Study on Thermal Decomposition of Intumescent Fire-Retardant Polypropylene by TG/Fourier Transform Infrared

The thermal decomposition processes of polypropylene formulations containing intumescent flame-retardant additives as well as the individual components in the composites have been studied using thermogravimetric analysis and real time Fourier transform infrared in both air and nitrogen atmospheres. The results show that the thermal decomposition processes of pure polypropylene (PP), polyamide, pentaerythritol, and intumecent flame-retarded PP (IFR-PP) composites in air are significantly different from that in nitrogen atmosphere. The existence of oxygen promotes the decomposition of the above materials. However, oxygen has little influence on the thermal decomposition of ammonium polyphosphate and zinc borate both in air and nitrogen atmospheres. All IFR-PP composites show an earlier onset of decomposition in comparison with pure PP both in nitrogen and air atmospheres. Accordingly, the initial release gases such as NH3 or H2O help to swell the melted PP polymer and improve the flame retardancy of IFR-PP composite. At temperature higher than 290 degrees C in air and 440 degrees C in nitrogen, the IFR-PP composites are more thermally stable than PP because of the incorporation of intumescent flame additives. The decomposition mechanisms of these materials are discussed based on the analysis of the results of TG/FTIR.