Rani, Joseph(Wiley InterScience, October 22, 2006)
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Abstract:
Poly(ethylene terephthalate) (PET) nanocomposites
with single-walled carbon nanotubes (SWNTs) have
been prepared by a simple melt compounding method. With
increasing concentration (0-3 wt %) of SWNTs, the mechanical
and dynamic mechanical properties improved, corresponding
to effective reinforcement. Melt rheological characterization
indicated the effective entanglements provided by SWNTs in
the melt state as well. Thermogravimetric analysis suggested no influence of SWNTs on the thermal stability of PET. Electrical
conductivity measurements on the composite films pointed
out that the melt compounded SWNTs can result in electrical
percolation albeit at concentrations exceeding 2 wt %.
Isora fibre-reinforced natural rubber (NR) composites were cured at 80, 100, 120 and
150°C using a low temperature curing accelerator system. Composites were also prepared using a
conventional accelerator system and cured at 150°C. The swelling behavior of these composites at
varying fibre loadings was studied in toluene and hexane. Results show that the uptake of solvent
and volume fraction of rubber due to swelling was lower for the low temperature cured vulcanizates
which is an indication of the better fibre/rubber adhesion. The uptake of aromatic solvent was higher
than that of aliphatic solvent, for all the composites. As the fibre content increased, the solvent
uptake decreased, due to the superior solvent resistance of the fibre and good fibre-rubber interactions.
The bonding agent improved the swelling resistance of the composites due to the strong interfacial
adhesion. Due to the improved adhesion between the fibre and rubber, the ratio of the change in
volume fraction of rubber due to swelling to the volume fraction of rubber in the dry sample (V,) was
found to decrease in the presence of bonding agent. At a fixed fibre loading, the alkali treated fibre
composite showed a lower percentage swelling than untreated one for both systems showing superior
rubber-fibre interactions.
A series of short-isora-fiber-reinforced natural
rubber composites were prepared by the incorporation of
fibers of different lengths (6, 10, and 14 mm) at 15 phr loading
and at different concentrations (10, 20, 30, and 40 phr) with a
10 mm fiber length. Mixes were also prepared with 10 mm
long fibers treated with a 5% NaOH solution. The vulcanization
parameters, processability, and stress-strain properties
of these composites were analyzed. Properties such as tensile
strength, tear strength, and tensile modulus were found to be
at maximum for composites containing longitudinally oriented
fibers 10 mm in length. Mixes containing fiber loadings of 30 phr with bonding agent (resorcinol-formaldehyde [RF]
resin) showed mechanical properties superior to all other
composites. Scanning electron microscopy (SEM) studies
were carried out to investigate the fiber surface morphology,
fiber pullout, and fiber-rubber interface. SEM studies showed
that the bonding between the fiber and rubber was improved
with treated fibers and with the use of bonding agent.
Rani, Joseph(Indian Academy of Sciences., September 30, 2005)
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Abstract:
Natural rubber/isora fibre composites were cured at various temperatures. The solvent swelling
characteristics of natural rubber composites containing both untreated and alkali treated fibres were investigated
in aromatic and aliphatic solvents like toluene, and n-hexane. The diffusion experiments were conducted by
the sorption gravimetric method. The restrictions on elastomer swelling exerted by isora fibre as well as the
anisotropy of swelling of the composite have been confirmed by this study. Composite cured at 100°C shows
the lowest percentage swelling. The uptake of aromatic solvent is higher than that of aliphatic solvent for the
composites cured at all temperatures. The effect of fibre loading on the swelling behaviour of the composite was
also investigated in oils like petrol, diesel, lubricating oil etc. The % swelling index and swelling coefficient of
the composite were found to decrease with increase in fibre loading. This is due to the increased hindrance exerted
by the fibres at higher fibre loadings and also due to the good fibre-rubber interactions. Maximum uptake
of solvent was observed with petrol followed by diesel and then lubricating oil. The presence of bonding agent in
the composites restrict the swelling considerably due to the strong interfacial adhesion. At a fixed fibre loading,
the alkali treated fibre composite showed lower percentage swelling compared to the untreated one.