Journal of Minerals and Materials Characterization and Engineering, 2012, 11, 807-812
Published Online August 2012 (http://www.SciRP.org/journal/jmmce)
Effect of Cenosphere Conc entration on the Mechanical,
Thermal, Rheological and Morphologica l P ropert i e s of
Nylon 6
Parag A. Wasekar, Pravin G. Kadam, Shashank T. Mhaske*
Department of Polymer and Surface Engineering, Institute of Chemical Technology, Mumbai, India
Received April 14, 2012; revised May 28, 2012; accepted June 17, 2012
ABSTRACT
Cenospheres are widely used as filler in thermoset plastics and concrete mainly for density reduction of the material.
But there is no work noted of using cenosphere as filler in thermoplastics. In this paper cenosphere concentration was
varied from 0 to 10 phr of nylon 6 and the effect of the same on the mechanical, thermal, rheological and morphological
properties of the composite were studied. Elongation was found to have increased by 83% and impact strength by 44%
at 2.5 phr loading of cenosphere. Flexural strength increased upto 25% at 10 phr content of cenosphere.
Keywords: Nylon 6; Cenosphere; Crystallinity; Reinforcing Agent
1. Introduction
In the previous studies use of cenosphere is noted to de-
crease the density of the material, due to its micro-
spherical nature. Cenosphere is a hydrophilic material
and found in fly ash [1]. So, for its use as filler in poly-
mers like PP, HDPE, PS, it is surface treated to induce
hydrophobicity gi ving bet ter com patibil ity wit h the matri x.
Abdullah et al. utilized amine containing silicone as
toughening agent and hollow cenosphere as filler in ep-
oxy resin. Their study was to understand the microstruc-
ture formed and its influence on mechanical properties
and free volume measurements of the composite. Tensile
strength increased and tensile modulus decreased with
increase in cenosphere content up to 30%, due to low
density of the filler [2]. Gu et al. studied epoxy filled
with cenosphere surface treated with different chemicals.
Surface modified cenosphere were observed to have dis-
tributed uniformerly into the epoxy matrix. Surface
modified cenosphere had a wider glass transition tem-
perature region and a higher loss factor, and had rela-
tively higher impact toughness [3]. Deepthi et al. studied
the mechanical and thermal properties of high density
polyethylene filled with cenosphere. They used ceno-
sphere as filler after silane treatment, and also with a
compatibilizer [4]. Cardoso et al. studied the effect of
particle size and surface treatment o f cenosphere as filler
on the properties of polyester resin [5]. Huo et al. studied
the preparation of poly-o-phenylenediamine (POPD)/
TiO2/fly ash cenosphere composite and its photo-degra-
dation properties [6]. Chaliven dra et al. studied the proc-
essing and mechanical characterization of lightweight
polyurethane composites using cenosphere. Polyurethane
was loaded with cenosphere upto 40% and was tested for
mechanical properties to estimate the fracture toughness
of the material. Cenosphere decreased the density of the
composite. The high strain rate constitutive behavior of
100% polyurethane showed monotonic stiffening whereas
the composite at higher cenosphere volume fractions (40%)
exhibited a stiffening-softening-stiffening behavior, due to
easy flowability induced by cenosphere micros pheres [7].
In this paper, cenosphere was used as reinforcing agent
in nylon 6 matrix. Cenosphere and nylon 6 both are hy-
drophilic materials, so they possessed good compatibilit y
requiring no use of compatibilizer or surface treatment of
cenosphere. Cenosphere obtained was used as such and
loaded as 2.5 phr, 5 phr, 7.5 phr and 10 phr in the nylon
matrix, and tested for mechanical, thermal, rheological
and morphological properties. As cenosphere was used in
very low concentration to affect the density of the matrix
material, density measurement was not done.
2. Experimental
2.1. Materials
Nylon 6 for was obtained from Next Polymers Ltd.,
Mumbai, India. Cenosphere was procured from Nasik
thermal power plant (India) having chemical composition
as shown in the Table 1. Cenosphere was used as ob-
*Corresponding author.

P. A. WASEKAR ET AL.
808
tained without any purification or chemical modification
or surface treatment. Finalux G3 (wetting agent) was
obtained fr o m Fine Organics Ltd., M umbai, India.
