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To curtail flammability risks and improve material properties, flame retardants (FRs) and fillers are mixed into rubbers. High loadings of aluminum trihydroxide (ATH) and carbon black (CB) are the most used FRs and reinforcing additive, respectively, in rubbers. To reduce loading without losing mechanical properties, partial substitution of ATH as well as CB by low amounts of multilayer graphene (MLG) nanoparticles is investigated. The high aspect ratio MLG is made of ten graphene sheets. In polybutadiene/chloroprene (BR/CR) nanocomposites 3 phr MLG replaced 15 phr CB and/or 3 phr ATH. Material and mechanical properties as well as fire behavior of the nanocomposites are compared to BR/CR with 20 phr CB both with and without 50 phr ATH. MLG appears as a promising nanofiller to improve the functional properties: replacement of CB improved rheological, curing, and mechanical properties; substitution of ATH improved nanocomposite properties without affecting flame retardancy.
Elastomers are usually reinforced by large amount of fillers like carbon black (CB) or silica in order to improve various mechanical properties, such as Young’s modulus, hardness, tear resistance, abrasion resistance, and gas barrier properties. In recent years, such improvements were also obtained by using nanoparticles at significantly lower filler loadings. Graphene is a twodimensional (2D) sheet of a thickness in the atomic scale, composed of a honeycomb structure of sp2 carbon atoms. Besides significant mechanical reinforcement, graphene harbors the potential to be used as a multifunctional filler, as it can also increase the conductivity and weathering stability of elastomer matrices. Ultraviolet (UV) irradiation and oxidative agents can lead to the degradation of elastomers due to a multistep photooxidative process, including the formation of radicals. Carbon-based fillers have an influence on these reactions, as they can absorb UV radiation and act as radical scavengers.
This chapter summarizes the results of our larger project on multilayer graphene (MLG)/elastomer nanocomposites, previously published, which present a comprehensive case study of MLG as a multifunctional nanofiller in elastomer/graphene nanocomposites. Different elastomeric matrices are compared in order to demonstrate the outstanding impact of MLG as a general benefit. The dependency of this effect on concentration is discussed in detail. Taking into account the key role of dispersion, different mixing procedures are compared, evaluating a facile implementation of graphene nanocomposites into conventional rubber processing. Finally, the most probable commercial uses of MLG nanofillers in combination with conventional CB are studied. The nanocomposites were prepared in the kg scale in order to obtain enough specimens to investigate various properties of the uncured and vulcanized rubbers at the highest quality level, including rheology, curing, morphology, several mechanical properties, abrasion, conductivity, gas permeation, burning behavior, and weathering stability. The structure property relationships are asserted and questioned, for example, by investigating the radical scavenging ability or aspect ratio of the MLG. This chapter illustrates the state of the art of graphene/rubber nanocomposites targeted for commercial mass applications.
In recent years, different nanoparticles have been proposed and successfully introduced as nanofillers in rubber nanocomposites. In this study, multilayer graphene (MLG) is proposed as a nanoparticle that functions efficiently at low concentrations. MLG consists of just 10 or so graphene sheets. Chlorine isobutyl isoprene rubber (CIIR)/MLG nanocomposites with different MLG loadings were prepared using an ultrasonically assisted solution mixing procedure followed by two-roll milling. The incorporation of MLG provides a clear improvement in the rheological, mechanical, curing, and gas barrier properties of the nanocomposites. Adding only 3 phr ofMLGto CIIR increased the Young’s modulus by more than two times and reduced the permeability ofO2 andCO2 by 30%. Higher nanofiller concentrations yielded further improvement in the properties of the nanocomposites. Moreover, CIIR/MLG nanocomposites showed reduced flammability.
In den letzten Jahren werden zunehmend Nanopartikel als Füllstoff für Polymere vorgeschlagen und auch erfolgreich in Elastomer-Nanocomposites eingesetzt. In dieser Arbeit wird Multilayergraphen (MLG) als Nanofüllstoff näher untersucht, der sich bereits bei geringen Konzentrationen als effizient erweist. MLG besteht aus nur etwa zehn Graphenlagen.
Chlorbutylkautschuk (CIIR)/MLG-Nanocomposites mit verschiedenen MLG-Gehalten wurden mit Hilfe eines ultraschallunterstützen Mischverfahrens in Lösung hergestellt und auf einem Walzwerk weiterverarbeitet. Das Einmischen von MLG führt zu einer deutlichen Verbesserung der rheologischen und mechanischen Eigenschaften, des Vernetzungsverhaltens sowie der Barrierewirkung gegenüber Gasen. Bereits der Zusatz von 3 phr MLG zu CIIR führt zu einem mehr als zweifach höheren E-Modul und zu einer Reduktion der Permeabilität von O2 und CO2 um 30 %. Höhere Konzentrationen an Nanofüllstoff resultieren in einer weiteren Verbesserung der Eigenschaften der Nanocomposites. Weiterhin zeigten die CIIR/MLG-Nanocomposites auch eine geringere Entflammbarkeit.
