TY - THES A1 - Wu, Guang Mei T1 - Quantitative Assessment and Optimization of Flame Retardancy by the Shielding Effect in Epoxy Nanocomposites N2 - Diese Arbeit trägt zum halogenfreien Flammschutz von Epoxidharzen durch Nanokomposite mit Phosphonium modifiziertem Schichtsilikat bei. Der Flammschutz resultiert aus der während der Pyrolyse entstehenden inorganisch-organischen Schutzschicht. Diese Brandrückstandsschicht wirkt als Hitzeschild für das darunterliegende Material. Ziel dieser Arbeit ist die experimentelle und quantitative Beschreibung dieses Effekts und die Optimierung der Flammschutzwirkung. Die während der erzwungenen Verbrennung im Cone Calorimeter auftretenden Wärmeflüsse und Materialoberflächentemperaturen wurden in selbst konzipierten Experimenten bestimmt. Der durch die Schutzschicht zurückgestrahlte Wärmefluß und die daraus resultierte Reduktion des in der Pyrolysezone effektiv in Brennstofffreisetzung umgesetzten Wärmeflusses wurden erfolgreich quantifiziert. Mit diesem effektiven Wärmefluß nahmen wichtige Brandeigenschaften wie die Wärmefreisetzungsrate ab. Zur Optimierung der Schutzschicht wurde drei Ansätze verfolgt: Variation der organischen Modifizierung, verbesserte Dispersion durch den Einsatz von interkaliertem Triphenylphosphat und die Optimierung der Morphologie der Schutzschicht durch die Kombination von Schichtsilikat mit niedrig schmelzenden Gläsern. Durch den Einsatz verschiedener organischer Kationen lässt sich die Verteilung der Nanopartikel, die Struktur der Schutzschicht und damit die Flammschutzwirkung optimieren. Obwohl die Interkalation von Triphenylphosphat eine deutliche Aufweitung der Schichtabstände im Schichtsilikat bewirkt, zeigen die entsprechenden Nanokomposite keine verbesserte Verteilung der Partikel, keine homogenere Schutzschicht und keine Erhöhung der Flammschutzwirkung im Vergleich zu analogen Mischsystemen, in denen additiv Triphenylphosphat zugegeben wurde. Die Kombination von organisch modifiziertem Schichtsilikat und niedrig schmelzenden Gläsern zeigen in den meisten der untersuchten Systeme antagonistische Effekte. Nur in wenigen Kombinationen ist, die Superposition bzw. sogar eine Synergie zwischen den Flammschutzeffekten beider Zusätze zu beobachten. Die erstmalige experimentelle Quantifizierung des Hitzeschildes in Polymernanokompositen ist ein wertvoller Beitrag für ein grundlegendes Verständnis der Flammschutzmechanismen in Nanokompositen. Die Abhängigkeit der Flammschutzwirkung von der Struktur der Schutzschicht wurde nachgewiesen. Zur Optimierung der Schutzschichtstruktur und damit des Flammschutzes wurden drei Ansätze vorgeschlagen. N2 - The motivation of this study was to pursue effective eco-friendly and economical flame retarded polymer materials. With wide-ranging advantages such as improved fire and physical properties, halogen-free and relatively low cost, layered silicate / epoxy nanocomposite (EP_LS) was targeted for high efficiency of flame retardancy. One main goal of this study was to increase the understanding of the flame retardancy phenomenon in EP_LS by assessing the shielding effect of the protection layer experimentally and quantitatively. Another main goal of this study was to optimize the flame retardancy by the shielding effect in EP_LS. T3 - BAM Dissertationsreihe - 77 KW - Flame retardancy KW - Shielding effect KW - Nanocomposite KW - Layered silicate KW - Low-melting glass PY - 2011 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-816 SN - 978-3-9814281-7-9 SN - 1613-4249 VL - 77 SP - 1 EP - 125 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-81 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wu, Guang Mei A1 - Schartel, Bernhard A1 - Kleemeier, M. A1 - Hartwig, A. T1 - FLAME RETARDANCY OF LAYERED SILICATE EPOXY NANOCOMPOSITES COMBINED WITH LOW MELTING INORGANIC GLASSES T2 - FRPM'09 12th European Meeting on Fire Retardant Polymers CY - Poznan, Poland DA - 2009-08-31 PY - 2009 AN - OPUS4-20015 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wu, Guang Mei A1 - Schartel, Bernhard A1 - Bahr, Horst A1 - Kleemeier, M. A1 - Yu, D. A1 - Hartwig, A. T1 - Nanocomposites - two new pieces of the puzzle: Combination with low-melting glasses and an experimental insight in the shielding effect T2 - International Symposium on Flame-Retardant Materials & Technologies 2010 (ISFRMT 2010) CY - Chengdu, China DA - 2010-09-17 PY - 2010 AN - OPUS4-22116 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yu, D. A1 - Kleemeier, M. A1 - Wu, Guang Mei A1 - Schartel, Bernhard A1 - Liu, W.Q. A1 - Hartwig, A. T1 - A low melting organic-inorganic glass and its effect on flame retardancy of clay/epoxy composites N2 - A low-melting organic-inorganic glass with a high molecular weight