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Kharagpur, India

Fernando M.,Tun Abdul Razak Research Center | Fei W.H.,Rubber Technology Center | Hull C.,Tun Abdul Razak Research Center
Rubber Chemistry and Technology | Year: 2012

Curing rubber is a complex process that involves the insertion of cross-links to convert the rubber into a useful functional material. The estimation of the cure time needed for product manufacture of small or thin walled products is often arrived at by means of a rheometer trace. Although this has been recognized as adequate for thin walled products, the production of large rubber articles requires a more rigorous analysis of cure kinetics for an essentially non-isothermal process. Often finite element analysis is used to generate non-isothermal temperature histories in a thick component, and then an appropriate cure kinetic equation is solved to predict the state of cure. In addition to generating the capability for cure time prediction, there is a need in the industry to minimize cycle time, improving productivity and therefore costs involved in product manufacture. For large products, the viability of the use of extrusion molding, where the rubber is extruded into a heated mold at the same temperature as the mold, has been demonstrated in previous reported work in this laboratory. The present work explores, via simulation, the feasibility of using extrusion molding as a manufacturing method for large components. The cure simulation module of Autodesk Moldflow has been used to compare the state of cure of a laminated bearing manufactured by conventional compression molding and extrusion molding. Previous experimental data on the temperature histories of a large laminated bearing manufactured using compression molding are compared with simulation data. Simulation data are then presented on manufacturing the bearing using extrusion molding. The aim is to demonstrate the usefulness of extrusion molding for very large components and to illustrate the advantages of using simulation codes to assist in shortening the cycle time in product manufacture.

Kumar Chaki T.,Rubber Technology Center | Khastgir D.,Rubber Technology Center
Journal of Applied Polymer Science | Year: 2016

In this study, we focused on the behavior of the direct-current (dc) conductivity/resistivity in a cryogenically low temperature region (10-300 K) for ethylene vinyl acetate copolymer, acrylonitrile butadiene copolymer, and their 50/50 blend composites filled with different conductive carbons. The composites were prepared through a melt-mixing technique. Different behaviors of the dc resistivity/relative resistivity for the composites were observed; these behaviors depended on the nature of the polymers, the filler types, and the filler concentration when plotted with respect to the temperature. The results of dc conductivity were fitted with some existing theoretical models, including Arrhenius, Kivelson, and Mott's variable range hopping, to check their applicability for these composite systems. We observed that none of the models was applicable within the entire range of measurement temperatures but were confined within limited temperature ranges. The reason behind the nonapplicability of the models is discussed with consideration of their drawbacks and limitations. © 2016 Wiley Periodicals, Inc.

Dey A.,High Energy Materials Research Laboratory | Maity A.,CSIR - Central Electrochemical Research Institute | Shafeeuulla Khan M.A.,High Energy Materials Research Laboratory | Sikder A.K.,High Energy Materials Research Laboratory | Chattopadhyay S.,Rubber Technology Center
RSC Advances | Year: 2016

A green method for the synthesis of a graphene-iron oxide nanocomposite (GINC) and its PVAc based polymer nanocomposites was reported in an earlier communication. The fabricated PVAc-GINC film exhibited a conductivity of 2.18 × 104 S m-1 with a Seebeck coefficient of 38.8 μV K-1. Hence, the power factor (PF) reached a value of 32.90 μW m-1 K-2 which is 27 fold higher than a thermoelectric material based on a PVAc-graphene composite as reported in the contemporary literature. In continuation of the above mentioned study, PEDOT:PSS was used to further enhance the power factor (PT) and figure of merit (ZT) of the system. During evaluation, a PEDOT:PSS/GINC composite (5:95) showed a remarkable increase in various thermoelectric properties like electrical conductivity (8.0 × 104 S m-1) with a Seebeck coefficient of 25.42 μV K-1 and thermal conductivity 0.90 W m-1 K-1. Hence PF and ZT reach up to 51.93 μW m-1 K-2 and 0.017, respectively. To improve the mechanical strength of the polymer composite, cellulose fibre was also employed. By the addition of cellulose fibre, though the mechanical strength of the composite increases the PF reaches 5.6, which is 10 times lower than the PEDOT:PSS/GINC composite. © The Royal Society of Chemistry 2016.

Manoharan P.,Rubber Technology Center | Naskar K.,Rubber Technology Center
Journal of Applied Polymer Science | Year: 2016

In this article, we provide an extensive analyses of various properties that are required for tire tread based on developed highly dispersible (HD) silica-filled epoxidized natural rubber composites. Silica in an HD form has become a staple filler in tire tread applications because of its inherent advantages. In this study, epoxidized natural rubber with 25 mol % epoxide (ENR 25) and natural rubber were mixed with two different types of HD silica for superior reinforcement. A standard tire tread formulation was used as the base compound. The magic triangle properties were conspicuously influenced by the viscoelastic characteristics of the vulcanizates. The introduction of polar rubber (ENR 25) into the HD silica greatly improved rheological, physicomechanical, bound rubber content, and dynamic mechanical properties, and this led to a better, fuel-efficient tire. We successfully achieved this, even in the absence of a silane coupling agent. ENR 25 played an imperative role in showing an extraordinary rubber-filler interactions and was primarily responsible for these observations. In this study, we explored the HD silica dispersion with transmission electron microscopy observations. Morphological studies revealed well-dispersed HD silica with the formation of a rubber-filler network. © 2016 Wiley Periodicals, Inc.

Annadurai P.,Naval Physical Oceanographic LaboratoryCochin682021 Kerala India | Kumar S.,Rubber Technology Center | Mukundan T.,Naval Physical Oceanographic LaboratoryCochin682021 Kerala India | Sarkar P.,Rubber Technology Center | Chattopadhyay S.,Rubber Technology Center
Polymer Composites | Year: 2015

Elastomeric composites based on nitrile rubber (NBR), carbon black (CB), and organically modified nanoclay (NC) were prepared using a laboratory two-roll mixing mill. Influences of the hybrid filler system (CB+NC) on various properties of NBR compound were analyzed. It was found that the addition of hybrid filler (CB+NC) over only carbon black enhances various properties. It was also found that the addition of nanoclay to the rubber matrix effectively improved key properties. Acoustics and electrical properties were modified with reduced water absorption because of layered clay platelets. The lower volume resistivity of NBR composites reflected better electrical conductivity attributed to the presence of nanoclay leading to effective filler connectivity. X-ray diffraction and transmission electron microscopy measurements revealed that nanoclays were mostly intercalated and were uniformly dispersed. Use of calcium stearate facilitated dispersion of nanoclay in the rubber matrix which was observed through the formation of nanostructures including “nano“ and “halo“ units. Time temperature superposition in dynamic mechanical analysis test of the composites indicated lower mechanical loss in the frequency range of interest. The advantages accruing due to overall property enhancement, including lower water absorption, and better electrical and excellent acoustic properties of NBR composites make it suitable as underwater acoustic transparent materials for transducer encapsulation application. © 2014 Society of Plastics Engineers.

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