Journal of Minerals & Materials Characterization & Engineering, Vol. 3, No.2, pp 65-72, 2004
jmmce.org Printed in the USA. All rights reserved
65
Effect Of Flyash On The Mechanical, Thermal, Dielectric,
Rheological And Morphological Properties Of Filled Nylon 6
1
Suryasarathi Bose and
2
P.A.Mahanwar
Plastics & Paints Division University Institute of Chemical Technology,
Matunga, Mumbai-400 019, India.
Phone: [phone]
1 2
Abstract:
Fillers are used along with various commodities as well as engineering polymers
to improve the properties of polymers. The performance of filled polymers is generally
determined on the basis of the interface attraction of filler and polymers. Fillers of widely
varying particle size and surface characteristics are responsive to the interfacial
interactions with polymers. The present study deals with the effect of particle size and its
concentration on the properties of flyash filled nylon 6.
Keywords: nylon 6, flyash, composites, mechanical properties, thermal properties,
dielectric properties, rheological properties, morphological properties.
1. Introduction
Particle filled polymer composites have become attractive because of their wide
applications and low cost. Incorporating inorganic mineral fillers into plastic resin
improves various physical properties of the materials such as mechanical strength,
modulus and heat distortion temperature. In general the mechanical properties of
particulate filled polymer composites depend strongly on size, shape and distribution of
filler particles in the matrix polymer and good adhesion at the interface surface. Nylons
are one of the most widely used engineering thermoplastics utilized in automobile,
electrical, electronic, packaging, textiles and consumer applications because of their
excellent mechanical properties. However limitations
1-6
in mechanical properties, such as
the low heat distortion temperature, high water absorption and dimension instability of
pure nylons have prevented their applications in structural components. Hence numerous
efforts have been undertaken to use nylons as matrix resins for composites by adding
inorganic fillers viz. aluminatrihydrate
6
, montmorrilonite, clays
6
, silica
6
mica
7,8,9
,
talc
2,6,10,11
, flyash
12
, wollastonite
2, 6, 10, 13
, kaolin, etc.
In a previous paper
14
the authors studied the effect of particle size of mica on
properties of nylon 6. In this investigation flyash mixed in different weight ratios, were
added to nylon 6 polymer and characterized for mechanical, thermal, dielectric,
rheological and morphological properties. Use of flyash as a filler
15-18
is not new. Flyash
is a fine ash byproduct commonly produced by the combustion of coal during the
generation of electrical power. The flyash is separated from the hot flue gases before it
escapes into the atmosphere. The inorganic oxide ash is generally spherical in form. The
results of many experimental studies conducted with flyash have shown that the addition

66
Suryasarathi Bose and P.A.MahanwarVol.3, No.2
of flyash filler does increase the stiffness of a plastic formulation, but similar to most
fillers, it reduces impact resistance. Flyash offers a significant economic advantage over
competing fillers, such as calcium carbonate, but does tend to impart a grayish color to
the plastic formulation (to a degree dependent on the unburned carbon concentration).
2. Experimental
Matrix material Nylon 6 was obtained from M/s Nirlon India ltd, Mumbai.Flyash
of different particle sizes as given in table 1 was obtained from M/s B.S.Mica, Mumbai,
India.Flyash was added to Nylon 6 in 5, 10, 20,25,30,35 and 40 % wt/wt ratios. Filler
additives viz.dispersing agent (1.5wt%), antioxidants (1wt%) and heat stabilizers (1 wt%)
were added and was obtained from M/s Fine Organics and M/s Ciba Specialty chemicals,
Mumbai, India respectively.
Table 1: Material used, suppliers list and physical properties of the matrix and the filler
Material
used
Avg.particle
size
(µ)
Particle size
distribution
(µ)
Specific
surface area
(m
2
/g)
Density
(g/cc)
Nylon-6------------------------------------------1.16
8 µ1.096-
416.868
1.692.3
Flyash
60 µ0.417-
724.436
0.341.99
The composite granules were prepared by using twin- screw extruder (M/s APV
Baker, UK, and Model: MP19PC). In this process, the temperature profiles in the barrel
were 200°C, 220°C, 230°C, 240°C, 250°C from hopper to die. The screw L/D was 25 and
screw rotation rate of 60 rpm was used. Tensile, Flexural and Izod impact samples
(according to ASTM D-638 M91, ASTM D 790 and ASTM D 256-92 respectively) were
prepared using an injection molding machine (M/s Boolani Engineering, Mumbai) with a
barrel temperature of 220°C, 250°C, 280°C.Uniaxial tensile tests were carried out using
Universal tensile testing machine LR 50k from Lloyd instruments ltd.U.K at a cross head
speed of 50mm per minute. The impact test was carried out at room temperature using an
Avery Denison impact tester. Heat distortion temperature (ASTM D 648) was measured
using Davenport Vicat Softening point instruments ltd.U.K.Dielecric strength (ASTM D
149) was measured (using a 2mm thick composite sheet) by Zaran electrical instruments
(input: 240V, 50Hz, 1PH; output: 0-50kV; capacity: 100mA; rating: 15 min). Rheological
properties of different compositions were measured using Haake RT 10 Rotovisco
(Germany) parallel plate viscometer.