2.2. Preparation of Composite
Concentration of cenosphere was varied upto 10 phr into
the nylon matrix. Firstly, dry blending of cenosphere and
nylon 6 was done in tumbler mixer for 15 - 20 min, using
finalux G3 as the wetting agent. Then the mix was melt
blended in a twin screw co-rotating extruder (Lab Tech
Engineering Co. Ltd., Germany) having L/D ratio of 32:1
and temperature profile from the hopper to the die as
170˚C, 190˚C, 200˚C, 210˚C, 220˚C, 230˚C, 240˚C and
250˚C. Extruded strands were water cooled at 30˚C and
pelettized. Pellets obtained were used for injection mold-
ing after pre-drying at 80˚C for 8 - 10 hrs. Injection
molding (Boolani machineries India ltd, Mumbai, India)
was done maintaining temperature profile as 210˚C,
230˚C and 250˚C from the hopper to the ejection nozzle.
Standard ASTM based samples for tensile, flexural and
impact testing were obtained from injection molding.
Samples for impact testing were notch cut before testing.
2.3. Characterization and Testing
2.3.1. Mechanica l Pro p e rties
Tensile properties; tensile strength and elongation at
break and flexural properties; flexural strength and flex-
ural modulus, were measured at ambient condition using
a universal testing machine (LR-50K, Lloyds Instrument,
UK), according to ASTM procedures D638 and D790; at
a crosshead speed of 50 mm/min and 2.8 mm/min re-
spectively. The notch for impact test was made using a
motorized notch-cutting machine (Polytest model 1, Ray
Ran, UK). Notched Izod impact strength was determined
at ambient condition according to ASTM D256 standard,
using impact tester (Avery Denison, UK) having striking
velocity of 3.46 m/s employing a 2.7 J striker.
2.3.2. Thermal Properties
Differential scanning calorimetry (Q 100 DSC, TA in-
struments Ltd., India) characterization was done to in-
vestigate the crystallization and melting behaviour of the
composite. Two consecutive heating scans were found to
minimize the influence of possible residual stresses in the
material due to any specific thermal history. Scanning
rate of 10˚C/min was maintained for both heating and
cooling cycle; whereas nitrogen gas purge rate main-
tained at 50 ml/min. Melting temperature was determined
from the second heating scan while the crystallization
temperature (Tc) from cooling scan.
2.3.3. Rheological Properties
The melt viscosity was measured using rotational rheometer
(MCR101, Anton Paar, India) with parallel plate assem-
bly having diameter of 35 mm. Samples were predried
before analysis. Viscosity was determined for sh ear rates
from 0.01 s–1 to 100 s–1 at the constant temperature of
250˚C.
2.3.4. M orp hologica l Properties
Scanning electron microscope (SEM) analysis was per-
formed with JEOL 6380 LA (Japan). Samples were frac-
tured under liquid nitrogen to avoid any disturbance to
the molecular structure and then coated with gold before
imaging.
2.3.5. X-Ray Diffr ac tion
The XRD analysis was carried out to determine the per-
centage crystallinity of the prepared co mposite. A normal
focus copper X-ray tube was operated at 30 kV and 15
mA. Sample scanning was done from 2.00˚ to 80.00˚ at
the rate of 3.00˚/min. The data processing was done us-
ing Jade 6.0 software.
2.4. Formulation
The formulations prepared are as shown in the Table 2.
Concentration of cenosphere was varied from 0 to 10 phr
of nylon 6, while concentration of wetting agent was
maintained constan t at 5 phr of nylon 6.
Table 1. Chemical composition of cenosphere obtained from Nasik thermal power plant.
Components Al2O3 SiO2 P
2O5 SO3 K 2O CaO TiO2 V 2O5 Fe2O3
wt% 24.559 50.300 0.409 0.060 6.765 1.109 5.129 0.102 11.566
Table 2. Formulation of cenosphere/nylon 6 composites.
Sr. No. Sample Name Nylon 6 (gm) Cenosphere (phr, gm) Wetting Agent (phr, gm)
1 VNY 500 0.0, 0.0 5, 25
2 NC 2.5 500 2.5, 12.5 5, 25
3 NC 5 500 5.0, 25.0 5, 25
4 NC 7.5 500 7.5, 37.5 5, 25
5 NC 10 500 10.0, 50.0 5, 25

P. A. WASEKAR ET AL. 809
3. Results and Discussion
3.1. X-Ray Diffrac tio n
X-ray diffraction pattern of the composites are shown in
the Figure 1; whereas percentage crystallinity of the
composites are noted in Table 3. It was found that per-
centage crystallinity was least for 2.5 phr cenosphere
loaded nylon 6; and increased with increase in ceno-
sphere concentration. But, percentage crystallinity re-
mained lower than the base polymer even for 10 phr
cenosphere loaded nylon 6.
