TY - JOUR A1 - Schartel, Bernhard A1 - Pötschke, P. A1 - Knoll, Uta A1 - Abdel-Goad, M. T1 - Fire behaviour of polyamide 6/multiwall carbon nanotube naocomposites N2 - Nanocomposites of polyamide 6 with 5 wt.% multiwall carbon nanotubes are investigated to clarify their potential as regards the fire retardancy of polymers. The nanocomposites are investigated using SEM, electrical resistivity, and oscillatory shear rheology. The pyrolysis is characterized using thermal analysis. The fire behaviour is investigated with a cone calorimeter using different external heat fluxes, by means of the limiting oxygen index and the UL 94 classification. The fire residue is characterized using SEM. The comprehensive fire behaviour characterization not only allows the materials’ potential for implementation in different fire scenarios and fire tests to be assessed, but also provides detailed insight into the active mechanisms. The increased melt viscosity of the nanocomposites and the fibre-network character of the nanofiller are the dominant mechanisms influencing fire performance. The changes are found to be adjuvant with respect to forced flaming conditions in the cone calorimeter, but also deleterious in terms of flammability. KW - Carbon Nanotubes KW - Nanocomposites KW - Flame retardancy KW - Rheology KW - Thermal Analysis KW - Fire retardancy KW - Cone Calorimeter PY - 2005 DO - https://doi.org/10.1016/j.eurpolymj.2004.11.023 SN - 0014-3057 SN - 1873-1945 VL - 41 IS - 5 SP - 1061 EP - 1070 PB - Elsevier CY - Oxford AN - OPUS4-7142 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schartel, Bernhard A1 - Bartholmai, Matthias A1 - Knoll, Uta T1 - Some comments on the use of cone calorimeter data N2 - The cone calorimeter has become one of the most important and widely used instruments for the research and development of fire retarded polymeric materials. The paper addresses three important ways in which the principal setup influences the results — factors which sometimes do not receive due consideration when drawing conclusions. The paper discusses in detail the impact on cone calorimeter results of the choice of external heat flux, the influence on the peak of heat release rate of sample thickness and thermal feedback from the back of the sample, and the influence on irradiance of the horizontal and vertical distances from the cone heater. KW - Cone Calorimeter KW - Fire retardancy KW - Fire testing KW - Nanocomposites KW - Intumescence PY - 2005 DO - https://doi.org/10.1016/j.polymdegradstab.2004.12.016 SN - 0141-3910 SN - 1873-2321 VL - 88 IS - 3 SP - 540 EP - 547 PB - Applied Science Publ. CY - London AN - OPUS4-7211 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Goering, Harald A1 - Maneck, Heinz-Eberhard A1 - Mach, Reinhard A1 - Knoll, Uta A1 - Oleszak, Franz A1 - Gajewski, Sven A1 - Brzezinka, Klaus-Werner T1 - Synthese von Nano-Materialien - Fullerene, Kohlenstoff-Nanoröhren, Nanopulver und Schichten T2 - Materialica 2002 ; 5. Internationale Fachmesse für Werkstoffanwendungen, Oberflächen und Product Engineering CY - München, Deutschland DA - 2002-09-30 PY - 2002 SP - 1 EP - 2 AN - OPUS4-2059 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gajewski, Sven A1 - Maneck, Heinz-Eberhard A1 - Knoll, Uta A1 - Neubert, Dietmar A1 - Dörfel, Ilona A1 - Mach, Reinhard A1 - Strauß, Birgid A1 - Friedrich, Jörg Florian T1 - Purification of single walled carbon nanotubes by thermal gas phase oxidation N2 - Single walled carbon nanotubes (SWNT) have been produced in an electric arc discharge by using a graphite rod as anode which is filled with a powder mixture of graphite and metallic catalysts like nickel and yttrium. The soot material containing approximately a third of SWNT was collected from the cathode region as a soft, voluminous material. The main by-products in this process are amorphous carbon and graphitic nanoparticles which have to be removed by an appropriate purification process. The as-produced soot material was purified by gas phase oxidation in air at 355 °C. The oxidation of amorphous carbon in air is advantageous against wet chemical methods because it is better controllable. Thermogravimetric analysis and electron microscopy were used to investigate the oxidation behavior of the different kinds of carbon. Oxidation of SWNT and amorphous carbon occurs simultaneously even at moderate temperatures, whereas amorphous carbon is more rapidly oxidized than SWNT. For optimizing the purification procedure by gas phase oxidation, kinetic studies were used to determine the oxidation time for each component in the soot at a given temperature. So it is possible to remove the amorphous carbon quantitatively with minimal losses of SWNT. But it was found that graphitic nanoparticles have the highest stability against oxidation and could therefore not be quantitatively removed by this method without the complete destruction of SWNT. Therefore, the electric arc discharge process has to be a controlled process for minimum production of graphitic nanoparticles to obtain a material with a high content of SWNT. KW - Nanotubes KW - Cathodic arc discharge KW - Amorphous carbon KW - Oxidation PY - 2003 DO - https://doi.org/10.1016/S0925-9635(02)00362-X