TECHNOLOGY FOCUS - POLYMERS - Preferred Membrane: The membrane comprises polypropylene (4.5-15.5, preferably 5-8 wt.%). Preferred Components: The polypropylene comprises isotactic polypropylene ( greater than or equal to 90.0 wt.%) having a molecular weight of greater than or equal to 6.0x 105, a molecular weight distribution (MWD) of less than or equal to 8.5 and a heat of fusion ( Delta Hm) of greater than or equal to 90.0 J/g. The polyethylene comprises a first polyethylene having a molecular weight of less than 1.0x 106 (preferably 4x 105 to 6x 105) and a MWD of 3-10; and a second polyethylene having a molecular weight of greater than or equal to 1.0x 106 (preferably 1x 106 to 3x 106), and a MWD of 4-15, where the first polyethylene is present in an amount of 69.5-90.5 (preferably 72-90) wt.%, and the second polyethylene is present in an amount of 5-15 or 5-20 wt.%. The first polyethylene has a terminal unsaturation amount of less than 0.20 per 1.0x 104 carbon atoms. The polyethylene is in the range of 84.5-95.5 wt.% based on the weight of polymer in the polymer-diluent mixture, and has a molecular weight of less than 1.0x 106. Preferred Method: The method further involves cooling the extrudate before step (b); stretching the membrane in at least one direction following step (c) and subjecting the membrane to a thermal treatment following step (c); and removing any remaining volatile species from the membrane after step (c). The stretching direction is transverse direction (TD), and the stretching of step (b) is conducted biaxially to a magnification factor in the range of 9-49-fold in area, while exposing the extrudate to 90-125 degrees C. EXAMPLE - A membrane comprising a polyethylene (90.0 wt.%) having a molecular weight of 5.6x 105, a molecular weight distribution (MWD) of 4.0, an amount of terminal unsaturation of less than or equal to 0.14 per 1.0x 104 carbon atoms, and a melting temperature (Tm) of 136 degrees C; a polyethylene (5.0 wt.%) having a molecular weight of 1.9x 106, MWD of 5.1, and a Tm of 136 degrees C; and an isotactic poly propylene (5.0 wt.%) having a molecular weight of 5.3x 105 and a heat of fusion ( Delta Hm) of 80 J/g was prepared.