This document discusses the use of nanocomposites to improve polymer properties by mixing carbon nanotubes (CNTs) or graphene into polymers. It summarizes that melt mixing is an effective way to disperse CNTs into polymers, and that the masterbatch dilution technique can achieve percolation between 1.0-0.5 wt% of multi-walled CNTs (MWNTs) in polycarbonate (PC), depending on processing conditions. Direct incorporation of CNTs results in percolation thresholds that depend on the type of CNT and processing method used. The document also reviews methods to fabricate graphene-polymer composites and their advantages in improving mechanical, thermal, barrier and electrical properties

1. Nanocomposites: mixing
CNTs into polymers

3. Outline
1.Introduction
2. Composites of multiwalled carbon nanotubes (MWNT) with
polycarbonate (PC) produced by masterbatch dilution technique
•Electrical resistivity
•Dispersion and alignment
•Influence of processing parameters on electrical resistivity
3. Composites of MWNT and SWNT with PC produced by direct
incorporation
•Percolation of different commercial MWNT in PC
•Percolation of SWNT in PC
•Stress-strain behaviour
4. Summary

4. – Electrical conductivity
– Improvement of mechanical properties, especially
strength
– Enhancement of thermal stability
– Enhancement of thermal conductivity
– Improvement of fire retardancy
– Enhancement of oxidation stability
– Effects at low CNT contents because of the very high
aspect ratio
Benefits of CNTs to polymers

5. How to introduce CNTs into
polymers

6. Melt mixing of CNT with
thermoplastic polymers

7. Preparation of the PC-MWNT
composites
• Masterbatch technology: polycarbonate(PC) +
PC based masterbatch (15 wt% MWNT)
– masterbatch (Hyperion Catalysis International, Inc,
Cambridge, USA) diluted with PC Iupilon E2000
(PC1), PC Lexan 121 (PC2) or PC as used for the
masterbatch (PC3)
– Haakeco-rotating, intermeshing twin screw extruder
with one kilogramm mixtures
– DACA Micro Compounder, conical twin screw
extruder (4.5 cm3
capacity)
– Brabender PL-19 single screw extruder

8. Characterization of the masterbatch
(PC + 15 wt% MWNT)

9. Dispersion in PC-MWNT
composites

10. Alignment in PC-MWNT
composites

11. Comparison for different set of PC
masterbatch dilution

12. Detection of percolation and influence of processing
conditions investigated by dielectric spectroscopy

13. Direct incorporation of different
kinds of commercial MWNT into PC

14. Comparison of direct incorporation of CNT,
masterbatch dilution, and CB addition

15. Direct incorporationof SWNT1 into PC

16. Direct incorporation of SWNT1 into PC

17. Direct incorporation of SWNT1 into PC

18. Direct incorporationof SWNT2 into PC

19. Direct incorporation of SWNT2 into PC

20. Summary
• Melt mixing is a powerful method to disperse CNT into polymers
• Masterbatch dilution technique (based on a PC masterbatch)
– percolation in the range of 1.0 wt% MWNT
– suitable processing conditions can shift percolation to lower values
(0.5wt%)
– effects of mixing equipment and PC viscosity on percolation are small
• Direct incorporation method
– percolation strongly depends on the kind of CNT, production method
(resulting in different sizes, purity and defect levels), and the
purifying/modification steps
– for commercial MWNT percolation occurs between 1.0 and 3.0 wt% and
is lower at lower MWNT diameters and higher purity
– HipCO-SWNT (CNI) percolation between 0.30 and 0.35 wt%
– stress-strain behavior of the composites: modulus and stress are
enhanced, elongation at break reduced especially above percolation
concentration

