Temperature programmed decomposition of polypropylene: in situ FTIR coupled with mass spectroscopy study

The temperature-programmed reaction (TPR) technique coupled with the in situ infrared (IR)/mass spectroscopy (MS) analysis has been employed to study the thermal decomposition of polypropylene. These techniques, especially when coupled with a gas chromatograph (GC), are effective for determining thermal stability, product distribution and product evolution as a function of temperature. The polymer decomposes at approximately 475 K yielding hydrocarbons in the C₁–C₇ range, with propylene, C₅ and C₆ composing the majority of gaseous products. Decomposition over alumina and 5 wt% Ni/Al₂O₃ with and without the presence of hydrogen does not affect thermal stability. Also, decomposition over alumina with and without the presence of hydrogen does not affect the depolymerization pathway. The popular β-scission/backbiting mechanism cannot fully explain observations from this study. Possible alternatives are explored.