The invention provides a TFE polymer capable of providing stretched
materials excellent in membrane homogeneity. The present invention is
related to a tetrafluoroethylene polymer having stretchability and
non-melt-processability and having a standard specific gravity of 2.140
to 2.165, wherein, with regard to the heat-of-fusion curve obtained by
subjecting the tetrafluoroethylene polymer in the form of an unbaked
polymer to be measured having no history of being heated to a temperature
of 300.degree. C. or higher to differential scanning calorimetry at a
programming rate of 2.degree. C./minute, the ratio between the amount of
heat, S.sub.2 mJ/mg, absorbed within the temperature range of from the
temperature T.sub.0.degree. C., which is lower by 2.5.degree. C. than the
temperature T.sub.p.degree. C. corresponding to the minimum point on the
curve (provided that 340.ltoreq.T.sub.p.ltoreq.345), up to 350.degree.
C., and the amount of heat, S.sub.1 mJ/mg, absorbed within the
temperature range of from 320.degree. C. up to the above-mentioned
T.sub.0.degree. C., namely the ratio [S.sub.2/S.sub.1], is not lower than
0.90.