Sunil,K Narayanankutty(Taylor & Francis, November 13, 2000)
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Abstract:
Cure characteristics and mechanical properties of short nylon fiber reinforced
acrylonitrile butadiene rubber-reclaimed rubber composites were studied. Minimum
torque, (maximum-minimum) torque and cure rate increased with fiber
concentration. Scorch time and cure time decreased by the addition of fibers.
Properties like tensile strength, tear strength, elongation at break, abrasion loss
and heat build up were studied in both orientations of fibers. Tensile and tear
properties were enhanced by the addition of fibers and were higher in the longitudinal
direction. Heat build up increased with fiber concentration and were
higher in the longitudinal direction. Abrasion resistance was improved in presence
of short fibers and was higher in the longitudinal direction. Resilience increased
on the introduction of fibers. Compression set was higher for blends.
Sunil,K Narayanankutty(OPA (Overseas Publishers Association), January 7, 1997)
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Abstract:
Cure characteristics of short polyester fiber-polyurethane composites with respect to
different bonding agents (MD resins) based on 4, 4' diphenylmethanediisocyanate (MDI)
and various diols like propyleneglycol (PG), polypropyleneglycol (PPG) and glycerol
(GL) were studied. Tmax. - Tmin. of composites having MD resin were found to be
higher than the composite without MD resin. Minimum torque and Tmax. - Tmin.,
scorch time and optimum cure time were increased with the increase of MDI equivalence.
Optimum ratio of MDI / -of in the resin was found to be within the range of
1-1.5. It was observed from the cure characteristics that for getting better adhesion
between short polyester fiber and the polyurethane matrix the best choice of MD resin
was one based on MDI and 1:1 equivalent mixture of polypropyleneglycol and glycerol.
Rani, Joseph(John Wiley & Sons, Inc., February 16, 1999)
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Abstract:
Microcellular (MC) soles based on polybutadiene (BR) and low-density
polyethylene (LDPE) blends for low-temperature applications were developed. A part of
BR in BR-LDPE blend was replaced by natural rubber (NR) for property improvement.
The BR-NR-LDPE blend-based MC sole shows good technical properties. Sulphur
curing and DCP curing were tried in BR-LDPE and NR-BR-LDPE blends. Study
shows that sulphur-cured MC sheets possess better technical properties than DCPcured
MC sheets. 90/10 BR-LDPE and 60/30/10 BR-NR-LDPE blend combinations are
found to be suitable for low-temperature applications.
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.
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.
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(Hutig & Wepf Verlag,Basel, October 5, 1987)
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Abstract:
Compounding of styrene-butadiene copolymer/polybutadiene , natural rubber/
ethylene-propylene-diene terpolymer and natural rubber/butadiene-acrylonitrile copolymer
blends was done in three different ways and their curing behaviour and the
tensile properties of the es are compared.
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.
Rani, Joseph(Wiley InterScience, February 18, 2006)
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Abstract:
In this paper we report the preparation and
dielectric properties of poly o-toluidine:poly vinyl chloride
composites in pellet and film forms. The composites were
prepared using ammonium persulfate initiator and HCl
dopant. The characterization is done by TGA and DSC. The
dielectric properties including dielectric loss, conductivity,
dielectric constant, dielectric heating coefficient, absorption
coefficient, and penetration depth were studied in the
microwave field. An HP8510 vector network analyzer with
rectangular cavity resonator was used for the study. Sbands (2-4 GHz), C band (5-8 GHz), and X band (8-12
GHz) frequencies were used in the microwave field. Comparisons
between the pellet and film forms of composites
were also included. The result shows that the dielectric
properties in the microwave field are dependent on the frequency
and on the method of preparation.
Rani, Joseph(Wiley lnterScience, September 4, 2006)
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Abstract:
The latex industry has expanded over the
years to meet the world demands for gloves, condoms,
latex thread etc. Because of the strict specifications for
the products and the unstable nature of the latex, as
high as 15%, of the final latex products are rejected.
Since waste latex rubber (WLR) represents a source of
high quality rubber hydrocarbon, it is a potential candidate
for generating reclaimed rubber of superior quality.
Two types of WLR with different amounts of polysulfidic
bridges are used in these experiments, which are
reclaimed with variation of the concentration of the
reclaiming agents, the reclamation temperature and time,
Di phenyldisultide, 2-aminophenyldisulfide and 2,2'-dibenzamidodiphenyldisulfide
(DBADPDS) are used as reclaiming
agents, and the effect of diphenyldisulfides (DPDS)
with different substituents, on the reclamation efficiency of WLR is investigated. A kinetic study of the reclamation
reaction with the three reclaiming agents is done.
The reaction rates and activation energies are calculated
and compared with literature values. The comparative
study of the three different reclaiming agents shows that
(DBADPDS) is able to break the crosslinks at temperature
levels 20'C below the temperature levels normally
used with DPDS. Another advantage of this reclaiming
agent is the reduced smell during the reclamation process
and of the final reclaims, one of the most important
shortcomings of other disulfides used for this purpose.
Rani, Joseph(John Wiley & Sons, Inc., June 21, 2001)
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Abstract:
ABSTRACT: Polyaniline was synthesized by using ammonium persulfate initiator in the
presence of 1M HC1. It was dried under different drying conditions like room temperature
drying (for 48 h), oven drying (at 50-60°C for 8 h under a vacuum), and vacuum
drying (at room temperature for 16 h). The conductivities of these samples were
measured at microwave frequencies. These samples were also pelletized and the
measurements were repeated. The cavity perturbation technique was used for the
study.
