8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 1/43
CHEG589: Polymer Nanocomposites
Chapter 1: Nanotechnology and Nanocomposites
Dr. Vikas Mittal, Summer 2015
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 2/43
The Beginning• In 1959, Physics Nobel Laureate Richard Feynman suggested: What I want
to talk about is the problem of manipulating and controlling things on a
small scale ... What are the limitations as to how small a thing has to be
before you can no longer mold it?
• The term nanotechnology was first used in 1974 by Norio Taniguchi to
refer to the precise and accurate tolerances required for machining and
finishing materials.
• In 1981, K. E. Drexler described a new "bottom‐up" approach, instead of
the top‐down approach discussed earlier by Feynman and Taniguchi. The
bottom‐up approach involved molecular manipulation and molecular
engineering to build molecular machines and molecular devices with
atomic precision.
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 3/43
What is Nanotechnology?• The term nano derives from the Greek word for dwarf. It is used as a prefix
for any unit such as a second or a meter, and it means a billionth of that unit.
Hence, a nanometer (nm) is a billionth of a meter, or 10‐9 meters.
• Nanotechnology means any technology on a nanoscale that has applications
in the real world. Nanotechnology encompasses the production and application of physical, chemical, and biological systems at scales ranging
from individual atoms or molecules to submicron dimensions, as well as the
integration of the resulting nanostructures into larger systems.
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 4/43
What is Nanotechnology?
• Despite the wide use of the word nanotechnology,
the term has been misleading in many instances. This is because some of the technology
deals with systems on the micrometer range and not on the nanometer
range (1‐100 nm).
• Nanomaterials are also not undiscovered materials. It is important to keep
in mind that some past technology such as, for example, nanoparticles of
carbon used to reinforce tires as well as nature's photosynthesis are
already a form of nanotechnology.
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 5/43
Approaches to Nanotechnologies
• top‐down approach: An operator first designs and controls a macroscale
entity to produce an exact copy of itself, but smaller in size. Subsequently, this downscaled entity, will make a replica of itself, but also a few times smaller in size. This process of reducing the scale continues until a nanosize entity is produced and is capable of manipulating nanostructures.
• One of the emerging fields based on this top‐down approach is the field of nano‐and micro‐electromechanical systems (NEMS and MEMS, respectively). MEMS research has already produced various micro
mechanical devices, smaller than 1 mm2, which are able to incorporate
microsensors, cantilevers, microvalves, and micropumps.
• An interesting example is the microcar fabricated by Nippondenso Co.
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 6/43
Approaches to Nanotechnologies
• The top‐down approach is not a friendly, inexpensive, and rapid way of producing nanostructures. Therefore, a bottom‐up approach needs to be
considered.
• The concept of the bottom‐up approach is that one starts with atoms or
molecules, which build up to form larger structures.
• In this context, there are three important enabling bottom‐up
technologies, namely (1) supramolecular and molecular chemistry, (2)
scanning probes, and (3) biotechnology.
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 7/43
Length Scale
Length scales ranging
from subatomic through
molecular, human, and
terrestrial to astronomic
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 8/43
Why is Nano Scale Important?• By creating nano‐scale structures, it is possible to control the
fundamental properties of materials, such as their melting
temperature, magnetic properties, charge capacity, and even their
color, without changing the materials’ chemical composition.
• Making use of this potential leads to new, high‐performance
products and technologies that were not possible before.
• Nanoscale structures such as nanoparticles and nanolayers have
very high surface to volume ratios, making them ideal for use in
polymeric materials.
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 9/43
Nanotechnology in NatureAbalone
• Abalone builds the shell from traditional
materials, namely calcium carbonate (CaCO3)and a protein, forming a layered
nanocomposite that is strong and resilient
• Looking at the shell under an electron
microscope at high magnifications, the shell
looks like a brick wall, with calcium carbonate "bricks" separated by the protein
"glue"
• The formation of the abalone shell starts with proteins, which self assemble into
"room walls" with a distribution of negatively charged sites. Inside each "room" there is seawater filled with calcium and carbonate ions, which are attracted to
the walls and eventually form crystals of CaCO3
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 10/43
Nanotechnology in NatureSpider Web
• The combined strength and flexibility of a spider web results from the
arrangement of nanocrystalline reinforcements embedded in a polymer matrix.
