Thermal Decomposition of Ethylene- and Propylene Tetrafluoroethylene Copolymers

Abstract

The decomposition products (C₁ to C₉ fluorinated compounds) of ethylene- and propylenetetrafluoroethylene copolymers (ETFE and TFEP) were identified and determined, after heating the polymers isothermally or dynamically in inert gas atmospheres. Kinetic analyses on the decomposition were also carried out for the two polymers.
There were little differences in the degradation products between ETFE and TFEP. ETFE, however, tends to decompose into low molecular weight compounds without secondary decom- position at high pyrolysis temperatures, and to give C₅ and C₆ compounds through cyclic transition structure at low pyrolysis temperatures.
Kinetic analyses show that while ETFE follows a random degradation with an activation energy of 49.1 kcal/mol, the decomposition of TFEP obeys the first order reaction with an activation energy of 59.7 kcal/mol. There was a great differences in the values of frequency factor between the isothermal and the dynamic measurement; this phenomenon is seemed to be due to structural changes of the polymers during the heating to the preset temperatures.
TG-MS method was also applied to the analysis of the degradation products, and fluorinated compounds from C₂ to C₆ were observed at all degradation temperature ranges showing no specific species as compared with the results of pyrolysis-gas chromatography.