TY - JOUR A1 - Dittrich, Bettina A1 - Wartig, K.-A. A1 - Hofmann, D. A1 - Mülhaupt, R. A1 - Schartel, Bernhard T1 - The influence of layered, spherical, and tubular carbon nanomaterials' concentration on the flame retardancy of polypropylene N2 - The characteristic influences of increasing concentrations of graphene, expanded graphite (EG), carbon black (CB), and multiwall carbon nanotubes (MWNT) are investigated on pyrolysis, reaction to small flame, burning behavior, and on electrical, thermal, and rheological properties of flame retarded polypropylene (PP-FR). The property-concentration dependency is different for the various material properties, as threshold, linear, and leveling off functions were observed. Increasing concentrations of carbon nanoparticles resulted in a decrease in the electrical resistivity of the polymer by crossing the percolation threshold. The developing nanoparticle network changes melt flow behavior for small shear rates, increases thermal conductivity and therefore, affects the UL 94 classification and oxygen index. The onset temperature of PP decomposition is shifted to temperatures up to 37°C higher; the peak heat release rate is reduced by up to 74% compared to PP-FR. Both effects leveled off with increasing particle concentration. Among the four carbon nanomaterials tested, graphene presents superior influence on composite properties over the tested concentration range and outperforms commercial CB, MWNT, and EG. POLYM. COMPOS., 36:1230–1241, 2015. KW - Graphene KW - Flame retardancy KW - Concentration dependency KW - Nanocomposite KW - Carbon nanomaterial PY - 2015 DO - https://doi.org/10.1002/pc.23027 SN - 0272-8397 SN - 1548-0569 VL - 36 IS - 7 SP - 1230 EP - 1241 PB - Society of Plastics Engineers CY - Manchester, NH AN - OPUS4-33619 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - 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? N2 - Carbon black (CB), multiwall carbon nanotubes (MWNT), expanded graphite, multilayer graphene and graphene were used and compared as adjuvant and flame retardants in nanocomposites with respect to different fire scenarios. During the anaerobic pyrolysis feeding the flame, the investigated carbon additives acted as inert fillers. They formed residual protective layers, reducing the peak heat release rate in particular. The efficiency of the protection layer was dependent on the particle dispersion within the nanocomposite. However, other nanocomposite properties also influence the complex fire behavior crucially, including viscosity, thermal conductivity and the depth of heat absorption. Induced flow limits influence the melt flow, dripping behavior and thus the flammability (reaction to small flame) monitored by OI and UL 94. Increased thermal conductivity and depth of heat absorption change the time to ignition. Structure-property relationships are described as a basis for deducing guidelines for future flame retarded carbon particle nanocomposites. T2 - 24th Annual conference on recent advances in flame retardancy of polymeric materials CY - Stamford, NY, USA DA - 20.05.2013 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 - 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 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 -