soluble in solvents was synthesized by hydrolytic polycondensation of phenyltriethoxysilane followed by a subsequent heat treatment. Softening point and thermostability were strongly increased after heat treatment. The composites of glass/epoxy and glass/clay/epoxy were studied with respect to their thermal properties, fire behavior and mechanical properties. Heat release rate as measured by cone calorimetry was remarkably reduced in the presence of glass, relative to neat epoxy resin and polymer/clay composites. The combination of glass and clay is a promising approach. It showed mainly superposition and even synergistic effects in some fire properties for higher filler concentrations due to the formation of an enhanced barrier. The structure of residue was investigated by transmission electron microscopy (TEM). KW - Low-melting glass KW - Clay KW - Epoxy resin PY - 2011 DO - https://doi.org/10.1016/j.polymer.2011.03.033 SN - 0032-3861 SN - 1873-2291 VL - 52 IS - 10 SP - 2120 EP - 2131 PB - Elsevier Ltd. AN - OPUS4-23858 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yu, D. A1 - Kleemeier, M. A1 - Wu, Guang Mei A1 - Schartel, Bernhard A1 - Liu, W.Q. A1 - Hartwig, A. T1 - Phosphorus and silicon containing low-melting organic-inorganic glasses improve flame retardancy of epoxy/clay composites N2 - New low-melting organic–inorganic glassy polymers containing phosphorus and silicon are synthesized by the reaction between phenylphosphonic acid and methyltrichlorosilane or methyltriethoxysilane. They possess both low-softening points and high onset decomposition temperatures, which are favorable for preparing flame retardant composites. Although the glass by itself is sensitive to water, the composites are not significantly affected in that way. For glass/clay/epoxy composites glass transition temperature (Tg) as well as storage modulus increase with the glass amount. The glasses improve flame retardancy significantly due to flame inhibition and the formation of fire residue working as protection layer during burning. The total heat evolved is reduced by 23–28% for using 5–15 wt.% glass and the maximum HRR even by 58–48%. The latter effect decreases with increasing glass amount due to an adulterate residue deformation. The combination of glass and clay is proposed as a possible route to enhance flame retardancy. KW - Clay KW - Epoxy resin KW - Flame retardancy KW - Organic-inorganic polymer KW - Low-melting glass PY - 2011 DO - https://doi.org/10.1002/mame.201100014 SN - 1438-7492 SN - 1439-2054 VL - 296 IS - 10 SP - 952 EP - 964 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-24516 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yu, D. A1 - Kleemeier, M. A1 - Wu, Guang Mei A1 - Schartel, Bernhard A1 - Liu, W.Q. A1 - Hartwig, A. T1 - The absence of size- dependency in flame retarded composites containing low-melting organic-inorganic glass and clay: Comparison between micro- and nanocomposites N2 - Due to optimised processing of epoxy based composite materials containing a low-melting organic–inorganic glass together with an organo clay, the size of the glass particles could be successfully reduced. Thus truly nano-dispersed composites were obtained, with glass particles in the range of 10 nm to 200 nm. The small particle size allowed efficient interaction of glass particles and organo clay layers. The flame retardancy as well as the thermo-mechanical properties were tested, and the results showed that the low-melting glass led to a remarkable reduction of peak heat release rate by forming an enhanced barrier layer. Nevertheless no further improvement could be achieved by lowering the particle size to the nanometre region. For good flame retardancy a microdispersion of the low-melting glass was already sufficient. KW - Epoxy resin KW - Nanocomposites KW - Low-melting glass KW - Clay KW - Flame retardancy PY - 2011 DO - https://doi.org/10.1016/j.polymdegradstab.2011.06.003 SN - 0141-3910 SN - 1873-2321 VL - 96 IS - 9 SP - 1616 EP - 1624 PB - Elsevier Ltd. CY - London AN - OPUS4-24211 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wu, Guang Mei A1 - Schartel, Bernhard A1 - Kleemeier, M. A1 - Hartwig, A. T1 - Flammability of layered silicate epoxy nanocomposites combined with low-melting inorganic ceepree glass N2 - Tetraphenylphosphonium modified layered silicate epoxy nanocomposite (EP/TPPMMT) combined with low-melting silicate glass, Ceepree (CP) is investigated by thermal analysis, flammability tests and cone calorimeter at different heat fluxes. Adding CP and TPPMMT does not change the pyrolysis apart from increasing inorganic residue. The total heat evolved (THE) is changed insignificantly, as neither relevant additional carbonaceous charring