The molecular structure of perfluorocarbon polymers. II. Pyrolysis of polytetrafluoroethylene

Vacuum pyrolysis of thin samples of polytetrafluoroethylene follows first‐order kinetics with monomer as the only important decomposition product in the temperature range 360–510°C. The rate constant for vacuum pyrolysis is independent of both the melt viscosity and the type of polymer and is characterized by an activation enthalpy of 83.0 kcal./mole and a frequency factor of 3 × 10 19 sec. −1 . The molecular weight is found to decrease during pyrolysis. A plausible reaction mechanism consistent with these facts involves random chain cleavage, depropagation with short kinetic chain length, and termination by disproportionation. For thick samples the rate of vacuum pyrolysis is controlled by diffusion of monomer. The course of pyrolysis is changed by the presence of monomer or gaseous pyrolysis products. Accumulation of monomer reduces the rate of pyrolysis as measured by the weight loss and results in formation of a waxy product consisting of low molecular weight fluorocarbons.