الفهرس 
CHAPTER (1). Introduction and Literature reviewOnly 14 pages are availabe for public view
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Abstract
Nanocomposite materials consisting of inorganic nanolayers of
montmorillonite clay and organic polymers have evoked intense research
interests lately because their unique characteristics create many potentially
commercial applications.
PCN are reported to promote the thermal, mechanical, molecular
barrier, flame retardant and corrosion protection properties of polymers at
low clay loading (>10%) based on the recently published literatures. The
earlier historical development involving the PCN materials can be traced
back to 1990 based on the research work of polyamide–clay nanocomposite
by Toyota’s research group.
The transition from microparticles to nanoparticles yields dramatic
changes in physical properties due to nanoscale materials have a large
surface area for a given volume.
The work carried out in this thesis is presented in four main chapters;
namely, introduction, experimental, and results and discussion.
“Introduction”
Includes a brief outline of Polymeric materials and
polymer nanocomposites. It gives also an overview on types, methods of
nanocomposites preparation and techniques used to characterize the
structures of nanocomposites.
“Experimental”
Includes the different materials employed, their chemical
compositions, and a detailed description of instruments used.
Clay (Na+-MMT) was mixed with natural rubber latex (NR), styrenebutadiene
rubber latex (SBR), poly(vinyl alcohol) (PVA) at loadings of 2, 4,
6 , 8 and 10 phr . Then, the specimens including NR, SBR and PVA were
exposed to gamma radiation at different irradiation doses namely 10, 25, 50,
75 and 100 KGy.
Furthermore, Na+-MMT was treated with intercalating agent
Octadecylamine (ODA) and Cetyltrimethylammonium (CTAB). The treated
organoclay then was mixed with NR after dissolution in solvent and also
PVA. SBR after evaporation of water don’t dissolved, therefore can’t be
mixed with organoclay by solvent method. The polymers NR and PVA are
mixed with only 6 phr treated clay (organoclay), then irradiated at 10 to 100
kGy.
“Results and Discussion”
is classified into four main parts:-
First part deals with the characterization of organic modified clay. The
results indicate that the salt molecules were successfully incorporated into
the clay structure.
“NR/clay nanocomposites (NR–CNs)”
The effect of irradiation doses and clay loading concentrations on the
various properties were as follows.
•XRD showed that there are separation of clay layers and dispersion of
NR between platelets of clay in both of two cases unmodified and
modified clay.
•from tensile strength measurement of NR, it can be seen that
increasing irradiation doses increase tensile strength up to 100 KGy,
mostly for all nanoclay concentration at all irradiation dose. Also,
increasing unmodified clay concentration increases tensile strength.
Addition of modified clay resulted in a decrease in tensile strength
properties than the addition of unmodified clay.
•The elongation at break data at two cases of addition unmodified and
modified clay reveals that increasing both irradiation dose and filler
concentrations decrease elongation compared to unloaded one.
•Volume fraction measurements of the NR/clay nanocomposites were
decreased with irradiation dose because of crosslinking that made
compacting of rubber.
As for NR loaded with clay modified with ODA and CTAB, the
volume fraction increase as irradiation dose increase.
•According to the TGA measurements, NR with ODA and CTAB
noticed to be improved in thermal stability compared to the
nanocomposites. In addition, it was found that the enhancement in
TGA for loaded ODA is higher than CTAB.
“SBR/clay nanocomposites (SBR –CNs)”
The behavior of SBR/Na+-MMT nanocomposites towards the effect of
increasing irradiation dose and inorganic clay concentration was as follows:-
•XRD patterns were indicated intercalation of the polymer chains
between interlayers of clay for 6, 8 and 10 phr of Na+-MMT with
SBR, but in case of 4 phr of Na+-MMT indicated exfoliation of
layered silicates.
•Tensile strength measurement of SBR for all loaded samples with
Na+-MMT increase up to 50 kGy then decline up to 100 kGy.
•Elongation at break decreases by increasing irradiation dose up to 50
kGy then increase again up to 100 kGy.
•Volume fraction of SBR/Na+-MMT increases with the increasing in
irradiation dose for all samples under investigation up to 75 kGy then
decrease at 100 kGy. Also, the increase in clay concentration
increases the value of volume fraction.
•TGA measurements indicated that irradiation at 100 kGy showed low
thermal properties than at 50 kGy.
“PVA/clay nanocomposites (PVA –CNs)”
•XRD patterns indicated that inorganic layered silicates are able to
exfoliate in water to form colloidal particles with PVA. Also, there is a
separation of organoclay layers and dispersion of PVA into clay layers
for all modified clay with ODA and CTAB.
•Tensile strength increases with irradiation dose increasing up to 100 kGy,
on the other hand; increasing of inorganic clay loading increase TS
values up to 8 phr, then decrease at 10 phr.
But, for PVA/organoclay samples; it was obvious that the modified clay
with CTAB has much influence on TS higher than loaded with ODA
overall irradiation doses.
•Elongation at break for PVA/Na+-MMT nanocomposites increases up to
50 kGy for almost all concentrations (except at 10 phr) with increasing
irradiation dose.
On the other hand, elongation of PVA/modified clay with ODA increase
up to 75 kGy then decrease at 100 kGy, but at case of CTAB elongation
increase up to 50 kGy then decrease till 100 kGy.
•TGA measurements showed that the decomposition temperature of the
PVA/modified is shifted to higher temperature than that of
PVA/unmodified clay nanocomposites.
On the other hand, PVA/ODA-MMT nanocomposites are more stable
than PVA/CTAB-MMT nanocomposites.