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- ItemA New Route to Highly Stretchable and Soft Inorganic–Organic Hybrid Elastomers Using Polydimethylsiloxane as Crosslinker of Epoxidized Natural Rubber(New York, NY [u.a.] : Wiley InterScience, 2021) Banerjee, Shib Shankar; Banerjee, Susanta; Wießner, Sven; Janke, Andreas; Heinrich, Gert; Das, AmitSulfur or peroxide crosslinking is the most common and conventional method to develop elastomeric materials. A new approach to crosslink epoxidized natural rubber (ENR) by aminopropyl terminated polydimethylsiloxane (AT-PDMS) is described, intending to develop a new kind of hybrid organic–inorganic elastomers. The curing reaction is accelerated by using hydroquinone as a catalyst. The formation of the hybrid structure is evident from the appearance of two glass transition temperatures, at −1 and −120 °C, for the ENR and PDMS phases, respectively. The curing reaction is found to be of first order with respect to amine concentration with the estimated activation energy of ≈62 kJ mol−1. Comparing the mechanical properties to a typical ENR-sulfur system leads to the conclusion that the ENR/AT-PDMS hybrid structure is highly stretchable and soft, as demonstrated by its relatively higher strain at failure (up to ≈630%), and lower hardness and modulus values. The higher stretchability and soft nature of the material are achieved by introducing flexible PDMS chains during the curing process resulting to a hybrid elastomer networks. This kind of soft but robust materials can find several applications in diverse fields, such as soft robotics, flexible, and stretchable electronics.
- ItemFerric Ions Crosslinked Epoxidized Natural Rubber Filled with Carbon Nanotubes and Conductive Carbon Black Hybrid Fillers(Basel : MDPI, 2022-10-18) Damampai, Kriengsak; Pichaiyut, Skulrat; Stöckelhuber, Klaus Werner; Das, Amit; Nakason, CharoenNatural rubber with 50 mol % epoxidation (ENR-50) was filled with carbon nanotubes (CNTs) and conductive carbon black (CCB) hybrid fillers with various CCB loadings of 2.5, 5.0, 7.0, 10.0 and 15.0 phr, and the compounds were mixed with ferric ion (Fe3+) as a crosslinking agent. The ENRs filled exclusively with CNTs, and CNT–CCB hybrid fillers exhibited typical curing curves at different CCB loadings, i.e., increasing torque with time and thus crosslinked networks. Furthermore, the incorporation of CNT–CCB hybrid fillers and increasing CCB loadings caused an enhancement of tensile properties (modulus and tensile strength) and crosslink densities, which are indicated by the increasing torque difference and the crosslink densities. The crosslink densities are determined by swelling and temperature scanning stress relaxation (TSSR). Increasing CCB loadings also caused a significant improvement in bound rubber content, filler–rubber interactions, thermal resistance, glass transition temperature (Tg) and electrical conductivity. A combination of 7 phr CNT and CCB with loading higher than 2.5 phr gave superior properties to ENR vulcanizates. Furthermore, the secondary CCB filler contributes to the improvement of CNT dispersion in the ENR matrix by networking the CNT capsules and forming CNT–CCB–CNT pathways and thus strong CNT–CCB networks, indicating the improvement in the tensile properties, bound rubber content and dynamic properties of the ENR composites. Moreover, higher electrical conductivity with a comparatively low percolation threshold of the hybrid composites was found as compared to the ENR filled with CNTs without CCB composite. The superior mechanical and other properties are due to the finer dispersion and even distribution of CNT–CCB hybrid fillers in the ENR matrix.
