Stabilized SPEEK Membranes with a High Degree of Sulfonation for Enthalpy Heat Exchangers

Abstract

Abstract:In this investigation, we explored for the first time the use of cross-linked sulfonated poly (ether ether ketone) (SPEEK) membranes in the fabrication of enthalpy heat exchangers. SPEEK is very sensitive to changes in relative humidity, especially when featuring high degrees of sulfonation (DS), though a poor mechanical stability may be observed in the latter case. Cross-linking is crucial in overcoming this issue, and here, we firstly employed the INCA method (ionomer counter-elastic pressure "n c " analysis) to assess the improvements in the mechanical properties. The cross-link was achieved following a simple thermal-assisted process that occurs directly on the performed membranes. After an initial screening, a degree of cross-link = 0.1 was selected as the better compromise between absorption of water vapor and mechanical properties. When implemented in the enthalpy heat exchanger system, these cross-linked SPEEK membranes enabled a high level of sensible heat exchange, as well as a remarkable variation in the mass (water vapor) transfer between the individual air flows. The performances resulted in being better than those for the system based on a benchmark commercially available perfluorinated Nafion membrane.

Air-to-Air Heat and Moisture Recovery in a Plate-Frame Exchanger Using Composite and Asymmetric Membranes

“…The best known porous hydrophilic polymer membranes proposed to be used for air dehumidification are ethyl cellulose (EC), polyvinyl alcohol (PVA), cellulose acetate (CA), polyimide (PI), Polyether block amide (PEBAX), and sulphonated poly (ether ether ketone) (SPEEK) [ 11 , 12 , 13 , 14 ]. Zhang et al compared the performance of three different membrane materials, i.e., kraft paper, cellulose acetate (CA), and the modified CA, as the core for the membrane heat exchanger at a steady state.…”

“…Most unmodified single polymer membranes are mechanically unstable despite acceptable and, in some cases, high permeability. On the other hand, some with sufficiently high mechanical stability do not have sufficient water permeability [ 14 ]. Therefore, many authors propose using asymmetric composite membranes containing a porous support layer and a hydrophilic active layer with a smaller pore size.…”

Study of Annealed Aquivion® Ionomers with the INCA Method †

“…We introduced a new methodology, called INCA (Ionomer n c Analysis), where n c is an index proportional to the force of the ionomer matrix, which balances the osmotic pressure of the inner proton solution at the different temperatures. The determination of the hydration number and the volume of the samples allow us to find the density, the molality and molarity of the internal solution in addition to the internal osmotic pressure [24,25,26,27,28,29,30,31,32]. The INCA method is based on the use of n c /T plots to determine some fundamental properties of an ionomer, such as the degree of crystallinity and the melting temperature.…”