J. Karger-Kocsis

Bio: J. Karger-Kocsis is an academic researcher from Budapest University of Technology and Economics. The author has contributed to research in topics: Ultimate tensile strength & Natural rubber. The author has an hindex of 1, co-authored 1 publications receiving 13 citations.

Binary and ternary composites of polystyrene, styrene–butadiene rubber and boehmite produced by water-mediated melt compounding: Morphology and mechanical properties

Abstract: Binary and ternary composites composed of polystyrene (PS), styrene–butadiene rubber (SBR), and synthetic boehmite alumina (BA) were produced by water-mediated melt compounding technique. SBR latex and/or aqueous BA suspension was injected into the molten PS in a twin-screw extruder to prepare toughened and/or reinforced polymer composites. The dispersion of the BA (two fractions with different mean particle sizes) and SBR was studied by scanning- and transmission electron microcopy techniques (SEM and TEM, respectively), and discussed. The mechanical properties of the composites were determined in static tensile, Charpy impact and short-time stress relaxation tests (performed at various temperatures). It was found that BA was mostly embedded in the SBR phase in the ternary PS/SBR/BA composite. BA incorporation increased the stiffness and tensile strength and reduced the elongation at break and impact toughness. Effect of the BA particle size was most pronounced in the tensile mechanical and stress relaxation tests. Additional incorporation of BA in the PS/SBR blend enhanced the tensile modulus and stress relaxation modulus compared to the PS/SBR blend. Relaxation master curves were constructed by applying the time–temperature superposition (TTS) principle. It was established that the inverse of the Findley power law model was fairly applicable to the stress relaxation results.

Effect of carbon nanotube type and functionalization on the electrical, thermal, mechanical and electromechanical properties of carbon nanotube/styrene–butadiene–styrene composites for large strain sensor applications

Abstract: Thermoplastic elastomer tri-block copolymer, namely styrene–butadiene–styrene (SBS) composites filled with carbon nanotubes (CNT) are characterized with the main goal of obtaining electro-mechanical composites suitable for large deformation sensor applications. CNT/SBS composites with different filler contents and filler functionalizations are studied by morphological, thermal, mechanical and electrical analyses. It is shown that the different dispersion levels of CNT in the SBS matrix are achieved for pristine or functionalized CNT with strong influence in the electrical properties of the composites. In particular covalently functionalized CNTs show percolation thresholds higher than 8 weight percentage (wt%) whereas pristine CNT show percolation threshold smaller than 1 wt%. On the other hand, CNT functionalization does not alter the conduction mechanism which is related to hopping between the CNT for concentrations higher than the percolation threshold. Pristine single and multiwall CNT within the SBS matrix allow the preparation of composites with electro-mechanical properties appropriate for strain sensors for deformations up to 5% of strain, the gauge factor varying between 2 and 8. Composites close to the percolation threshold show larger values of the gauge factor.

Polymer/boehmite nanocomposites: A review

Abstract: Boehmite is an aluminum oxyhydroxide [AlO(OH)] which is preferentially used as precursor for the production of (transition) aluminum oxides. Boehmite alumina (BA) nanoparticles are available in various morphologies due to versatile synthesis routes, which are briefly introduced. The peripheral hydroxyl groups of BA offer manifold functionalization possibilities for tailoring the dispersion and filler/matrix adhesion properties. The incorporation of BA nanofillers, with and without surface treatments, may yield improved mechanical and novel functional properties in polymers. BA can be introduced in polymers and polymer composites through different methods. This comprehensive overview covers the basic results reported on polymer/BA nanocomposites in the open literature. In this review, polymer matrices are grouped into thermoplastics, thermosets, and rubbers. Using literature results and our own findings, we have identified promising R&D trends with polymer/BA nanocomposites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45573.

Water-Assisted Production of Thermoplastic Nanocomposites: A Review

Abstract: Water-assisted, or more generally liquid-mediated, melt compounding of nanocomposites is basically a combination of solution-assisted and traditional melt mixing methods. It is an emerging technique to overcome several disadvantages of the above two. Water or aqueous liquids with additives, do not work merely as temporary carrier materials of suitable nanofillers. During batchwise and continuous compounding, these liquids are fully or partly evaporated. In the latter case, the residual liquid is working as a plasticizer. This processing technique contributes to a better dispersion of the nanofillers and affects markedly the morphology and properties of the resulting nanocomposites. A survey is given below on the present praxis and possible future developments of water-assisted melt mixing techniques for the production of thermoplastic nanocomposites.

Functionalised graphene-multiwalled carbon nanotube hybrid poly(styrene-b-butadiene-b-styrene) nanocomposites

Abstract: Combinations of functionalised graphene (fG) and functionalised multiwalled carbon nanotubes (fMWCNT) were dispersed into poly(styrene-b-butadiene-b-styrene) (SBS) matrix, where the ratios of individual fillers were varied in each nanocomposite. The synthesis of fG started from thermal expansion of expandable graphite (EG), followed by modified Hummer's method to produce graphene oxide (GO), and functionalisation of GO with 1-bromobutane (C4H9Br). The resultant fG displayed stable and strong compatibility to non-polar organic solvents. The polymer nanocomposites were prepared and characterised for their morphology, thermal stability, mechanical properties and electrical conductivity. Polymer nanocomposites with hybrid nanofillers showed improvement in thermal and electrical properties than their single nanofiller counterparts. Both the properties have maximum improvement with same weight ratios of fG and fMWCNT, with each 1.5%·w/w in SBS matrix. For mechanical properties, the improvement depends on the dominance of nanofiller. For the hybrid nanofillers, fG improved the elastic behaviour of SBS, while fMWCNT gave the overall stiffness.