[en] In order to avoid the effects of number of polymer particles on polymerization and bubbles generated by mixing of gaseous monomer and emulsifier-water solution at the early stage of emulsion polymerization, seeded copolymerization of tetrafluoroethylene with propylene by radiation was studied in flow apparatus equipped with tank and pipe type reactors under a pressure of 30 kg/cm² and a temperature of 40⁰C. The polymerization rate increases with dose rate and its dose rate exponent changes from 1.0 to 0.5 with increase of dose rate from 10⁵ to 10⁶ rad/h. In the series of investigation, it was found that the polymer concentration in latex tended to increase accelerately with reaction time. The effects of mean residence time of latex in the reactor and recycle rate of gaseous monomer on the polymerization could not be elucidated because of the acceleration of polymer concentration in latex. The acceleration is assumed to be due to repression of termination reaction by decreases of propylene concentration and mobility of polymer radical in particles with proceeding the polymerization. (author)