TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The polypropylene is present at 1-15 wt.%, the first polyethylene is present at 70-85 wt.%, and the second polyethylene is present at 1-19 wt.%. The membrane has a meltdown temperature of greater than or equal to 145 degrees C and normalized pin puncture strength of greater than or equal to 3.2x 102 mN/ mu m, and a traverse directions (TD) tensile strength of greater than or equal to 1.4x 105 kPa. The membrane has porosity of 20-80%, a normalized air permeability of less than or equal to 50 seconds/100 cm3/ mu m, and a TD of 105 degrees C with heat shrinkage of less than or equal to 10%, preferably less than or equal to 6%. The polypropylene comprises greater than or equal to 90 wt.% of isotactic polypropylene having an Mw of greater than or equal to 6x 105, an molecular weight distribution (MWD) of 8.5 and a Delta Hm of 90 J/g. The first polyethylene has an Mw of 4-6 x 105 and an MWD of 3-10, and the second polyethylene has an Mw of 1-3x 106 and an MWD of 4-15. The membrane is a monolayer. The first polyethylene has a terminal unsaturation of less than 0.2 per 1x 104 carbon atoms. Preferred Method: The step of processing includes stretching the extrudate in at least one planar direction and removing at least a portion of the diluent from the extrudate. The step of processing is devoid of any step of stretching the extrudate after the step of removing the solvent. The step of processing optionally includes stretching the extrudate after the step of removing the solvent to a magnification factor of less than or equal to 1.1 and excludes any stretching of the extrudate after the step of removing the solvent at a magnification factor of greater than 1.1. The method further comprises: cooling the extrudate; subjecting the membrane to a thermal treatment; and removing any remaining volatile species from the membrane. The stretching step is conducted biaxially to a magnification factor of 9-49 folds in area, while exposing the extrudate at 90-125 degrees C. EXAMPLE - Diluent and a polymer blend of a first polyethylene (PEla), a second polyethylene (PE2), and a polypropylene (PP1) were combined. The polymer blend comprised (in wt. %) of: PE1 (185) having an weight average molecular weight (Mw) of 5.6x 105, an molecular weight distribution (MWD) of 4, terminal unsaturation 0.14 per 1x 104 carbon atoms, and a melting temperature (Tm) of 136 degrees C (PE1); PE2 (10) having a Mw of 1.9x 106, and MWD of 5.1, and a Tm of 136 degrees C; and isotactic point (PP1) having an Mw of 5.3x 105 and a melting enthalpy ( Delta Hm) of 114 J/g. The polymer blend was charged into a strong blending double-screw extruder, and liquid paraffin (50 cst at 40 degrees C) was supplied to the double-screw extruder via a side feeder. Mixing was conducted at 220 degrees C and 320 rpm to produce the polymer-diluent mixture. The polymer-diluent mixture was conducted from the extruder to a sheet-forming die, to form an extrudate. The die temperature was 210 degrees C. The extrudate was cooled by contact with cooling rollers controlled at 20 degrees C. The cooled extrudate was biaxially stretched at 112.5 degrees C to a magnification of 5 folds in both machine direction and transverse direction by a tenter-stretching machine. The stretched three layer gel-like sheet was then immersed in a bath of methylene chloride controlled at 25 degrees C to remove liquid paraffin to 1 wt.% based on the weight of the liquid paraffin in the polymer-diluent mixture. The membrane was then dried by air flow at room temperature. While holding the size of the membrane substantially constant the membrane was heat-set by exposing the membrane to a heat set temperature of 128 degrees C for 10 minutes to produce the final microporous membrane.