Solvent-Free Preparation of Electrically Conductive Polyetherimide Membranes Using Carbon Nanotubes

Abstract

A chemical‐free option to reduce membrane fouling is the use of electrical fields for membranes. To maximize the strength of the electric field in compact membrane module constructions, electrically conductive membranes are preferred to only conductive supports. Conductive, porous membranes are sintered from polyetherimide powder particles that are surface‐covered with multi‐walled carbon nanotubes (MWCNT). The fusion of the surface‐covered particles forms a conductive MWCNT network in the composite, with a large number of inter‐MWCNT contacts. Membranes with a high specific electrical conductivity of up to 2.28 Sm−1 at a concentration of 3.0 wt% MWCNT are produced in an adapted sintering process. The sintering behavior of decorated particles depends on the coverage of the polymer particles with MWCNT.

Porous UHMWPE Membranes and Composites Filled with Carbon Nanotubes: Permeability, Mechanical, and Electrical Properties

“…Most nonagglomerated MWCNT appear to have sunken under the UHMWPE matrix surface, as was also observed in the previous study using polyetherimide particles . At a few selected sites, MWCNT stick out from the surface and agglomerates are clearly not fully absorbed, but rather partially penetrated or enveloped by the UHMWPE matrix.…”

“…The sintered membrane was demolded from the aluminum foil and the final membrane was cut out from the middle using a punch press with an inner tool diameter of 20 mm. All samples showed great flexibility during demolding and were easy to handle, which was in strong contrast to results from our previous work using polyetherimide …”

“…The agglomerates for all concentrations vary in size which ranges from a few microns up to an order of magnitude higher than the size of the UHMWPE particles. This level of agglomerates was not observed in a previous work with polyetherimide, in which the polymer particles were significantly larger and had a higher volumetric mass density . As MWCNT are basically chemically inert at the sintering temperature of UHMWPE, they can act as partial flow barriers for the UHMWPE matrix and change the local sintering behavior.…”

“…The different sample types for electrical conductivity measurements and the two different methods were used, because the measured values for the compression molded samples for a given MWCNT concentration were either far higher or lower than expected from the previous work with polyetherimide . This might indicate either insufficient contact of the probes with the sample surfaces or a too irregular depth distribution of the MWCNT under the surface.…”

“…In a previous work, the preparation of electrically conductive, porous membranes from amorphous polyetherimide using powder particles decorated with multiwalled carbon nanotubes was shown to be an effective and simple approach to generate a MWCNT network . This decorated powder limits the handling of free nanotubes to the powder production.…”