Journal of Minerals & Materials Characterization & Engineering, Vol. 3, No.1, pp 23-31, 2004
jmmce.org Printed in the USA. All rights reserved
Effect of Particle Size of Filler on Properties of Nylon-6
Suryasarathi Bose and P.A.Mahanwar
*
Plastics & Paints Division
University Institute of Chemical Technology,
University of Mumbai, Matunga,
Mumbai-400 019, India.
Phone: [phone] Fax: [phone].
*
Particulate reinforced thermoplastic composites are designed to improve
the properties and to lower the overall cost of engineering plastics. In this study
the effects of adding mica with variable particle size on the mechanical, thermal,
electrical and rheological properties of nylon-6 was investigated. Composites of
nylon-6 with varying concentrations (viz. 5 to 40 weights %) of mica were
prepared by twin screw extrusion. The composite showed improved mechanical,
thermal as well electrical properties on addition of filler. It is also observed that
mechanical properties, electrical properties as well as thermal properties increases
with decrease in particle size.
Key Words: Particulate composites, nylon-6, mica, filled nylon 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
deflection temperature
1
. 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
2
are among the most widely used
engineering thermoplastics in automobile, electrical, electronic, packaging, textiles and
consumer applications because of their excellent mechanical properties. However, limitations in
mechanical properties, such as low heat deflection temperature, high water absorption and
dimension instability of pure nylons have prevented their application in structural components.
Hence numerous efforts have been undertaken to use nylons as matrix resins in composites by
adding inorganic fillers such as aluminatrihydrate, montmorrilonite, clays, talc, mica, silica,
flyash, wollastonite, kaolin etc. In this investigation mica of variable particle size was added to
nylon-6. Influences of the addition of these fillers on the mechanical, thermal, rheological and
electrical properties were examined.

24 Suryasarathi Bose and P.A.Mahanwar Vol. 3, No. 1
2. EXPERIMENTAL
2.1 Experimental Plan
The schematic representation of experimental plan is shown in the following figure:
Base resin Fillers
(Predried, 80
O
C ) (Predried, 80
O
C)
Dry mixing Additives
Melt mixing (APV twin-screw extruder)
Pelletization
Injection moulding
Testing of samples
Ø Mechanical
Ø Thermal
Ø Rheological
Ø Electrical
2.2 Material used
Material used are listed in the following table:
Material used Function Grade Supplier
Nylon-6 Polymer matrix Nirmide E 35 M/sNirlon India
Limited
Mica Filler Water
ground(75µ)
M/s BS
Mica,Mumbai,India
Mica Filler Dry ground(37 µ) M/s
HMP,Mumbai,India
Finnawax Dispersing agent FinnawaxSS M/s Fine
Organics,Mumbai,India
------------ Antioxidant Irganox 1076 M/s
CIBA,Mumbai,India
------------ Heat Stabilizer Irgafos168 M/s
CIBA,Mumbai,India

Vo1. 3, No. 1 Effect of Particle Size of Filler on Properties of Nylon-6 25
2.3 Compounding
Before compounding, the fillers were dried at 80
o
C for 8 hours in an air circulated oven
and then dry mixed with nylon-6 and other additives. Composition shown in the table was mixed
and extrudated in a co-rotating twin extruder (APV Baker Ltd. England).The L/D ratio of the
screw is 25:1.Mixing speed of 60 rpm was maintained for all the compositions. The extrudates
from the die were quenched in a tank at 20-30
o
C and then palletized .In all the above set of
experiments 1.5% of dispersing agent, 1% each of antioxidant and heat stabilizing agents were
mixed. For the melt blending the temperature profile of the extrusion were Zone 1(205
0
C) Zone
2(235
0
C) Zone 1(245
0
C) Zone 1(255
0
C) and Die (265
0
C). The extrudates of the compositions
shown in the table above were palletized in Boolani’s pelletizing machine. The rpm of the
pelletizer was maintained between the ranges of 60-80.
2.4 Injection Molding
The granules of the extrudates were predried in an air circulated oven at 80
0
C for 8 hours
and injection molded in a microprocessor based Boolani’s injection moulding machine fitted
with a master mould containing the cavity for tensile strength, flexural and impact specimens.
After its ejection from the mould, specimens were cooled in ice–water. Processing parameters
are Zone 1(200
0
C) Zone 2(235
0
C) Zone 1(260
0
C).
2.5 Characterization
2.5.1 Mechanical properties
Tensile strength as per ASTM D 638 M91 was evaluated using universal tensile testing
machine LR50k from Lloyd instruments Ltd.,U.K at a crosshead speed of 50mm/min. Flexural
properties according to ASTMD790 were tested using LR 50K from Lloyd instruments Ltd.,
U.K. Izod impact test were carried out using an Avery Denison impact tester (ASTM D 256-92).
A 2.75J energy hammer was used and the striking velocity was 3.46m/sec. For Izod impact test
specimens the notch was cut using a motorized notch-cutting machine (Rayran U.K). The unit of
expression is J/m.
2.5.2 Thermal properties
Heat Distortion temperature was measured using Vicat Softening Point machine, Davenport,
UK (ASTM D 1525, D648). The sample position was edgewise, test span was 100mm and surface
stress was 1820KPa (264psi).
2.5.3 Electrical properties
Dielectric strength was measured by Zaran electrical instruments, India.
2.5.4 Rheological properties
Shear viscosity (at 0.1sec
-1
shear rate and 250
0
C) of different compositions were
measured using Haake RT 10 Rotovisco (Germany) parallel plate viscometer.
3.0 RESULTS AND DISCUSSION
3.1 Tensile properties

