Thermal properties of the polyimide foam prepared from aromatic dianhydride and isocyanate

Abstract

A new type of polyimide foam (PIF) was prepared successfully based on a one-pot process by the reaction of a first solution and a second solution. The first solution comprised pyromellitic dianhydride (PMDA), N, N-dimethyl formamide (DMF), methanol, polyethylene glycol and water. The second solution contained polyaryl polymethylene isocyanate (PAPI). The thermal properties of the polyimide foam were thoroughly investigated by thermogravimetry–Fourier transform infrared spectroscopy (TG–FTIR) and high-resolution pyrolysis gas chromatography–mass spectroscopy (PyGC–MS) at various temperatures. The results of TG–FTIR indicated that polyimide foam was thermally stable and experienced a weight loss of less than 2% before the scanning temperature reached 280.7 °C. It showed a two-stage degradation process during the whole decomposition. The major decomposition products were carbon dioxide (CO2), carbonic oxide (CO) and methyl formate. The results of PyGC–MS indicated that no pyrolysis products were indentified when the test temperature was 250 °C. Certain pyrolyzates such as oxygen, carbon dioxide and methyl formate was identified as the pyrolysis temperature increased. According to the degradation behaviors and the structure and relative content of pyrolysis products, a proposed pyrolysis mechanism of polyimide is presented in this article.