SN - 0925-9635 VL - 12 IS - 3-7 SP - 816 EP - 820 PB - Elsevier CY - New York, NY AN - OPUS4-2516 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schartel, Bernhard A1 - Knoll, Uta A1 - Hartwig, A. A1 - Pütz, D. T1 - Phosphonium-modified layered silicate epoxy resins nanocomposites and their combinations with ATH and organo-phosphorus fire retardants N2 - Phosphonium-modified layered silicate epoxy resin nanocomposites were evaluated by testing the thermal/thermo-mechanical properties [differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), torsional pendulum, Sharpy toughness], flammability (limiting oxygen index LOI) and fire behavior (cone calorimeter with different irradiations). The morphology of the composites was determined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The drying conditions of phosphonium-modified layered silicate were varied in order to improve the nanocomposite formation and properties. The results were compared with using a commercial ammonium-modified montmorillonite. Enhanced nanocomposite formation was found for the commercial systems due to the amount of excess surfactant, but this effect was overcompensated through the advanced morphology of the phosphonium-modified systems. Several fire retardancy mechanisms and their specific influence on the different fire properties, such as ignitability, flammability, flame spread, total heat release (fire load), and the production of CO and smoke were discussed comprehensively. The main mechanism of layered silicate is a barrier formation influencing the flame spread in developing fires. Several minor mechanisms are significant, but important fire properties such as flammability or fire load are hardly influenced. Hence combinations with aluminum hydroxide and organo-phosphorus flame retardants were evaluated. The combination with aluminum hydroxide was a promising approach since it shows superposition in properties such as the fire load and only in some properties very little antagonism. The combination with an organo-phosphorus flame retardant disillusions, since it was characterized mainly by antagonism. KW - Flame retardance KW - Nanocomposites KW - Organoclay KW - Epoxy resin KW - Cone calorimeter PY - 2006 DO - https://doi.org/10.1002/pat.686 SN - 1042-7147 SN - 1099-1581 VL - 17 IS - 4 SP - 281 EP - 293 PB - John Wiley & Sons, Ltd. CY - Chichester AN - OPUS4-12519 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Perez, R.M. A1 - Sandler, J.K.W. A1 - Altstädt, V. A1 - Hoffmann, T. A1 - Pospiech, D. A1 - Ciesielski, M. A1 - Döring, M. A1 - Braun, Ulrike A1 - Knoll, Uta A1 - Schartel, Bernhard T1 - Effective halogen-free flame retardants for carbon fibre-reinforced epoxy composites N2 - DOPO-based flame retardants with tailored chemical structures are proposed for carbon fibre reinforced epoxy composites. Critical properties related to the fracture toughness are maintained, effectively allowing the use of such compounds in composites for demanding applications. KW - Fire retardancy KW - DOPO KW - Epoxy resin KW - LOI KW - UL94 PY - 2006 DO - https://doi.org/10.1007/s10853-006-0134-4 SN - 0022-2461 SN - 1573-4803 VL - 41 IS - 15 SP - 4981 EP - 4984 PB - Springer Science + Business Media B.V. CY - New York, USA AN - OPUS4-12641 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Braun, Ulrike A1 - Knoll, Uta A1 - Schartel, Bernhard A1 - Hoffmann, T. A1 - Pospiech, D. A1 - Artner, J. A1 - Ciesielski, M. A1 - Döring, M. A1 - Perez-Graterol, R. A1 - Sandler, J.K.W. A1 - Altstädt, V. T1 - Novel Phosphorus-Containing Poly(ether sulfone)s and Their Blends with an Epoxy Resin: Thermal Decomposition and Fire Retardancy N2 - Summary: The decomposition of novel phosphorus-containing poly(oxyphenylene-sulfonyl-phenylene-oxy-diphenyl phenylene phosphine oxide) (PSU_I), 2,5-dihydroxy-1-biphenylene-phosphine oxide based polysulfone (PSU_II), poly(sulfonyl-diphenylphenylene phosphonate) (PSU_P) and bisphenol A-based polysulfone (PSU) is studied. The influence of the chemical structure, charring and phosphorus release is discussed based on the mass loss, kinetics and products. The pyrolysis and fire behaviour of blends with epoxy resin (EP) are studied. For EP-PSU_II, phosphorus initiates water elimination and changes the decomposition pathway of EP. The fire behaviour of EP-PSU shows some improvements, whereas the heat release rate is crucially reduced for EP-PSU_II due to simultaneous char formation and flame inhibition. KW - Epoxy KW - Flame retardance KW - High performance polymers KW - Polysulfones KW - Thermogravimetric analysis (TGA) PY - 2006 DO - https://doi.org/10.1002/macp.200600182 SN - 1022-1352 SN - 1521-3935 VL - 207 IS - 16 SP - 1501 EP - 1514 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-12650 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rzepka, M. A1 - Bauer, E. A1 - Reichenauer, G. A1 - Schliermann, T. A1 - Bernhardt, B. A1 - Bohmhammel, K. A1 - Henneberg, E. A1 - Knoll, Uta A1 - Maneck, Heinz-Eberhard A1 - Braue, W. T1 - Hydrogen Storage Capacity of Catalytically Grown Carbon Nanofibers N2 - In 1996, R. T. K. Baker, and N. M. Rodriguez claimed to have synthesized a new type of carbon nanofiber