus with temperature for the blends (N80, N50 and N20)
is shown in Figure 5.7. The plot shows that the blends exhibit two loss maxima
corresponding to the glass transitions of PA (around 50°C) and PS (around
100°C) phases indicating the immiscibility of the blends.
-100 -50 0 50 100 1500
50
100
150
200
250
300
350
E"(
MP
a)
Temperature°C
N80 N50 N20
Figure 5.7: Variation of loss modulus (E”) of uncompatibilised (N80, N50
& N20) blends with temperature.
11
Theoretical modelling of the dynamic mechanical properties Theoretical models including parallel, series and Coran’s model have
been applied to predict the storage modulus of the binary blends. The upper
bound parallel model is given by
E = E1φ1 + E2φ2 (5.1)
Where E is the property of the composite, E1 and E2 are the corresponding
properties of components 1 and 2, respectively. In a parallel model the
components are arranged parallel to one another so that an applied stress
elongates each component by the same amount. In the case of the lower
bound series model, where the components are arranged in series with the
applied stress, the equation is
1
1 2
1
LE E E2φ φ
= + (5.2)
The properties of an incompatible blend usually are in between
upper bound parallel model (MU) and lower bound series model (ML).
According to Coran’s equation [36]
( )U L LM f M M M= − + (5.3)
where f can vary between zero and unity. The value of f is given by
(5.4) ( 1nH Sf V nV= )+
where n contains the aspects of phase morphology. VH and VS are the
volume fractions of the hard phase and soft phase, respectively.
Takayanagi proposed a series-parallel model [37, 38] in which, the concept
of percolation is introduced. It is a phenomenological model consisting of
12
mixing rule between two simple models involving connection in series (Reuss
prediction) or in parallel (Voigt prediction) of the components. According to
this model,
(5.5) E = (1-λ)E1 + λ[ (1-φ)/E1 + (φ/E2)]-1
E1 is the property of the matrix phase, E2 is the property of the dispersed
phase, and φ is the volume fraction of the dispersed phase and is related to
the degree of series-parallel coupling. The degree of parallel coupling of
the model can be expressed by
(5.6) % parallel= [φ (1- λ) / (1- φ λ)] x 100
Experimental and theoretical curves of the storage modulus of the
PA/PS blends at 70°C are shown in Figure 5.8(a). The experimental curve
lies between the parallel and series model. Takayanagi model based on
series parallel coupling gives the best fit with the experimental observation.
This model takes into account the contribution from the respective
components related to their volume fractions. The theoretical values are
calculated on the basis of % parallel coupling obtained using equation (5.6).
For a value of n=5, the Coran’s model agrees well with the experimental
values as evident from the Figure 5.8 (a). This is mainly because Coran’s
model takes into account the aspects of phase morphology and hence shows
good agreement with the experimental values.
13
0 25 50 75 1000
1000
2000
3000
43
Stor
age
mod
ulus
(E')
[MPa
]
Wt % of PA
Experimental parallel [1] series [2] Coran (n=5) [3] Takayanagi [4]
1
2
Figure 5.8 (a): Experimental and theoretical curves of storage modulus of
uncompatibilised PA/PS blends as a function of wt % of PA at 70°C.
Comparison of experimental values with theoretical predictions has been
made for the whole temperature range for N20 and N80 blends and is
plotted in Figure 5.8 (b) and Figure 5.8 (c). Both the N80 and N20 blends
show good agreement with the Takayanagi and Coran’s model especially in
the temperature range in between the Tgs of the component polymers.
Takayanagi shows good agreement with the experimental values for N20
and N80 blends at 5% parallel coupling which accounts the contribution of
each phases relative to their volume fractions. As mentioned earlier the
model considers the morphological aspects of the system and the term ‘f’ in
the equation is a function of phase morphology. If only the soft phase were
continuous, ‘f’ would be low (f=0.02 for N80 blends, where PA forms the
continuous phase), ‘f’is closer to unity if the hard phase is continuous
(f=0.6 for N20 blends, where PS forms the continuous phase). Thus for the
compositions with dispersed phase morphology, the model shows good
14
agreement with the suggested ‘f’ values thus resulting in good correlation
between the experimental and predicted values. The model proposed by
Takayanagi also shows good agreement with the experimental values for
N20 and N80 blends at 5% parallel coupling.