26 Suryasarathi Bose and P.A.Mahanwar Vol. 3, No. 1
Fig. 1 shows the variation of tensile strength with filler concentration of mica. There was
a significant increment in the strength as the filler loading increased larger mica particle sizes
showed higher increments. The increment may be due to the platy structure of the mica filler
providing good reinforcement. Elongation properties as seen from Fig. 2 decreased with the
presence of filler that indicates an interference
4
by the filler in the mobility
5
or deformability of
the matrix. This interference was created through the physical interaction and immobilization
6
of
the polymer matrix by imposing mechanical restraints.
Figure 1. Variation of the Tensile Strength of Nylon 6 with Filler Content
Variation of the elongation at break
of nylon 6 with wt% of filler content
0
10
20
30
40
50
60
70
80
01020304050
filler content(wt%)
Elongtion at break(%)
mica(37microns)mica(75microns)
Figure 2. Variation of the Elongation at Break of Nylon 6 with Filler Content
Variation of the tensile strength of nylon
6 with filler content in wt%
58
60
62
64
66
68
70
01020304050
filler content(wt%)
Tensile strength(MPa)
mica(75microns)mica(37microns)

Vo1. 3, No. 1 Effect of Particle Size of Filler on Properties of Nylon-6 27
3.2 Flexural properties
Fig. 3 depicts the variation in flexural modulus with varying concentrations of mica. The
flexural modulus increased with the increase in filler concentration of mica. The rate of increase
of flexural modulus was comparable to the increase in concentration of mica and the increase in
particle size. Thus it was confirmed that the total area available to deformation stress
9
played an
important role. Fig. 4 presents the variation in flexural strength. It is seen that flexural strength
10
increased with the increase in concentration of filler.
Figure 3. Variation of the Flexural Modulus of Nylon 6 with Filler Content
Figure 4. Variation of the Flexural Strength of Nylon 6 with Filler Content
Variation of the flexural modulus of
nylon6 with wt% of filler content
0
1000
2000
3000
4000
5000
6000
010203040
filler content(wt%)
flexural
modulus(MPa)
mica(37microns)mica(75microns)
Variation of the flexural strength of
nylon6 with wt% of filler content
0
25
50
75
100
125
01020304050
filler content(wt%)
flexural stength (MPa)
mica(37microns)mica(75microns)

28 Suryasarathi Bose and P.A.Mahanwar Vol. 3, No. 1
3.3 Impact properties
Fig. 5 illustrates the variation of impact strength with filler by weight percentage. It is
clear from this figure that the strength increment
12
at low weight percentage of filler may be
attributed to the formation of small sized crystallites, i.e. spherulites, as well
13
as the capacity to
absorb more energy by increased portion of matrix. A further increase in weight percentage
reduced the deformability of the matrix, and, in turn, reducing the ductility
15
in the skin area so
that the composite tended to form a weak structure.
Figure 5. Variation of the Impact Strength of Nylon 6 with Filler Content
3.4 Thermal properties
Heat distortion temperature
Fig. 6 illustrates the variation of heat distortion temperature with varying filler
percentage. It is clear from this figure that the heat distortion temperature increased steeply with
the increase in filler loading. A significant increase in heat distortion temperature was expected
because inorganic fillers have high thermal stability. Lower particle size of mica resulted in
higher heat distortion. This was attributed to the increase in interstitials volume or the increase in
matrix filler surface contact.
Variation of the impact strength of nylon
6 with weight% of filler content
0
50
100
150
01020304050
filler content (wt%)
Impact strength(J/m)
mica(37microns)mica(75microns)

