The high‐temperature degradation of poly(2,6‐dimethyl‐1,4‐phenylene ether)

Abstract

AbstractThe thermal degradation of poly(2,6‐dimethyl‐1,4‐phenylene ether) has been investigated to 1000°C in an inert atmosphere. X‐ray diffraction, thermogravimetric analysis, and differential scanning calorimetry were employed to study the physical changes in the polymer, and vapor‐phase chromatography, infrared spectroscopy, and mass spectrometric thermal analysis were used to elucidate the chemical aspects of the degradation process. It was found that degradation occurs in two steps: (1) a rapid exothermic process occurs between 430 and 500°C, leading to the evolution of phenolic products, water, and a black, highly crosslinked residue, and (2) a slower, char‐forming process occurs above 500°C, characterized by the evolution of methane, carbon monoxide, and hydrogen. The chars formed in process 2 were found by x‐ray analysis to be amorphous. The infrared spectrum of a sample heated to 510°C is nearly identical with that of the starting polymer, indicating that oxidative reactions are not important in the first process. The data for the low‐temperature process are consistent with a thermal degradation scheme based on the radical‐redistribution reaction of polyphenylene ethers and/or the degradation of o‐benzylphenols formed by the thermal rearrangement of o‐methyl diphenyl ethers. The char‐forming process is best explained by simultaneous operation of the Szwarc mechanism of toluene pyrolysis, producing hydrogen and methane and reactions that cleave the aromatic rings and produce carbon monoxide.