Vol. 3, No.2 Effect of Flyash on the Properties of Filled Nylon 6
67
3.Results and Discussions
3.1 Effect of particle size of flyash on Mechanical properties of Nylon 6 / flyash
composite
It was observed that as the
concentration of filler increased tensile
strength decreased. The rate of decrease of
strength was higher when larger particle
size was used. It was also observed that
the percentage elongation decreased
drastically on addition of filler in both the
larger and smaller particle sizes of flyash
but the rate of change of percentage
elongation with varying percentage of
filler was higher in the case of smaller
particle size as compared to larger particle
size of flyash. It was also seen that at
higher filler loading the reduction of
tensile strength was higher in case of
larger particle size. The rate of reduction
of percentage elongation was higher in
case of smaller particle size up to 20%
filler loading whereas, it was higher at
higher filler loading in case of larger
particle size flyash. This variation may
have been due to wide particle size
distribution (p.s.d) of larger particle size
flyash than that of smaller particle size
flyash and at higher filler loading the
interstitial volume must have been
occupied by smaller particles as filler and
there may have been an insufficient matrix
available for contributing to the percentage
of elongation. The trend of variation of
tensile strength and percentage of
elongation of different particle sizes of
flyash with varying concentration is presented in Fig. 1 and Fig. 2 respectively. It was
also seen that flexural strength increased with an increase in concentration of filler
loading in both the cases whereas the rate of increase in flexural strength was higher
when smaller particle size flyash was used. It was observed that flexural strength
increased and attained maxima at lower filler concentration when smaller particle size
flyash was used as compared to larger particle size flyash. This may have been due to
agglomeration of smaller particle size flyash after certain concentration. In the case of
larger particle size (wide p.s.d) the smaller filler particles occupied the interstitial volume
0
10
20
30
40
50
60
70
0204060
Filler content(wt%)
Tensile
stren
g
th
(
MPa
)
60µ8µ
Fig. 1. Variation in tensile strength of different
particle size flyash with varying
concentration
0
10
20
30
40
50
60
70
80
01020304050
Filler content(wt%)
Elon
g
ation
@
break
(
%
)
60µ8µ
Fig. 2. Variation in elongation at break of
different particle size flyash with varying
concentration

68
Suryasarathi Bose and P.A.MahanwarVol.3, No.2
and hence the surface area available for
deformation force was higher in the case
of a smaller particle size than that of larger
particle size (wide p.s.d) material. The
phenomenon of agglomeration and surface
area of filler available was also confirmed
by early onset of flexural strength
decreasing in the case of smaller particle
size flyash as compared to larger particle
size flyash. It was also clear that at higher
concentration the flexural strength was
almost same in both of the cases, which
may be due to insufficient matrix available
for encapsulating individual filler particles
and agglomerates. The flexural modulus
increased continuously with increasing
concentration of filler loading of both the
smaller and larger particle sizes where as
at higher loading for larger particle size
the values of flexural modulus was more
than that of smaller particle size filler
indicating phenomenon of agglomeration
of smaller particle size filler than that of
larger particle size filler. The flexural
modulus was reduced by addition of
higher concentration of filler (40%) for
larger particle size where as in case of
smaller particle size the flexural modulus
continued increasing thereby indicating
that the saturation level of filler matrix
composition was influenced by agglomeration. The trend of variation of flexural strength
and flexural modulus of different particle sizes of flyash with varying concentrations is
presented in Fig. 3 and Fig. 4 respectively. The impact strength decreased with increasing
concentration of filler in the case of larger particle size flyash whereas in case of smaller
particle size the impact strength initially increased or remained almost same up to 25%
filler loading, which confirmed the void space available in the larger particle size material
and thereby demonstrated that stress propagation was greater in the case of a larger
particle size filled composites than that of a smaller particle size composites. The impact
strength values of higher filler loading composites (40 wt%) of smaller particle size as
well as that of larger particle size flyash with the same filler loading were almost
identical, which indicated the agglomeration of smaller particle size filler and thereby
generated increasing void space, which was responsible for stress propagation. It was also
observed that rate of change of impact strength was same at higher filler loading i.e above
25 wt% of both the particle sizes and this indicated that the total surface area available for
matrix remained almost same in case of both the larger particle size and smaller particle
size agglomerates. The trend in variation of impact strength of different particle size
0
10
20
30
40
50
60
70
80
90
01020304050
Filler content(wt%)
Flexural strength
(MPa)
60µ8µ
Fig. 3. Variation in flexural strength of different
particle size flyash with varying concentration.
0
500
1000
1500
2000
2500
3000
3500
01020304050
Filler content(wt%)
Flexural
modulus
(
MPa
)
60µ8µ
Fig. 4. Variation in flexural modulus of different
particle size flyash with varying concentration