-100 -50 0 50 100 150
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
2
Log
E' (
MP
a)
Temperature (°C)
Expt Parallel [1] Series [2] Coran (n=5) [3] Takayanagi [4]
134
Figure 5.8 (b): Experimental and theoretical curves of storage modulus
for N20 blends in the whole temperature range
-100 -50 0 50 100 1500.5
1.0
1.5
2.0
2.5
3.0
3.5
2
LogE
'(MP
a)
Temperature (°C)
Experimental parallel [1] series [2] Coran (n=5) [3]
N801
3
4
Figure 5.8 (c): Experimental and theoretical curves of storage modulus
for N80 blends in the whole temperature range
15
Viscoelastic properties of compatibilised blends The storage modulus curves for N80 blends compatibilised with SMA8 are
shown in Figure 5.9. The Figure shows that there is an increase in storage
modulus upon compatibiliser addition. The influence of comaptibiliser
concentration on the storage modulus of the blends at three different
temperatures 1. 25°C (below the Tg of both the components); 2. 80°C (in
between the Tg of both the components and 3. 120°C (above the Tg of both
the components) are shown in Figure 5.10.The storage modulus shows high
values below the Tg of the component polymers and shows a drastic drop
beyond the Tgs. The blends exhibited a maximum storage modulus at room
temperature on addition of 2% SMA8. This result shows good correlation
with the morphology of the system, where a minimum particle size is
observed for blends with 2% compatibiliser addition and is discussed in
chapter 3.
-100 -50 0 50 100 1500.5
1.0
1.5
2.0
2.5
3.0
3.5
Log
E' (
MP
a)
Temperature°C
N80 SMA8 (1%] SMA8 (2%) SMA8 (4%)
Figure 5.9: Variation of storage modulus as a function of temperature for
N80 blends compatibilised with SMA8
16
0 1 2 3 4 5
2.0
2.2
2.4
2.6
2.8
3.0
3.2
Log
E'(M
Pa)
Wt% of SMA8
25°C 80°C 120°C
Figure 5.10: Effect of compatibiliser (SMA8) concentration on the storage
modulus of N80 blends
The tan δ curves for compatibilised N80 blends are depicted in Figure 5.11.
The plot shows the α and β relaxation peaks for the polyamide phase. The
Tg of polyamide shifts towards high temperature upon compatibilisation
which indicates that compatibiliser addition resulted in interfacial chemical
reaction. The grafted copolymers that are formed in-situ during melt mixing
preferentially reside at the interface, improve interfacial adhesion through
chemical linkages, and allow a finer dispersion. A minimum domain size was
obtained for 2% compatibiliser loading. Further addition of compatibiliser
does not have much effect on the domain size and we can say that by 2%
addition there is almost a leveling off in particle size (chapter 3). We
obtained a maximum storage modulus for the system compatibilised with
2% SMA which can be attributed to the finest and most uniform dispersion
of PS phase in the PA matrix.
17
-100 -50 0 50 100 150
0.00
0.05
0.10
0.15
0.20
0.25
0.30
tan δ
Temperature (°C)
N80 SMA8 (1%) SMA8 (2%) SMA8 (4%
Figure 5.11: Effect of compatibilisation (SMA8) on the damping behaviour
of N80 blends
Tg of PS does not show any change upon compatibilisation. But the tan δ
maximum corresponding to the PS phase increases upon SMA addition
which can be attributed to the increase in polystyrene concentration with
increased SMA content.
The effect of compatibilisation on the viscoelastic properties of N20 blends
using SMA8 has also been analysed. The influence of SMA loading on the
storage modulus of N20 blends are shown in Figure 5.12. It can be seen
that at temperatures lower than the Tg of PS, the storage modulus increases
upon compatibiliser loading which almost levels off by the addition of
0.5% compatibiliser. The observation is more clearly depicted in Figure 5.13,
where the storage modulus variation at two temperatures for different
compatibiliser loading is plotted. At temperatures beyond Tg of PS the
storage modulus remains almost the same for both the uncompatibilised
and compatibilised blends. In this case also the increase in storage modulus
upon SMA loading can be attributed to the compatibilising action of SMA
18
resulting from the interfacial chemical reaction between anhydride groups
of SMA and amine end groups of PA as depicted in scheme 3.1.
