Abraham, Thomas N; George,K E(Taylor & Francis, 2007)
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Abstract:
Short fiber reinforced thermoplastics have generated much
interest these days since fibrous materials tend to increase both
mechanical and thermal properties, such as tensile strength, flexural
strength, flexural modulus, heat deflection temperature, creep
resistance, and some times impact strength of thermoplastics. If
the matrix and reinforcement are both based on polymers the composite
are recyclable. The rheological behavior of recyclable composites
based on nylon fiber reinforced polypropylene (PP) is reported
in this paper. The rheological behavior was evaluated both using a
capillary rheometer and a torque rheometer. The study showed that
the composite became pseudoplastic with fiber content and hence
fiber addition did not affect processing adversely at higher shear
rates. The torque rheometer data resembled that obtained from
the capillary rheometer. The energy of mixing and activation energy
of mixing also did not show much variation from that of PP alone.
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.
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.
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.
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.