21. Graphene–polymer composite
• Graphite oxide was prepared by the Hummers method from SP-1 graphite
(Bay Carbon), and dried for a week over phosphorus pentoxide in a vacuum
desiccator. Dried graphite oxide (50 mg) was suspended in anhydrous DMF
(5 ml, Dow-Grubbs solvent system), treated with phenyl isocyanate (2 mmol,
Sigma-Aldrich) for 24 h, and recovered by filtration through a sintered glass
funnel (50 ml, medium porosity). Stable dispersions of the resulting phenyl
isocyanate-treated graphite oxide materials were prepared by ultrasonic
exfoliation (Fisher Scientific FS60, 150 W, 1 h) in DMF (1 mg ml-1).
Polystyrene (Scientific Polymer Products, approximate Mw = 280 kD, PDI =
3.0) was added to these dispersions and dissolved with stirring (Fig. 1d,
left). Reduction of the dispersed material (Fig. 1d, right) was carried out with
dimethylhydrazine (0.1 ml in 10 ml of DMF, Sigma-Aldrich) at 80 °C for 24 h.
Upon completion, the coagulation of the polymer composites was
accomplished by adding the DMF solutions dropwise into a large volume of
vigorously stirred methanol (10:1 with respect to the volume of DMF used).
The coagulated composite powder (Fig. 1e) was isolated via filtration;
washed with methanol (200 ml); dried at 130 °C under vacuum for 10 h to
remove residual solvent, anti-solvent, and moisture; crushed into a fine
powder with a mortar and pestle, and then pressed (Fig. 1f) in a hydraulic
hot press (Model 0230C-X1, PHI-Tulip) at 18 kN with a temperature of
210 °C.

23. Process flow of graphene–
polymer composite fabrication
• a, SEM and digital image (inset) of natural graphite. b, A typical
AFM non-contact-mode image of graphite oxide sheets deposited
onto a mica substrate from an aqueous dispersion (inset) with
superimposed cross-section measurements taken along the red line
indicating a sheet thickness of 1 nm. c, AFM image of phenyl
isocyanate-treated graphite oxide sheets on mica and profile plot
showing the 1 nm thickness. d, Suspension of phenyl isocyanate-
treated graphite oxide (1 mg ml-1) and dissolved polystyrene in
DMF before (left) and after (right) reduction by N,N-
dimethylhydrazine. e, Composite powder as obtained after
coagulation in methanol. f, Hot-pressed composite (0.12 vol.% of
graphene) and pure polystyrene of the same 0.4-mm thickness and
processed in the same way. g, Low (top row) and high (bottom row)
magnification SEM images obtained from a fracture surface of
composite samples of 0.48 vol.% (left) and 2.4 vol.% (right)
graphene in polystyrene.

24. Advantages of Nanosized Additions
The Nanocomposites 2000 conference has revealed clearly the
property advantages that nanomaterial additives can provide in
comparison to both their conventional filler counterparts and base
polymer. Properties which have been shown to undergo substantial
improvements include:
• Mechanical properties e.g. strength, modulus and dimensional stability
∀ Decreased permeability to gases, water and hydrocarbons
∀ Thermal stability and heat distortion temperature
∀ Flame retardancy and reduced smoke emissions
∀ Chemical resistance
∀ Surface appearance
∀ Electrical conductivity
∀ Optical clarity in comparison to conventionally filled polymers

25. Disadvantages of Nanosized
Additions
• To date one of the few disadvantages associated with
nanoparticle incorporation has concerned toughness and
impact performance. Some of the data presented has
suggested that nanoclay modification of polymers such
as polyamides, could reduce impact performance.
Clearly this is an issue which would require consideration
for applications where impact loading events are likely.
In addition, further research will be necessary to, for
example, develop a better understanding of
formulation/structure/property relationships, better routes
to platelet exfoliation and dispersion etc.

26. Examples of Mechanical Property
gains due to Nanoparticle Additions
• Data provided by Hartmut Fischer of TNO in the Netherlands
relating to polyamide – montmorillonite nanocomposites indicates
tensile strength improvements of approximately 40 and 20% at
temperatures of 23ºC and 120ºC respectively and modulus
improvements of 70% and a very impressive 220% at the same
temperatures. In addition Heat Distortion Temperature was shown to
increase from 65ºC for the unmodified polyamide to 152ºC for the
nanoclay-modified material, all the above being achieved with just a
5% loading of montmorillonite clay. Similar mechanical property
improvements were presented for polymethyl methacrylate – clay
hybrids.
• Further data provided by Akkepeddi of Honeywell relating to
polyamide-6 polymers confirms these property trends. In addition,
the further benefits of short/long glass fibre incorporation, together
with nanoclay incorporation, are clearly revealed.

27. Area of Applications
• Such mechanical property improvements have resulted
in major interest in nanocomposite materials in
numerous automotive and general/industrial
applications. These include potential for utilization as
mirror housings on various vehicle types, door handles,
engine covers and intake manifolds and timing belt
covers. More general applications currently being
considered include usage as impellers and blades for
vacuum cleaners, power tool housings, mower hoods
and covers for portable electronic equipment such as
mobile phones, pagers etc.

