34 Journal of Polymer Engineering and Technology, 2005, 11, 34-37

http://polymer.aut.ac.ir/

Nano Composites
Sajjadi, Seyed Pooyan (s.pooyan@sajjadi.me)
Polymer Engineering Department, Amirkabir university of Technology
P.O.Box: 15875-4413, Tehran, Iran.
Received: February12, 2005; Published: June 8, 2005.

Abstract
Nano composites are an emerging class of mineral-filed plastics that contain relatively small amounts
(<10%) of nanometer-sized clay articles. These mineral significantly enhance the mechanical and
thermal properties of the base resin, as well as improve barrier performance and flame retardancy. All
of these performance benefits are available without increasing the density or reducing light
transmission properties of the base polymer. First developed by Toyota over 10 years ago. Nano
composites are just becoming viable commercial product and nylon 6 was the first polymer to be used
in the development of Nano composites. Although some reports glorify the discovery of nano
composites as revolutionary break thought in science and technology, it should be noted that the basic
synthetic concept has been established for many decades.

Keywords: Nano composites

In fact, pioneering research of Toyota on polyamide structure, and surface characteristics of reinforcing
nanocmosites during the 1980, s, the renewed interest agents were three main factors that effect or decide its
in chemical nanotechnology and the quest for reinforcing ability, especially the particle size.
upgrading of old polymers have stimulated Experiments showed that the tensile strength of ultra
nanocmosites development. Most R&D is focused on fine CaCO3/ Styrenebutadiene rubber (SBR)
automotive parts and packaging, although a divers composites was improved and 3 times higher than that
range of disposable and durable applications are under of a regular size CaCO3 /SBR blend.
development. Clay is an inexpensive natural mineral so it has been
Nanocmposites incorporate low loading (typically less used as a filler for rubber and plastic for many years,
than 5% by weight) of high aspect ratio mineral or but its reinforcing ability is poor because of its big
carbon nanotube fillers that have a unique structure. particle size and low surface activity, and can only be
The resultant high surface area and high aspect ratio used for conventional micro composites. A new way to
fillers provide similar reinforcing performance of improve the reinforcing ability of clay was recently
traditional minerals and fibers used in plastics, and yet found. Clay has a layer structure; among the layers
do not increase density since levels are low. Due to the there are some ions that can be exchanged with other
nanometer size of particles, which is smaller than the organic ions. The layers can not be separated from each
wavelength of visible light, the reinforced polymer other through general rubber processing means. In
remains transparent. Other characteristics of the recent years the interest in nanoscale materials was
composites include high barrier performance and inspired by the fact that nanoscale materials often
improved thermal stability, which make these exhibited physical and chemical properties that were
compounds suitable for many applications. dramatically different from their bulk counterparts. A
Development activities in nancmosites field have novel idea was put forth that polymer could be
spread to all regions of the world, and active programs intercalated to the clay layer galleries to from
are now focused on creating comounds based on PP, nanocmposites through a special method, and many
PET, PVC, acrylics, TPEs, and a range of elastomers, kinds of material sprung up that had an ultra fine phase
as well as traditional thermosets. Over the coming 10 dimension. Nanocmposites possess unique properties
years, nanoclay composites of nearly 20 polymers are such as stiffness, strength and gas barrier action for
expected to be commercialized. their dispersion structure.
Carbon black used to be the most important reinforcing The structures of polymer-clay nanocmosites are
agent in the rubber material industry. But its polluting usually characterized by X-ray diffraction (XRD),
nature, the monotonous black color of the rubber transmission electron microscopy (TEM), atomic force
material, and its dependence on petroleum caused microscopy (AFM), etc.
researchers to develop other satisfying reinforcing Clay minerals, such as montmorillonite and vermiculite
agents instead. It was well known that the particle size, have been widely used to prepare polymer-clay
35 Journal of Polymer Engineering and Technology, 2005, 11, 34-37
http://polymer.aut.ac.ir/

