kept constant 2 kg of 25 ammonia in water was added the vessel was pressurized with tfe and hfp to 17 bar such that the partial pressure of hfp was 12 5 bar the polymerization was started by adding 1600 g of ammonium persulfate diluted in 5 l deionized water within 10 min the pressure was kept constant by feeding a gaseous mixture of tfe hfp into the reactor the tfe hfp weight ratio was 0 14 after 6 hours the reaction is stopped by interrupting the monomer feed the monomers were vented off the reactor was cooled to room temperature and discharged the solid content of the polymer dispersion was 29 the dispersion was practically free of coagulum the mfi value was 20 g min the hfp content of the copolymer was 13 w the melting point was 255 u00b0 c the copolymer had 660 cooh endgroups per 10 6 carbon atoms mw mn was measured to 1 7 a mw mn value of 1 6 was calculated from the polymerization rate time curve the dispersion was coagulated with a homogenizator and agglomerated with gasoline the agglomerate was washed three times with deionized water and dried for 6 hours at 180 u00b0 c in a tumble drier first by purging with nitrogen and then under vacuum the resulting agglomerate was divided into 2 parts one part was subsequently melt pelletized water treated and dried it had a coffee brown color it was then fluorinated and again water treated to remove residual cof endgroups the discoloration disappeared this sample is called a0 the material had 43 endgroups per million carbon atoms the other part of the agglomerates was first fluorinated melt pelletized and treated with water and dried this sample is.