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.
Eby Thomas, Thachil; Bindu, Sharmila T K; Ajalesh, Nair B; Beena, Abraham T; Sabura Begum, P M(Elsevier, May 22, 2014)
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Abstract:
Graphene has captured the attention of scientific community due to recently emerging high performance
applications. Hence, studying its reinforcing effects on epoxy resin is a significant step. In this study,
microwave exfoliated reduced graphene oxide (MERGO) was prepared from natural graphite for subsequent
fabrication of epoxy nanocomposites using triethylenetetramine (TETA) as a curing agent via insitu
polymerization. Thermogravimetric analysis (TGA), X-ray diffraction (XRD), Raman spectroscopy,
Fourier transform infrared spectroscopy (FTIR), C13 NMR spectroscopy, X-ray photoelectron spectroscopy
(XPS) and ultravioletevisible (UVevis) spectroscopy were employed to confirm the simultaneous
reduction and exfoliation of graphene oxide. The reinforcing effect of MERGO on epoxy resin was
explored by investigating its static mechanical properties and dynamic mechanical analysis (DMA) at
MERGO loadings of 0 to 0.5 phr. The micro-structure of epoxy/MERGO nanocomposites was investigated
using scanning electron microscope (SEM), transmission electron microscope (TEM) and XRD techniques.
The present work reports an enhancement of 32%, 103% and 85% in tensile, impact and flexural strength
respectively of epoxy by the addition of even 0.25 phr MERGO. At this loading elastic and flexural moduli
also increased by 10% and 65%, respectively. Single-edge-notch three-point-Bending (SEN-TPB) fracture
toughness (KIC) measurements were carried out where a 63% increase was observed by the introduction
of 0.25 phr MERGO. The interfacial interactions brought about by graphene also benefited the dynamic
mechanical properties to a large extent in the form of a significant enhancement in storage modulus and
slightly improved glass transition temperature. Considerable improvements were also detected in
dielectric properties. The epoxy nanocomposite also attained an ac conductivity of 10 5 S/m and a
remarkable increase in dielectric constant. The simple and cost effective way of graphene synthesis for
the fabrication of epoxy/MERGO nanocomposites may be extended to the preparation of other MERGO
based polymer nanocomposites. This remarkable class of materials has thrown open enormous opportunities
for developing conductive adhesives and in microelectronics
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.
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.
Unsaturated polyester resins (UPRs) are extensively
used by the fiber-reinforced plastic (FRPs) industry.
These resins have the disadvantages of brittleness and
poor resistance to crack propagation. In this study, UPRs
were chemically modified by reactive blending with polyurethane
prepolymers having terminal isocyanate groups.
Hybrid networks were formed by copolymerisation of unsaturated
polyesters with styrene and simultaneous reaction
between terminal hydroxyl groups of unsaturated polyester
and isocyanate groups of polyurethane prepolymer. The
prepolymers were based on toluene diisocyanate (TDI) and
each of hydroxy-terminated natural rubber (HTNR), hydroxy-
terminated polybutadiene (HTPB), polyethylene glycol
(PEG), and castor oil. Properties like tensile strength,
toughness, impact resistance, and elongation-at-break of the
modified UPRs show considerable improvement by this
modification. The thermal stability of the copolymer is also
marginally better
Description:
Journal of Applied Polymer Science, Vol. 100, 449–456 (2006)
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.