EQUILIBRIUM HEAT OF FUSION OF POLYTETRAFLUOROETHYLENE

The reliability of the values of equilibrium heat of fusion, △H_m, 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 △H_m vs. V_(sp) of the thermally aged PTFE virginas-polymerized samples prepared in accord with ASTM D 1457-81a, △H_m~o=79.6J/g (19.0 cal/g)and V_(sp) (specific volume of amorphous PTFE at 23℃)=0.480 cm~3/g (or ρ_a=2 .08g/cm~3) were ob-tained. The heats of fusion, △H_m, of the thermally aged and γ-irradiated samples are different irrespec-tive of the same V_(sp) value for both samples. A qualitative explanation of this phenomenon was givenbased on the H_v patterns of SALS and Kawai's model.

EQUILIBRIUM HEAT OF FUSION OF POLYTETRAFLUOROETHYLENE*

 The reliability of the values of equilibrium heat of fusion, △H_m, 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 △H_m vs. V_sp of the thermally aged PTFE virginas-polymerized samples prepared in accord with ASTM D 1457-81a, △H_m^o=79.6J/g (19.0 cal/g)and V_sp (specific volume of amorphous PTFE at 23℃)=0.480 cm³/g (or ρ_a=2 .08g/cm³) were ob-tained. The heats of fusion,△H_m,of the thermally aged and γ-irradiated samples are different irrespective of the same V_sp value for both samples.A qualitative explanation of this phenomenon was given based on the H_V patterns of SALS and Kawai's model.