Vol. 3, No.2 Effect of Flyash on the Properties of Filled Nylon 6
69
flyash with varying concentration is
presented in Fig. 5. This assumption of
agglomeration of smaller particle size
filler was also confirmed by a higher rate
of increase of Young’s modulus in the
case of smaller particle size filler than that
of larger particle size filler at higher filler
loading .The Young’s modulus remained
unchanged with the increase in
concentration of larger particle size flyash
up to 20% filler loading where as in case
of smaller particle size Young’s modulus
was lower than that of virgin nylon 6 up to
20% filler loading. This variation in
Young’s modulus in both the cases
indicated good dispersion of smaller
particle size within the filler than that of
larger particle size at lower filler loading.
The smaller particle size filler
agglomerates hence reduced the strain
value by restricting the mobility of matrix
chains. The mobility of matrix chains and
agglomeration of smaller particle size
filler is clearly indicated by the increase in
Young’s modulus with a higher rate than
that of larger particle size filler. This was
also supported by the observation of
Young’s modulus at 40% filler loading of
both particle sizes, which was almost
same.
The trend of variation of Young’s
modulus of different particle size flyash
with varying concentration is presented in
Fig. 6.
3.2 Effect of particle size of flyash on
Dielectric and Thermal properties of
Nylon 6 / flyash composite.
It was observed that on addition of
flyash the dielectric strength increased
drastically in both of the cases. The larger
particle size filler shows a peak at lower
concentration but the strength decreased and remained constant at higher loading,
whereas in the case of smaller particle size, the dielectric strength increased but then
0
10
20
30
40
50
60
01020304050
Filler content(wt%)
Im
p
act stren
g
th
(
J/m
)
60µ8µ
Fig. 5. Variation in Impact strength of different
particle size flyash with varying concentration
0
500
1000
1500
2000
2500
3000
01020304050
Filler content(wt% )
Youngs
modulus(MPa)
60µ8µ
Fig. 6. Variation in Young’s Modulus of different
particle size flyash with varying concentration
0
2
4
6
8
10
12
14
0204060
Filler content(wt%)
Dielectric
stren
g
th
(
kV/mm
)
60µ8µ
Fig. 7. Variation in dielectric strength of different
particle size flyash with varying concentration

70
Suryasarathi Bose and P.A.MahanwarVol.3, No.2
remained almost unchanged at any
concentration of filler loading. This may
have been due to the leakage of current
from un encapsulated interstitial filler
particle at higher filler loading with larger
particle size where as in case of smaller
particle size there was proper dispersion
which did not affect the dielectric
properties. The heat distortion temperature
increased with increasing concentration of
filler in both of the cases. The extent of
increase in heat distortion temperature at
lower filler loading of larger particle size
flyash filled nylon 6 composite was higher
than that of smaller particle size flyash.
The rate of change of heat distortion
temperature was higher and gradual in
case of smaller particle size filler than that
of larger particle size at any filler
concentration. The heat distortion
temperature was higher at higher filler
loading (40 wt%) with smaller particle
size as compared to larger particle size,
whereas at other concentrations the heat
distortion temperature was lower for
smaller particle size filler composites than
that of larger particle size filler
composites, which indicated that at higher
filler loading the extent of agglomeration
of smaller particle size increased and the
total surface area of filler matrix
interaction remained almost same in both
cases of the particle size. The trend of
variation of dielectric strength and heat
distortion temperature of different particle
size flyash with varying concentration is
presented graphically in Fig. 7 and Fig. 8
respectively.
3.3 Effect of particle size of flyash on
rheological behavior of flyash filled
nylon 6 composites.
Fig. 9 and Fig. 10 depicts the
variation in shear viscosity versus shear
rates at 250°C of 60 µ flyash and 8µ
0
20
40
60
80
100
120
140
160
180
01020304050
Filler content(wt%)
Heat Distortion
Tem
p
C
60µ8µ
Fig. 8. Variation in Heat Distortion Temperature
of different particle size flyash with varying
concentration
1
10
100
1000
10000
0.010.1110100
shear rate(1/sec)
viscosity(Pasec)
vnylon 65%10%20%30%
Fig. 9. Variation in shear viscosity of Nylon 6
with filler content (60 µ flyash
)
10
100
1000
10000
0.010.1110
shear rate(1/sec)
viscosity(Pasec)
vnylon5%10%20%30%
Fig. 10. Variation in shear viscosity of Nylon 6
with filler content (8 µ flyash)

