TY - JOUR A1 - Schartel, Bernhard A1 - Perret, Birgit A1 - Dittrich, Bettina A1 - Ciesielski, M. A1 - Krämer, J. A1 - Müller, P. A1 - Altstädt, V. A1 - Zang, L. A1 - Döring, M. T1 - Flame retardancy of polymers: the role of specific reactions in the condensed phase JF - Macromolecular materials and engineering N2 - Condensed-phase mechanisms play a major role in fire-retardant polymers. Generations of development have followed the concept of charring to improve fire properties. Whereas the principal reactions are believed to be known, the specific description for multicomponent systems is lacking, as is the picture across different systems. A two-step approach is proposed in general, and also presented in greater detail. The second step covers the specific reactions controlling charring, whereas the actual reactants are provided in the preceding step. This model consistently incorporates the variety of structure–property relationships reported. A comprehensive case study is presented on seven phosphorus flame retardants in two epoxy resins to breathe life into the two-step approach. KW - Charring KW - Epoxy KW - Flame retardancy KW - Pyrolysis KW - Thermogravimetric analysis (TGA) PY - 2016 DO - https://doi.org/10.1002/mame.201500250 SN - 1438-7492 SN - 1439-2054 VL - 301 IS - 1 SP - 9 EP - 35 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-35273 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? 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 - BOOK A1 - Schubert, Martina A1 - Schartel, Bernhard A1 - Lang, M. A1 - Yin, Huajie A1 - Dittrich, Bettina A1 - Heidemeyer, P. A1 - Bastian, Martin T1 - Wirkungsweise von halogenfreien Flammschutzmitteln in WPC N2 - Das Ziel des Forschungsvorhabens war die Untersuchung der Wirkungsweise von halogenfreien Flammschutzmitteln in WPC. Eine große Anzahl verschiedener Flammschutzmittel wurde hinsichtlich ihrer Wirkmechanismen umfassend untersucht, um ein Verständnis für die ablaufenden Prozesse zu entwickeln. Hierbei wurden verschiedene Brandtests eingesetzt, um die Materialien bezüglich verschiedener Applikationen (E&E, Transportwesen, Bauwesen) zu beleuchten. Die verschiedenen Untersuchungen liefern aber auch ein umfassendes Bild vom Brandverhalten in den verschiedenen Eigenschaften, wie Entflammbarkeit und Brandausbreitung. Die prinzipiellen Ansätze wurden anhand von verschiedenen Flammschutzmitteln beleuchtet, ihre Pyrolyse und ihre Performance in verschiedenen Brandtests gegenübergestellt. Bei der angestrebten geringen Zusatzmenge ist durch den Zusatz eines einzigen Flammschutzmittels keine zufriedenstellende Reduktion der Brandeigenschaften zu erwarten. Multikomponentensysteme zur Steigerung der Effizienz sind angezeigt. Einige prinzipielle Kombinationsmöglichkeiten wurden für alle Hauptflammschutzmittel durchgespielt. Die teilweise deutlichen Verbesserungen zeigen Wege zur erfolgreichen Produktentwicklung auf. So konnten bei den Spritzgießcompounds Eigenschaften erzielt werden, die eine UL 94 V0 Klassifizierung ermöglichen. Ein Einsatz der im Forschungsvorhaben hergestellten Compounds als Baustoff ist aufgrund des Brandverhaltens in den baustoffspezifischen Prüfungen nicht möglich. Hier sind weitere Flammschutz-Konzepte zu erproben. Gleitmittel nehmen bei den untersuchten Extrusionscompounds keinen Einfluss auf das Brandverhalten. Haftvermittler nehmen ebenfalls keinen signifikanten Einfluss auf das untersuchte Brandverhalten, können aber zu einer veränderten Verteilung der Füllstoffe und damit zur Ausbildung einer effektiveren Schutzschicht führen. Feinere Holzpartikel schneiden bei den Brandprüfungen besser ab als grobe Holzpartikel. Bei Einsatz von grobem Holz wird eine schlechtere Rückstandsstruktur ausgebildet, was das Brandverhalten negativ beeinflusst. Der Einsatz von vorbehandeltem Holz brachte nicht die erwartete Verbesserung. Die neu konzipierte Aufbereitungsanlage auf Basis des Planetwalzenextruders konnte erfolgreich in Betrieb genommen werden. Vergleichende Versuche mit dem Doppelschneckenextruder zeigten, dass der PWE-Aufbau eine gute Alternative zur etablierten DSE-Aufbereitung darstellt. Zusätzlich wurden an Compounds vielversprechender Flammschutzansätze weitere Materialprüfungen (Biegeversuch, Schlagversuch, Wasseraufnahme) durchgeführt, um den Einfluss der FSM auf die spezifischen Eigenschaften der WPC zu beleuchten. N2 - The objective of the research project was to investigate the effect of halogen-free flame retardants in WPC. A large number of different flame retardants was thoroughly examined regarding their effect mechanisms to develop an understanding for the processes taking place. Different fire tests were used to examine the materials with respect to the different applications (E&E, transportation, construction). Additionally, the different investigations provide a comprehensive picture of the fire behavior regarding the different properties, such as flammability and fire spread. The fundamental approaches were examined by means of different flame retardants and their pyrolysis and performance were compared in different fire tests. A satisfactory reduction of the fire properties by adding only one flame retardant cannot be expected with the intended low added amount. Multi-component systems to increase the efficiency are indicated. Some basic combination options were tried out for all main flame retardants. The partially considerable improvements illustrate ways for successful product development. This way, properties could be achieved in injection molding compounds, which allow for a UL 94 V0 classification. It is not possible to use the compounds introduced in the research project as building material due to the fire behavior in the building material specific tests. Further flame protection concepts need to be tested in this area. Slip agents do not have an influence on the fire behavior of the examined extrusion compounds. Adhesion promoters also do not have a significant influence on the examined fire behavior but can lead to a change in the distribution of the fillers and thus to the formation of a more effective protective layer. Finer wood particles performed better in the fire tests than coarse wood particles. When using coarse wood, an inferior residual structure is formed, which has an adverse effect on the fire behavior. The use of pretreated wood fibers did not bring the expected improvement. The newly conceived processing technique based on a planetary roller extruder (PRE) was successfully put into operation. Comparative tests with twin-screw extruders (TSE) showed that the PRE configuration is a good alternative to the established TSE processing. Additionally, further material testing (bending test, impact test, water absorption) was performed on promising flame retarded compounds to examine the influence of the fire retardants on the specific properties of the WPC. KW - Wood plastic composite KW - Halogen free KW - Flame retardancy PY - 2016 SN - 978-3-8440-4645-8 SN - 2364-754X SP - 1 EP - 88 PB - Shaker Verlag CY - Aachen AN - OPUS4-37482 LA - deu 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 - The influence of layered, spherical, and tubular carbon nanomaterials' concentration on the flame retardancy of polypropylene JF - Polymer composites 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 -