The melting behavior of poly(ethylene-alt-tetrafluoroethylene) γ-irradiated in air and vacuumwas studied by DSC. From the results of DSC and density measurements the equilibrium heat offusion

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and the density of the amorphous phase

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of the polymer were estimated as 172J/gand 1.63g/cm3 respectively. Thereby the degree of crystallinity of this copolymer can be evaluatedby both density and calorimetric methods. The crystal structure was damaged gradually and eventuallycompletely destroyed with the increase in radiation dose from 0.3 to 900 Mrads.Exclusion of air was advantageous in lessening the damage of the crystal while increase in the degree of vacuum favored the formation of crosslinks.Small peaks appearing both on the DSC endotherm(600K) and on the exotherm(540K) resulted from the presence of small amount of tetrafluoroethylene blocks along the main chain of poly(ethylene-alt-tetrafluoroethylene).