nor flame inhibition occurs. However, flame retardancy is clearly observed due to an inorganic-carbonaceous surface protection layer. The peak heat released rate (PHRR) is reduced by around 32–42% when 5 wt% TPPMMT is added, and 51–63% when 10 wt% CP is added. PHRR reduction less than expected is observed when both additives are combined. The reduction is greater than that achieved by using TPPMMT but less than when only CP is used. The morphology of fire residue is investigated by scanning electron microscope on different length scales and turns out to be the key to understanding the efficiency of flame retardancy. The fire residue of EP/CP shows a layered structure, whereas separated columns limit the barrier properties for EP/5%TPPMMT on the micrometer scale. Columns dominating the fire residue structure of EP/5%TPPMMT/10%CP deteriorate the fire retardancy, whereas a more integral structure at the top of the residue causes the improvement over EP/5%TPPMMT. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers KW - Flame retardancy KW - Nanocomposites KW - Low melting glasses KW - Epoxy resin KW - Ceepree PY - 2012 DO - https://doi.org/10.1002/pen.22111 SN - 0032-3888 SN - 1548-2634 VL - 52 IS - 3 SP - 507 EP - 517 PB - Wiley CY - Hoboken, NY AN - OPUS4-25590 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wu, Guang Mei A1 - Schartel, Bernhard A1 - Yu, D. A1 - Kleemeier, M. A1 - Hartwig, A. T1 - Synergistic fire retardancy in layered-silicate nanocomposite combined with low-melting phenysiloxane glass N2 - Tetraphenyl phosphonium-modified layered silicate (LS) and low-melting phenylsiloxane glass (G) are combined for more efficient halogen-free flame retardancy in epoxy resin (EP_LSG). Particularly, the peak heat release rate (PHRR) is decreased (by up to 60%), but levels off at additive concentrations ≥10 wt%. The performance of EP_LSG is compared to EP_LS and EP_G assuming an absolute and a relative flame retardancy effect, respectively, and based on the same amount of each filler and, alternatively, with EP_G containing the same overall amount of filler. EP_LSG behaves close to superposition but shows a strong tendency toward synergism due to a superior structural integrity of the fire residues. Apart from LS, adding G in particular is a promising approach when its content is ≤5 wt%, as is LSG for ≥10 wt%. KW - Low-melting glass KW - Layered silicate KW - Flame retardancy KW - Nanocomposites KW - Epoxy resin PY - 2012 DO - https://doi.org/10.1177/0734904111422417 SN - 0734-9041 SN - 1530-8049 VL - 30 IS - 1 SP - 69 EP - 87 PB - Sage CY - London AN - OPUS4-25359 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wu, Guang Mei A1 - Schartel, Bernhard A1 - Bahr, Horst A1 - Kleemeier, M. A1 - Yu, D. A1 - Hartwig, A. T1 - Experimental and quantitative assessment of flame retardancy by the shielding effect in layered silicate epoxy nanocomposites N2 - A quantitative experimental assessment of flame retardancy by the heat shielding in epoxy layered silicate nanocomposite (EP/TPPMMT) is presented. Online heat flux measurements and temperature monitoring within the specimen are performed during the burning in the cone calorimeter. For EP the surface layer equals a pyrolysis front. The reradiation by the hot surface corresponds to the fourth power of the pyrolysis temperature. The surface reradiation (around 10 kW m-2) is thus fairly invariable over burning time and different external heat fluxes. Further, the thermal feedback of the flame is approximated to 20 kW m-2 for both EP and EP/TPPMMT and invariable over different irradiations. Thus the net heat fluxes transformed to the fuel release rate within the pyrolysis front of EP are increased to 45–80 kW m-2 when irradiations of 35–70 kW m-2 are applied. For a residue-forming EP/TPPMMT the surface temperature and thus the reradiation (42–68 kW m-2) crucially increases compared to EP and with increasing irradiation. The net heat fluxes are reduced to 13–22 kW m-2 accordingly. This quantitative assessment of the heat shielding in EP/TPPMMT goes along with proportional and consistent improvement in the fire performance, such as the pyrolysis front velocity, the heat release rate (HRR) characteristics such as averaged and quasi-steady-state HRR and the peak HRR (PHRR). The heat shielding is proven to be the only major flame retardancy effect occurring in nanocomposites based on non-charring polymers. KW - Nanocomposites KW - Heat shielding KW - Flame retardancy KW - Shielding effect PY - 2012 DO - https://doi.org/10.1016/j.combustflame.2012.07.003 SN - 0010-2180 SN - 1556-2921 VL - 159 IS - 12 SP - 3616 EP - 3623 PB - Elsevier CY - New York, NY AN - OPUS4-26841 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -