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- Cone Calorimeter (15) (entfernen)
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.
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.
The exploration of condensed phase mechanisms such as charring and intumescence has been pushed forward in the last decades, since it is believed that focusing on these concepts will bring materials closer to an efficient and ecologically friendly fire retardancy. They promise to concentrate efficient fire retardancy at the key position between pyrolysis zone and gas phase. Examples of residue/char forming and intumescent materials are used to illustrate the influence of mass and heat barrier effects on the fire behavior of materials and general results are presented. A comprehensive understanding of the mechanisms and structure-property relationships in fire retardancy is presented.