Sunil,K Narayanankutty(Taylor & Francis LLC, 2005)
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Abstract:
The thermal degradation of short nylon-6 fiber reinforced acrylonitrile
butadiene rubber (NBR) composites with and without epoxy-based bonding
agent has been studied by thermogravimetric analysis (TGA). It was found that
the onset of degradation shifted from 330.5 to 336.1°C in the presence of short
nylon fiber, the optimum fiber loading being 20 phr. The maximum rate of degradation
of the composites was lower than that of the unfilled rubber compound,
and it decreased with increase in fiber concentration. The presence of epoxy
resin-based bonding agent in the virgin elastomer and the composites improved
the thermal stability. Results of kinetic studies showed that the degradation of
NBR and the short nylon fiber reinforced composites followed first-order
kinetics.
Blends of styrene butadiene rubber (SBR) with maleic anhydride
grafted whole tire reclaim (MA-g-WTR) have been prepared and the
cure and mechanical properties have been studied with respect to the
reclaim content. The grafting was carried out in the presence of
dicumylperoxide (DCP) in a Brabender Plasticorder at 150'C. The
presence of anhydride group on the WTR was confirmed by infrared
spectrometry (IR) study. The properties were compared with those of
the blends containing unmodified WTR. Though the cure time was marginally higher, the mechanical properties of the blends containing
grafted WTR were better than that of the unmodified blends.
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.
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.
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.
Sunil,K Narayanankutty(Taylor & Francis Inc., August 23, 2004)
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Abstract:
The rheological characteristics of short Nylon-6 fiber-reinforced Styrene
Butadiene rubber (SBR) in the presence of epoxy resin-based bonding agent were
studied with respect to the effect of shear rate, fiber concentration , and temperature
on shear viscosity and die swell using a capillary rheonzeter. All the composites
containing bonding agent showed a pseudoplastic nature, which decreased
with increasing temperature. Shear viscosity was increased in the presence of
fibers. The temperature sensitivity of the SBR matrices was reduced on introduction
of fibers. The temperature sensitivity of the melts was found to be lower at
higher shear rates. Die swell was reduced in the presence of fibers. Relative viscosity
of the composites increased with shear rate. In the presence of epoxy resin
bonding agent the temperature sensitivity of the mixes increased. Die swell was
larger in the presence of bonding agent.
The rheological behavior of a short-polyester-fiber-filled polyurethane
elastomer composite containing different bonding agents
has been studied in the temperature range 120-160°C and in the
shear rate range 63-608 s-'. The composite with and without
bonding agents showed a pseudoplastic behavior which decreased
with the increase of temperature. Composites containing bonding
agents based on polypropyleneglycol and 4,4'-diphenylmethanediisocyanate
showed the lowest viscosity values at a particular
shear rate, whereas composites containing a glycerol- (GL) based
bonding agent showed the highest viscosity. The viscosity of the
composite decreased sharply after a particular temperature (140°C) and the fall was less drastic in the composite containing
a GL-based bonding agent.
Sunil,K Narayanankutty(Taylor & Francis Inc., 2005)
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Abstract:
The rheological characteristics of short Nylon-6 fiber reinforced styrene butadiene
rubber (SBR) were studied using a capillary rheometer. The study was done with
respect to the effect of shear rate, fiber concentration, and temperature on shear
viscosity and die swell. All the melts showed pseudoplastic nature, which
decreased with increasing temperature. Shear viscosity increased in the presence
of fibers. Introduction of fiber reduces the temperature sensitivity of the rubber
matrix. A reduction in die swell was found in presence of fibers.
Sunil,K Narayanankutty(Gordon and Breach Science Publishers, December 10, 1991)
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Abstract:
Tear and wear properties of short kevlar fiber, thermoplastic polcurethane (TPU) composite with
respect to fiber loading-and fiber onentation has been studied and the fracture surfaces were examined
under scanning electron microscope (SEM). Tear strength first decreased up to 20 phr fiber loading
and then gradually increased with increasing fiber loading. Anisotropy in tear strength was evident
beyond a fiber loading of 20 phr. Tear fracture surface of unfilled TPU showed sinusoidal folding
characteristics of high strength matrix. At low fiber loading the tear failure was mainly due to fibermatrix failure whereas at higher fiber loading the failure occurred by fiber breakage. Abrasion loss
shows a continuous rise with increasing fiber loading, the loss in the transverse orientation of fibers
being higher than that in the longitudinal orientation. The abraded surface showed lone cracks and
ridges parallel to the direction of abrasion indicating an abrasive wear mechanism. In the presence of
fber the abrasion loss was mainly due to fiber low.