• A closer look at the spider web microstructure reveals the existence of strongly oriented nanocrystals, which adhere to the protein that composes their surrounding polymeric matrix. In other words, the spider web is a nanocomposite material composed of relatively stiff nanocrystals dispersed
within a stretchy matrix
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 11/43
Nanotechnology in NatureRhinoceros Horn
• The horn is a composite made of two types of keratin.
• One type is in the form of tubules that are densely packed. These tubules, which range from 300 to
500 μm, comprise around 40 layers of cells.
• Surrounding these tubules is another type of keratin that is continuous and acts as a matrix.
• Because the matrix and the tubules are the same material, the interfacial strength is very good, which
leads to a rigid material that is very tough to break.
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 12/43
Classes of Materials• Nanomaterials: The nanomaterial class of materials is extremely broad
because it can include all the previous classes of materials, provided they
are composed of a structural component at the nanoscale or they exhibit
one of the dimensions at the nanoscale.
• Nanomaterials are typically categorized according to the number of
dimensions that are not at the nanoscale
0‐D (nanoparticles),
1‐D (nanowires, nanotubes, and nanorods),
2‐D (nanofilms and nanocoatings),
3‐D (bulk)
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 13/43
Classification of Nanomaterials• The most typical way of classifying
nanomaterials is to identify them
according to their dimensions.
• Nanomaterials can be classified as (1)
zero‐dimensional (0‐D), (2) one‐
dimensional (1‐D), (3) two‐
dimensional (2‐D), and (4) three‐
dimensional (3‐D).
• This classification is based on the
number of dimensions, which are not
confined to the nanoscale range (<100
nm).
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 14/43
Classification of Nanomaterials0‐D
The most common representation of zero‐dimensional
nanomaterials are nanoparticles. These nanoparticles
can:
• Be amorphous or crystalline
• Be single crystalline or polycrystalline
• Be composed of single or multichemical elements
• Exhibit various shapes and forms • Exist individually or incorporated in a matrix
• Be metallic, ceramic, or polymeric
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 15/43
Classification of Nanomaterials1‐D
1‐D nanomaterials differ from 0‐D nanomaterials in that
the former have one dimension that is outside the
nanoscale. This difference in material dimensions leads to
needle‐shaped nanomaterials. One‐dimensional
nanomaterials include nanotubes, nanorods, and
nanowires. 1‐D nanomaterials can be:
• Amorphous or crystalline
• Single crystalline or polycrystalline
• Chemically pure or impure
• Standalone materials or embedded in within another
medium
• Metallic, ceramic, or polymeric
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 16/43
Classification of Nanomaterials2‐D
2‐D nanomaterials are materials in which two of the
dimensions are not confined to the nanoscale. As a result,
2‐D nanomaterials exhibit platelike shapes. Two‐
dimensional materials can be:
• Amorphous or crystalline
• Made up of various chemical compositions
• Used as a single layer or as multilayer structures
• Deposited on a substrate
• Integrated in a surrounding matrix material
• Metallic, ceramic, or polymeric
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 17/43
Classification of Nanomaterials3‐D
These materials have three dimensions above 100 nm.
Despite their bulk dimensions, these materials possess a
nanocrystalline structure or involve the presence of features
at the nanoscale. With respect to the presence of features at
the nanoscale, 3‐D nanomaterials can contain dispersions of
nanoparticles, bundles of nanowires, and nanotubes as well as multinanolayers. Three‐dimensional nanomaterials can be:
• Amorphous or crystalline
• Chemically pure or impure
• Composite materials
• Composed of multinanolayers
• Metallic, ceramic, or polymeric
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 18/43
Classification of Nanomaterials• The 2‐D nanomaterial may be called a
nanocrystalline film because of two features:
(1) the material exhibits an overall exterior
thickness with nanoscale dimensions, and (2)
its internal structure is also at the nanoscale.
• Though this example helps illustrate two
possible ways of categorizing of 2‐D
nanomaterials, both these restrictions do not
need to be in place for the material to be
considered a nanomaterial.
• In fact, if the exterior thickness remains at the nanoscale, it is possible for the same film to
have a larger (above 100 nm) internal grain
structure and still qualify the entire material
as a nanoscale material.
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 19/43
Classification of Nanomaterials• Generally, 2‐D nanomaterials, are deposited on
a substrate or support with typical dimensions
above the nanoscale. In these cases, the overall
sample thickness dimensions become a
summation of the film's and substrate's
thickness. When this occurs, the 2‐D
nanomaterial can be considered a nanocoating.
• When the substrate thickness does have
nanoscale dimensions or when multiple layers,
with thicknesses at the nanoscale are deposited sequentially, the 2‐D nanomaterial can be
classified as a multilayer 2‐D nanomaterial.
Within each layer, the internal structure can be
at the nanoscale or above it.
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 20/43
Classification of Nanomaterials• For 3‐D nanomaterials: from our previous
definition, bulk nanomaterials are
materials that do not have any dimension
at the nanoscale. However, bulk
nanomaterials still exhibit features at the
nanoscale. Bulk nanomaterials with
dimensions larger than the nanoscale can be composed of crystallites or grains at the
nano scale. These materials are then called
nanocrystalline materials.
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 21/43
Classification of NanomaterialsAnother group of 3‐D nanomaterials are called nanocomposites. These
materials are formed of two or more materials with very distinctive
properties that act synergistically to create properties that cannot be
achieved by each single material alone. The matrix of the nanocomposite,
which can be polymeric, metallic, or ceramic, has dimensions larger than the
nanoscale, whereas the reinforcing phase is commonly at the nanoscale.
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 22/43
Classification of Nanomaterials
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 23/43
What is
a Polymer?
• A GIANT molecule
• Made up of units
called monomers
• If a carbon atom was the size of a tennis
ball:
PE = 30km
DNA = 70,000km
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 24/43
Uses of Polymers
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 25/43
Petrochemical Value Chain based on Cracker
Source: Linde
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 26/43
Definitions
• Monomer ‐ simple molecular unit which when reacted
together forms a polymer.
• Oligomer ‐ low molecular weight compound with
several repeat units joined together.
• Polymer ‐ substance composed of molecules with a
large molecular weight formed from repeating units
covalently bonded together.
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 27/43
Types
of
Polymers
natural polymers
- cellulose
- proteins
- DNA
- natural rubber
- shellac
- amber
synthetic polymers
- polyethylene
- polypropylene
- poly(vinylchloride)
- synthetic rubber
- polyamides- polyurethanes
- melamine resins
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 28/43
28
• The dimer of ethylene is a gas, but
oligomers with a DP of 3 or more are
liquids, with the liquid viscosity increasing
with the chain length.
• Polyethylenes with DPs of
about 30 are grease like, and those with
DPs around 50 are waxes.
• As the DP value exceeds 400 or the
molecular weight exceeds about 10,000,
polyethylenes become hard resins with
softening points about 100°C. The increase
in softening point with chain length in thehigher-molecular-weight range is small.
Importance of DP
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 29/43
29
• Tensile strength properties
increase rapidly first as the chain length
increases and then level off
• The melt viscosity continues to increase
rapidly with molecular weight
• Polymers with very high molecular
weights have superior mechanicalproperties but are difficult to process and
fabricate due to their high melt viscosities.
• The range of molecular weights chosen
for commercial polymers represents acompromise between maximum properties
and processability.
Importance of Molecular Weight
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 30/43
Uniqueness of Nanostructured Materials
• What is unique to nanofillers compared to micrometer‐scale
traditional fillers, and how do the composites compare to
their macroscopic counterparts?
Small size of filler particles (optical clarity)No stress concentration
Exceptionally large interfacial area
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 31/43
Uniqueness of Nanostructured Materials
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 32/43
Uniqueness of Nanostructured Materials
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 33/43
Nanocomposites• Nanocomposites are a class of materials in which one or more phases with
nanoscale dimensions (0‐D, 1‐D, and 2‐D) are embedded in a metal,
ceramic, or polymer matrix.
