2020, Vaikuntam, Sankar Raman, Bhagavatheswaran, Eshwaran Subramani, Xiang, Fei, Wießner, Sven, Heinrich, Gert, Das, Amit, Stöckelhuber, Klaus Werner

The article focuses on comparing the friction, abrasion, and crack growth behavior of two different kinds of silica-filled tire tread compounds loaded with (a) in-situ generated alkoxide silica and (b) commercial precipitated silica-filled compounds. The rubber matrix consists of solution styrene butadiene rubber polymers (SSBR). The in-situ generated particles are entirely different in filler morphology, i.e., in terms of size and physical structure, when compared to the precipitated silica. However, both types of the silicas were identified as amorphous in nature. Influence of filler morphology and surface modification of silica on the end performances of the rubbers like dynamic friction, abrasion index, and fatigue crack propagation were investigated. Compared to precipitated silica composites, in-situ derived silica composites offer better abrasion behavior and improved crack propagation with and without admixture of silane coupling agents. Silane modification, particle morphology, and crosslink density were identified as further vital parameters influencing the investigated rubber properties. © 2020 by the authors.

2022-10-18, Damampai, Kriengsak, Pichaiyut, Skulrat, Stöckelhuber, Klaus Werner, Das, Amit, Nakason, Charoen

Natural 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.

2022-01-05, Kamble, Vikram G., Mersch, Johannes, Tahir, Muhammad, Stöckelhuber, Klaus Werner, Das, Amit, Wießner, Sven

The preparation of intelligent structures for multiple smart applications such as soft-ro-botics, artificial limbs, etc., is a rapidly evolving research topic. In the present work, the preparation of a functional fabric, and its integration into a soft elastomeric matrix to develop an adaptive fiber-elastomer composite structure, is presented. Functional fabric, with the implementation of the shape memory effect, was combined with liquid polybutadiene rubber by means of a low-temperature vulcanization process. A detailed investigation on the crosslinking behavior of liquid polybutadiene rubber was performed to develop a rubber formulation that is capable of crosslinking liquid rubber at 75 °C, a temperature that is much lower than the phase transformation temperature of SMA wires (90–110 °C). By utilizing the unique low-temperature crosslinking protocol for liquid polybutadiene rubber, soft intelligent structures containing functional fabric were developed. The adaptive structures were successfully activated by Joule heating. The deformation behavior of the smart structures was experimentally demonstrated by reaching a 120 mm bending distance at an activation voltage of 8 V without an additional load, whereas 90 mm, 70 mm, 65 mm, 57 mm bending distances were achieved with attached weights of 5 g, 10 g, 20 g, 30 g, respectively.

2020, Hait, Sakrit, Valentín, Juan López, Jiménez, Antonio González, Ortega, Pilar Bernal, Ghosh, Anik Kumar, Stöckelhuber, Klaus Werner, Wießner, Sven, Heinrich, Gert, Das, Amit

The 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

2021, Hait, Sakrit, De, Debapriya, Ghosh, Prasenjit, Chanda, Jagannath, Mukhopadhyay, Rabindra, Dasgupta, Saikat, Sallat, Aladdin, Al Aiti, Muhannad, Stöckelhuber, Klaus Werner, Wießner, Sven, Heinrich, Gert, Das, Amit

From an environmental and economic viewpoint, it is a win–win strategy to use materials obtained from renewable resources for the production of high-performance elastomer composites. Lignin, being a renewable biomass, was employed as a functional filler material to obtain an elastomer composite with a higher degree of mechanical performance. In the presence of a suitable coupling agent, an elevated temperature was preferred for the reactive mixing of lignin with polybutadiene rubber (BR). It is quite fascinating that the mechanical performance of this composite was comparable with carbon black-filled composites. The extraordinary reinforcing behavior of lignin in the BR matrix was understood by an available model of rubber reinforcement. In rubber composite preparation, the interfacial interaction between polybutadiene rubber and lignin in the presence of a coupling agent enabled the efficient dispersion of lignin into the rubber matrix, which is responsible for the excellent mechanical properties of the rubber composites. The rubber composites thus obtained may lead to the development of a sustainable and cost-effective end product with reliable performance. This novel approach could be implemented in other type of elastomeric materials, enabling a genuine pathway toward a sustainable globe.