Rani, Joseph(OPA (Overseas Publishers Association) N.V., July 23, 1997)
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Abstract:
Selected grades of low density polyethylene (LDPE) polystyrene (PS) were extruded in a
laboratory extruder by varying the feeding rate at different revolutions per minute and
temperatures. The mechanical properties of the extruded plastic sheets were determined.
LDPE shows a marked variation in mechanical properties with feeding rate while PS
shows a marginal change in mechanical properties with feeding rate. However, for both
plastics there is a particular feeding rate in the starved region which results in maximum
mechanical properties.
The effect of various processing parameters, such as nip gap, friction ratio
and roll temperature, on the tensile properties of short Kevlar aramid
fibre-thermoplastic polyurethane composite has been investigated and the tensile
and tear fracture surfaces have been characterised using a scanning electron microscope.
A nip gap of 0.45 mm, a friction ratio of 1.15 and a roll temperature of 62°C
was found to give optimum mechanical properties. Scanning electron microscopy
study revealed a higher extent of fibre orientation in the milling direction in the
above condition.
Chloroprene rubber was blended with whole tire reclaimed rubber
(WTR) in presence of different levels of a coupling agent Si69 [bis-
(3-(triethoxysilyl)propy1)tetrasuIfide] and the cure characteristics and
mechanical properties were studied. The rate and state of cure were
also affected by the coupling agent. While the cure time was increased,
the cure rate and scorch time were decreased with increasing silane
content. Tensile strength, tear strength, and abrasion resistance were
improved in the presence of coupling agent. Compression set and
resilience were adversely affected in presence of silane-coupling agent.Aging studies showed that the blends containing the coupling agent
were inferior to the unmodified blends.
Blends of nitrile rubber and reclaimed rubber containing different levels of a
coupling agent, Si 69 (bis(3- triethoxysilyl propyl)(tetrasulphide) were prepared
and the cure characteristic's and mechanical properties were studied. Optimum
loading of Si-69 was found to be a function of blend ratio. 3 phi- of Si 69 in a
70:30. Blend was found to be the optimum combination with respect to the
mechanical properties. The rate and state of cure were also affected bv the
conp/ing agent. Tensile strength, tear strength and abrasion resistance were
improved in the presence of coupling agent. While the state of cure improved,
the cure rate and scorch time decreased with increasing silane content. Ageing
studies showed that the blends containing the coupling agent were inferior to
the unmodified blends.
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.
The cure characteristics and mechanical properties of short nylon fiber- styrene
/whole tyre reclaim (SBR/WTR) composites with and without
an interfacial bonding agent based on 4,4 diphenyl methane diisocyanate and
polyethylene glycol (MDI/PEG) have been studied. An 80:40 blend of SBR/
WTR reinforced with 20 phr of short nylon fiber has been selected and the MDI/
PEG ratio has been changed from 0.67:1 to 2:1. The minimum and maximum
torques increased with isocyanate concentration. The scorch time and cure time
showed an initial reduction. The cure rate showed an initial improvement.
Tensile strength, tear strength and abrasion resistance increased with MDI/PEG
ratio, these values were higher in longitudinal direction. Resilience and
compression set increased with isocyanate concentration.
Blends of chlorobutyl rubber (CIIR) with two grades of ethylene-propylene diene
monomer rubber (EPDM) were prepared and the effect of blend ratio on the cure
characteristics, hot air ageing resistance, steam ageing resistance, and mechanical
properties were evaluated. The blend of CIIR with EPDM grade 301 T showed
additive behavior and the blend with the other grade of EPDM (NDR 4640)
showed synergistic behavior.
Unsaturated polyester resins (UPRs) are
used widely in the fiber-reinforced plastics (FRPs) industry.
These resins have the disadvantages of brittleness and poor
resistance to crack propagation. In this study, hybrid polymer
networks (HPNs) based on UPR and epoxidized phenolic
novolacs (EPNs) were prepared by reactive blending.
A HPN is composed of a backbone polymer containing two
types of reactive groups that can take part in crosslinking
reactions via different mechanisms. EPNs were prepared by
glycidylation of novolacs using epichlorohydrin. The novolacs
had varying phenol: formaldehyde ratios. Blends of unsaturated
polyester with EPN were then prepared. The
physical properties of the cured blends were compared with
those of the control resin. EPN shows good miscibility and
compatibility with the resin and improves the toughness
and impact resistance substantially. Considerable enhancement
of tensile strength is also noticed at about 5% by
weight of epoxidized novolac resin. TGA, DMA, and DSC
were used to study the thermal properties of the toughened
resin and the fracture behavior was studied using SEM. The
blends are also found to have better thermal stability. Blending
with EPN can be a useful and cost-effective technique for
modification of UPR
Description:
Journal of Applied Polymer Science, Vol. 100, 457–465 (2006)
Hybrid polymer networks (HPNs) based on unsaturated polyester resin (UPR) and epoxy resins were synthesized by
reactive blending. The epoxy resins used were epoxidised phenolic novolac (EPN), epoxidised cresol novolac (ECN) and
diglycidyl ether of bisphenol A (DGEBA). Epoxy novolacs were prepared by glycidylation of the novolacs using epichlorohydrin.
The physical, mechanical, and thermal properties of the cured blends were compared with those of the control resin.
Epoxy resins show good miscibility and compatibility with the UPR resin on blending and the co-cured resin showed substantial
improvement in the toughness and impact resistance. Considerable enhancement of tensile strength and toughness
are noticed at very low loading of EPN. Thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and
diVerential scanning calorimetry (DSC) were employed to study the thermal properties of the toughened resin. The EPN/
UPR blends showed substantial improvement in thermal stability as evident from TGA and damping data. The fracture
behaviour was corroborated by scanning electron microscopy (SEM). The performance of EPN is found to be superior to
other epoxy resins