Cenosphere and nylon 6 both are hydrophilic material,
providing better compatib ility between the two materials.
But, the intermolecular forces of attraction between the
nylon 6 polymer chains are better than that between ny-
lon 6 and cenosphere. Due to the micro-spherical nature
of cenosphere, nylon 6 polymer chains come in contact
with cenosphere only at a single tangential point or may
be a little more, depending on the molecular arrange ment.
But, the chance of nylon 6 chains to completely cover the
surface of cenosphere is negligible.
At 2.5 phr concentration of cenosphere, particles are
uniformly dispersed in the nylon 6 matrix. So, the num-
ber of nylon 6 polymer chains contacting cenosphere
tangentially at one point is more. Also, the spherical na-
ture of the cenosphere remained intact at lower concen-
tration, increasing flowability of nylon 6 polymer chains
onto each other. As the concentration of cenosphere in-
creased, it started forming agglomerates, decreasing the
spherical nature of the cenosphere. This decreases the
flowability of nylon 6 molecular chains over it, increas-
ing crystallinity. Due to agglomerate formation, the con-
tact area between cenosphere and nylon 6 also increases,
making nylon 6 polymer chains to align more properly
increasing crystallinity.
3.2. Mechanical Properties
Mechanical properties; tensile, flexural and impact strengths,
are reported in Table 4. Tensile strength remained nearly
constant with incre ase in ceno sph ere con cen tr ation, where as
tensile modulus, elongation at break, impact strength,
flexural strength and flexural modulus increased.
Elongation at break was highest for 2.5 phr cenosphere/
nylon 6 composites and started decreasing with increase
in concentration. But, even for maximum cenosphere
content, elongation is still higher than virgin nylon 6.
Impact strength was also highest for 2.5 phr cenosphere.
Impact strength is proportional to elongation property of
the material. At 2.5 phr cenosphere content elongation at
break increased by 83% and impact strength by 44%.
Impact strength decreased with increase in cenosphere
content. But, even for maximum cenosphere content, it
was still higher than virgin nylon 6. X-ray diffraction
showed lowest crystallinity for 2.5 phr cenosphere/nylon
6 composites. This correlated with the increase in elon-
gation at break and impact strength of the material.
Figure 1. X-r ay differaction pattern of nylon 6 and nylon 6/
cenosphere composites.
Table 3. Percentage crystallinity of the ny lon 6 a nd nyl on 6/
cenosphere composites.
Sr. No. Sample Name Crystallinity (%)
1 VNY 5.15
2 NC 2.5 4.49
3 NC 5 4.58
4 NC 7.5 4.83
5 NC 10 4.99
Table 4. Mechanical properties of nylon 6 and nylon 6/cenosphere composites.
Sr. No. Sample
Name Tensile Strength (MPa) Tensile Modulus (MPa) % E @ BreakImpact Strength (J/m) Flexural Strength (MPa) Flexural Modulus (MPa)
1 VNY 51.25 1937.8 90.94 56.46 70.66 2455.4
2 NC 2.5 57.93 2061.8 165.71 81.17 72.88 2521.7
3 NC 5 53.29 2277.1 119.57 70.83 87.32 3020.5
4 NC 7.5 49.59 2303.0 119.13 68.33 88.88 3121.3
5 NC 10 50.35 2330.8 79.53 71.50 88.37 3123.3

P. A. WASEKAR ET AL.
810
More amorphous the material b ecomes, better it is able
to transfer the impact force, without undergoing cracking.
This increases the impact strength of the material. The
spherical nature of the cenosphere was thus best utilized
for increasing amorphous characteristic of the nylon 6.
Flexural strength increased with increase in cenosphere
content. For 10 phr cenosphere/nylon 6 composite, flex-
ural strength was found to have increased by about 25%.
3.3. Thermal Properties
Heating and cooling scans of the nylon 6 and nylon 6/
cenosphere composites are shown in Figures 2 and 3
respectively. Table 5 reports enthalpy of melting, melt-
ing temperature, enthalpy of crystallization and crystalliza-
tion temperature of nylon 6 and nylon 6/cenosphere com-
posites.
Enthaply of heating was found to be least for 2.5 phr
cenosphere/nylon 6 composites, and started increasing
with increase in cenosphere content. But, enthalpy of
composite containing highest cenosphere content was
still less than that of the virgin nylon 6. Even en thalpy of
crystallization gave the same trend. Melting temperature
and crystallization temperature didn’t change appreciably
with change in cenosphere content. Enthalpy of the mate-
rial is proportional to the crystallinity, thus 2.5 phr ceno-
sphere/nylon 6 showed lowest enthalpy of melting, which
increased with cenosphere concentration. While enthalpy
of crystallization increased with increase in cenosphere
content.
