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- Fire retardancy (12)
- Flame retardancy (8)
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- Pyrolysis (6)
- Cone calorimeter (5)
- Flame retardance (5)
- Red Phosphorus (5)
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- TG-FTIR (4)
Organisationseinheit der BAM
The reactivity of the flame retardant and its decomposition temperature control the condensed-phase action in bisphenol A polycarbonate/acrylonitrile–butadiene–styrene/polytetrafluoroethylene (PC/ABSPTFE) blends. Thus, to increase charring in the condensed phase of PC/ABSPTFE + aryl phosphate, two halogen-free flame retardants were synthesized: 3,3,5-trimethylcyclohexylbisphenol bis(diphenyl phosphate) (TMC-BDP) and bisphenol A bis(diethyl phosphate) (BEP). Their performance is compared to bisphenol A bis(diphenyl phosphate) (BDP) in PC/ABSPTFE blend. The comprehensive study was carried out using thermogravimetry (TG); TG coupled with Fourier transform infrared spectrometer (TG-FTIR); the Underwriters Laboratory burning chamber (UL 94); limiting oxygen index (LOI); cone calorimeter at different irradiations; tensile, bending and heat distortion temperature tests; as well as rheological studies and differential scanning calorimeter (DSC). With respect to pyrolysis, TMC-BDP works as well as BDP in the PC/ABSPTFE blend by enhancing the cross-linking of PC, whereas BEP shows worse performance because it prefers cross-linking with itself rather than with PC. As to its fire behavior, PC/ABSPTFE + TMC-BDP presents results very similar to PC/ABSPTFE + BDP; the blend PC/ABSPTFE + BEP shows lower flame inhibition and higher total heat evolved (THE). The UL 94 for the materials with TMC-BDP and BDP improved from HB to V0 for specimens of 3.2 mm thickness compared to PC/ABSPTFE and PC/ABSPTFE + BEP; the LOI increased from around 24% up to around 28%, respectively. BEP works as the strongest plasticizer in PC/ABSPTFE, whereas the blends with TMC-BDP and BDP present the same rheological properties. PC/ABSPTFE + TMC-BDP exhibits the best mechanical properties among all flame-retarded blends.
Bench scale performance based cone calorimeter investigations were conducted on glass fibre reinforced polyamide 66 (PA-66) and high impact polystyrene (HIPS) materials. Red phosphorus and magnesium hydroxide were used as fire retardants. Dilution, heat sink, barrier and charring mechanisms are considered to be active in the condensed phase. Dilution, cooling and flame poisoning mechanisms are discussed for the gas phase. Cone calorimeter data are used to give a comprehensive fire behaviour assessment in terms of the propensity to cause a quick growing fire and of the propensity to cause a fire of long duration. The external heat flux is varied between 30 and 75 kW/m2 so that the results for combustion behaviour and flame retardancy, respectively, are valid for different fire scenarios and fire tests. Results on the intrinsic contribution of the steady heat release rate per unit area reveal information about the flammability behaviour. UL 94 results are predicted in close correspondence to UL 94 experiments.
Pyrolysis and fire behavior of high impact polystyrene (HIPS) containing red phosphorus and melamine polyphosphate were investigated. The thermal and thermo-oxidative decomposition were characterized using thermogravimetry coupled with FTIR and MS, respectively. The fire behavior was monitored with a cone calorimeter using different external heat fluxes and determining the LOI. Red phosphorus reduced the heat release in HIPS due to radical trapping in the gas phase. The reduction in effective heat of combustion was accompanied by an increase of incomplete combustion products such as smoke and carbon monoxide. Melamine polyphosphate in HIPS acted in the condensed phase with barrier formation. The heat release rate was reduced, whereas the total heat evolved, smoke and carbon monoxide formation were not influenced significantly. Using both fire retardants, the resulting fire retardancy was characterized mainly by superposition.
Microplastic particles are currently detected in almost all environmental compartments. The results of detection vary widely, as a multitude of very different methods are used with very different requirements for analytical validity.
In this work four thermoanalytical methods are compared and their advantages and limitations are discussed. One of them is thermal extraction-desorption gas chromatography mass spectrometry (TED-GC/MS), an analysis method for microplastic detection that has become established in recent years. In addition, thermogravimetric analysis coupled with Fourier-transform infrared spectroscopy (TGA-FTIR) and mass spectrometry (TGA-MS) were applied, two methods that are less common in this field but are still used in other research areas. Finally, microscale combustion calorimeter (MCC) was applied, a method not yet used for microplastic detection.
The presented results are taken from a recently published interlaboratory comparison test by Becker et al. (2020). Here a reference material consisting of suspended matter and specified added polymer masses was examined, and only the results of the recoveries were presented. In the present paper, however, the results for the individual polymers are discussed in detail and individual perspectives for all instruments are shown.
It was found that TED-GC/MS is the most suitable method for samples with unknown matrix and unknown, variable kinds and contents of microplastic. TGA-FTIR is a robust method for samples with known matrix and with defined kinds of microplastic. TGA-MS may offer a solution for the detection of PVC particles in the future. MCC can be used as a very fast and simple screening method for the identification of a potential microplastic load of standard polymers in unknown samples.
The fire retardancy mechanism of aluminium diethyl phosphinate (AlPi) and AlPi in combination with melamine polyphosphate (MPP) was investigated in glass-fibre reinforced polyamide 6 (PA6/GF) by analysing the pyrolysis, flammability and fire behaviour. AlPi in PA6/GF-AlPi partly vaporises as AlPi and partly decomposes to volatile diethylphosphinic acid (subsequently called phosphinic acid) and aluminium phosphate residue. In fire a predominant gas-phase action was observed, but the material did not reach a V-0 classification for the moderate additive content used. For the combination of both AlPi and MPP in PA6/GF-AlPi-MPP a synergistic effect occurred, because of the reaction of MPP with AlPi. Aluminium phosphate is formed in the residue and melamine and phosphinic acid are released in the gas phase. The aluminium phosphate acts as a barrier for fuel and heat transport, whereas the melamine release results in fuel dilution and the phosphinic acid formation in flame inhibition. The higher amount of aluminium phosphate in PA6/GF-AlPi-MPP stabilised the residue in flammability tests in comparison to PA6/GF-AlPi, so that this material achieved a V-0 classification in the UL 94 test.
The thermal decomposition and the fire behavior of glass fiber reinforced polyamide 66 (PA-66) and high impact polystyrene (HIPS) containing red phosphorus (P4) were investigated. For glass fiber reinforced PA-66, P4 promotes char formation in the condensed phase. Barrier effects and the reduction of combustible volatiles were identified as fire retardancy mechanisms. For HIPS, P4 acts in the gas phase, mainly trapping radicals. The heat release per mass loss polymer is reduced due to an incomplete combustion.
A comprehensive characterization of the thermal and the fire behaviour is presented for polypropylene (PP) flax compounds containing ammonium polyphosphate (APP) and expandable graphite as fire retardants. Thermogravimetry coupled with an evolved gas analysis (TG-FTIR) was performed to ensure a significant thermal analysis. The fire response under forced flaming conditions was studied using a cone calorimeter. The external heat flux was varied between 30 and 70 kW m-2 so that the results could be evaluated for different fire scenarios and tests. Different flammability tests (UL 94, limiting oxygen index, glow wire test, GMI 60261) were performed and the results compared with the cone calorimeter data. The different char forming mechanisms are described and the resulting fire retardancy is classified. The successful and ecological friendly fire retardancy is a technological breakthrough for PP/flax biocomposites.