George, K E; Rajan, M; Agarwal, U S; Bally, C; Lemstra, P J(Wiley InterScience, 2005)
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Abstract:
We describe the synthesis of diblock and triblock copolymers by sequential
atom transfer radical polymerization of styrene and acetoxymethylstyrene. Contrary to
the usual block copolymerization involving isolation of the macroinitiator, a convenient
one-pot procedure is developed. This is possible because of the preferential polymerization
of acetoxymethylstyrene, even in the presence of residual styrene, as inferred
from characterization of the intermediate polystyrenes and the block copolymers by size
exclusion chromatography, 1H NMR, Fourier transform infrared spectroscopy, differential
scanning calorimetry, and GPEC techniques. The latent acetoxy functionalities
in these block copolymers are shown to be easily unmasked to OOH and OBr functionalities,
with the potential for block ionomers and dense graft architectures.
Rani, Joseph(Wiley InterScience, December 13, 2004)
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Abstract:
Prevulcanized natural rubber latex was prepared
by the heating of the latex compound at 55°C for
different periods of time (2, 4, 6, 8, and 10 h). The changes in
the colloidal stability and physical properties were evaluated
during the course of prevulcanization. The prevulcanized
latex compounds were stored for 300 days, and the
properties were monitored at different storage intervals (0,
20, 40, 60, 120, 180, 240, and 300 days). During prevulcanization,
the mechanical stability time increased, and the viscosity
remained almost constant. The tensile strength increased
during storage for a period of 20 days. The degree of
crosslinking, modulus, elongation at break, and chloroform
number were varied with the time of storage.
George, K E; Jacob, Sinto; Suma, K K; Mendaz, Jude Martin; George, Abhilash(Wiley InterScience, 2009)
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Abstract:
Poly(propylene) (PP) reinforced with short glass fiber was modified with
precipitated nanosilica (pnS) by melt mixing. The weight of the glass fiber was varied
by keeping the pnS at optimum level. The properties of the composites were studied
using universal testing machine, dynamic mechanic analyser (DMA), differential
Scanning calorimetry (DSC) and thermo gravimetric analyser (TGA). The amount of the
glass fiber required for a particular modulus could be reduced by the addition of
nanosilica.
Reactive extrusion is an attractive means of polymer processing since the shaping
and reaction take place in a single operation. In this paper we report the silane
grafting of polyethylenes in a single screw extruder. The optimum conditions for
silane grafting, viz. temperature, shear rate, silane and DCP concentrations, were
determined on a torque rheometer and then actual extrusion was performed
using these conditions. The study shows that an optimum low level of grafting/
crosslinking can be introduced into polyethylene during its extrusion for better
mechanical behavior and=or thermal stability without affecting the processability.
Low-protein content natural rubber latex
was produced by using a nonionic surfactant-polyethylene
glycol (PEG). Extractable protein content of natural rubber
latex was found to decrease with PEG treatment and
reduction increased with increase in the molecular weight
of PEG. The low-protein latex samples were characterized
by tensile testing, Fourier transform infrared and thermogravimetric
analysis. The results have shown 35% reduction in the extractable protein content, without any compromise
on the mechanical properties of the latex; however,
thermal stability of low-protein latex was found to be
reduced marginally with PEG treatment.
George, K E; Komalan, C; Kumar, P A S; Varughese, K T; Thomas, S(eXPRESS Polymer Letters, 2007)
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Abstract:
The dynamic mechanical properties such as storage modulus, loss modulus and damping properties of blends of
nylon copolymer (PA6,66) with ethylene propylene diene (EPDM) rubber was investigated with special reference to the
effect of blend ratio and compatibilisation over a temperature range –100°C to 150°C at different frequencies. The effect of
change in the composition of the polymer blends on tanδ was studied to understand the extent of polymer miscibility and
damping characteristics. The loss tangent curve of the blends exhibited two transition peaks, corresponding to the glass
transition temperature (Tg) of individual components indicating incompatibility of the blend systems. The morphology of
the blends has been examined by using scanning electron microscopy. The Arrhenius relationship was used to calculate the
activation energy for the glass transition of the blends. Finally, attempts have been made to compare the experimental data
with theoretical models.
Rani, Joseph(Wiley Inter Science, December 14, 2005)
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Abstract:
Polypyrrole/poly (vinyl chloride) semi-interpenenzrtirtg
networks of different compositions are prepared using anunonitun per
sulfate initiator at room temperature in pellet.form and lilrrt form and
their dielectric properties are studied at different microwave frequencies.
An HP 8510 Vector network analyzer interfaced with a computer
is used. The cavity-perturbation technique is employed for the
study
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.
In this article, we report the preparation of
conducting natural rubber (NR) with polyaniline (Pani). NR
was made into a conductive material by the compounding
of NR with Pani in powder form. NR latex was made into a
conductive material by the in situ polymerization of aniline
in the presence of NR latex. Different compositions of Pani-
NR semi-interpenetrating networks were prepared, and the
dielectric properties of all of the samples were determined
in microwave frequencies. The cavity perturbation techpique was used for this study. A HP8510 vector network analyzer
with a rectangular cavity resonator was used for this
study. S bands 2-4 GHz in frequency were used. Thermal
studies were also carried out with thermogravimetric analysis
and differential scanning calorimetry.