3.4. Rheological Properties
Figure 4 shows the rheological properties of nylon 6 and
nylon 6/cenosphere composites. It was found that, at
lower shear rate viscosity of nylon 6 and nylon 6/ceno-
sphere composites is same, but at higher shear rate differ-
ence becomes prominent. Viscosity of nylon 6 was found
to be highest, while that of 2.5 phr cenosphere loaded ny-
lon 6 composites was found to be lowest. Viscosity in-
creased with increase in cenosphere content, but even at
maximum loading it was lower than the base polymer.
Lowest viscosity at 2.5 phr loaded cenosphere is due
to maximum amorphicity and flowability th at it posseses.
Viscosity increased with increase in cenosphere concen-
tration. This correlates with the increase in crystallinity
as shown by X-ray diffraction, mechanical properties and
thermal properties. Also as cen osph ere con tent in crea sed,
it started forming agglomerate, decreasing the spherical
nature of the material. This decreased the flowability of
the composite material, increasing viscosity. All samples
showed drastic shear thinning after the shear rate of 10.
Zero shear viscosity of all the sample was also found to
be nearly same, i.e. at 1000 Pa·s.
Figure 2. Heating scan of vergin nylon 6/cenosphere com-
posites.
Figure 3. Cooling scan of virgin nylon 6/cenosphere com-
posites.
Table 5. Thermal properties of nylon 6 and nylon 6/cenosphere composites.
Sr. No. Sample Name Enthalpy of
melting (J/g) Melting temperature (˚C) Enthalpy of crystallization (J/g) Crystallization temperature (˚C)
1 VNY 69.16 221.23 82.92 192.65
2 NC 2.5 46.68 222.26 48.43 193.50
3 NC 5 59.64 223.24 61.04 191.02
4 NC 7.5 65.61 221.81 65.02 191.16
5 NC 10 66.13 223.24 80.32 191.71

P. A. WASEKAR ET AL. 811
Figure 4. Viscosity vs shear rate graph of nylon 6/ceno-
sphere composites.
Figure 5. SEM image of 2.5 phr cenosphere loaded nylon 6
at 5000× showing particle size distribution.
(a) (b)
(c) (d)
Figure 6. Showing particle size of (a) SEM image of 2.5 phr cenosphere loaded nylon 6 at 20000×; (b) SEM image of 5 phr
cenosphere loaded nylon 6 at 5000×; (c) SEM image of 7.5 phr cenosphere loaded nylon 6 at 5000×; (d) SEM image of 10 phr
cenosphere loaded nylon 6 at 5000×.
3.5. Morphological Properties
Morphological properties of the cenosphere/nylon 6
composites were found using scanning electron micros-
copy (SEM). SEM images of 2.5 phr cenosphere/nylon 6
lon 6 composites showing cenosphere particle size, 5 phr
composites showing dispersion, 2.5 phr cenosphere/
r cenosphere/ny-
here/nylon 6 com-
pectively.
3.9 to 4.2 µm, as
nosphere content, ny-
cenosphere/nylon 6 composites, 7.5 ph
lon 6 composites and 10 phr cenosp
posites are show n in Figures 5 and 6 res
Particle size of cenosphere is about
evident from Figure 6. At 2.5 phr ce

P. A. WASEKAR ET AL.
812
cenosphere are un iformly distributed in th e nylon matrix,
giving better flowability to the nylon 6 matrix. As the
cenosphere content increases in the nylon 6 matrix, it
forms agglomerate, increasing particle size. Increase in
pa
agent in nylon 6. By use of cenosphere as
n nylon 6 matrix, elongation at break
pact strength by 44%; at 2.5 phr
NCES
Materials Charing, Vol. 1, No. 1,
rticle size is gradual with increase in cenosphere con-
centration.
4. Conclusion
Cenosphere has always been used as a material to reduce
the density of the material due to its micro-spherical na-
ture. However, cenosphere can be effectively used as
reinforcing
reinforcing agent i
increased by 83%, im
content. Flexural strength increased with increase in
cenosphere content. Flexural strength increased by 25%
at 10 phr cenosphere content. Cenosphere decreased crys-
tallinity and also increased flowability of nylon 6. No
change in tensile strength of the composites was ob-
served with change in cenosphere content.
5. Acknowledgements
The authors gratefully acknowledge the financial support
from The University Grant Commission under the SAP
scheme for their financial support.
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