Flame retardancy through carbon nanomaterials: Carbon black, multiwall nanotubes, expanded graphite, multi-layer graphene and graphene in polypropylene

• Published in: Polymer degradation and stability Vol. 98; no. 8; pp. 1495 - 1505
• Main Authors: Dittrich, Bettina, Wartig, Karen-Alessa, Hofmann, Daniel, Mülhaupt, Rolf, Schartel, Bernhard
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.08.2013; Elsevier
• Subjects: absorption; additives; Applied sciences; Carbon; Carbon black; Carbon nanomaterials; combustion; Composites; Exact sciences and technology; fire behavior; Flame retardancy; Forms of application and semi-finished materials; Graphene; Graphite; heat; mechanical properties; melting; Multilayers; Nanocomposites; Nanomaterials; nanoparticles; Nanotubes; Polymer industry, paints, wood; Polypropylene; Polypropylenes; soot; Technology of polymers; temperature; Thermally reduced graphite oxide; viscosity; Thermally reduced graphite oxide; Flame retardancy; Nanocomposites; Polypropylene; Graphene; Carbon nanomaterials; Particle size; Carbon nanotubes; Dispersion reinforced material; Composite material; Isotactic polymer; Olefin polymer; Nanocomposite; Carbon black; Propylene polymer; Mechanical properties; Tensile property; Experimental study; Thermal properties; Multiwalled nanotube; Morphology; Graphite; Flammability; Property structure relationship; Rheological properties
• ISSN: 0141-3910; 1873-2321
• DOI: 10.1016/j.polymdegradstab.2013.04.009

Herein we investigate the influence of carbon additives with different particle sizes and shapes on the flame retardancy and mechanical properties of isotactic polypropylene. Thermally reduced graphite oxide (TRGO) and multi-layer graphene (MLG250), consisting of few graphene layers, are compared with spherical, tubular and platelet-like carbon fillers such as carbon black (CB), multiwall nanotubes (MWNT) and expanded graphite (EG). The different morphologies control the dispersion of the carbon particles in PP and play a key role in structure–property relationships. Uniformly dispersed CB, MLG250 and TRGO shift the onset temperature of PP decomposition to temperatures around 30 °C higher, induce a flow limit in the composites' melt viscosity and change drastically their fire behaviour. The prevented dripping and significantly increased heat absorption result in decreased time to ignition and hardly any change in the reaction to a small flame. Under forced-flaming conditions reductions in the peak heat release rate of up to 74% are achieved due to the formation of a protective layer of residue during combustion. The described effects of carbon nanomaterials on the properties of PP composites are most pronounced for well-exfoliated graphenes, making them preferable to less exfoliated, micron-sized expanded graphite or conventional spherical and tubular carbon nanoparticles.