Microporous material from ethylene-chlorotrifluoroethylene copolymer and method for making same

A microporous material, comprising:

• a first layer comprised of a first layer spherulitic matrix comprising a plurality of individual polymer domains of a first layer ethylene chlorotrifluoroethylene copolymer connected to one another by radiating fibrils and a plurality of first layer pores extending through the first layer spherulitic matrix and having an average pore size greater than about 0.01 micrometer;
• a first layer polymer crystallization nucleating agent uniformly dispersed within the first layer ethylene chlorotrifluoroethylene copolymer in an amount between 0.05 wt % and 1.0 wt %;
• a second layer comprised of a second layer spherulitic matrix comprising a plurality of individual polymer domains of a second layer ethylene chlorotrifluoroethylene copolymer connected to one another by radiating fibrils and a plurality of second layer pores extending through the second layer spherulitic matrix and having an average pore size greater than about 0.01 micrometer;
• a second layer polymer crystallization nucleating agent uniformly dispersed within the second layer ethylene chlorotrifluoroethylene copolymer;
• and
• wherein, the average pore size of the first layer spherulitic matrix and the average pore size of the second layer spherulitic matrix are different.