Update on Nanofillers in Nanocomposites - From Introduction to Application

170 Pages·2013·2.28 MB·English

by  Haghi

Update on Nanofillers
in Nanocomposites:
From Introduction to
Application
Akbar K. Haghi and Gennady E. Zaikov
A Smithers Group Company
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First Published in 2013 by
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reface
Technical and technological development demands the creation of
new materials, which are stronger, more reliable and more durable,
i.e., materials with new properties. Up-to-date projects in the creation
of new materials tend to use nanotechnology.
Nanotechnology can be referred to as a new era in human progress.
This is a wide concept, which can affect many other areas: information
technologies, medicine, military equipment, robotics and so on. In this
book the concept of nanotechnology is quite narrow and is considered
with the reference to polymeric materials including composites.
The prefix nano means a billionth and is usually referred to as 10-9.
It is usually used for prefixing units of time and length. As fantastic
as it may sound, scientific research reached the nanolevel a long
time ago. Unfortunately, at the moment everything connected with
such developments and technologies is impossible to apply to mass
production because of the low productivity and high cost, so more
research needs to be done on this.
That means that nanotechnology and nanomaterials are only accessible
in research laboratories for now, but it is only a matter of time before
they become mainstream. What sort of benefits and advantages will
the manufacturers have after the implementation of nanotechnology
and once they start to use nanomaterials? Nanoparticles of any
material have very different properties compared to those of micro-or
macro-particles. This results from the fact that as well as a reduction
of the particles’ sizes of the materials to nanometres, the physical
properties of a substance change too. For example, the transition of
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Update on Nanofillers in Nanocomposites
palladium to nanocrystals leads to an increase in its thermal capacity
of more than 1.5 times. It causes the increase of solubility of bismuth
in copper to 4000 times and the self-diffusion coefficient of copper
at room temperature increases by 21 times.
Such changes in the properties of substances are explained by the
quantitative change of surface and volume atoms’ ratio of individual
particles, i.e., by the high-surface area. Insertion of such nanoparticles
into a polymeric matrix of an old and known material gives them
new properties and hence, new possibilities for their use.
Nanocomposites based on thermoplastic matrix and containing
natural, laminated inorganic structures are referred to as laminated
nanocomposites. Such materials are based on ceramics and polymers,
however, they can be created using natural laminated inorganic
structures such as montmorillonite or vermiculite which are present,
for example, in clays. A layer of filler ~1 nm thick is saturated
with monomer solution and later polymerised. The laminated
nanocomposites in comparison with initial polymeric matrix possess
much smaller permeability for liquids and gases. These properties
mean they can be applied to the medical and food-processing
industries. Such materials can be used in the manufacture of pipes
and containers for carbonated beverages.
These composite materials are eco-friendly, absolutely harmless
to humans and possess fire-resistant properties. The derived
thermoplastic laboratory samples have been tested and to confirm
these statements.
It should be noted that the manufacturing technique of thermoplastic
materials causes difficulties, notably the dispersion of silicate
nanoparticles in the monomer solution. To solve this problem it
is necessary to develop a dispersion technique, which could be
transferred from laboratory conditions into industrial ones.
The advantages the manufacturers can have, if they decide to
reorganise their manufacture processes to use such materials, can be
predicted even today. As these materials possess more mechanical
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Preface
and gas-barrier potential in comparison with the initial thermoplastic
materials, then their application in the manufacture of plastic
containers or pipes will lead to a saving in the cost of raw materials
by being able to reduce the product thickness.
On the other hand, the improvement of physical and mechanical
properties allows application of nanocomposite products under
higher pressures and temperatures. For example, the problem of
thermal treatment of plastic containers can be solved. Another
example of the application of the valuable properties of laminated
nanocomposites concerns the motor industry.
As mentioned earlier, another group of materials is the metal
containing nanocomposites. Thanks to the ability of metal particles
to create the ordered structures (clusters), metal containing
nanocomposites can possess a variety of valuable properties. The
typical sizes of metal clusters from 1 to 10 nm corresponds to their
huge specific surface area. Such nanocomposites demonstrate the
property of superparamagnetism and catalytic properties, therefore,
they can be used for manufacturing semiconductors, catalysts, optical
and luminescent devices, and so on.
Such valuable materials can be produced in several ways, for example,
by means of chemical or electrochemical reactions to isolate metal
particles from solutions. In this case, the major problem is not so
much the problem of metal restoration but the preservation of its
particles, i.e., the prevention of agglutination and formation of large
metal pieces.
For example under laboratory conditions metal is deposited in such a
way on thin polymeric films capable of catching nano-sized particles.
The metal can be evaporated by using high energy and nano-sized
particles can be produced, which should then be preserved. Metal
can be evaporated while using explosive energy, high-voltage electric
discharge or simply high temperatures in special furnaces.
The practical application of metal-containing nanocomposites (not
giving details about high technologies) can involve the creation of
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Update on Nanofillers in Nanocomposites
polymers possessing some valuable properties of metals. For example,
a polyethylene plate containing 10% of palladium possesses very
similar catalytic properties to a plate made of pure palladium.
An example of applying metallic composite is the production of
packing materials containing silver and possessing bactericidal
properties. Some countries have already been using paints and the
polymeric coverings containing silver nanoparticles. Owing to their
bactericidal properties, they are applied to public facilities (painting
of walls, coating of handrails and so on).
The technology of polymeric nanocomposites manufacture is being
developed to be simpler and the production processes of composite
materials with nanoparticles in their structure are being researched
to make them less expensive. However, the nanotechnologies develop
at high rates, what seemed impossible yesterday, will be accessible
commercially tomorrow.
The prospects in the field of polymeric composite materials upgrading
are retained by nanotechnologies. Ever-increasing demands
manufacturers for new and superior materials stimulates the scientists
to find new ways of solving tasks on the nano level.
The fast implementation of nanomaterials in mass production, which
is highly desirable, depends on the efficiency of cooperation between
the scientists and the manufacturers in many respects. Today’s high
technology problems in application of nanofillers are successfully
solved by close co-operation of the scientific and business worlds.
