Abstract:

The biaxially stretched wet separators were prepared at different stretching temperatures through systematically changing the stretching temperature in the longitudinal and transverse directions， and their internal pore appearance， pore structure， and air permeability were characterized using scanning electron microscope， the Gurley′s instrument， and pore size analyzer. In addition， differential scanning calorimetry was used to analyze the crystallinity of the micro⁃crystals inside the wet separators. The results indicated that there was no effect from the change of the longitudinal stretching temperature on the pore size of the wet separators. The pore size of the wet separators was only closely related to the transverse stretching temperature. As the transverse stretching temperature increased from 90 to 120 ºC， the pore size increased from 18.3 to 45.4 nm. Owing to a change in pore size， the air permeability of the wet separators decreased from 149.8 to 62.2 s， both of which exhibited a good linear relationship. When the transverse stretching temperature was 120 ºC， the melting and re⁃crystallization occurred inside of the wet separators， resulting in an increasing in the degree of crystallinity from 17 % to 20 %. Meanwhile， the interior of the separators showed a three⁃dimensional network structure comprising the shish⁃kebab crystals.

Key words: wet separator, stretching temperature, pore structure, Gurley′s value, shish?kebab crystal