René Jurk

Rubber-Clay Nanocomposites: Some Recent Results

In order to produce high-performance elastomeric materials, the incorporation of different types of nanoparticles such as layered silicates, layered double hydroxides (LDHs), carbon nanotubes, nanosilica, etc. into the elastomer matrix is now a growing area of rubber research. However, the reflection of the “nanoeffect” on the properties and performance can be realized only through a uniform and homogeneous dispersion of filler particles in the rubber matrix. Generally, the properties and the performance of a reinforced elastomeric composite predominantly depend on the crosslinking chemistry of the rubbers, the nature of the fillers, the physical and chemical interaction of the fillers with the rubber matrix and, especially, on the degree of filler dispersion in the rubber matrix. This article is therefore aimed exclusively at addressing the prevailing problems related to the filler dispersion, intercalation, and exfoliation of layered clays in various rubber matrices and compositions to produce advanced high-performance elastomeric nanocomposites. The effect of two chemically distinct layered nanofillers, namely montmorillonite and LDH, on the curing behavior, mechanical, thermo-mechanical, and dielectric properties, etc. are systematically discussed with respect to various elastomeric systems. Different attempts, such as melt interaction, master batch dilution techniques, and further chemical modification of the organoclay, have been taken into consideration and a major portion of this paper will be dedicated to these works.

Nanoalloy Based on Clays : Intercalated-Exfoliated Layered Silicate in High Performance Elastomer

A novel method is described for the preparation of nanocomposites comprising a high performance rubber for tire application and layered silicates clay. In this work nanocomposites of solution‐styrene butadiene rubber (S‐SBR) with montmorillonite layered silicate were prepared with carboxylated nitrile rubber (XNBR), a polar rubber, as a compatibilizer. A sufficient amount of organomodified layered silicate was loaded in carboxylated nitrile rubber (XNBR) and this compound was blended as a master batch in the S‐SBR. Mixed intercalated/exfoliated morphologies in the nanocomposite are evinced by X‐ray diffraction measurements and transmission electron microscopy. Dynamic mechanical analysis also supports the compatibility of the composites. A good dispersion of the layered silicate in the S‐SBR matrix was reflected from the physical properties of the nanocomposites, especially in terms of tensile strength and high elongation properties.

Silica‐Ethylene Propylene Diene Monomer Rubber Networking by In Situ Sol‐Gel Method

Triethoxysilyl‐grafted ethylene propylene diene monomer rubber (EPDM) was prepared with the silane coupling agent, bis‐[‐3‐(triethoxysilyl)‐propyl]‐tetrasulfide (TESPT), and thus modified rubber has been treated by an in situ sol‐gel method with the objective to grow silica particles inside the rubber matrix. TESPT grafted EPDM rubber, filled with the silica particles grown by making use of the described method, was found to exhibit excellent physical properties, despite the fact that the fraction of silica fillers in this material is found to be very low. In particular, thus produced filled rubber has higher reinforcing efficiency that is attributed to the formation of a rubber‐silica network. In addition, better silica dispersion is observed in the shear modulus measurements at low dynamic deformation amplitudes, which is in qualitative agreement with the ‘Payne’ effect that quantifies the ability of fillers to promote the formation of rubber‐filler networks. No such effect of network formation was observed when an in situ sol‐gel experiment was performed in the absence of TESPT. TEM observations showed that even if the amount of silica fillers in rubber is as small as 5 phr or less, the uniform mono‐dispersed distribution of the silica primary particles is still the main factor responsible for the reinforcement of the rubber matrix.

Processing and Properties of Nanocomposites Based on Layered Silicate and Carboxylated Nitrile Rubber

Nanocomposites based on carboxylated nitrile rubber (XNBR) and organomodified clay were prepared under different mixing conditions. At higher mixing temperatures, a mixed intercalated/exfoliated morphology was obtained as evidenced by X-ray diffraction studies and transmission electron microscopy. A remarkable improvement of physical properties was achieved when the layered silicates were mixed at high temperatures. The presence of carboxylic group in the rubber improves the interaction and exfoliation process which can be shown by IR studies. With the increase of the organoclay loading and processing temperature, a considerable effect on dynamic properties was found during strain sweep analysis which was explained by ‘Payne’-like effects. Finally, a mechanism of the layered silicate dispersion in carboxylated nitrile rubber has been proposed.

A Novel Thermotropic Elastomer based on Highly-filled LDH-SSB Composites

Elastomeric composites are prepared based on solution styrene butadiene elastomer and zinc-aluminium layered double hydroxides (LDH), using a conventional sulphur cure system. Up to 100 parts per hundred rubber of LDH are incorporated into the elastomer matrix. The composites exhibit an interesting phenomenon of thermoreversible transparency, i.e. the transparent sample becomes opaque at warm condition and restores the transparency at room temperature. The transparency is found to be increased as the amount of LDH was increased. The addition of LDH gradually improved the mechanical, dynamic mechanical performance and thermal stability of the base elastomer. These developped elastomers could be utilised as smart materials in different applications.

Correction: Nano-scale morphological analysis of graphene–rubber composites using 3D transmission electron microscopy

In this work three-dimensional transmission electron microscopy (3D-TEM) is exploited to characterize a soft graphene based nano-composites structure and the constituted morphology in a qualitative way. The reconstruction of the two dimensional slides into a three dimensional tomographic image is a powerful tool, when the images of the nano-object are reflected into a quasi-distinguishable object due to superposition effect. By using this technique it is possible to mark the contour area of the nano-sized object inside the soft rubber matrix. To extract information about the filler network, the clustering process of the fillers or the existence of single or multiple graphene sheets, a solution polymerised styrene butadiene rubber was selected as a soft matrix which was filled with carbon black (CB) and graphene nano-platelets (GnP). The dispersion/exfoliation of the stacked graphene sheets into individual single sheets was facilitated by the presence of carbon black in the system as understood from TEM, X-ray diffraction and Raman spectroscopic studies. The existence of oligo-layer graphene sheets was detected by this 3D-TEM, especially when the rubber matrix exists in a complex morphology arisen from filler–filler networks in all spatial dimensions.

Elastomer–carbon nanotube composites

Abstract: Different techniques to disperse multi-walled carbon nanotubes (MWCNT) in elastomers using an internal mixer are applied and the physical properties of the resulting composites are evaluated. It is demonstrated that the dispersion can be improved if the CNT are suspended in a liquid agent in a first step to break up the bonds. Here, ethanol proved to be a good dispersion agent without any additional surfactant and could be vaporized during the mixing process. These investigations are extended to technologically more relevant filler hybrid systems, where parts of the reinforcing filler are exchanged by CNT. Additionally, the use of ionic liquids for improved CNT–polymer interaction is discussed. The dielectric properties, electrical DC conductivity, thermal diffusivity, dynamic-mechanical as well as the stress–strain and fracture mechanical behavior of CNT-filled composites are investigated. The effect of nanoscopic gaps between adjacent CNT on the electrical and thermal conductivity of the composites and the missing percolation behavior of the thermal conductivity are discussed.

Assessment of the dynamic behavior of a new generation of complex natural rubber-based systems intended for seismic base isolation

This work, conceived as a second step in the development of high-performance damping materials suitable for seismic application, describes the preparation and characterization of complex natural rubber-based composites containing hybrid nano- and conventional fillers. The cluster–cluster aggregation model was used to assess the apparent filler networking energy. The values obtained suggested that the presence of the hybrid nanofiller strengthens the filler networking. The same model was used to understand the mechanisms of energy dissipation. The damping coefficient was found to be in the sought range between 10% and 20% (at 0.5 Hz and high shear strain).