The self adhesion behaviour of thermoplastic polyurethane (TPU) in itself and its
composite with short Kevlar fibre with respect to contact time, temperature, pressure, and fibre
loading has been studied. The adhesion strength showed two linear increments of different slopes
with respect to the square root of time: with temperature and pressure of contact, the adhesion
strength was improved. The maximum strength was obtained with 20 phr of short fibre in only one of
the mating substrates in the peel test sample. The duration for wetting and diffusion was shifted to
longer time intervals with fibres loaded in both the substrates.
Sunil,K Narayanankutty(Technomic Publishing Co., Inc., April , 1998)
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Abstract:
The stress relaxation behavior of polyurethane elastomer and
short polyester fiber filled elastomer composites with and without bonding
agents at different strain levels and strain rates was studied. It was found that
these compounds exhibit a multistage relaxation mechanism and that the rate
of relaxation and cross-over time depend on the strain level and strain rate.
The incorporation of fibers reduced the stage-I relaxation rate and increased
the cross-over time of the gum vulcanisate. A higher rate of relaxation (first
stage) was shown by the composites with longitudinal fiber orientation and
composites with bonding agents.
Sunil,K Narayanankutty(Sage Publications, April , 2002)
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Abstract:
Cure characteristics and mechanical properties of acrylonitrile
butadiene rubber/reclaimed rubber blends were studied. Minimum torque,
(ma)dmum -minimum) torque, scorch time, cure time and cure rate decreased in
presence of reclaimed rul3ber. Tensile strength, elongation at break and
compression set increased'with increase in reclaim content. Resilience and
abrasion resistance decreased with reclaim loading. Heat build up was higher for
the blends. The ageing resistance of the blends was inferior to that of the gum
compound.
Sunil,K Narayanankutty(Sage Publications, April , 2002)
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Abstract:
Acrylonitrile butadiene rubber (NBR) matrix was reinforced with
different levels of short nylon fiber loading. Cure characteristics and mechanical
properties of composites in longitudinal and transverse directions have been
studied. Cure time was reduced while processability, as indicated by the
minimum torque, was marginally reduced with increase in fiber loading. Tensile
and tear properties improved with fiber concentration and the values were
higher in longitudinal direction of fiber orientation. Abrasion resistance,
resilience and compression set were increased in presence of fibers. Elongation
at break values showed a drastic drop on introduction of fibers. Heat build up
was higher for composites.
Blends of Acrylonitrile rubber with Maleic anhydride grafted Whole Tyre
Reclaim WTR (MA-g-WTR) have been prepared and the cure and mechanical
properties have been studied with respect to reclaim content. Control
compounds containing unmodified WTR were also prepared for comparison.
Grafting was confirmed by IR studies. Blends containing grafted WTR showed
higher minimum torque and (max-min) torque. They also showed longer cure
time, scorch time and lower cure rate. Grafting of the WTR with maleic
anhydride also resulted in the improved tensile strength, abrasion resistance,
compression set and resilience. However, the heat build up under dynamic
loading was marginally higher for the blends containing grafted reclaimed
rubber.
The cure characteristics of short fiber-polyurethane elastomer
were studied with respect to different fiber-matrix bonding agents. A hexamethylenetetramine-
resorcinol -hydrated silica based bonding agent was found to affect
the stability of the composite. A new bonding agent, TP resin, based on polymeric
toluenediisocyanate and polypropylene glycol has been developed. Cure characteristics
of the composite with and without TP resin at different fiber loadings were
also compared. Minimum torque, scorch time and optimum cure time increased
with fiber content. Maximum torque was consistently higher with TP resin at all
fiber loadings.
The effect of an external flaw on the tensile strength of short kevlar fiber-thermoplastic
composites has been studied with respect to fiber content, fiber orientation,
location of the external flaw, and the temperature of test. The composites showed
a three-step reduction in tensile strength with increasing flaw size. The critical flaw-length
region was shifted to higher flaw-size levels with increasing fiber content. With increasing
temperature, the critical flaw length was increased in the case of unfilled TPU, whereas it
remained more or less constant in the case of short kevlar fiber-filled-TPU composite.