Fourier Transform Infrared Analysis of Evolved Gases in Polymerization and Pyrolysis Processes

Abstract

The use of Fourier transform infrared (FT-IR) spectroscopy for characterizing evolved gases produced during polymerization and pyrolysis processes is demonstrated. Several polyimides were polymerized and the evolved gases were identified and quantitatively determined by FT-IR spectroscopy. By monitoring of the infrared absorbance of the O-H bending vibrational mode of water as a function of temperature, different sources of the evolved water were observed. We also found a correlation between the temperature at which the maximum evolution of alcohol occurs in different polyimides and the strength of the alcoxy bond to the amic acid; a comparison of the data suggests the strong dependency of the mechanism of polyimidization upon the nature of the alcoxy group. We have also studied the decomposition products of poly(ethylene terephthalate) (PET) at temperatures higher than 300°C in a nitrogen atmosphere and found that carbon monoxide, carbon dioxide, benzoic acid, and an acid para-substituted aromatic ester are the major decomposition products; these observations suggest that under the experimental conditions PET degrades by cleavage of the C-O bonds on the ethylate part of the chain and produces benzoxy and aromatic ester groups.