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Natural keratin fibres derived from Mexican tannery waste and coconut fibres from coconut processing waste were used as fillers in commercially available, biodegradable thermoplastic starch-polyester blend to obtain sustainable biocomposites. The morphology, rheological and mechanical properties as well as pyrolysis, flammability and forced flaming combustion behaviour of those biocomposites were investigated. In order to open up new application areas for these Kinds of biocomposites, ammonium polyphosphate (APP) was added as a flame retardant. Extensive flammability and cone calorimeter studies revealed a good flame retardance effect with natural fibres alone and improved effectiveness with the addition of APP. In fact, it was shown that replacing 20 of 30 wt. % of APP with keratin fibres achieved the same effectiveness. In the case of coconut fibres, a synergistic effect led to an even lower heat release rate and total heat evolved due to reinforced char residue. This was confirmed via scanning electron microscopy of the char structure. All in all, these results constitute a good approach towards sustainable and biodegradable fibre reinforced biocomposites with improved flame retardant properties.
Flame-retarded biocomposites of thermoplastic starch and natural fibres are successfully processed according to state-of-the-art extrusion and injection moulding. Using agave fibres and henequen fibres recovered from local industrial waste is a convincing contribution to sustainability. A systematically varied set of biocomposites is investigated comprehensively, e.g. electron microscopy is used for characterizing the morphology, rheology for the melt viscosity, tensile and impact resistance for the mechanical properties, thermal analysis for the pyrolysis, UL 94 burning chamber and oxygen index for the flammability, and cone calorimeter for the fire behaviour. Achieving sufficient mechanical properties was not the goal in our pre-competitive study but may be tackled by adding compatibilizer in future. The combination of well-dispersed natural fibres, aluminium diethylphosphinate (AlPi) and a special silicone synergist (Si) is proposed as promising innovative route for V-classified biocomposites. The flame-retardancy modes of action in the gas phase (fuel dilution and flame inhibition) and in the condensed phase (charring, protective layer formation) are discussed in detail, as is the role of combining the ingredients. This work is a convincing proof of principle of how to prepare industrial-waste fibres biocomposites, to apply the synergistic combination of AlPi and Si for future flame-retarded technical polymer materials that are based on renewable resources and compostable.
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.
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.
The rapid mass calorimeter based on reduced‐size specimens is proposed for accelerated fire
testing and put up for discussion, particularly for flame retarded polymeric materials. A mass loss
calorimeter is combined with a semiautomatic sample changer. Experiments on specimens of
reduced size were conducted on poly(methyl methacrylate), poly(propylene), polyamide 66,
poly(ether ether ketone), and pine sapwood square samples with edge lengths of 100, 75, 50,
25, 20, and 10 mm. Specimens of 20 × 20 mm2 were selected to achieve a crucial reduction in
specimen size and a measuring protocol developed. A total of 71 different polymeric materials
were investigated in the rapid mass calorimeter and cone calorimeter for comparison and several
materials with different heat release rate characteristics in the pyrolysis combustion flow calorimeter to test this additional screening method as well. The important fire properties obtained in the rapid mass calorimeter show reasonable correlation with the cone calorimeter results but also with the oxygen index. All in all, the rapid mass calorimeter produces reliable and meaningful results and, despite acceleration and size reduction, still allows for a certain degree of burning behavior interpretation. Material savings of 96% and time savings of around 60%‐70% are achieved compared to measure cone calorimeter.
Modern flame retardant polymeric materials often stand for multicomponent systems consisting of different ingredients. Using a variety of flame retardants, fillers, additives, synergists and adjuvants as well as applying different concentrations, particle size distributions, encapsulation, and so forth lead to a vast multidimensional matrix of possible formulations. Actual, comprehensive elucidations are no longer possible due to time, material and cost limitations. The task is dying for accelerated procedures, for high-throughput methods. Therefore we developed the Rapid Mass Calorimeter based on a Mass Loss Calorimeter with attached thermopile chimney and a linear motion unit for semi-automatic sample change. Together with the reduction in specimen size (2 cm x 2 cm), a saving of time around 70% and a saving of material of 96% is achieved not considering the strongly reduced calibration and maintenance efforts required for the Mass Loss Calorimeter. The correlations between the results of the Rapid Mass Calorimeter and the Cone Calorimeter as well as to the Oxygen Index and UL94 classification are described; the effects such as when reducing the specimen size are discussed.
The pyrolysis, flammability and fire behavior of polypropylene (PP) containing an intumescent flame retardant and sepiolite nanoparticles were investigated by performing thermogravimetry, oxygen index (LOI), UL-94, and cone calorimeter tests. The combination of 0.5 wt% of premodified sepiolite (OSEP) with 12 wt% of a commercial intumescent flame retardant showed a clear synergy in LOI, UL-94 ranking and peak heat release rate. The ternary formulation achieved a V-0 classification and, consequently, allowed a reduction in the amount of flame retardant necessary to achieve this result. Whereas OSEP and pristine sepiolite nanoparticles (SEP) affect the performance in PP nanocomposites quite similarly, OSEP outperformed SEP in the combination with intumescent flame retardant. The cone calorimeter results and dynamic rheological measurements confirmed the synergistic effect between the nanofiller and the flame retardant resulting from the improved properties of the residual protective layer.