Abstract: The free radical concentration of plasma polymerized hexafluoropropene (PPHFP) wasfound to be 9.97?10¹⁹ spins/gram using CuSO₄·5H₂O single-crystal as a standard. Thehalf-life of the radical in Ar gas was near half a year at room temperature.There was oneradical in every two PPHFP chains. The activation energy and rate constants of the radicaldeterioration at different temperature have been calculated. Twenty hyperfine lines in ESRspectra were recorded for gascous products during plasma polymerization. The radicals ofgascous products have similar stability.

Key words: ESR spectra, Plasma polymer, Hexafluoropropene