Reducing the flammability of polymeric materials is a serious problem that needs to be solved. The paper presents the results of a study of the effect of iron nanopowders, used as filler, on the flammability of epoxy polymers. Epoxy composites filled with 5 wt. % of iron nanopowder and 10 wt. % of boric acid separately, as well as in combination were prepared. The flammability of the prepared samples was evaluated by determining the ignition temperature and time-to-ignition.
The thermooxidative degradation behavior of the epoxy composites filled with metal nanopowders has been investigated by thermogravimetric analysis under nonisothermal conditions in air atmosphere. The mechanical characteristics of epoxy composites were also studied by three-point bending method. The comparison of two different types of metal nanopowder was made. Aluminum and copper nanopowders prepared by electrical explosion of wires were used as fillers separately as well as in combination with conventional fame-retardant boric acid. It was shown that aluminum nanopowder increased slightly thermal stability of the epoxy composites. On the contrary, the introduction of copper nanopowder in epoxy resin led to rapid degradation of the epoxy composite. The combination of metal nanopowders and boric acid improved thermal stability of the epoxy composites. The highest flexural properties showed the epoxy composite filled with copper nanopowder.
The epoxy composites filled with 5 and 10 mass % of sodium bicarbonate were prepared. Sodium bicarbonate at the heating decomposes into sodium carbonate, carbon dioxide and water. As a result, sodium bicarbonate is able to slow down the combustion process when it used as polymer filler. The thermal stability of the prepared samples was investigated at the heating in air using thermal analysis. The mechanical characteristics of epoxy composites were also studied. The gaseous products of thermal oxidative degradation were studied using mass spectrometric analysis. It was found that sodium bicarbonate accelerates the process of thermal oxidative degradation of the epoxy composites in the initial stage, but enhances thermal stability in the final stage. The addition of boric acid to sodium bicarbonate as filler is recommended to improve the thermal stability of the epoxy polymer.
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