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.
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.
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.
Ethylene-propylene-diene rubber (EPDM) and isobutylene-isoprene rubber (IIR) were
compounded, precured to a low degree, and then were blended with natural rubber (NR).
The compounding ingredients for NR were then added and the final curing was done. NR/
EPDM and NR/IIR blends, prepared using this method, were found to possess much
improved mechanical properties as compared to their conventional counterparts. The optimum
precuring crosslink density that has to be given to the EPDM and IIR phases has
been determined.
A novel method of blending natural rubber with polyvinylchloride in the latex
stage was developed, Dioctyl phthalate (DOP) and Amine terminated natural rubber
(ATNR) were used as plasticisers, for improving the mechanical properties of
these blends. Properties of the latex stage blends were compared with those of
dry blends. Latex stage blends showed superior mechanical properties compared
to the blends prepared in the dry state. The ageing resistance, oil resistance and
processability were found to be improved by latex stage blending.
ABSTRACT: Linseed oil is used in the dual roles of the plasticizer and the fatty
acid component of the activator in nitrile rubber vulcanizates. The study shows
that the substitution can substantially improve the mechanical properties in
addition to other advantages such as increased cure rate, reduced leachability
and reduced compound cost.
Zinc salts of ethyl, isopropyl, and butyl xanthates are prepared
in the laboratory, and the effect of these xanthates with zinc diethyl
dithiocarbamate (ZDC) on the vulcanization of HAF-filled nitrile butadiene
rubber (NBR) compounds has been studied at different temperatures. The cure
times of these compounds have been compared with that of NBR compounds
containing TMTD/MBTS. The rubber compounds with the three xanthate
accelerators and ZDC are cured at various temperatures from 60 to 150°C.
The sheets are molded and properties such as tensile strength, tear strength,
cross-link density, elongation at break, compression set, abrasion resistance,
flex resistance, etc. have been evaluated. The properties show that zinc salt
of the xanthate/ZDC accelerator system has a positive synergistic effect on the
cure rate and mechanical properties of NBR compounds.
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.
The mechanism of devulcanization of sulfur-vulcanized natural rubber with aromatic disulfides and aliphatic
amines has been studied using 23-dimethyl-2-butene (C5H1,) as a low-molecular weight model compound. First C6H12
was vulcanized with a mixture of sulfur, zinc stearate and N-cyclohexyl-2-benzothiazylsulfenamide (CBS) as accelerator
at 140 °C, resulting in a mixture of addition products (C(,H 1 i-S,-C5H 1 i ). The compounds were isolated and identified
by High Performance Liquid Chromatography (HPLC) with respect to their various sulfur ranks. In it second stage, the
vulcanized products were devulcanized using the agents mentioned above at 200 °C. The kinetics and chemistry of the
breakdown of the sulfur-hridges were monitored. Both devulcanization agents decompose sulfidic vulcanization products
with sulfur ranks equal or higher than 3 quite effectively and with comparable speed. Di phenyldisulfide as devulcanization
agent gives rise to a high amount of mono- and disulfidic compounds formed during the devulcanization,
hexadecylamine, as devulcanization agent, prevents these lower sulfur ranks from being formed.
Natural rubber, styrene-butadiene rubber, and polybutadiene
rubber were used to replace part of the butadieneacrylonitrile
rubber in a 70/30 butadiene-acrylonitrile rubber/
poly(vinyl chloride) blend. Such replacement up to 15%
of the total weight of the blend improved the mechanical
properties, while decreasing the cost of the blend. Styrenebutadiene
rubber could replace butadiene-acrylonitrile
rubber up to 30% of the total weight of the blend without
deterioration in the mechanical properties.
Rani, Joseph(Gordon and Breach Science Publishers, Inc., May 20, 1985)
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Abstract:
Polychloroprene (neoprene) has been blended with polyvinylchloride (PVC) in different
proportions using a new stabiliser system (magnesium oxide and zinc oxide with
stearic acid) for PVC. The physical properties of the blends show that they can
advantageously replace neoprene in many applications.
New oligomer-bound antioxidants have been prepared by condensation reaction. The efficiency and permanence of these oligomer-
bound paraphenylene diamines as antioxidants has been compared with conventional amine type antioxidants in NR, SBR,
IIR and NBR and in elastomer blends like NR/BR and NR/SBR. The oligomer-bound antioxidants are found to impart improved
ozone, flex resistance and mechanical properties to the vulcanizates of NR, SBR, IIR and NBR and to blends of NR/BR and NR/
SBR in comparison with those containing conventional antioxidants.
Zinc salts of ethyl, isopropyl, and butyl xanthates
were prepared in the laboratory. The effect of these
xanthates in combination with zinc diethyldithiocarbamate
(ZDC) on the vulcanization of silica-filled NBR compounds
has been studied at different temperatures. The cure times
of these compounds were compared with that of NBR compounds
containing tetramethylthiuram disulphide/dibenzthiazyl
disulphide. The rubber compounds with the xanthates
and ZDC were cured at various temperatures from
60 to 150°C. The sheets were molded and properties such as tensile strength, tear strength, crosslink density, elongation
at break, compression set, abrasion resistance, flex resistance,
heat buildup, etc. were evaluated. The properties
showed that zinc salt of xanthate/ZDC combination has a
positive synergistic effect on the cure rate and mechanical
properties of NBR compounds.
Rani, Joseph(Indian Academy of Sciences, February 24, 2003)
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Abstract:
Significant results of our experimental investigations on the dependence of pH on real time
transmission characteristics on recording media fabricated by doping PVC with complexed methylene blue
are presented. The optimum pH value for faster bleaching was found to be 4 . 5. In typical applications, the
illumination from one side, normal to the surface of this material, initiates a chemical sequence that records
the incident light pattern in the polymer. Thus direct imaging can be successfully done on this sample. The
recorded letters were very legible with good contrast and no scattering centres. Diffraction efficiency
measurements were also carried out on this material.
Poly(ethylene terephthalate) (PET) based nanocomposites have been prepared with single walled carbon nanotubes
(SWNTs) through an ultrasound assisted dissolution-evaporation method. Differential scanning calorimetry studies
showed that SWNTs nucleate crystallization in PET at weight fractions as low as 0.3%, as the nanocomposite melt crystallized
during cooling at temperature 24 °C higher than neat PET of identical molecular weight. Isothermal crystallization
studies also revealed that SWNTs significantly accelerate the crystallization process. Mechanical properties of the PETSWNT
nanocomposites improved as compared to neat PET indicating the effective reinforcement provided by nanotubes
in the polymer matrix. Electrical conductivity measurements on the nanocomposite films showed that SWNTs at concentrations
exceeding 1 wt% in the PET matrix result in electrical percolation. Comparison of crystallization, conductivity and
transmission electron microscopy studies revealed that ultrasound assisted dissolution-evaporation method enables more
effective dispersion of SWNTs in the PET matrix as compared to the melt compounding method
Rani, Joseph(American Institute of Physics, January 13, 2007)
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Abstract:
Poly(methyl)methacrylate was made photoconducting by molecular doping and the
photoconductivity was investigated using modulated photocurrent technique . Low-temperature
current-voltage measurements showed that the transport mechanism was thermally activated
hopping. An experimental investigation of the photoconductivity action spectrum along with
theoretical calculation enabled an estimation of the diffusion coefficient of the material. The
presence of states with a distribution of lifetimes could be understood from the frequency response
of the photocurrent . The photocurrent was due to the field-assisted dissociation of these states