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
This 'study' deals with a preliminary study of automatic beam
steering properly in conducting polyaniline . Polyaniline in its undoped and
doped .state was prepared from aniline by the chemical oxidative polymerization
method. Dielectric properties of the samples were studied at S-band
microwave frequencies using cavity perturbation technique. It is found that
undoped po/vanihne is having greater dielectric loss and conductivity contpared
with the doped samples. The beam steering property is studied using
a perspex rod antenna and HP 85/OC vector network analyzer. The shift in
the radiated beam is studied for different do voltages. The results show that
polyaniline is a good nutterial far beam steering applications.
Rani, Joseph(Gordon and Breach Science Publishers, Inc., November 28, 1986)
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Abstract:
Polymer-solvent interaction parameters for the blends of natural rubber (NR) with
styrene-butadiene rubber (SBR) and polybutadiene rubber ( BR) are calculated using
the Flory-Rehner equation by equating the network density of the vulcanizates in
two solvents.
ABSTRACT: Phenol was chemically attached to low molecular weight
chlorinated polyisobutylene and stearic acid respectively. These phenolic
antioxidants were characterised by IR, 1H NMR and TGA. The efficiency and
permanence of these bound antioxidants were compared with conventional
antioxidants in natural rubber vulcanisates. The vulcanisates showed comparable
ageing resistance in comparison to vulcanisates containing conventional
antioxidants. The presence of liquid polymer bound phenol reduce the amount of
plasticiser required for compounding.
Rani, Joseph(Wiley InterScience, October 22, 2006)
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Abstract:
Polymers exhibit low electron density and
they are radiolucent. Polymers can be made radiopaque
by different techniques. We report a method for the preparation
of radiopaque material from natural rubber (NR).
NR in its latex form was iodinated. Iodinated natural
rubber (INR) was characterized by using UV, thermo
gravimetric analysis (TGA), and X-ray images. INR was
compounded at high and low temperatures and its physical properties were measured. The low temperature
cured samples show good radiopacity and conductivity.
The optical density of low temperature cured samples
was measured.
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.
Rani, Joseph(Wiley lnterScience, February 12, 2006)
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Abstract:
It is observed that reclamation of natural rubber
latex based rubber using 2,2'-dibenzamidodiphenvldisulphide
as reclaiming agent is an optional methodology for
recycling of waste latex rubber (WLR). For progressive replacement
of virgin natural rubber by the reclaim, two alternatives
curing system were investigated: adjustment or reduction of
the curing system with increasing reclaim content, to compensate
for the extra amount of curatives brought along by the reclaim.
For fixed curing system, as if the reclaim were equivalent
to virgin NR. The cure behavior, final crosslink density
and distribution, mechanical properties, and dynamic
viscoelastic properties of the blends with reclaimed WLR are
measured and compared with the virgin compound. The morphology of the blends, sulfur migration, and final distribution
are analyzed.The mechanical and dynamic viscoelastic
properties deteriorate for both curing systems, but to a lesser
extent for fixed curing system compared to adjusted curing
system. With the fixed cure system, many properties like tensile
strength and compression set do still deteriorate, but tan 6
and Mrrr„/Murxr, representative for the rolling resistance of tires
are improved. On the other hand, with the adjusted cure system
both mechanical and dynamic properties still deteriorate.
A new photopolymerizable recording media is introduced based on poly
(vinyl alcohol) and vinyl acetate sensitized with methylene blue. It is observed
that this MBPVA/VAc system can be reused a number of times without
significant decrease in diffraction efficiency. The PVA-VAc ratio was optimized
at 2:1. Diffraction efcienc4y of 6.3% was obtained without any fixing at a dye
concentration of 9.3 x 10- mol/l at an exposure of 750mJ/cm2. The material is
attractive on account of its reusability.