Geleen, Netherlands
Geleen, Netherlands

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Miloskovska E.,TU Eindhoven | Miloskovska E.,Dutch Polymer Institute | Friedrichs C.,Max Planck Institute for Polymer Research | Hristova-Bogaerds D.,TU Eindhoven | And 5 more authors.
Macromolecules | Year: 2015

Rubber-silica nanocomposites containing 10 wt % silica were prepared using in situ hydrolysis and condensation of tetraethyl orthosilicate (TEOS) in the presence of n-hexylamine as catalyst in two rubber matrices, namely, natural rubber and ethylene-propylene diene rubber. The structure of sol-gel synthesized silica, mapped by solid-state NMR spectroscopy and XPS, indicated the presence of remnant ethoxy groups inside the silica particles and on the silica surface, while hexylamine resided preferentially at the silica surface stabilized via hydrogen bonding of the ethoxy and chemisorption of the hexylamine. Thus, the preparation of sol-gel synthesized silica results in the formation of so-called "hairy" silica particles with increased hydrophobic properties. The combinatory technique FTIR-TGA-MS confirms the complex chemistry of the sol-gel synthesized silica as well as the low amount of residual ethanol present in the particles and the in situ rubber-silica nanocomposite, the latter aspect being important when industrial manufacturing and application of in situ rubber-silica nanocomposites is considered. It is further shown that (i) the particular surface chemistry, (ii) the phenomena of entrapped rubber chains inside the silica nanoparticles, and (iii) morphology of the sol-gel synthesized silica nanoparticles lead to a more intimate interaction with the rubber matrix, which may be fine-tuned toward improved mechanical properties. © 2015 American Chemical Society.

Miloskovska E.,TU Eindhoven | Hristova-Bogaerds D.,TU Eindhoven | Hristova-Bogaerds D.,Dutch Polymer Institute | Van Duin M.,LANXESS Elastomers RandD | De With G.,TU Eindhoven
European Polymer Journal | Year: 2015

In situ rubber nanocomposites prepared via reactive batch mixing and via reactive extrusion were studied. Materials produced via reactive batch mixing showed a significantly higher silica content for a similar reaction time as compared to previously prepared in situ nanocomposites using a diffusion process under static conditions, but an approximately 10% lower modulus over the strain range investigated (0.5-1000%). While the microstructure of the nanocomposites using static conditions was homogeneous with monosized silica particles, the structure of the composites obtained via reactive batch mixing was significantly different, consisting not only of single silica particles but also of aggregates and densely packed silica regions. The nanocomposites obtained via reactive extrusion had a maximum loading of 3.2 wt% silica, possessed a uniform dispersion of silica particles and a similar modulus (≈120 kPa) as conventional nanocomposites, prepared by mixing silica and rubber, containing 10 wt% silica and a coupling agent. © 2015 Elsevier Ltd. All rights reserved.

Lu K.,TU Eindhoven | Lu K.,Dutch Polymer Institute | Lu K.,Royal DSM | Van Duin M.,LANXESS Elastomers RandD | And 4 more authors.
Polymer (United Kingdom) | Year: 2012

The phase organisation of thermoplastic vulcanisates (TPVs) has been analysed in detail by applying scanning transmission electron microscopy (STEM) tomography. High contrast between the crosslinked rubber (EPDM) and the isotactic polypropylene (iPP) phases has been achieved without staining the samples. STEM tomography at low-converge-angle conditions allows for the investigation of micrometre thick samples enabling analysis of dispersion and (possible) connectivity of the phases in the TPVs for ultra-large (>50 μm 3) volumes. EPDM is dispersed in the iPP phase in a TPV with low EPDM content, whereas it forms a co-continuous phase in a TPV with high EPDM content. The latter could up to now not been demonstrated unambiguously and has impact on the rheological behaviour of the TPV. Moreover, it is demonstrated that zinc oxide and talc particles used as additives in the TPV formulation are located exclusively in the iPP phase of the TPV blend, which suggests that wetting of the solid particles by the relatively low viscous iPP phase during dynamic vulcanisation determines the location of these inorganic additives. © 2012 Elsevier Ltd.

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