A radiation-crosslinking method to determine the molecular weight of a fluoropoly-mer is suggested and described. For PEP copolymer with different melt indices

its dose of gelation increases with the melt index. G value of erosslinking is 1.2 as determined by elastic modulus measurement of the radiated samples at a temperature above its melting point. The molecular weight (Mw) of this copolymer calculated from the G value of erosslinking and the dose of gelation relates to its melt index aslog Mw ∝ 3.5 log This is quite consistent with awell-known relation between melt viscosity and molecular weight determined with aconventional method.