nanocmposites. The layer structure of montmorillonite layer can be steadily dispersed in water for the
(MMT) consists of two silica tetrahedral sheets to an hydration of the ion among the layers; the layers are
edge-shared octahedral sheet of either aluminum or separated from each other. Some polar compounds can
magnesium hydroxide. Stacking of the layers of ca 1- intercalate to the clay layer galleries. These
nm thickness by a weak dipolar force leads to characteristics provided a way to prepare the rubber-
interlayer or galleries between the layers. The galleries clay nanocomposites. The molecular weight of the
are normally occupied by actions such as K+, Na+, rubber was higher than plastic; it had very high
Ca2+, Mg2+ and Cg+, by which is easy to form the viscosity in the process state, and most of the rubbers
organosilicate by an alkylammonium ion-exchange gad latex forms and could blend with a clay-water
reaction. The organosilicates can be broken down into dispersion without coagulation. A new method has
their nanoscale building blocks and uniformly developed to prepare rubber-clay nanocomposites
dispersed in the polymer matrix to from exfoliated through mixing and coagulation of rubber latex, which
nanocmposites during the compounding process. has named the latex method. Figure 2. Shows a
Today it is well recognized that silicate modification schematic of the formation of the nanocomposites use
and especially interfacial coupling must be tailored latex method.
very carefully to achieve property improvements.
Example of nanocomposites preparation
Example of organo clay preparation use in situ polymerization
NA+” type montmoriilonte (NA-MMT) with a cation The surface of silica was modified by aminobutyric
exchange capacity of 119 meq (100 g) was gradually acid first, then the modified silica was dried in an oven
added to a solution of dimethyl distearyl ammounium for the preparation of nylon 6 silica nanocomposites.
bromide and vigorously stirred at 70 c for 24 h. The The preparation of nylon 6 silica nanocomposites
treated clay was washed repeatedly with deionized included two processes; the modified silica particles
water until no further AgBr formation was observed were dispersed in E-caproamide at 90 C, and
through titration with 0.1N AgNO3. The product was naminocapric acid as the initiator was introduced at the
filtered and dried in a vacuum oven at 50 c for 24h and same time; then this mixture was polymerized at a high
was termed Org-MMT. temperature under a nitrogen atmosphere.
To prepare NBR/clay nanocomposites, the Org-MMT
was mixed as 15 parts per hundred rubber (phr) with Example of nanocomposites preparation
NBR in a Banbury type internal mixer at 60 rev min-1
and at 50 C for 10 min. A small amount (1 phr) of use solution method:
dicumyl peroxide as a curative was then mixed in a A suspension of an industrial sodium montmorillonite
towrol mill. For comparison, Na-MMT and modified by means of sodium cation exchange with 38
conventional carbon black (N-220 type, Lucky Carbon wt% diemethyl distearyl ammoinium salt in toluene
Black, Korea) was also mixed with NBR using the was mixed with a toluene solution containing the same
same procedure. The mixed composites were cured at amount of rubber-butadiene rubber (BR) or styrene-
170 C for 15 min in a heated press under a pressure of butadiene rubber (SBR)- followed by stirring for 24h
29.4 Mpa. Table 1. Shows the tensile and tear and subsequent solvent evaporation in vacuum for 5d
properties of the NBR composites. Figure 1. Shows the at 40 C. in a second filler preparation process, 10phr
organo-clay structure and intercalated and exfoliated bid (triethoxylilylproyl)- tetrausuflfan TESPT was
nanocomposites. added to the toluene solution of the elastomer. The
increase of interlayer distance increased from 1.26nm
for montmorillonite to 2.59nm for the organo clay and
Methods for Nanocomposites preparation: ranged from 3.59 to approximately 6nm for the rubber
The methods for nanocomposites included in situ swollen organocaly. Then samples were treated on a
ploymerization, solution intercalation, and melting improving filler dispersion. The compounds were
intercalation. In situ polymerization needs special vulcanized for 30 min at 165 C in a hot stage press
monomers and clay treatment; this limits its application under vacuum containing sulfur, vulcanization initiator
in other polymers. The solution method needs a N-cyclohexylbenzothiazole-2-sulfenamide (CBS) and
compatible polymer-solution system and organically accelerator zinc distearate.
modified clay; its disadvantage is that the solvent must
be deabsorbed. Melting intercalation can be applied to
most polymers, especially plastic, but it needs polymer
that has good properties in the melting state.
Clay can be modified with organic quaternary
ammonium salts; thus, some modified clay can be
swollen in nonpolar solvents such as toluene. The clay
36 Journal of Polymer Engineering and Technology, 2005, 11, 34-37
http://polymer.aut.ac.ir/

Example of nanocomposites preparation mixed for a period of time. It was coagulated in dilute
use melt intercalation: hydrochloric acid solution, washed with water until its
The melt compounding of PP/clay composites was pH was about 7, and dried at 50 C.
carried out with a Brabender single-screw extruder. For SBR Wang et la. Showed that the mechanical
The clay (organoclay) and polymer samples were dried properties of the nanocomposites produced by the latex
in an air circulatory oven at 65 C for 8h prior to method were better than those produced by the solution
compounding. method.
The temperature zones ranged from 160 to 200 C, and The improved properties of the former could be
the revolutions-per-minute rate was 45. One interpreted to be its better dispersion of silicate layers.
composition containing polymer (84%) compatibilizer Table II summarize the mechanical properties of
(12%), and clay (4%) was prepared for each clay. nanocomposites and other reinforced SBR. Material
had different proporties with different reinforcing
methods. The data exhibited that clay was a good
Example of nanocomposites preparation reinforcing agent like the carbon black in the studied
use latex method: range.
Clay was dispersed in water with strong stirring (2%
disperesed in water); then the latex was added and

Fig 1. a schmatic of the formation of the nanocomposites.

Fig 2. Organo clay

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