• The general idea behind the addition of the nanoscale second phase is to
create a synergy between the various constituents, such that novel
properties capable of meeting or exceeding design expectations can be
achieved.
• The properties of nanocomposites rely on a range of variables, particularly
the matrix material, loading, degree of dispersion, size, shape, and
orientation of the nanoscale second phase and interactions between the
matrix and the second phase.
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 34/43
NanocompositesPolymer‐matrix nanocomposites
• Polymer type: thermoset, thermoplastic, elastomer• Reinforcement: nanoparticles (0‐D), nanotubes (1‐D) and nanoplates (2‐D)
Polymer‐matrix nanocomposites with 0‐D materials
• Depending on the type of nanoparticles added, the mechanical, electrical,
optical, and thermal properties can be altered
• In the case of mechanical properties, modulus and strength depend on the
degree of interaction between the particle and the polymer. For example, in poly(methyl methacrylate) (PMMA) nanocomposites reinforced with
alumina, the modulus decreases due to the weak interaction, whereas in
polystyrene nanocomposites reinforced with silica nanoparticles, the
modulus increases due to a strong bonding.
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 35/43
NanocompositesPolymer‐matrix nanocomposites with 1‐D materials
• Carbon nanotubes (CNTs) are widely used as reinforcement.
• Several critical factors need to be addressed:
(1) uniform dispersion of carbon nanotubes within the polymer matrix,
(2) alignment of CNTs in the nanocomposite,
(3) good interfacial bonding between the CNTs and the polymer matrix.
• With respect to the dispersion of CNTs, they
exhibit smooth surfaces and intrinsic Van der Waals
interactions, which tend to promote clustering when
dispersed in a polymer matrix
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 36/43
NanocompositesPolymer‐matrix nanocomposites with 2‐D materials
• Plate like layered materials (layered silicates)
with a thickness on the order of 1 nm but with
an aspect ratio of 25 or above.
• Significant improvements in different properties
• For these layered silicates to be useful in
nanocomposites, the layers must be separated
and dispersed within the polymer matrix.
However, these layers are highly hydrophilic, and
thus individual layers do not easily disperse in
relatively hydrophobic species, such as an
organic polymer.
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 37/43
Nanocomposites• The resulting nanocomposites can exhibit
various microstructures.
• Intercalated nanocomposites, when the
polymer diffuses into the clay layers, thereby
expanding the distance between the clay layers,
but the order (or periodicity) is still maintained
• Exfoliated nanocomposites when individual
delaminated silicate layers are dispersed in a
polymer matrix, thus completely disturbing the
order of the clay layers.
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 38/43
Mechanical Properties
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 39/43
Mechanical Properties
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 40/43
Role of Aspect Ratio on Properties
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 41/43
Other Properties
• Apart from mechanical and permeation properties, other properties attributed to polymer nanocomposites are:
improved thermal resistance
improved flame resistance
improved moisture resistance
improved charge dissipation
improved chemical resistance
ff f l
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 42/43
Size Effects: Surface‐to‐Volume
Ratio Versus Shape
• Properties of large‐scale traditional materials are determined by the
properties of their bulk, due to the relatively small contribution of a small
surface area, however, for nanomaterials this surface‐to‐volume ratio is
inverted.
• a nanomaterial's shape is of great interest because various shapes will produce
distinct surface‐to‐volume ratios and
therefore different properties.
Sphere A/V = 3/r
Cylinder A/V = 2/r
Cube A/V = 6/L
Si Eff S f V l
8/16/2019 1. Nanotechnology and Nanocomposites
http://slidepdf.com/reader/full/1-nanotechnology-and-nanocomposites 43/43
Size Effects: Surface‐to‐Volume
Ratio Versus Shape
How much of an increase in surface area will result from a spherical particle
of 10 μm diameter to be reduced to a group of particles with diameter of 10
nanometer, assuming that the volume remains constant?