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Rigid polyurethane foams (RPUFs) typically exhibit low thermal inertia, resulting in short ignition times and rapid flame spread. In this study, the fire phenomena of RPUFs were investigated using a multi-methodological approach to gain detailed insight into the fire behaviour of pentaneand water-blown polyurethane (PUR) as well as pentane-blown polyisocyanurate Polyurethane (PIR) foams with densities ranging from 30 to 100 kg/m3. Thermophysical properties were studied using thermogravimetry (TG); flammability and fire behaviour were investigated by means of the limiting oxygen index (LOI) and a cone calorimeter. Temperature development in burning cone calorimeter specimens was monitored with thermocouples inside the foam samples and visual investigation of quenched specimens’ cross sections gave insight into the morphological changes during burning. A comprehensive investigation is presented, illuminating the processes taking place during foam combustion. Cone calorimeter tests revealed that in-depth absorption of radiation is a significant factor in estimating the time to ignition. Cross sections examined with an electron scanning microscope (SEM) revealed a pyrolysis front with an intact foam structure underneath, and temperature measurement inside burning specimens indicated that, as foam density increased, their burning behaviour shifted towards that of solid materials. The superior fire performance of PIR foams was found to be based on the cellular structure, which is retained in the residue to some extent.
The individual and collective impacts of additives in melt dripping behaviour were studied under UL 94 vertical test conditions. A set of polyamide 6 (PA6) based materials compounded with melamine cyanurate (MCA) – a ˝dripping agent˝ – and glass fibre (GF) – a ˝non-dripping agent˝ - was investigated in detail. Dripping quantification was carried out during first and second ignition. The materials and their drops were investigated with respect to thermal decomposition, melt viscosity, and others properties. PA6 with V-2 classification improves to V-0 when MCA is added; and is worsened to HB in presence of glass fibre. Together, PA6/GF/MCA achieved V-2. The non-flaming drops of PA6/MCA are formed by oligomeric fragments. The flaming drops of PA6/GF contain a high amount of glass fibre. The dripping behaviour of PA6/GF/MCA under fire is a complex response of the specimen, but not explained by an easy superposition of the materials’ properties. The dripping behaviour is influenced by the interaction and concurrence of the different phenomena.
Thermoplastic starch polymer blends as biodegradable materials are well known and used mainly as packaging material. In order to exploit new application fields for these materials, additional properties such as flame retardancy or increased mechanical strength are required. This work focuses on the flammability and fire behavior of a thermoplastic starch/polyester blend reinforced with natural fibers derived from Mexican industry processes wastes, such as keratin fibers from the tannery industry or coconut fibers[1]. Different fiber contents as well as combinations of varying contents of aluminum trihydroxide, expandable graphite or ammonium polyphosphate were tested in LOI, UL94, cone calorimeter and TG-FTIR in order to investigate and assess the concentration dependence of the fibers and flame retardants as well as synergistic effects between both components. In combination with ammonium polyphosphate, the coconut fibers induce a synergistic effect by reinforcing the char residue and creating a more stable heat barrier during forced flaming combustion in the cone calorimeter. Synergism is also observed in the oxygen test. The recycling of otherwise wasted material is a true challenge in material development, thus this work is a first step in the direction of sustainable and biodegradable materials.