28. Gas Barrier
• The gaseous barrier property improvement that can result from
incorporation of relatively small quantities of nanoclay materials is
shown to be substantial. Data provided from various sources indicates
oxygen transmission rates for polyamide-organoclay composites
which are usually less than half that of the unmodified polymer.
Further data reveals the extent to which both the amount of clay
incorporated in the polymer, and the aspect ratio of the filler
contributes to overall barrier performance. In particular, aspect ratio is
shown to have a major effect, with high ratios (and hence tendencies
towards filler incorporation at the nano-level) quite dramatically
enhancing gaseous barrier properties. Such excellent barrier
characteristics have resulted in considerable interest in nanoclay
composites in food packaging applications, both flexible and rigid.
Specific examples include packaging for processed meats, cheese,
confectionery, cereals and boil-in-the-bag foods, also extrusion-
coating applications in association with paperboard for fruit juice and
dairy products, together with co-extrusion processes for the
manufacture of beer and carbonated drinks bottles. The use of
nanocomposite formulations would be expected to enhance
considerably the shelf life of many types of food.

29. Fuel Tanks
• The ability of nanoclay incorporation to reduce solvent
transmission through polymers such as polyamides has
been demonstrated. Data provided by De Bievre and
Nakamura of UBE Industries reveals significant
reductions in fuel transmission through polyamide–6/66
polymers by incorporation of a nanoclay filler. As a
result, considerable interest is now being shown in these
materials as both fuel tank and fuel line components for
cars. Of further interest for this type of application, the
reduced fuel transmission characteristics are
accompanied by significant material cost reductions.

30. Films
• The presence of filler incorporation at nano-levels has also been
shown to have significant effects on the transparency and haze
characteristics of films. In comparison to conventionally filled
polymers, nanoclay incorporation has been shown to significantly
enhance transparency and reduce haze. With polyamide based
composites, this effect has been shown to be due to modifications in
the crystallisation behaviour brought about by the nanoclay
particles; spherilitic domain dimensions being considerably smaller.
Similarly, nano-modified polymers have been shown, when
employed to coat polymeric transparency materials, to enhance
both toughness and hardness of these materials without interfering
with light transmission characteristics. An ability to resist high
velocity impact combined with substantially improved abrasion
resistance was demonstrated by Haghighat of Triton Systems.

31. Environmental Protection
• Water laden atmospheres have long been regarded as one of the
most damaging environments which polymeric materials can
encounter. Thus an ability to minimize the extent to which water is
absorbed can be a major advantage. Data provided by Beall from
Missouri Baptist College indicates the significant extent to which
nanoclay incorporation can reduce the extent of water absorption in a
polymer. Similar effects have been observed by van Es of DSM with
polyamide based nanocomposites. In addition, van Es noted a
significant effect of nanoclay aspect ratio on water diffusion
characteristics in a polyimide nanocomposite. Specifically, increasing
aspect ratio was found to diminish substantially the amount of water
absorbed, thus indicating the beneficial effects likely from nanoparticle
incorporation in comparison to conventional microparticle loading.
Hydrophobic enhancement would clearly promote both improved
nanocomposite properties and diminish the extent to which water
would be transmitted through to an underlying substrate. Thus,
applications in which contact with water or moist environments is likely
could clearly benefit from materials incorporating nanoclay particles.

32. Preparation and Characterization of
Novel Polymer/Silicate Nanocomposites
• Five categories cover the majority of composites
synthesized with more recent techniques being
modifications or combinations from this list.
• Type I: Organic polymer embedded in an
inorganic matrix without covalent bonding
between the components.
• Type II: Organic polymer embedded in an
inorganic matrix with sites of covalent bonding
between the components.

33. Preparation and Characterization of
Novel Polymer/Silicate Nanocomposites
• Type III: Co-formed interpenetrating networks of
inorganic and organic polymers without covalent
bonds between phases.
• Type IV: Co-formed interpenetrating networks of
inorganic and organic polymers with covalent
bonds between phases.
• Type V: Non-shrinking simultaneous
polymerization of inorganic and organic
polymers.

34. Preparation and Characterization of
Novel Polymer/Silicate Nanocomposites
• The great majority of nanocomposites
incorporate silica from tetraethoxysilane
(TEOS). The formation of the inorganic
component involves two steps, hydrolysis
and condensation as seen in Scheme 1.