Vol. 3, No.2 Effect of Flyash on the Properties of Filled Nylon 6
71
flyash filled nylon 6 composite
respectively. It was seen that addition of
flyash of any particle size increased the
shear viscosity but the slip of particulate
filler occurred at early concentrations (at
10 wt %) in the case of larger particle size
flyash than that of smaller particle flyash
(where the slip is at 20 wt %). The
increase in the viscosity may have been
attributed to the properties of filler such as
its maximum packing fraction. The rate of
increase in the viscosity was dependent
upon the ratio (ø/ ø
µ
) where ø = volume
fraction of the filler and ø
µ
=Maximum
Packing fraction. The flyash used (60 µ)
has almost 1-2 % hollow sphere which
explains to the early slip between filler and
matrix whereas in case of smaller particle
size flyash even though there were no
hollow spheres, the slip must have been
due to the agglomerates of smaller particle
size flyash and thereby causing the
increase in ratio of packing fraction. For a
better comparison Fig. 11 depicts the
variation of zero shear viscosity at 0.1
shear rate (extrapolated values) at 250°C
of flyash filled Nylon 6.
3.4 Effect of particle size of flyash on
morphology of flyash filled nylon 6
composite.
Fig. 12 and Fig. 13 presents the
Scanning Electron Microscope (SEM)
micrograph of 60 µ flyash and 8µ flyash at
30 wt% filler loading respectively. It was
observed that the polymer matrix was
insufficient to encapsulate the individual
filler particles in both of the cases. In the
case of particle size, the smaller particles
had occupied the interstitials volume and
thereby the total packing fraction remained unchanged whereas in case of lower particle
size, all the filler particles were separate but were not encapsulated. Thus the total surface
area at 30 wt% filler loading at larger and smaller particle size remained almost the same,
thereby the total filler matrix interaction forces remained the same due to melt viscosity
which remained the same as can also be seen from the Fig. 9 and Fig. 10.
0
200
400
600
800
1000
1200
1400
010203040
Filler content (wt%)
Shear viscosit
y(
Pa sec
)
60µ8µ
Fig. 11. Variation in zero shear viscosity at 0.1
sec
-1
shear rate at 250°C of flyash filled nylon 6 /
composite
Fig. 12. SEM micrograph of 60µ flyash
Fig. 13. SEM micrograph of 8µ flyash

72
Suryasarathi Bose and P.A.MahanwarVol.3, No.2
4. Conclusions
• The larger particle size flyash showed improvement in mechanical
properties on increasing concentration of flyash as compared to lower
particle size but the lower particle size flyash showed improvement in
dielectric properties as compared to larger particle size flyash.
• Inorganic fillers such as flyash added to the polymer improved their rigidity, heat
resistance, and dimension stability.
• A significant increase in the heat distortion temperature was found with increase
in the filler loading as in the case of both the particle size.
• Thus the mechanical property of composite is a function of the particle size, the
dispersion, the particle orientation, the interfacial interaction between the minerals
and the polymer matrix.
5. References
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New York, 1996.
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London/Newyork, 1974.
6) Nielsen, L.E, “Mechanical properties of Polymers and Composite”; Marcel
Dekker; New York, 1974.
7) Watari, T; Yamane, T; Moriyama, S; Torikai, T; Imaoka, Y; Suchiro, K and
Tateyama H, Mater. Res. Bull, 32,719(1997).
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15) Technical Bulletin, American Coal Ash Association, Alexandria, VA 22314-4553
(1999).
16) Technical Bulletin, Southeastern Flyash Co., West Columbia, S.C. 29169.
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