AUTHOR=Zheng X. X. , Böttger A. J. , Jansen K. M. B. , van Turnhout J. , van Kranendonk J. 

TITLE=Aging of Polyphenylene Sulfide-Glass Composite and Polysulfone in Highly Oxidative and Strong Alkaline Environments

JOURNAL=Frontiers in Materials

VOLUME=Volume 7 - 2020

YEAR=2020

URL=https://www.frontiersin.org/journals/materials/articles/10.3389/fmats.2020.610440

DOI=10.3389/fmats.2020.610440

ISSN=2296-8016

ABSTRACT=Alkaline water electrolysis becomes increasingly important for the supply of renewable energy,
and of raw material for the chemical industry. An attractive choice for the encapsulation of the
electrolyte cell is an (advanced) engineering polymer. The objective of this paper is to find a
suitable one that can withstand for many years: 30wt% KOH solution and pure oxygen at a high
pressure of 50 bar and at an elevated temperature of 90 SOC. Using CES EduPack, 12 possible
thermoplastic polymers were selected, of which polyphenylene sulfide (PPS) and polysulfone
(PSU) were further investigated using accelerated testing. The polymers have been exposed to
three KOH concentrations (15, 30 and 45wt%), two oxygen pressures (pure O2 at 5 bar and air
with pO2=20%), and three temperatures (90, 120 and 170 SOC). Extensive characterisation of the
exposed samples has been carried out using various techniques, including weight, tensile, DMA,
and creep-recovery measurements, as well as DSC, FTIR, XRD and SEM. After 12 weeks of
ageing, glass fibre reinforced PPS failed in a strong alkaline solution at high temperatures, due to
the dissolution of the glass fibres. The PPS matrix itself and PSU turned out to be resistant to
thermo-oxidative and chemical degradation under the conditions tested. Only marginal changes
in mechanical, visco-elastic and thermal behaviour were observed, which can be ascribed to
physical rather than chemical ageing. In view of the brittle nature of PPS, it could be concluded
that PSU is the most promising candidate for the long-term application in alkaline electrolysis.
Extrapolating the data using time-temperature superposition, it is predicted that PSU will retain
its integrity and mechanical properties for a period of 20 years of operation.