1) The document reports on a study that examined how the concentration of graphene nanofiller within polypropylene nanocomposites affects flame retardancy, impact strength resistance, and melting point. 2) The study found that increasing the graphene concentration improved flame retardancy but reduced impact strength resistance and lowered the melting point. 3) This is because the mismatch between polypropylene and graphene properties introduced stresses that weakened the nanocomposite structure at the nanoscale.

1. STONY BROOK UNIVERSITY
COLLEGE OF ENGINEERING AND APPLIED SCIENCES
Chemical and Molecular Engineering Program
Chemical Engineering Laboratory II:
CME 320
Basic Properties of Polypropylene/Graphene Nanocomposites
By
Marcin Kielkiewicz
Team Members: Jennifer Imbrogno & Kathryn Margaret Caducio
TA: Yichen Guo & Yuan Xue
Submitted to:
Prof. Miriam Rafailovich and Dr. Pinkas-Sarafova
Submitted: March 25, 2015

2. Marcin Kielkiewicz 108225444 CME 320 Nanocomposites March 25, 2015 Page1
Abstract
The relationship between the concentrations of graphene nanofiller within a predominantly
polypropylene nanocomposite was examined using a UL 94 flame retardancy test, an Izod strength
resistance test, and differential scanning calorimetry. Two nanocomposites, one with 10% graphene by
mass and the other with 50% graphene by mass were manufactured and then tested against pure
polypropylene. Increasing the graphene concentration within the polymer matrix increased the flame
retardancyof the nanocomposite;bothpure polypropylene andthe 10% graphene nanocomposite were
non-grade while the 50% graphene nanocomposite was non-flammable andassignedagrade of V0. The
mismatch between physical and mechanical properties of polypropylene and graphene resulted in
residual stress at the nanoscale that weakened the overall structure of the nanocomposite. This was
corroborated by the results of the impact resistance test and the melting point measurements. An
increasingconcentrationof graphene withinthe polymermatrix reducedthe impactstrengthresistance;
the average values are as follow: 16.139 J/m for pure polypropylene, 15.82 J/m for the 10% graphene
nanocomposite,and12.647 J/mforthe 50% graphene nanocomposite.The meltingpointof the materials
was reduced with increasing graphene concentration; the results are as follow: 167.114 °C for pure
polypropylene, 166.49 °C for the 10% graphene nanocomposite, and 164.65 °C for the 50% graphene
nanocomposite.
Introduction
A nanocomposite is defined as a material that
exists in either one-dimensional, two-
dimensional,orthree dimensional formmade of
distinctly dissimilar components which are
mixed at the nanometer scale. The mechanical,
electrical, thermal, optical, electrochemical,
and/or catalytic properties of the
nanocomposite will differmarkedlyfromthatof
the componentmaterials.1
Inmechanical terms,
nanocomposites differ from
conventional composites due to the
exceptionallyhighsurface to volumeratioof the
nanofiller and its high aspect ratio.2
Polymer nanocomposites often have
properties that differ considerably from the
original polymer material by simply capitalizing
on the nature and properties of the nanofiller.
Control over the nanofillers’ dispersion within
the nanocomposite allowsforthe fine-tuningof
physical properties and modification of novel
behaviorsthatare absentinthe unfilledmatrices
of the pure polymer.3
Some examples of such
new properties are flame retardancy and
accelerated biodegradability.4
In this experiment several
nanocomposites will be manufactured with
polypropylene (PP) serving as the polymer
matrix and graphene (Gr) as the nanofiller.
Polypropyleneislowcostthermoplasticpolymer
with many industrial applications and
widespread use in consumer products due to it
being relatively non-toxic, its high resistance to
degradation, and its chemical stability in most
environments.5
Graphene is an allotrope of
carboninthe formof atwo-dimensional,atomic-
scale,hexagonallattice inwhichone atomforms
each vertex. It is the basic structural element of
other carbon allotropes, including graphite,
carbon nanotubes, and fullerenes. It can be
considered as an indefinitely large

3. Marcin Kielkiewicz 108225444 CME 320 Nanocomposites March 25, 2015 Page2
aromatic molecule.6
Several properties of pure
polypropylenewere comparedtothose of 90:10
(by mass) PP:Gr nanocomposite and 50:50 (by
mass) PP:Grnanocomposite. A flame retardancy
testwasconductedinaccordance withthe UL94
standard,anIzodImpactstrengthtestmeasured
the materials resistances to impact from a
swinging pendulum. The melting point of the
materials was determined using scanning
differentialcalorimetry.Bystudyingthe physical
changesassociatedwithintroducingananofiller
to a low cost polymer unique applications of
industrial significance could be envisioned from
this research.
Method and Materials
Two 45 g batchesof PP/Gr nanocomposite were
made by weighing PP (Amco Polymer LLC; PP-
3825) and Gr (XG Sciences; xGnp H5) on a mass
balance (OhalisCS200).The firstnanocomposite
was a 90:10 mixture of PP:Gr by mass, the
second nanocomposite made was a 50:50 of
PP:Gr by mass. The nanocompositeswere made
using a C.W. Brabender mixer. The mixer was
firstheatedto 170 °C (the meltingpointof PP).9
To clean the mixer approximately fifty grams of
pure PPwere addedtothe mixerwiththe rotary
speedsetto 20 rpm. After1 min.the speedwas
increasedto100 rpm for 15 min.To remove the
PP and any impuritiesthe speedwasreducedto
2 rpm, the mixing unit disassembled, and the
liquid PP removed (the PP had to be removed
quickly due to rapid cooling and hence
crystallization). Once the mixer was clean the
90:10 nanocomposite was made by adding 40.5
g ± 0.1 g PPto the unitat 20 rpmand 170 °C and
then adding 4.5 g ± 0.1 g of Gr. The speed was
then increased to 100 rpm for 15 minutes. The
resulting nanocomposite was removed by
reducingthe speedto2rpmandscrapingoutthe
mixture. The unit was then cleaned again with
the following the same procedure as outlined
above with around fifty grams of PP. Once the
mixer was clean the 50:50 nanocomposite was
made bysimultaneouslyadding22.5 g ± 0.1 g PP
and 22.5 g ± 0.1 g of Gr to the mixer (a mixture
of the two was easier to insert into the unit
because the light Grpowderwouldnotenterthe
mixer at an appreciable rate on its own) at 20
rpm and 170 °C. The speed was then increased
to 100 rpm for 15 minutes. The resulting
nanocomposite was removed by reducing the
speed to 2 rpm and scraping out the mixture.
Once the nanocomposite was removed the
mixer was cleaned with polystyrene pellets via
the same procedure that was done with PP.
Throughout the whole procedure caution was
taken when operating the mixer because the
unitwas extremelyhot.
A portion of the 90:10 nanocomposite,
the 50:50 nanocomposite, and pure PP were
molded into five samples each (approximately
2.5 in × 0.5 in × 0.125 in) for the Izod strength
test and one sample each (approximately 5 in x
0.5 in x 0.125 in) for the flame retardancy test
usinga moldingpress(FredS. Carve Inc.; Carver
Model C, S/N 40,000-370). The nanocomposites
had to be broken down into smaller piecesand
placed into the molds to fill as much of the free
space as possible. The molds were then placed
inside the moldingpresswhichwassetto365 °F.
Each sample tookapproximatelyfiveminutesto
partially melt at which point the molds were
sealedat using15,000 Lbs of pressure forseven
minutes. The molds were thentaken out of the
molding press, cooled over a stream of cool air,
and thenclippedfromthe molds.Heatresistant
gloveswere usedwhenplacingthe moldsinside

4. Marcin Kielkiewicz 108225444 CME 320 Nanocomposites March 25, 2015 Page3
the molding press and when taking the molds
out.