Elastomers are usually reinforced and employed in different applications. Various different nanoparticles, including layered silicates, carbon nanotubes, and expanded graphite, are currently being used as nanofiller. Multilayer Graphene (MLG) is proposed as promising nanofiller to improve the functional properties of Chlorine-Isobutylene-Isoprene Rubber (CIIR), Nitrile-Butadiene Rubber (NBR), Natural Rubber (NR) and Styrene–Butadiene Rubber (SBR) at low concentrations. MLG is constituted by only approximately 10 graphene sheets. Nanocomposites with extremely low MLG content (3 phr) showed evident improvement in rheological, mechanical and curing properties. The Young's modulus of the nanocomposites increased more than twice in comparison with the unfilled rubbers. MLG also improved the weathering resistance of the different rubbers. The nanocomposites conserved their initial mechanical properties against weathering exposure.
High loadings of carbon black (CB) are usually used to achieve the properties demanded of rubber compounds. In recent years, distinct nanoparticles have been investigated to replace CB in whole or in part, in order to reduce the necessary filler content or to improve performance. Multilayer graphene (MLG) is a nanoparticle made of just 10 graphene sheets and has recently become commercially available for mass-product nanocomposites. Three phr (part for hundred rubbers) of MLG are added to chlorine isobutyl isoprene rubber (CIIR)/CB composites in order to replace part of the CB. The incorporation of just 3 phr MLG triples the Young’s modulus of CIIR; the same effect is obtained with 20 phr CB. The simultaneous presence of three MLG and CB also delivers remarkable properties, e.g. adding three MLG and 20 phr CB increased the hardness as much as adding 40 phr CB. A comprehensive study is presented, showing the influence on a variety of mechanical properties. The potential of the MLG/CB combination is illustrated to reduce the filler content or to boost performance, respectively. Apart from the remarkable mechanical properties, the CIIR/CB/MLG nanocomposites showed an increase in weathering resistance.
Multilayer graphene/chlorine-isobutene-isoprene rubber nanocomposites: the effect of dispersion
(2016)
Multilayer graphene (MLG) is composed of approximately 10 sheets of graphene. It is a promising nanofiller just starting to become commercially available. The Dispersion of the nanofiller is essential to exploit the properties of the nanocomposites and is dependent on the preparation method. In this study, direct incorporation of 3 parts per hundred of rubber (phr) MLG into chlorine-isobutene- isoprene rubber (CIIR) on a two-roll mill did not result in substantial enhancement of the material properties. In contrast, by pre-mixing the MLG (3 phr) with CIIR using an ultrasonically assisted solution mixing procedure followed by two-roll milling, the properties (rheological, curing, and mechanical) were improved substantially compared with the MLG/CIIR nanocomposites mixed only on the mill. The Young’s moduli of the nanocomposites mixed in solution increased by 38%. The CIIR/MLG nanocomposites produced via solution showed superior durability against weathering exposure.
Es wurde die Wirksamkeit von zwei neuen Klassen polymergebundener Alterungsschutzmittel (PAS) auf der Basis von N-substituierten p-Phenylendiamin PPD`s (Thioether und Sulfoxide) im Vergleich zu N-Phenyl-N'- (1,3-dimethylbutyl)-p-phenylendiamin (6PPD) in verschiedenen Alterungsbeanspruchungen an unterschiedlichen Elastomeren getestet, der chemische Einbau als Ursache für das günstigere Verhalten hinsichtlich der Minimierung der Rissbildung bei Ozoneinwirkung, Verfärbung und Kontaktverfärbung sowie der Bildung von primären aromatischen Aminen (PAA) analytisch nachgewiesen.
Multilayer Graphene (MLG), a nanoparticle with a specific surface of BET = 250 m²/g and thus made of only approximately 10 graphene sheets, is proposed as a nanofiller for rubbers. When homogenously dispersed, it works at low loadings enabling the replacement of carbon black (CB), increase in efficiency, or reduction in filler concentration. Actually the appropriate preparation yielded nanocomposites in which just 3 phr are sufficient to significantly improve the rheological, curing and mechanical properties of different rubbers, as shown for Chlorine-Isobutylene-Isoprene Rubber (CIIR), Nitrile-Butadiene Rubber (NBR), Natural Rubber (NR), and Styrene-Butadiene Rubber (SBR). A mere 3 phr of MLG tripled the Young’s modulus of CIIR, an effect equivalent to 20 phr of carbon black. Similar equivalents are observed for MLG/CB mixtures. MLG reduces gas permeability, increases thermal and electrical conductivities, and retards fire behavior. The later shown by the reduction in heat release rate in the cone calorimeter. The higher the nanofiller concentration is (3 phr, 5 phr, and 10 phr was investigated), the greater the improvement in the properties of the nanocomposites. Moreover, the MLG nanocomposites improve stability of mechanical properties against weathering. An increase in UV-absorption as well as a pronounced radical scavenging are proposed and were proved experimentally. To sum up, MLG is interesting as a multifunctional nanofiller and seems to be quite ready for rubber development.