This study characterized a graphene-reinforced immiscible polymer blend by injection molding graphene-reinforced polystyrene (G-PS) with high density polyethylene (HDPE) at various concentrations. Fourier transform infrared spectroscopy (FTIR) and flexural testing showed that adding higher concentrations of G-PS increased the flexural modulus of the HDPE blend. FTIR also indicated molecular interactions between G-PS and HDPE through distinct absorption peaks. The aim was to determine the effect of G-PS on HDPE mechanical properties and their molecular interactions.

1. Characterization of a Graphene-Reinforced Immiscible Polymer Blend
Divas Singh, Professor Jennifer Lynch, Justin Hendrix
Materials Science and Engineering Department
Abstract
Background
Conclusion
NPY
NPY POMC
Results
Methods
Graphene has exceptional electrical, thermal, and
mechanical properties, and engineers are trying to combine it
with different polymers to create a composite with beneficial
properties. In this work, graphene was melt-blended with
polystyrene (G-PS) to create a stiff graphene-reinforced
polymer matrix composite (G-PMC). Then, G-PS was injection
molded with high density polyethylene (HDPE), a less stiff but
tough thermoplastic, at various concentrations. The aims of
this project are to determine the effect of G-PS on the flexural
mechanical properties of HDPE and the resulting molecular
interactions between G-PS and HDPE. The molecular
interactions were determined using Fourier Transform Infrared
Spectroscopy (FTIR) on each concentration.
4
5
6
• Multifunctional composites are currently are important to
many industries
• Graphene-reinforced polymer matrix composites may
provide structural components with barrier, thermal, or
electrical property benefits
• Materials studied in this work include
• Graphene nanoflakes
• A form of carbon, covalently bonded in an hexagonal
pattern with secondary bonding between layers
• Offers exceptional mechanical, barrier, electrical, and
thermal properties
• Polystyrene: an inexpensive, rigid but brittle polymer
• 35 wt. % graphene nanoflakes melt-blended with PS (G-
PS)
• Polyethylene: and inexpensive, tough polymer
• Most common polymer
• G-PS and HDPE were injection molded at
10, 20, 25, 30, 35, 40, 45, 50, 60, and 80
wt. % (G-PS) in HDPE
• Mechanical properties were characterized
in flexural mode, according to ASTM D790
• Span length of 5 cm
• Cross head rate of 1.33 mm/min
• FTIR (Fourier Transform Infrared
Spectroscopy analyzes the absorption of a
material
• Plots wavenumber versus absorbance
pinpointing the molecular interactions
occurring on the sample.
• In our tests, we used Agilent
Technologies’s 4100 ExoScan FTIR.
• Three samples scanned per blend
• Tested at 6 regions (shown below)
• One sample was etched and tested at
varying depths
• 1.5mm, 2.0mm, 2.5mm
.
Wavenumber Mechanism
3030-3080 Aromatic CH stretching vibration
2000 - 1650 Aromatic CH combination frequency overtones
1625-1475 Aromatic CC bonds stretching vibration
1250-900 Aromatic CH deformation vibration
900-650 Aromatic CH deformation vibration
Wavenumber Mechanism
3445 O-H stretching vibrations
1030 C-O stretching vibrations
1565 C=C skeletal vibrations
1644 C=C skeletal vibrations
The different depths the sample was
etched at.
Figure 5. Flexural results for varying concentration of (G-PS) in HDPE. (a) Flexural stress-strain curves and
(b) Flexural modulus, showing and increase in modulus with increasing concentration of G-PS.
Figure 6. FTIR results for varying concentration of G-PS in HDPE. Different compositions have different
absorbances, but there are distinct peaks at 2850 and 2925.
• Flexural modulus and strength increase with increasing concentration of G-PS in HDPE
• Molecular interactions indicated deformation vibrations in the polystyrene around 700
cm^-1, and stretching vibrations at other distinct peaks, showing the molecular interactions
of that specific region
The different regions scanned by
the FTIR.
(a)
(b)(a)
(b)
Table 1. Polystyrene FTIR key Table 2. Graphene FTIR key
0
2
4
6
8
10
12
0 10 20 30 40 50 60 70 80 90 100
FlexuralModulus(GPa)
% (G-PS) in HDPE
Modulus
(35% G-PS)-HDPE
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
2800 2850 2900 2950 3000 3050 3100
ABSORBANCE
WAVENUMBER (1/CM)
HDPE
10%
20%
25%
30%
35%
40%
45%
50%
60%
80%
(%G-PS)
0
10
20
30
40
50
60
0 0.01 0.02 0.03 0.04 0.05
FlexraulStress(MPa)
Flexural Strain (mm/mm)
G-PS
80
60
50
45
40
35
30
25
20
10
HDPE
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
650 850 1050 1250 1450 1650 1850
Absorbance
Wavenumbers [1/cm]
80%
60%
50%
45%
40%
35%
30%
25%
20%
10%
HDPE
% G-PS
• Bahadur, P., and N. V. Sastry. Principles of Polymer Science.
Harrow, U.K.: Alpha Science International, 2005. Print.
• "Agilent | 4100 ExoScan Series FTIR (handheld)." Agilent | 4100
ExoScan Series FTIR (handheld). N.p., n.d. Web. 27 Apr. 2016.
References