36. Polymers considered: PEO, PEO/PPO,
PVAc, PVA, PAN, MEEP
• A general synthesis for a base, acid, or salt catalyzed polyphosphazene,
polyethylene oxide (PEO), and polyethylene oxide/polypropylene oxide
(PPO/PEO) block nanocomposite is as follows: 300 mg of polymer is
dissolved into 10 mL of a 50/50 by volume tetrahydrofuran (THF)/ethanol
mixed solvent in a capped vial. To this solution is added TEOS (336 mg). A
catalyst is then introduced as an aqueous solution (150 μl) and the mixture
is capped and sonicated at 50o
C for 30 minutes. The solution is aged from
hours to days depending upon the catalyst used in a sealed vial and poured
into a Teflon mold and loosely covered at room temperature. The
nanocomposite self assembles as the volatile solvent slowly escapes during
the condensation process.
• The synthesis of polyvinyl acetate (PVAc)/silicate nanocomposites requires
a different approach from the other nanocomposites. PVAc (300 mg) is
dissolved into an 50/50 by volume acetic acid/methanol (10 mL) mixed
solvent in a capped vial. To this solution is added TEOS (373 mg). The
solution is then sonicated for 5 minutes in a sealed vial at room temperature
and poured into a Teflon mould and loosely covered at room temperature.
The nanocomposite self assembles during the curing process, which
typically lasts up to 24 hours. Additional heating at 100 °C for 30 minutes
aids in removing lingering acetic acid from the nanocomposite.

37. Applications
• One of the most interesting of these applications is as solid polymer
electrolytes (SPE) for lithium batteries. The polyphosphazene MEEP
is a well-known SPE with very high room temperature conductivity,
however it lacks the mechanical stability to be used in a practical
device (12). Traditional stabilization methods, such as deep UV or
electron beam crosslinking methods do improve the physical
stability of SPEs, however this crosslinking lowers ionic conductivity
– tests performed in our laboratory revealed this to be a factor of 30-
45 for MEEP-like phosphazene polymers. This reduction is due to
the additional covalent linkages formed during the crosslinking
process that inhibit chain segmental motion and ion transfer. Since
the nanocomposites formed by the ceramic condensation process
do not form bonds to the polymer component, (Type I
nanocomposites) mechanical stabilization is achieved without a
great loss of ionic conductivity (13). However, these
nanocomposites have the highest tensile strength of any of the
catalyst types studied; yet they were also found to be glassy and
brittle.

38. Goal for Type I Nanocomposites
• The goal in the process is to form a
completely interpenetrating network (IPN)
of both inorganic and organic phases.
Homogeneous nanocomposites with good
IPNs are often stronger, more resilient,
and optically transparent, whereas
heterogeneous composites are often
mechanically weaker and opaque.

39. Novel Rubber Nanocomposites with
Adaptable Mechanical Properties
• Silica particles have become more important in tire applications
since the introduction of the Green Tire® by Michelin. As a filler,
silica has greater reinforcing power, such as improving tear
strength, abrasion resistance, age resistance and adhesion
properties than carbon black [6-8]. However, due to the strong inter-
particle hydrogen bonds between hydroxyl groups, the
agglomeration nature of silica is generally believed to be
responsible for the significant Payne effect which brings about
considerable rolling resistance for tire applications. In order to
reduce the filler-filler interaction and/or to enhance the mechanical
properties of silica filled composites, researchers have been working
for many years on different strategies to improve silica-rubber
interaction and, in turn, to reduce the rolling resistance. Among
these strategies, chemical modifications of rubbers by attaching
functional groups interacting with silica [9-22] and surface
treatments of silica by reducing surface polarity with different silane
coupling agents [22-36] are the most popular techniques.
•

40. Novel Rubber Nanocomposites with
Adaptable Mechanical Properties
• However, these techniques admittedly have quite a few drawbacks.
For the former technique, the chemical modification reaction of
rubber was usually not applicable to commercial production and its
degree of modification was usually very low [9,11,14,18,22].
Additionally, the chemical modification was limited to rubber chain
ends [12,17,20], meaning that the final silica composite was
unsatisfactory in terms of reducing silica agglomeration. For the
latter, the used coupling agents are expensive and it could possibly
lower the crosslinking density by reacting with the chemical
ingredients for vulcanization. This technique would lead to lower
overall cure rates [34,35], and at the same time it degraded the
mechanical performance of such silica filled material for tire
applications. In summary, due to these flaws none of the methods
mentioned above could simultaneously ensure both the ability in
reducing the silica agglomeration and improving the material
performance.

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