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The effects of reducing specimen size on the fire behavior of polymeric materials were investigated by means of the rapid mass calorimeter, a high-throughput Screening instrument. Results from the rapid mass calorimeter were compared with those from the cone calorimeter. Correlation coefficients between the different measures of each method and between the two methods are discussed to elucidate the differences and similarities in the two methods. Materials with characteristic heat release rate (HRR) curves in the cone calorimeter were evaluated in detail. The rapid mass calorimeter produces valuable and interpretable results with HRR curve characteristics similar to cone calorimeter results. Compared to cone calorimeter measurements, material savings of 96% are achieved, while maintaining the Advantages of a macroscopic fire test.
Nanotechnology is one of the key technologies of the 21st century. The exploitation of 'new' effects that arise from materials structured on the nano-scale has also been proposed successfully for flame retardancy of polymers since the end of the 90s. Of all of the approaches these include, at this time the use of nanocomposites offers the best potential for industrial application, also some other ideas are sketched, such as using electrospun nanofibers mats or layer-by-layer deposits as protection coatings, as well as sub-micrometer multilayer coatings as effective IR-mirrors. The general phenomena, inducing a flow limit in the pyrolysing melt and changing the fire residue, are identified in nanocomposites. Key experiments are performed such as quasi online investigation of the protection layer formation to understand what is going on in detail. The flame retardancy mechanisms are discussed and their impact on fire behaviour quantified. With the latter, the presentation pushes forward the state of the art. For instance, the heat shielding is experimentally quantified for a layered silicate epoxy resin nanocomposite proving that it is the only import mechanism controlling the reduction in peak heat release rate in the investigated system for different irradiations. The flame retardancy performance is assessed comprehensively illuminating not only the strengths but also the weak points of the concepts. Guidelines for materials development are deduced and discussed. Apart from inorganic fillers (layered silicate, boehmite, etc.) not only carbon nanoobjects such as multiwall carbon nanotubes, multilayer graphene and graphene are investigated, but also nanoparticles that are more reactive and harbor the potential for more beneficial interactions with the polymer matrix.
Das Brandverhalten stellt wie das ausgezeichnete elektrische Isolationsverhalten, die geringen elektrischen Verluste, die Verarbeitbarkeit und Formbarkeit eine der wesentlichen Schlüsseleigenschaften im Eigenschaftsprofil von Polymerwerkstoffen in der Elektronik und der Elektrotechnik dar. Dabei bedarf es einer Ausrüstung der Polymerwerkstoffe mit Flammschutzmittel. Die Entwicklung von immer effizienteren, synergistischen und multifunktionalen Multikomponentensystemen ist dabei eine herausragende Quelle für Innovation. Die Entwicklung und Verbesserung der werkstoff- und anwendungsspezifischen Flammschutzlösungen bestimmen die aktuellen und zukünftigen Polymermaterialien in der Elektronik und Elektrotechnik mit. Der Vortrag stellt anhand von Beispielen einige der erfolgreichen Konzepte dar. Es wird versucht, über das wissenschaftlich-systematische Verständnis Grundprinzipien und vielversprechende Lösungsstrategien zu verdeutlichen.
Although the main flame retardant modes of action are known, in practise the detailed scientific understanding usually falls short, when it comes to modern multicomponent systems, the important tiny optimizations, or quantifying in terms of specific fire properties. Thus instead of a textbook-like overview of different flame retardant modes of action, this talk tries to deliver thought-provoking impulses. Some overseen details are picked up as well as basic questions raised. Rethinking of concepts memorised long ago is encouraged to discover something new. Furthermore, the talk tries to fill the gap between flame retardant modes of action and fire performance.
Eyewitnesses describe burning pavement surfaces in extreme fire scenarios. However, it was believed that the pavement plays a negligible role in comparison to other items feeding such an extreme fire at the same time. The asphalt mixtures used differ widely, thus raising the question as to whether this conclusion holds for all kinds of such materials. Three different kinds of asphalt mixtures were investigated with the aim of benchmarking the fire risks. Cone calorimeter tests are performed at an irradiance of 70kWm-2. All three investigated asphalts burn in extreme fire scenarios. The fire response (fire load, time to ignition, maximum heat release rate and smoke production) is quite different and varies by factors of up to 10 when compared to each other. The fire load per mass is always very low due to the high content of inert minerals, whereas the effective heat of combustion of the volatiles is quite typical of non-flame retarded organics. The heat release rate and fire growth indices are strongly dependent on the fire residue and thus the kind of mineral filler used. Comparing with polymeric materials, the investigated Mastic Asphalt and Stone Mastic Asphalt may be called intrinsically flame resistant, whereas the investigated Special Asphalt showed a pronouncedly greater fire risk with respect to causing fire growth and smoke. Thus the question is raised as to whether the use of certain kinds of asphalts in tunnels must be reconsidered. Apart from the binder used, the study also indicates varying the kind of aggregate as a possible route to eliminate the problem.
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.
Flame retardancy mechanisms of aluminium phosphinate in glass fiber reinforced thermoplastics
(2008)
Polyurethane (PU) bilden eine der vielseitigsten Klassen der Polymerwerkstoffe. Kein anderer Kunststoff wird sowohl als Thermoplast, als Elastomer wie auch als Duroplast verarbeitet und eingesetzt. Entsprechend vielfältig sind auch die Anforderungen an den Flammschutz. Je nach Material und Anwendung müssen spezifische Brandnormen erfüllt werden. Der vorliegende Aufsatz gibt einen Überblick über die verfügbaren Ansätze, um durch geeignete Auswahl der Rohstoffe und der Flammschutzmittel diese verschiedensten Anforderungen an das Brandverhalten zu erfüllen.
Polyurethanes (PU) represent one of the most versatile classes of plastics. They are processed and used as thermoplastic, elastomer, and thermoset. The requirements regarding flammability are correspondingly versatile. Depending on the material and the field of application, specific fire tests have to be fulfilled. This paper describes the different concepts used to fulfil these requirements by choosing the right raw materials and flame retardants.