-100 -50 0 50 100 1500
1
2
3
4
N20 SMA8 (0.1%) SMA8 (0.2%) SMA8 (0.5%) SMA8 (1%)
Log
E' (
MP
a)
Temperature (°C)
Figure 5.12: Variation of storage modulus as a function of temperature for N20 blends compatibilised with SMA8
0.0 0.2 0.4 0.6 0.8 1.0
3.20
3.25
3.30
3.35
3.40
3.45
Log
E'(M
Pa)
Wt% of SMA8
25°C 80°C
Figure 5.13: Effect of compatibiliser (SMA8) concentration on the storage modulus of N20 blends
19
The compatibilising action of the copolymer SMA8 is evident from the
morphology of the compatibilised N20 blends. As in the case of N80 blends
here also the incorporation of SMA has resulted in reduction of domain size
(discussed in chapter 3). The reduction in domain size along with the increase in
storage modulus on compatibilisation suggests that SMA8 can be considered as
a good compatibiliser for PA/PS system.
The variation of tan δ of compatibilised N20 blends is shown in Figure 5.14. We
can see that on compatibiliser loading the Tg of PS is shifted slightly to lower
temperatures which suggest that the blends become more compatible with the
addition of SMA8. The shift in PA Tg is not obvious due to the low PA
concentration in the system, but seems that the peak is slightly broadened which
is an indication of improved compatibility. Thus in N20 system, the Tg of the
components shows a tendency to become closer suggesting the improved
compatibility of the blends upon the addition of SMA8.
The loss modulus curve for N80 and N20 blends compatibilised with SMA8 is
shown in Figure 5.15.
-50 0 50 100 150
0.0
0.4
0.8
1.2
1.6
tan δ
Temperature (°C)
N20 SMA8 (0.2%) SMA8 (0.5%) SMA8 (1%)
20
Figure 5.14: Effect of compatibilisation (SMA8) on the damping behaviour of N20 blends
-100 -50 0 50 100 1500
100
200
300
400
E' (
MP
a)
Temperature (°C)
N80 (SMA8 (1%)] N20 (SMA8 (1%)]
Figure 5.15: Loss modulus curves as a function of temperature for N80 and
N20 blends compatibilised with SMA8 (1%)
In addition to SMA8, influence of SEBS-g-MA and SMA28 on the visco
elastic properties of N80 blends were investigated. Based on phase
morphology studies (chapter 3) and mechanical properties (chapter 4)
SEBS-g-MA proved to be a good compatibiliser in PA/PS blends. In this
section we investigated the compatibilisation efficiency of SEBS-g-MA on
the viscoelastic properties of N80 blends. Effect of addition of SEBS-g-MA
on the storage modulus of N80 blends is shown in Figure 5.16. The storage
modulus of the compatibilised blends is higher than that of the
uncompatibilised blend. But it can be observed from the figure that at
higher loadings of SEBS-g-MA, the modulus reduces which may be due to
the flexible nature of the compatibiliser.
21
-100 -50 0 50 100 1500.5
1.0
1.5
2.0
2.5
3.0
3.5
LogE
' (M
Pa)
Temperature(°C)
N80 SEBS-g-MA (1%) SEBS-g-MA (5%) SEBS-g-MA (8%)
Figure 5.16:Effect of compatibiliser (SEBS-g-MA) concentration on the
storage modulus of N80 blends
The influence of SEBS-g-MA incorporation on the dissipation factor (tan δ)
of N80 blends is given in Figure 5.17. From the Figure it is well evident
that the Tg corresponding to PA experienced a positive shift with the
addition of SEBS-g-MA. This is due to the interfacial chemical reaction
taking place between the MA groups of the compatibiliser and the amine
end groups of PA.
22
-100 -50 0 50 100 1500.00
0.05
0.10
0.15
0.20
0.25
Temperature (°C)
N80 SEBS-g-MA (1%) SEBS-g-MA (5%) SEBS-g-MA (8%)
Figure 5.17: Effect of compatibilisation (SEBS-g-MA) on the damping
behaviour of N80 blends
Effect of compatibilisation using SMA28 on the storage modulus of N80
blends are shown in Figure 5.18. It can be observed from the figure that up to
0.5% addition of the compatibiliser the storage modulus of the blends has been
increased in the whole range of temperature studied. The addition of the
compatibiliser beyond 1% resulted in a decrease of storage modulus. The
phase morphology studies of SMA28 compatibilised blends showed that at
higher concentration, the compatibiliser failed to act as an interfacial modifier
(chapter 3). Analysis of mechanical properties also suggested that after 0.5%
loading SMA28 could not produce enhancement of mechanical properties
(chapter 4). We assume that owing to the high polarity of SMA28, the
compatibiliser at higher concentrations might have formed micelles in the PA
phase instead of locating at the interface [39, 40]. This might have resulted in
the increased domain size and inferior properties. According to the studies of
Harrats et al. [41] the heavily grafted copolymer formed during the interfacial
23
reaction might have been expelled from the interface due to its energetically
unfavourable design and formed micelles.
-100 -50 0 50 100 150
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Log
E' (
MP
a)
Temperature (°C)
N80 SMA28 (0.2%) SMA28 (0.5%] SMA28 (1%) SMA28 (2%)
Figure 5.18: Effect of compatibiliser (SMA28) concentration on the
storage modulus of N80 blends
-100 -50 0 50 100 150
0.00
0.05
0.10
0.15
0.20
0.25
tan δ
Temperature (°C)
N80 SMA28 (0.2%) SMA28 (0.5%) SMA28 (1%) SMA28 (2%)
Figure 5.19: Effect of compatibilisation (SMA28) on the damping
behaviour of N80 blends
The tan δ curves for SMA28 compatibilised N80 blends are plotted in
Figure 5.19.With the incorporation of compatibiliser an increase in the Tg
corresponding to PA is observed. This can be attributed to the interfacial
24
chemical reaction taking place between the compatibiliser and the PA
phase. This in turn reduces the segmental mobility and hence increases the
Tg of the blends as evident from Figure 5.19.
Representative plots showing the variation of loss modulus with temperature
for N80 blends compatibilised with SEBS-g-MA and SMA 28 are given in
Figure 5.20. The plot shows two Tgs corresponding to PA and PS, indicating
that the blends remain immiscible even after compatibilisation with the
styrenic co-polymers.
-100 -50 0 50 100 1500
50
100
150 SEBS-g-MA (5%) SMA28 (0.5%)
E" (M
Pa)
Temperature (°C)
Figure 5.20: Loss modulus curves as a function of temperature for N80
blends compatibilised with SEBS-g-MA (5%) and SMA28 (0.5%)
The efficiency of the three compatibilisers was compared based on their
influence on the viscoelastic properties of the N80 blends. The storage
moduli for N80 blends compatibilised with the three different
compatibilisers are shown in Figure 5.21. The figure indicates that SMA8
resulted in higher storage modulus followed by SMA28 .
25
-100 -50 0 50 100 1501.0
1.5
2.0
2.5
3.0
3.5
N80 SMA8 (2%) SMA28 (0.5%] SEBS-g-MA (5%)
Log
E' (M
Pa)
Temperature (°C)
Figure 5.21: Storage modulus for uncompatibilised and compatibilised 80 blends
The damping properties of the three compatibilisers are shown in Table 5.2.
where tan δ max due to PA and PS in the compatibilised blends are
presented. Damping due to PS seems to be unaffected upon
compatibilisation, whereas tan δ(max) due to PA increases on
compatibilisation. The table indicates, N80 blends compatibilised with
SEBS-g-MA exhibits the maximum damping. This observation can be
devoted to the high damping nature of the rubbery polymer when compared
with the other compatibilisers
26
Table 5.2: Damping properties of compatibilised N80 blends.
Sample tanδ (max) due to PA
tanδ (max) due
to PS
N80 0.151 0.214
SMA8 (2%) 0.157 0.222
SMA28 (0.5%) 0.167 0.210
SEBS-g-MA (5%) 0.175 0.212
The storage modulus obtained for compatibilised blends are compared with
theory. The compatibilised blends exhibited a positive deviation with
respect to Coran’s and Takayanagi models which fit well with the
uncompatibilised blends. The deviation from Coran’s model which was
proposed for incompatible blends suggests that with the incorporation of
the styrenic copolymers the blends have become compatible. The positive
deviation with respect to Takayanagi model can be attributed to the
synergism in storage modulus obtained through compatibilisation.
27
-100 -50 0 50 100 1500.5
1.0
1.5
2.0
2.5
3.0
3.5
Log
E'(M
Pa)
Temperature(°C)
N80 parallel series Coran (n=5) Takayanagi SMA8(2%) SEBS-g-MA[5%] SMA28(0.5%]
Conclusion Blends of PA copolymer/polystyrene were prepared in a brabender
plasticorder. The dynamic mechanical properties such as storage modulus,
loss modulus and damping behaviour of the hompolymers and their blends
were analysed in temperature range of -100 to 150°C.The blends exhibited
two Tgs corresponding to the individual polymers indicating that the blends
are immiscible. All the blends showed modulus value in between the
component polymers of which the PS rich blends exhibited moderately large
values at room temperature. N50 blends with a co continuous morphology
28
showed the lowest value of storage modulus at room temperature. The Tg
of PA phase shifted slightly towards the higher temperature with PS content
which may be due to the low moisture absorption of the blends compared to
neat PA.
While analysing the compatibilised blends (with three different
compatibilisers, SMA8, SEBS-g-MA and SMA28), it was found that the
storage modulus increased up on compatibilisation. A slight shift in the Tg
of PA phase was obtained in the case of compatibilised N80 blends. The
increase in storage modulus as well as the positive shift in Tg can be
attributed to the interfacial chemical reaction. The DMTA results showed
good correlation with the blend morphology. In the case of
compatibilisation with SMA8, for N80 blends the maximum storage
modulus and the minimum particle size was obtained for 2% loading. In the
case of N20 blends with a less amount of compatibiliser (0.5 %) we
obtained a leveling off in the case of storage modulus as well as the domain
size. Upon compatibilisation with SEBS-g-MA, the storage modulus
increased. In this case a decrease in storage modulus was obtained at higher
concentration which can be attributed to the rubbery nature of the
copolymer.
Analysis of viscoelastic properties using SMA28 revealed that beyond 1%
addition the compatibiliser exhibited inferior properties. This could be
attributed to the poor miscibility of the highly polar SMA28 with PS phase
along with the probability of heavily grafted copolymer formed to be
expelled from the interface. The morphology analysis indicated that the
domain size increases with high concentration of SMA28. Among the three
copolymers used for compatibilisation, SMA8 resulted in maximum
29
improvement of storage modulus, while SEBS-g-MA exhibited the
maximum damping behaviour. The results from the dynamic mechanical
analysis showed that with the addition of the compatibilisers, the blends
became more compatible, suggesting that the copolymers function as
interfacial modifiers in the system. Theoretical models were applied to
evaluate the storage modulus of the binary blends of which the Coran’s and
Takayanagi models shows good agreement with the experimental values.
30
References: 1. G. Guerrica-Echevarria, J.I Eguiazabal, J. Nazabal, Polym. Eng. Sci., 46, 2,
172, 2006.
2. S .Jose, B.Francis, S, Thomas, J. Karger-Kocsis, Polymer, 47, 11, 3874, 2006.
3. F.-P. Tseng, J.-J Lin, C.-R Tseng, F.-C Chang, Polymer, 42, 2, 713, 2000.
4. S. Jose, S.V Nair, S.Thomas, J.Karger-Kocsis, J. Appl. Polym. Sci.,99,5,
2640, 2006.
5. N. Abacha, S.Fellahi, Polym. Intern., 54, 6, 909, 2005.
6. M.Modesti, A. Lorenzetti, D. Bon, S.Besco, Polym. Degrad Stab., 91, 4, 672,
2006.
7. M-L .Xue, Y-L. Yu, J. Sheng, H. H. Chuah, C-H.Geng, J. Macromol. Sci.,
Part B: Phys., 44, 3. 317, 2005.
8. G. Aenovese, R. A. Shanks, Macromol. Mat. Eng., 289,1, 20, 2004 .
9. K. Kawaguchi, Y. Tajima, J. Appl. Polym. Sci., 100, 6, 4375, 2006.
10. H. Liu, T. Xie, Y. Zhang, Y. Ou, G. Yang, J. Polym. Sci., Part B: Polym.
Phys., 44, 7,1050, 2006.
11. S-H. Oh, J-S Kima, K. Shin, Polymer, 45, 3313, 2004.
12. B. Nandan, L.D. Kandpal, G.N. Mathur, Polymer, 44, 1267, 2003.
13. J. Li, M.Liang, S.Guo, V.Kuthanova, B.Hausnerova, J. Polym. Sci., Part B:
Polym. Phys., 43, 1260, 2005.
14. T. S. Omonov, C. Harrats, N. Moussaif, G. Groeninckx, Sh. G. Sadykov, N.
R.Ashurov, J. Appl. Polym. Sci., 94, 2538, 2004.
15. N.K.Kalfoglou, D.S.Skafidas, J.K Kallitsis, J.C Lambert, L. Vanderstappen.
Polymer, 36, 23, 4453, 1995.
31
16. G.G. Bandyopadhyay, S.S Bhagawan, Ninan K.N, S. Thomas. J. Appl.
Polym. Sci., 72, 165, 1999.
17. G.G. Bandyopadhyay, S. S Bhagawan., K. N Ninan, S. Thomas, J. Polym.
Sci. Part B: Polym. Phys., 42, 1417, 2004.
18. K.A. Moly, S.S. Bhagawan, G. Groeninckx, S. Thomas, J. Appl. Polym. Sci.,
100, 4526, 2006.
19. B. John, K. T. Varughese, Z. Oommen, P. Po¨tschke, S. Thomas, J. Appl.
Polym. Sci., 87, 2083, 2003.
20. G. G. Bandyopadhyay, S. S. Bhagawan, K. N Ninan, S. Thomas, J. Polym.
Sci. Part B: Polym. Phy., 42, 1417, 2004.
21. S. George, N.R Neelakantan, K.T Varughese, S. Thomas, J. Polym. Sci. Part
B: Polym. Phys., 35, 2309, 1997.
22. S. Al-Malaika, W. Kong, Polymer, 46, 228, 2005.
23. D. Pinoit, R.E. Pud’homme.; Polymer, 43, 2321, 2002
24. R. E. Wetton, P. J. Corish, Polym. Test. 8, 303, 1989.
25. J. J. Scobbo Jr, Polym. Test., 10, 279, 1991.
26. X.Jiang, H. Huang, Y. Zhang, Y. Zhang; Polym. Polym. Comp., 12, 29,
2004
27. Q. Lu, C.W. Macosko, Polymer, 45, 1981, 2004.
28. A.Genovese, A.S.Robert, Macrmol. Mater. Eng., 289, 20, 2004.
29. Yu.Zhang, Y. Huang, K. Mai, J. Appl. Polym. Sci., 96, 2038, 2005.
30. G. Schreyer, ‘Konstuieren mit Konstoffen’, Hanser, Munchen, 446, 1972.
31. R. Gadekar, A. Kulkarni, J. P. Jog, J. Appl. Polym. Sci., 69, 161, . 1998.
32. M.Castro, C. Carrot, F. Prochazka, Polymer, 45, 4095, 2004.
32
33. N.G. Mccrum, J. Polym. Sci., 34, 355, 1959.
34. N.G. Mccrum, Makromol. Chem., 34, 50, 1959.
35. J.Ma, Y.X.Feng, J.Xu, M.L.Xiong, Y.J. Zhu, L.Q. Zhang, Polymer, 43, 937,
2002.
36. A. Y. Coran, Hand Book of Elastomers: New Development and Technology,
A. K. Bhowmick and H. L.Stephens, Eds., Marcel Dekker, New York, p. 249,
1988.
37. R.A. Dickie, J. Appl. Polym. Sci., 17, 45, 1973.
38. M. Holsto-Miettiner, J.Y. Seppala, O.T. Ikkala, I. T. Reima, Polym. Eng. Sci.,
34, 395 1994.
39. K. Dedecker; Ph.D. Thesis, Katholieke University, Leuven 1998
40. J.H. Kim, J. W. Barlow, D. R. Paul, J. Polym. Sci. Part B: Polym. Physics,
27, 223, 1989
41. C. Harrats, K. Dedecker, G. Groeninckx, R. Jérôme, Macromol Symp., 198,
183, 2003.