ASYMMETRIC MEMBRANES AND RELATED METHODS
Microporous polymer membranes and related methods of fabrication are provided. An asymmetric microporous membrane embodiment includes, but is not limited to, a thermoplastic polymer substrate defining a plurality of micropores, the thermoplastic polymer including one or more of polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), and a combination thereof; and a polymethylpentene (PMP) polymer skin positioned on the thermoplastic polymer substrate, wherein when the thermoplastic polymer substrate includes PMP, the PMP polymer skin has a crystallinity that differs from a crystallinity of the PMP in the polymer substrate.
1 . A asymmetric microporous membrane comprising:
a thermoplastic polymer substrate defining a plurality of pores, the thermoplastic polymer substrate comprising polymethylpentene (PMP), and the thermoplastic polymer substrate made from a PMP substrate resin having a first crystallinity; and
a polymethylpentene (PMP) polymer skin positioned on the thermoplastic polymer substrate by co-extrusion, the PMP polymer skin made from a PMP polymer skin resin having a second crystallinity, and wherein the first crystallinity and the second crystallinity differ such that the PMP polymer skin has a crystallinity that differs from a crystallinity of the PMP of the thermoplastic polymer substrate.
2 . The asymmetric microporous membrane of claim 1 , wherein the thermoplastic polymer substrate defining a plurality of micropores.
3 . The asymmetric microporous membrane of claim 1 , wherein the PMP polymer skin is less porous than the thermoplastic polymer substrate.
4 . The asymmetric microporous membrane of claim 1 , wherein the PMP polymer skin is a nonporous PMP polymer skin.
5 . The asymmetric microporous membrane of claim 1 , wherein the crystallinity of the PMP polymer skin resin is about 40% or less than about 40%.
6 . The asymmetric microporous membrane of claim 1 , wherein the crystallinity of the PMP polymer skin resin is less than about 40%, and wherein the crystallinity of the PMP substrate resin of the thermoplastic polymer substrate is greater than about 40%.
7 . The asymmetric microporous membrane of claim 6 , wherein the crystallinity of the PMP substrate resin of the thermoplastic polymer substrate is about 60% or greater than about 60%.
8 . The asymmetric microporous membrane of claim 1 , wherein the PMP polymer skin has a thickness of less than about 2 microns.
9 . The asymmetric microporous membrane of claim 1 , wherein the PMP polymer skin has a thickness of less than about 0.5 microns.
10 . The asymmetric microporous membrane of claim 1 , wherein the thermoplastic polymer substrate has a thickness of between about 10 microns and 150 microns.
11 . The asymmetric microporous membrane of claim 1 , wherein the thermoplastic polymer substrate has a thickness of between about 30 microns and 75 microns.
12 . The asymmetric microporous membrane of claim 1 , wherein the thermoplastic polymer substrate has a thickness of between about 40 microns and 60 microns.
13 . The asymmetric microporous membrane of claim 1 , wherein the thermoplastic polymer substrate has a thickness of between about 5 microns and 10 microns.
14 . The asymmetric microporous membrane of claim 1 , wherein the asymmetric microporous membrane is a non-homogeneous membrane.
15 . The asymmetric microporous membrane of claim 1 , wherein the PMP skin completely covers the thermoplastic polymer substrate.
16 . A multi-layered membrane comprising the asymmetric microporous membrane of claim 1 , wherein the PMP skin comprises an outer layer and/or an inner layer of the multi-layered membrane.