material capable of storing large amounts of hydrogen at room temperature and pressures above 100 bar, thus making it a powerful candidate for a very efficient energy storage system in mobile applications. Consequently, many scientists all over the world tried to test and verify these findings, however, with partly inconsistent results. We present here for the first time independent hydrogen storage measurements for several types of nanofibers, both synthesized by our group following precisely the specifications given in the literature as well as original samples supplied by Rodriguez and Baker for this study. The hydrogen storage capacities at room temperature and pressures up to 140 bar were quantified independently by gravimetric and volumetric methods, respectively. No significant hydrogen storage capacity has been detected for all carbon nanofibers investigated. KW - Energy storage KW - Hydrogen storeage KW - Storage capacity KW - Carbon nanofiber KW - Carbon nanofiber synthesis PY - 2005 DO - https://doi.org/10.1021/jp051371a SN - 1520-6106 SN - 1520-5207 SN - 1089-5647 VL - 109 IS - 31 SP - 14979 EP - 14989 PB - Soc. CY - Washington, DC AN - OPUS4-13763 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schartel, Bernhard A1 - Bartholmai, Matthias A1 - Knoll, Uta T1 - Some comments on the main fire retardancy mechanisms in polymer nanocomposites N2 - Barrier formation and increasing the melt viscosity are addressed as the two main general fire retardancy mechanisms of polymer nanocomposites. They result in specific impacts on fire properties that consequentially cause varying flame retardancy efficiency in different fire tests. The barrier formation retards mainly flame spread (peak of heat release rate) in developing fires, but does not reduce fire load (total heat evolved), ignitability or flammability (limiting oxygen index, UL 94). Furthermore, this flame retardancy effect increases with increasing irradiation and vanishes with decreasing irradiation. The increased melt viscosity prevents dripping, which is beneficial or disadvantageous depending on the fire test used. In some test, it become the dominant influence, transforming self-extinguishing samples into flammable materials or causing wicking. Advantages and the limits are sketched comprehensively for exploiting the main general fire retardancy mechanisms of polymer nanocomposites. It is concluded that barrier formation and changing the melt viscosity in nanocomposites are not sufficient for most applications, but must be accompanied by additional mechanisms in special systems or in combination with other flame retardants. KW - Flame retardance KW - Nanocomposites KW - Organoclay KW - Cone calorimeter KW - Flammability PY - 2006 DO - https://doi.org/10.1002/pat.792 SN - 1042-7147 SN - 1099-1581 VL - 17 IS - 9-10 SP - 772 EP - 777 PB - John Wiley & Sons, Ltd. CY - Chichester AN - OPUS4-13868 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Braun, Ulrike A1 - Balabanovich, Aliaksandr A1 - Schartel, Bernhard A1 - Knoll, Uta A1 - Artner, J. A1 - Ciesielski, M. A1 - Döring, M. A1 - Perez, R. A1 - Sandler, J.K.W. A1 - Altstädt, V. A1 - Hoffmann, T. A1 - Pospiech, D. T1 - Influence of the oxidation state of phosphorus on the decomposition and fire behaviour of flame-retarded epoxy resin composites N2 - A systematic and comparative evaluation of the pyrolysis of halogen-free flame-retarded epoxy resins containing phosphine oxide, phosphinate, phosphonate, and phosphate (phosphorus contents around 2.6 wt.%) and the fire behaviour of their carbon fibre composites is presented. Decomposition pathways are proposed based on the thermal analysis (TG), TG coupled with evolved gas analysis (TG-FTIR), kinetics and analysis of the residue with FTIR and XPS. All organophosphorus-modified hardeners containing phenoxy groups lead to a reduced decomposition temperature and mass loss step for the main decomposition of the cured epoxy resin. With increasing oxidation state of the phosphorus the thermally stable residue increases, whereas the release of phosphorus-containing volatiles decreases. The flammability of the composites was investigated with LOI and UL 94 and the fire behaviour for forced-flaming conditions with cone calorimeter tests performed using different irradiations. The flame retardancy mechanisms are discussed. With increasing oxidation state of the phosphorus additional charring is observed, whereas the flame inhibition, which plays the more important role for the performance of the composites, decreases. The processing and the mechanical performance (delamination resistance, flexural properties and interlaminar bonding strength) of the fibre-reinforced composites containing phosphorus were maintained at a high level and, in some cases, even improved. The potential for optimising flame retardancy while maintaining mechanical properties is highlighted in this study. KW - Fire retardant KW - Composites KW - Organophosphorus-containing epoxy resin PY - 2006 DO - https://doi.org/10.1016/j.polymer.2006.10.022 SN - 0032-3861 SN - 1873-2291 VL - 47 IS - 26 SP - 8495 EP - 8508 PB - Springer CY - Berlin AN - OPUS4-14054 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -