EQUILIBRIUM HEAT OF FUSION OF POLYTETRAFLUOROETHYLENE

The reliability of the values of equilibrium heat of fusion, △Hm, of polytetrafluoroethylene (PTFE)reported in the literature and the inadequacy of the generally accepted value of 13 .7 or 14.6 cal/gwere discussed. Through extrapolating linear plot of △Hm vs. Vsp of the thermally aged PTFE virginas-polymerized samples prepared in accord with ASTM D 1457-81a, △Hmo=79.6J/g (19.0 cal/g)and Vsp (specific volume of amorphous PTFE at 23℃)=0.480 cm3/g (or ρa=2 .08g/cm3) were ob-tained. The heats of fusion,△Hm,of the thermally aged and γ-irradiated samples are different irrespective of the same Vsp value for both samples.A qualitative explanation of this phenomenon was given based on the HV patterns of SALS and Kawai's model.