The flame retardancy test performed
withrespecttoUL 94, the StandardforSafetyof
Flammability of Plastic Materials for Parts in
DevicesandAppliancestesting.The pure PPand
both nanocomposites were clamped vertically
on a ring stand and subjected to a blowtorch
flame for ten seconds. Cotton was placed
underneaththe ringstand to see whetherliquid
dropletswouldignite it.The flammabilityof each
species was determined using the following
criteria: The material was designated non-grade
if it could not self-extinguish within 30 seconds
afterbeingignited;V-2if burningstoppedwithin
30 seconds on a vertical specimenwith drips of
flamingparticlesallowed;V-1if burningstopped
between 10 and 30 seconds after ignition with
drips of particles allowed as long as they were
not inflamed; V-0 if burning stopped within 10
secondswithdripsof particlesallowedaslongas
they were not inflamed.7
The time
measurements were taken using a cell-phone
stopwatch.
An Izod impact strength test was
performed to measure the impact resistance of
the materials. Five samples per material were
tested (TMI monitor impact testing machines
Inc., w = 3.2, 1200, pendulum=5.5 J) with the
according to the international standard for the
testingof plastics(ASTMD256).The resultswere
expressed in energy lost per unit of thickness
(J/m) at the notch of the sample.8
The average
impact resistance and the sample standard
deviation were calculated using the following
equations:
The melting point of the
nanocomposites were measured using a
differentialscanningcalorimeter.Thistechnique
isthe mostuseful foraccurate formeasuringthe
melting point of polypropylene because the
individual polymer chains vary in molecular
weight and the methyl groups have varying
spatial orientations to one another; therefore
the melting point of polypropylene occurs at a
range and the melting point is determined by
finding the highest temperature of on the
differential scanningcalorimetrychart.Perfectly
isotactic PP (where all the methyl substituents
are located on the same side of the polymer
backbone) has a melting point of 171 °C.
Commercial isotacticPPhasa meltingpointthat
ranges from 160 to 166 °C, depending on the
atacticity of the polymer (where methyl
substituents have random orientation on the
polymerbackbone).9
OurTA sentusdata forand
80:20 nanocomposite and a 60:40
nanocomposite that we did not make.
Results/Discussion
The results of the flame test are as follow: Pure
PP was easily ignited and did not self-extinguish
within 30 seconds. Non-flaming drops of liquid
PPignitedcottonthatwasat the base of the ring
stand. The polymer is therefore non-grade. The
90:10 composite did not self-extinguish within
30 seconds after being ignited. No liquid drops
were observed for this sample. The sample is
non-grade.The 50:50 nanocomposite wouldnot
ignite within ten seconds therefore it is zero
grade. The sample was tested a second time
except this time subjected to a 20 sec flame.
Equation 1. Average. Equation 2. Sample Standard
Deviation.

5. Marcin Kielkiewicz 108225444 CME 320 Nanocomposites March 25, 2015 Page4
Combustion lasted for 1 sec. after flame
removal. We can deduce from this result that
increasingthe concentrationof Gr withinthe PP
matrix reduces the materials flammability.
The resultsforthe Izodstrengthtestare
shown in Tables 1-3. Pure PP had the highest
impact strength resistance, the 90:10
nanocomposite had the second highest
resistance, and the 50:50 expressed the lowest
value of resistance.Equations1and2 were used
to obtain the average and the sample standard
deviationfromthedata. A graphical relationship
between the amount of graphene in the matrix
and the impact strength resistance is shown in
Fig. 1. The manufacturing process used to make
the samples may have produced non-uniform
samples by introducing air pockets or other
structural defects via melting/cooling. This may
explain the large discrepancy between the
samples for impact strength resistance of each
material. The trendline in Fig. 1 shows that
impact strength resistance decreases as the
concentration of Gr increases in the PP matrix.
Because of to a difference in physical and
mechanical properties of PP and Gr, residual
stresses are created within the nanocomposites
at the nanoscale due toamismatchbetweenthe
properties of the matrix and the nano-filler.10
Due to a lack of liquid nitrogen in the
laboratory, differential scanning calorimetry
tests were performed independently by the TA.
