Abstract
A porous polypropylene (PP) film was fabricated by an original crazing process using bending. The film has a lot of porous layers which are independent each other, and has possibility to apply as a Li‐ion battery separator. Moreover, we paid attention that a craze is generated from the outer surface of the bending part during the crazing process. Therefore, the outer surface of the bending part of PP film was coated with polystyrene or polymethylmethacrylate, and the crazing process was carried out. As a consequence, it was revealed that the composite structure of the craze could be controlled by surface coating of polymer which has lower craze‐generating stress than PP. And its composite structure derived from that of the coated layer. By this method, a separator film which has many more porous layer and high gas permeability was fabricated.
