Thermal degradation behavior of carborane-containing phenylethynyl terminated imide systems

Carborane-containing imide compound (Carb-PEPA) was synthesized and added into fluorinated phenylethynyl terminated imide oligomer (AFR-PEPA). The thermal degradation of Carb-PEPA was studied by thermogravimetric analyzer coupled with Fourier transform infrared analysis (TG-FTIR), in situ FTIR and pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS). The results show that the Carb-PEPA possesses high char yield in both air and nitrogen due to the formation of BO bonds in thermal degradation process as identified by TG-FTIR and in situ FTIR. A thermal degradation mechanism for the Carb-PEPA was proposed. The Carb-PEPA crosslinks to form polyimide in the early heating process. Then the degradation of Carb-PEPA happens at higher temperatures, while further degradation could be effectively prevented due to the formation of a protection layer of boron oxide compound. The thermal stabilities of AFR-PEPA and AFR-PEPA containing 15 wt% Carb-PEPA (AFR-PEPA-Carb-15) were also studied by TGA and TG-FTIR. It was observed that AFR-PEPA's residual weight ratios at 800 °C in air and nitrogen increased by 20% and 13.3% respectively with the addition of 15 wt% Carb-PEPA.