Abstract
Phosphorus-based flame retardants were incorporated into different, easily preparable matrices, such as polymeric thermoset resins and paraffin as a proposed model for polyolefins and investigated for their flame retardancy performance. The favored mode of action of each flame retardant was identified in each respective system and at each respective concentration. Thermogravimetric analysis was used in combination with infrared spectroscopy of the evolved gas to determine the pyrolysis behavior, residue formation and the release of phosphorus species. Forced flaming tests in the cone calorimeter provided insight into burning behavior and macroscopic residue effects. The results were put into relation to the phosphorus content to reveal correlations between phosphorus concentration in the gas phase and flame inhibition performance, as well as phosphorus concentration in the residue and condensed phase activity. Total heat evolved (fire load) and peak heat release rate were calculated based on changes in the effective heat of combustion and residue, and then compared with the measured values to address the modes of action of the flame retardants quantitatively. The quantification of flame inhibition, charring, and the protective layer effect measure the non-linear flame retardancy effects as functions of the phosphorus concentration. Overall, this screening approach using easily preparable polymer systems provides great insight into the effect of phosphorus in different flame retarded polymers, with regard to polymer structure, phosphorus concentration, and phosphorus species.
Highlights
Nowadays, the ever growing numbers of different flame retardants for all kinds of applications, along with their variations in concentration, particle size distribution and so on, create a need for screening methods that allow time and material savings while yielding significant results and enabling reasonable conclusions
Here a screening approach is presented that uses cone calorimeter investigations on different thermosets and on paraffin, which is proposed as a model for polyolefins, to address different phosphorous flame retardants in different concentrations
Compared to the residue analysis results from TGA, the increase in residue was much more evident in the cone calorimeter, with an increase of 10% for the highest investigated flame retardant load
Summary
The ever growing numbers of different flame retardants for all kinds of applications, along with their variations in concentration, particle size distribution and so on, create a need for screening methods that allow time and material savings while yielding significant results and enabling reasonable conclusions. Several different approaches have been taken to accelerate fire testing, such as the microscale combustion calorimeter, the rapid cone calorimeter and the rapid mass calorimeter [1,2,3,4]. These methods are designed for screening the fire performance of large numbers of samples. All of the methods require specific sample preparation, such as extrusion and injection molding, to ensure homogenous implementation of the flame retardant in the thermoplastic.
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