The
chemical structure of the membranes was by Fourier
transform infrared spectroscopy (FT-IR, Bruker VERTEX 70). The
mechanical property was measured using an Inston-3300 universal
testing machine (USA) at a stretching speed of 1.66 mm sec−1 with the
sample straps of about 1 cm wide and 8 cm long. The experiment on
mechanical properties was carried out for four times. To evaluate its
thermal shrinkage behavior, the separator was placed in an oven and
heated at 200 °C for 0.5 h. Thermal stability of the separator was
examined by a differential scanning calorimeter (Diamond DSC,
PerkinElmer) ranging from 50 to 300 °C at 10 °C min−1 under a N2
atmosphere