- ItemPoly(acrylonitrile-co-butadiene) as polymeric crosslinking accelerator for sulphur network formation(London [u.a.] : Elsevier, 2020) Hait, Sakrit; Valentín, Juan López; Jiménez, Antonio González; Ortega, Pilar Bernal; Ghosh, Anik Kumar; Stöckelhuber, Klaus Werner; Wießner, Sven; Heinrich, Gert; Das, AmitThe major controlling factors that determine the various mechanical properties of an elastomer system are type of chemical crosslinking and crosslink density of the polymer network. In this study, a catalytic amount of acrylonitrile butadiene copolymer (NBR) was used as a co-accelerator for the curing of polybutadiene (BR) elastomer. After the addition of this copolymer along with other conventional sulphur ingredients in polybutadiene compounds, a clear and distinct effect on the curing and other physical characteristics was noticed. The crosslinking density of BR was increased, as evidenced by rheometric properties, solid-state NMR and swelling studies. The vulcanization kinetics study revealed a substantial lowering of the activation energy of the sulphur crosslinking process when acrylonitrile butadiene copolymer was used in the formulation. The compounds were also prepared in the presence of carbon black and silica, and it was found that in the carbon black filled system the catalytic effect of the NBR was eminent. The effect was not only reflected in the mechanical performance but also the low-temperature crystallization behavior of BR systems was altered. © 2020 The AuthorsMaterials science; Materials chemistry; Crosslinking accelerator; Sulphur network; Solid state NMR; Curing kinetics; Activation energy; Acrylonitrile butadiene; Polybutadiene; Low-temperature; Crystallization. © 2020 The Authors
- ItemMorphology and Physico-Mechanical Threshold of α-Cellulose as Filler in an E-SBR Composite(Basel : MDPI, 2021) Chowdhury, Soumya Ghosh; Chanda, Jagannath; Ghosh, Sreedip; Pal, Abhijit; Ghosh, Prasenjit; Bhattacharyya, Sanjay Kumar; Mukhopadhyay, Rabindra; Banerjee, Shib Shankar; Das, AmitIn the current context of green mobility and sustainability, the use of new generation natural fillers, namely, α-cellulose, has gained significant recognition. The presence of hydroxyl groups on α-cellulose has generated immense eagerness to map its potency as filler in an elastomeric composite. In the present work, α-cellulose-emulsion-grade styrene butadiene rubber (E-SBR) composite is prepared by conventional rubber processing method by using variable proportions of α-cellulose (1 to 40 phr) to assess its reinforce ability. Rheological, physical, visco-elastic and dynamic-mechanical behavior have clearly established that 10 phr loading of α-cellulose can be considered as an optimized dosage in terms of performance parameters. Morphological characterization with the aid of scanning electron microscope (SEM) and transmission electron microscopy (TEM) also substantiated that composite with 10 phr loading of α-cellulose has achieved the morphological threshold. With this background, synthetic filler (silica) is substituted by green filler (α-cellulose) in an E-SBR-based composite. Characterization of the compound has clearly established the reinforcement ability of α-cellulose.
- ItemEffect of prestrain on the actuation characteristics of dielectric elastomers(Basel : MDPI, 2020) Kumar, Mayank; Sharma, Anutsek; Hait, Sakrit; Wießner, Sven; Heinrich, Gert; Arief, Injamamul; Naskar, Kinsuk; Stöckelhuber, Klaus Werner; Das, AmitDielectric elastomers (DEs) represent a class of electroactive polymers that deform due to electrostatic attraction between oppositely charged electrodes under a varying electric field. Over the last couple of decades, DEs have garnered considerable attention due to their much-coveted actuation properties. As far as the precise measurement systems are concerned, however, there is no standard instrument or interface to quantify various related parameters, e.g., actuation stress, strain, voltage and creeping etc. In this communication, we present an in-depth study of dielectric actuation behavior of dielectric rubbers by the state-of-the-art “Dresden Smart Rubber Analyzer” (DSRA), designed and developed in-house. The instrument allowed us to elucidate various factors that could influence the output efficiency of the DEs. Herein, several non-conventional DEs such as hydrogenated nitrile rubber, nitrile rubber with different acrylonitrile contents, were employed as an electro-active matrix. The effect of viscoelastic creeping on the prestrain, molecular architecture of the matrices, e.g., nitrile content of nitrile-butadiene rubber (NBR) etc., are also discussed in detail.