TY - CONF A1 - Dittrich, Bettina A1 - Schartel, Bernhard A1 - Hofmann, D. A1 - Wartig, K.-A. A1 - Mülhaupt, R. ED - Wilkie, C. T1 - Carbon black, multiwall nanotubes and graphene - promising approach to flame retarded nanocomposites? T2 - 24th Annual conference on recent advances in flame retardancy of polymeric materials T2 - 24th Annual conference on recent advances in flame retardancy of polymeric materials CY - Stamford, NY, USA DA - 2013-05-20 KW - Graphene KW - Flame retardancy KW - Carbon nanoparticle KW - Nanocomposite PY - 2013 SN - 1-56965-218-X SP - 1 EP - 9(?) CY - Wellesley, MA, USA AN - OPUS4-28637 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dittrich, Bettina A1 - Wartig, K.-A. A1 - Hofmann, D. A1 - Mülhaupt, R. A1 - Schartel, Bernhard T1 - Flame retardancy through carbon nanomaterials: carbon black, multiwall nanotubes, expanded graphite, multi layer graphene and graphene in polypropylene JF - Polymer degradation and stability N2 - 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. KW - Polypropylene KW - Flame retardancy KW - Nanocomposites KW - Graphene KW - Carbon nanomaterials KW - Thermally reduced graphite oxide PY - 2013 DO - https://doi.org/10.1016/j.polymdegradstab.2013.04.009 SN - 0141-3910 SN - 1873-2321 VL - 98 IS - 8 SP - 1495 EP - 1505 PB - Applied Science Publ. CY - London AN - OPUS4-28638 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dittrich, Bettina A1 - Wartig, K.-A. A1 - Hofmann, D. A1 - Mülhaupt, R. A1 - Schartel, Bernhard T1 - Carbon black, multiwall carbon nanotubes, expanded graphite and functionalized graphene flame retarded polypropylene nanocomposites JF - Polymers for advanced technologies N2 - Herein, we examine the influence of adding functionalized graphene (FG), distinct expanded graphites and carbon nanofillers such as carbon black and multiwall carbon nanotubes on mechanical properties, morphology, pyrolysis, response to small flame and burning behavior of a V-2 classified flame-retarded polypropylene (PP). Among carbon fillers, FG and multilayer graphene (MLG) containing fewer than 10 layers are very effectively dispersed during twin-screw extrusion and account for enhanced matrix reinforcement. In contrast to the other fillers, no large agglomerates are detected for PP-FR/FG and PP-FR/MLG, as verified by electron microscopy. Adding FG to flame-retardant PP prevents dripping due to reduced flow at low shear rates and shifts the onset of thermal decomposition to temperatures 40°C higher. The increase in the onset temperature correlates with the increasing specific surface areas (BET) of the layered carbon fillers. The reduction of the peak heat release rate by 76% is attributed to the formation of effective protection layers during combustion. The addition of layered carbon nanoparticles lowers the time to ignition. The presence of carbon does not change the composition of the evolved pyrolysis gases, as determined by thermogravimetric analysis combined with online Fourier-transformed infrared measurements. FG and well-exfoliated MLG are superior additives with respect to spherical and tubular carbon nanomaterials. KW - Graphene KW - Flame retardancy KW - Nanocomposites KW - Polypropylene KW - Carbon nanoparticles PY - 2013 DO - https://doi.org/10.1002/pat.3165 SN - 1042-7147 SN - 1099-1581 VL - 24 IS - 10 SP - 916 EP - 926 PB - John Wiley & Sons, Ltd. CY - Chichester AN - OPUS4-29337 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hofmann, D. A1 - Wartig, K.-A. A1 - Thomann, R. A1 - Dittrich, Bettina A1 - Schartel, Bernhard A1 - Mülhaupt, R. T1 - Functionalized graphene and carbon materials as additives for melt-extruded flame retardant polypropylene JF - Macromolecular materials and engineering N2 - Functionalized graphene nanosheets TRGO and MLG 250, prepared from thermally reduced graphite oxide, represent attractive carbon additives for improving the performance of flame retardant polypropylene (PP-FR). The influence of carbon nanofiller type and content on morphology, thermal, mechanical, and electrical properties as well as the fire behavior of melt-extruded PP-FR is investigated. In contrast to conventional nano- and micron-sized carbon fillers such as expanded graphite (EG 40), nano-scaled carbon black (CB), and multiwall carbon nanotubes (CNT), only TRGO and MLG 250 afford uniform dispersion combined with simultaneously improved stiffness (+80%), electrical conductivity (3 × 10-5 S · cm-1) and enhanced flame retardancy of PP-FR, as expressed by lower peak heat release rate (-76%). KW - Extrusion KW - Flame retardance KW - Graphene KW - Nanocomposite KW - Polypropylene PY - 2013 DO - https://doi.org/10.1002/mame.201200433 SN - 1438-7492 SN - 1439-2054 VL - 298 IS - 12 SP - 1322 EP - 1334 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-29817 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yin, Huajie A1 - Dittrich, Bettina A1 - Farooq, Muhammad A1 - Kerling, S. A1 - Wartig, K.-A. A1 - Hofmann, D. A1 - Huth, Christian A1 - Okolieocha, C. A1 - Altstädt, V. A1 - Schönhals, Andreas A1 - Schartel, Bernhard T1 - Carbon-based nanofillers/poly(butylene terephthalate): thermal, dielectric, electrical and rheological properties JF - Journal of polymer research N2 - The influence of distinct carbon based nanofillers: expanded graphite (EG), conducting carbon black (CB), thermally reduced graphene oxide (TRGO) and multi-walled carbon nanotubes (CNT) on the thermal, dielectric, electrical and rheological properties of polybutylene terephthalate (PBT) was examined. The glass transition temperature (Tg) of PBT nanocomposites is independent of the filler type and content. The carbon particles act as nucleation agents and significantly affect the melting temperature (Tm), the crystallization temperature (Tc) and the degree of crystallinity of PBT composites. PBT composites with EG show insulating behaviour over the tested concentration range of 0.5 to 2 wt.-% and hardly changed rheological behaviour. CB, CNT and TRGO induce electrical conductivity to their particular PBT composites by forming a conducting particle network within the polymer matrix. CNT reached the percolation threshold at the lowest concentration (<0.5 wt.-%), followed by TRGO (<1 wt.-%) and CB (<2 wt.-%). With the formation of a particle network, the flow behaviour of composites with CB, CNT and TRGO is affected, i.e., a flow limit occurs and the melt viscosity increases. The degree of influence of the carbon nanofillers on the rheological properties of PBT composites follows the same order as for electrical conductivity. Electrical and rheological results suggest an influence attributed to the particle dispersion, which is proposed to follow the order of EG<< CB