The data he provided us with gave the melting
pointdata for an 80:20 PP:GR nanocomposite,a
60:40 PP: Gr nanocomposite,andpure PP.Glass
transition temperatures were not provided.
Using a polynomial trendline to satisfy a
relationship between the differences in melting
pointbetweenthe materials (Fig.2),the melting
point of the 90:10 nanocomposite was
interpolated to be 166.49 °C and the melting
point of the 50:50 nanocomposite was
extrapolated to be 164.65 °C. The melting point
of pure PP was 167.114 °C.
Table 1. The impact strength resistance of pure
polypropylene. Avg. stands for average while sigma
stands for the sample standard deviation.
Table 2. The impact strength resistance of the 90:10
nanocomposite. Avg. stands for average while sigma
stands for the sample standard deviation.
Table 3. The impact strength resistance of the 50:50
nanocomposite. Avg. stands for average while sigma
stands for the sample standard deviation.
Figure 1. Average Impact strength vs. Polypropylene
concentration. The uncertainty in the y-axis is one
standard deviation. The uncertainty in the x-axis is
negligible. A linear trendline is shown.

6. Marcin Kielkiewicz 108225444 CME 320 Nanocomposites March 25, 2015 Page5
From the results it is easy to see that an
increase in concentration of Gr within the PP
matrix reducesthe meltingpointof the material.
Just as the material becomes structurallyweaker
as shown by the impact resistance test, the
difference in physical and mechanical properties
between PP and Gr cause that weaken the
internal structure and lower the melting point.
Conclusion
The relationshipbetween the concentrations of
graphene nanofiller within a predominantly
polypropylene nanocomposite was examined
using a UL 94 flame retardancy test, an Izod
strength resistance test, and differential
scanning calorimetry. Increasing the graphene
concentration within the polymer matrix
increased the flame retardancy of the
nanocomposite. However, mismatch between
physical and mechanical properties of
polypropylene and graphene created residual
stresses at the nanoscale that weakened the
overall structure of the nanocomposite. An
increasingconcentrationof graphene withinthe
polymer matrix reduced the impact strength
resistance of the material and reduced the
melting point of the nanocomposite.
References
1) Kamigaito, Osami. "What Can Be Improved by
Nanometer Composites?” Journal of the Japan
Society of Powder and Powder Metallurgy. 38.3
(1991): 315-21.
2) Ajayan, P. M., L. S. Schadler, and P. V.
Braun. Nanocomposite Science and Technology.
Weinheim: Wiley-VCH, 2003.
3) Manias, Evangelos. "Nanocomposites: Stiffer by
Design." Nature Materials .6.1 (2007): 9-11.
4) Morgan, Alexander B., and Charles A.Wilkie. Flame
Retardant Polymer Nanocomposites. Hoboken, NJ:
Wiley-Interscience, 2007.
5) Johnson, Todd. "What Is Polypropylene and What
Is It Used For?" About.com. Web. 19 Mar. 2015.
6) "Graphene." Cambridge Dictionaries Online.
Cambridge University Press. Web. 21 Mar. 2015.
7) "UL 94, the Standard for Safety of Flammability of
Plastic Materials for Parts in Devices and Appliances
testing". UL. Retrieved 17 October 2013.
8) "Izod Impact (Notched) ASTM D256, ISO
180."Intertek. Intertek Group Plc.Web. 21 Mar.2015.
9) Maier, Clive, and Teresa Calafut. Polypropylene:
The Definitive User's Guide and Databook. Norwich,
NY: Plastics Design Library, 1998.
10) Shokrieh, Mahmood M. "Residual Stresses in
Composite Materials." Woodhead Publishing (2014):
xix-xx. Science Direct.
Figure 2. Material melting point vs. Polypropylene concentration.
There are no uncertainties in either x or y axes. A polynomial
trendline is shown.