Vo1. 3, No. 1 Effect of Particle Size of Filler on Properties of Nylon-6 29
Figure 6. Variation of the Heat Distortion Temperature of Nylon 6 with Filler Content
3.5 Electrical properties
Dielectric strength
It is clear from Fig. 7 that the dielectric strength
14
increased with the increase in filler
concentration and attained maxima. At higher filler loading the dielectric strength values
remained constants with the increase in filler but the dielectric strength values were higher for
larger particles as compared to small particle sizes. The trend in variation of dielectric strength
in mica was attributed to the total surface area available based on the dispersion of filler particles
at a lower loading. At higher loading the dispersion of platy structure is impeded and hence the
total strength gets reduced.
Figure 7. Variation of the Dielectric Strength of Nylon 6 with Filler Content
Variation of the heat distortion
temperature of nylon 6 with wt% of filler
content
0
100
200
300
01020304050
filler content(wt%)
Heat distortion
temperature(C)
mica(37microns)mica(75microns)
Variation of the dielectric strength of
nylon 6 with weight% of filler content
5
7
9
11
13
15
010203040
filler content(wt%)
Dielectric
strength(kV/mm)
mica(37microns)mica(75microns)

30 Suryasarathi Bose and P.A.Mahanwar Vol. 3, No. 1
3.6 Rheological Properties
Fig. 8 illustrates the variation of shear viscosity at 250
0
C (in Pascal second) with filler
concentration at a shear rate at 0.1 sec
-1
. Increase in the viscosity
7
may be attributed to the
properties of the filler such as maximum packing fraction. Rate of increase in the viscosity
depended upon the ratio (ø/ ø
µ
) where ø = vol. fraction of the filler and ø
µ
= Max. packing
fraction. Increase in the viscosity was also due to the ability of fine particles of fillers to form a
large network that caused tighter packing. The porous and irregular shaped filler particles
introduced discontinuity in the base matrix. The extent of discontinuity increased with the
increase in filler content in the composite. Thus it appears that melt viscosity of base matrix
increased due to the increasing
16
obstruction to the flow caused by these irregular shaped filler
particles
17
. Addition of filler did not alter the pseudoplastic behavior of the polymer matrix. With
an increase in filler content the viscosity of the component increased. Lower viscosity of filled
compounds may indicate slip
18
between filler particles and polymer matrix. In polymer
processing, the increased viscosity of filled plastics at high shear rates is of continuing interest.
Variation of shear viscosity at
0.1 shear rate at 250Cof mica
filled nylon 6
0
500
1000
1500
2000
01020304050
filler content (wt%)
viscosity(Pa sec)
mica(75microns)mica(37microns)
Figure 8. Variation of Shear Viscosity at 0.1 Shear Rate at 250ºC of Mica Filled Nylon 6
4.0 CONCLUSIONS
1) There was a significant increment in the flexural properties with an increase in the filler
loading.
2) The toughness and elongation at break decreased as particle size and agglomeration
concentration increased in the case of both of fillers.
3) Inorganic fillers, such as mica, added to the polymer improved rigidity, heat resistance, and
dimension stability.
4) A significant increase in the heat distortion temperature was found with increase in the filler
loading as in the case of both of the fillers.

Vo1. 3, No. 1 Effect of Particle Size of Filler on Properties of Nylon-6 31
5) Addition of filler did not alter the pseudoplastic behavior of the polymer matrix. With increase
in the filler content the viscosity of the composites increased.
6) There was a significant increase in the dielectric strength.
7) The mechanical properties of the composite were found to be a function of the particle size,
aspect ratio, the dispersion, the particle orientation, the interfacial interaction between the
minerals and the polymer matrix. Platy filler such as mica gave significant improvement in
stiffness.
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