Porous Films via PE/PEO
Cocontinuous Blends
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Abstract
The design of a porous membrane support layer derived
from cocontinuous
polymer blends is presented. We investigate the effect of blend composition,
shear rate, residence time, and annealing time on the cocontinuous
morphology of polyethylene (PE)/poly(ethylene oxide) (PEO) blends.
Porous PE sheets were generated by water extraction of PEO and used
as a support layer for gas separation membranes. The PE/PEO blends
using nonfunctional and maleic anhydride functional PE (PE-<i>g</i>-MA) were mixed in a batch microcompounder and in a pilot
plant scale corotating twin-screw extruder. Using PE-<i>g</i>-MA resulted in pore size reduction from 10 to 2 μm and suppression
of coarsening of the morphology during further annealing of the blends
due to formation of PE–PEO graft copolymers. Equilibrium interfacial
tension, estimated by fitting the rheology of droplet blends to the
Palierne viscoelastic droplet model, was 3 and 0.4 mN/m for PE/PEO
and PE-<i>g</i>-MA/PEO systems, respectively. The specific
interfacial area and phase size distribution were calculated from
3D images acquired by laser scanning electron microscopy (LSCM). We
prepared gas separation membranes by solvent casting an acetone solution
of ionic gel into porous PE sheets and discussed the effect of type
of processing, average pore size, pore size distribution, and pore
wall functionality on their performance