Nanocomposites are polymers containing nanofillers. The
microstructure of nanocomposites has inhomogeneities in the
nanometer range. Nanocomposite materials cover the range between
inorganic glasses and organic polymers. Fillers of polymers have
been used for a long time with the goal of enhanced performance of
polymers, and especially of rubber.
The number of nanofillers has increased over the years, as has the
matrix in which they are used and their interactions with traditional
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Preface
fillers. Nowadays, the development of polymer nanocomposites
is one of the most active areas of development of nanomaterials.
The properties imparted by the nanoparticles are various and
focus particularly on strengthening the electrical conduction and
barrier properties to temperature, gases and liquids as well as
the possible improvement of fire behaviour. As a method, which
consists of reinforcing polymer chains at the molecular scale in the
same way that fibres are used as reinforcement at the macroscopic
scale, nanocomposites represent the new generation of two-phased
materials, associating a basic matrix to nanofillers inserted between
polymer chains. Nanofillers can significantly improve or adjust the
different properties of the materials into which they are incorporated.
The properties of composite materials can be significantly impacted
by the mixture ratio between the organic matrix and the nanofillers.
Fillers play important roles in modifying the desirable properties of
polymers and reducing the cost of their composites. In conventional
polymer composites, many inorganic filers with dimensions in the
micrometer range, e.g., calcium carbonate, glass beads and talc
have been used extensively to enhance the mechanical properties
of polymers. Such properties can indeed be tailored by changing
the volume fraction, shape, and size of the filler particles. A further
improvement of the mechanical properties can be achieved by using
filler materials with a larger aspect ratio such as short glass fibres. It
is logical to anticipate that the dispersion of fillers with dimensions in
the nanometer level having a very large aspect ratio and stiffness in a
polymer matrix could lead to even higher mechanical performances.
These fillers include layered silicates and carbon nanotubes. Rigid
inorganic nanoparticles with a smaller aspect ratio are also promising
as reinforcing and/or toughening materials for the polymers. The
dispersion of nanofillers in the polymers is rather poor due to their
incompatibility with polymers and large surface-to-volume ratio.
Therefore, organic surfactant and compatibiliser additions are needed
in order to improve the dispersion of these nanofillers in polymeric
matrices. For example, layered silicate surfaces are hydrophilic and
proper modification of the clay surfaces through the use of organic
surfactants is needed. The product obtained is known as ‘organoclay’.
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Update on Nanofillers in Nanocomposites
In this context, organoclays can be readily delaminated into nanoscale
platelets by the polymer molecules, leading to the formation of
polymer–clay nanocomposites. These nanocomposites belong to an
emerging class of organic–inorganic hybrid materials that exhibit
improved mechanical properties at very low loading levels compared
with conventional microcomposites.
The behaviour of polymer–nanofiller composites is directly related
to their hierarchical microstructures.
Therefore, the mechanical properties of polymer–nanofiller
composites are controlled by several microstructural parameters such
as properties of the matrix, properties and distribution of the filler
as well as interfacial bonding, and by the synthetic or processing
methods. The interfaces may affect the effectiveness of load transfer
from the polymer matrix to nanofillers. Thus, surface modification
of nanofillers is needed to promote better dispersion of fillers and
to enhance the interfacial adhesion between the matrix and fillers.
Fabrication of homogeneous polymer nanocomposites and advanced
computational techniques remains a major scientific challenge for
materials scientists.
Akbar K. Haghi
University of Guilan, Rasht, Iran
Gennady E. Zaikov
Russian Academy of Sciences, Moscow, Russia
2013
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ontents
Preface ..........................................................................................v
1. Nanofillers and Nanocomposites: A New Outlook ...............1
1.1 Introduction .................................................................1
1.2 Experimental ................................................................5
1.3 Results and Discussion .................................................6
1.4 Concluding Remarks ..................................................33
References ..........................................................................35
2. Rheological Properties of Nanofiller Particles .....................39
2.1 Introduction ...............................................................39
2.2 Experimental ..............................................................41
2.3 Results and Discussion ...............................................42
2.4 Concluding Remarks ..................................................49
References ..........................................................................50
3. Particular filled Nanoclays in a Fibre-formed Matrix .........53
3.1 Introduction ...............................................................53
3.2 Experimental ..............................................................54
3.3 Results and Discussion ...............................................56
3.4 Concluding Remarks ..................................................61
References ..........................................................................62
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Update on Nanofillers in Nanocomposites
4. Polymer/Organoclay Nanocomposite .................................67
4.1 Introduction ...............................................................67
4.2 Experimental ..............................................................69
4.3 Results and Discussion ...............................................69
4.4 Concluding Remarks ..................................................76
References ..........................................................................77
5. Application of Nanofiller Particles in Cement-based
Composites .........................................................................79
5.1 Introduction ...............................................................79
5.2 Experimental ..............................................................80
5.3 Results and Discussion ...............................................83
5.4 Concluding Remarks ..................................................89
References ..........................................................................90
6. Nano-adhesion Effects of Nanofillers .................................95
6.1 Introduction ...............................................................95
6.2 Experimental ..............................................................95
6.3 Concluding Remarks ................................................113
References ........................................................................114
Appendix 1 ..............................................................................117
Appendix 2 ..............................................................................127
Abbreviations ...........................................................................133
Index ........................................................................................139
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