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Kotal M.,Indian Institute of Technology Kharagpur | Srivastava S.K.,Indian Institute of Technology Kharagpur | Bhowmick A.K.,Indian Institute of Technology Kharagpur | Chakraborty S.K.,Indian Rubber Manufacturers Research Association
Polymer International | Year: 2011

In the past few years, layered double hydroxides (LDHs) with monolayer structure have been much studied for the development of polymer nanocomposites. LDHs with intercalated stearate anions form a bilayer structure with increased interlayer spacing and are expected to be better nanofillers in polymers. In the work reported, thermoplastic polyurethane (PU)/stearate-intercalated LDH nanocomposites were prepared by solution intercalation and characterized. X-ray diffraction and transmission electron microscopy confirmed the exfoliation at lower filler loading followed by intercalation at higher filler loading in PU matrix. As regards mechanical properties, these nanocomposites showed maximum improvements in tensile strength (45%) and elongation at break (53%) at 1 and 3 wt% loadings. Maximum improvements in storage and loss moduli (20%) with a shift of glass transition temperature (15 °C) and an increase in thermal stability (32 °C) at 50% weight loss were observed at 8 wt% loading in PU. Differential scanning calorimetry showed a shift of melting temperature of the soft segment in the nanocomposites compared to neat PU, possibly due to the nucleating effect of stearate-intercalated LDH on the crystal structure of PU. All these findings are promising for the development of mechanically improved, thermally stable novel PU nanocomposites. Copyright © 2011 Society of Chemical Industry Polyurethane (PU)/stearate-intercalated layered double hydroxide (LDH) nanocomposites have been prepared by solution blending and characterized to investigate the influence of stearate intercalation in LDH on the properties of the nanocomposites. © 2011 Society of Chemical Industry.

Patil A.G.,National Institute of Technology Karnataka | Poornachandra S.,National Institute of Technology Karnataka | Gumageri R.,National Institute of Technology Karnataka | Rajkumar K.,Indian Rubber Manufacturers Research Association | Anandhan S.,National Institute of Technology Karnataka
Journal of Material Cycles and Waste Management | Year: 2016

This paper outlines the preparation and characterization of chitosan (CS) composites reinforced with mechano-chemically activated fly ash (MCA-FA). A series of composite films was prepared by solution casting method with varying filler content. Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) analyses showed good compatibility between the CS matrix and MCA-FA. The surface roughness and irregularity in shape of MCA-FA resulted in its efficient mechanical interlocking with the polymer matrix. This, in turn enhanced the mechanical properties of these composites. All the composite films exhibited a higher tensile strength and a lower percentage of elongation-at-break compared with the pure CS film. The highest tensile strength was observed for the composite films with 1 wt% of filler loading and the reduction in the tensile properties at higher filler loading was due to agglomeration of filler and polymer–filler interface debonding. The tensile strength data were analyzed using Nielsen and Pukanzsky models to understand the interface formation and polymer–filler interactions. Thermal properties showed a marginal improvement due to the incorporation of MCA-FA. Overall, this study indicates that MCA-FA could be used as value added filler in polymer matrix composites. © 2016 Springer Japan

Bansod N.D.,Visvesvaraya National Institute of Technology | Kapgate B.P.,Visvesvaraya National Institute of Technology | Kapgate B.P.,Indian Rubber Manufacturers Research Association | Das C.,Visvesvaraya National Institute of Technology | And 4 more authors.
Journal of Sol-Gel Science and Technology | Year: 2016

Abstract: Controlled growth of in situ silica, into natural rubber (NR)/nitrile rubber (NBR) blend (40/60 composition by weight) following solution sol–gel method, results in a coherent blend morphology with enhanced composite properties. Similar composites, i.e., in situ silica-filled NR/NBR blend (40/60 by weight), showed better mechanical properties than any other composition that were prepared by soaking sol–gel method in earlier study. However, silica content in the rubber blend was limited to 20 phr (parts per hundred parts of rubber) and could not be increased under experimental condition following soaking sol–gel method. In the present work, silica content is increased (up to 30 phr) beyond that limit for the same blend composition. Accordingly, mechanical properties of the NR/NBR composites are improved. Use of a silane coupling agent, viz., bis-(3-triethoxysilylpropyl)-tetra sulfide, in the reactive sol–gel system during in situ silica generation brings in remarkable effect in silica distribution, rubber–filler interaction and mechanical properties of the composites. TEM micrographs of the selected composites reveal that silica is mostly grown at the interfacial region, when silane is used in particular. This results in further enhancement in mechanical properties and compatibility of the blend at the same silica content as evident from stress–strain and dynamic mechanical analysis studies. The reinforcement of effect in situ silica is assessed by Guth–Gold equation and modified form of Guth equation (with shape factor f = 2.53). The results are supported by the detailed studies on rheological, morphological, mechanical and viscoelastic properties of the composites. Graphical Abstract: [Figure not available: see fulltext.] © 2016 Springer Science+Business Media New York

Dubey K.A.,Bhabha Atomic Research Center | Bhardwaj Y.K.,Bhabha Atomic Research Center | Chaudhari C.V.,Bhabha Atomic Research Center | Goel N.K.,Bhabha Atomic Research Center | And 3 more authors.
Polymers for Advanced Technologies | Year: 2011

Varying compositions of styrene-butadiene rubber (SBR) and ethylene-propylene diene monomer (EPDM) 50:50 blend containing multiple walled carbon nanotube (MWNT) as nanoparticulate filler (0.5-5%) were prepared and their efficacy for radiation vulcanization was analyzed by gel-content, Charlesby-Pinner parameter, and crosslinking density measurements. Radiation sensitivity of the nanocomposites increased with increase in the MWNT fraction and radiation dose in the dose range studied. The elastic modulus, tensile strength increased with the radiation dose, while elongation at break exhibited downward trend. The extent of reinforcement as assessed using Kraus equation suggested high reinforcement of blend on MWNT addition. The reinforcing mechanism of nanocomposites was studied by various micromechanics models which predicted higher modulus than the experimentally observed results, indicating agglomeration in the nanocomposites. The thermal stability of the composites increased with increase in MWNT loading has been attributed to the antioxidancy induced by nanotubes and higher crosslinking extent of the nanocomposites. © 2010 John Wiley & Sons, Ltd.

Dubey K.A.,Bhabha Atomic Research Center | Bhardwaj Y.K.,Bhabha Atomic Research Center | Rajkumar K.,Indian Rubber Manufacturers Research Association | Panicker L.,Bhabha Atomic Research Center | And 3 more authors.
Journal of Polymer Research | Year: 2012

Synergistic effect of MWNT induced reinforcement and high energy radiation induced crosslinking on the physico-mechanical and thermal characteristics of poly-chloroprene rubber (PCR)/ethylene-propylene diene rubber (EPDM)/MWNT elastomeric nanocomposites was investigated. The extent of reinforcement, as assessed using the Kraus equation suggested high reinforcement of the blend on MWNT addition; though, the thermal stability and glass transition of the PCR and EPDM components were not significantly affected by MWNTs. The elastic modulus increased with the radiation dose as well as with the increase in MWNT content. The reinforcing mechanism of the nano-composites was studied by various micro-mechanics models all of which predicted higher moduli than the experimentally observed results, indicating agglomeration in the nano-composites. Nevertheless, in all the composites synergistic effect of radiation crosslinking and MWNT induced reinforcement were seen, suggesting radiation induced cross-linking between polymer and MWNT interface. © Springer Science+Business Media B.V. 2012.

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