DMFC Performance of Polymer Electrolyte Membranes Prepared from a Graft-Copolymer Consisting of a Polysulfone Main Chain and Styrene Sulfonic Acid Side Chains
Polymer electrolyte membranes (PEMs) for direct methanol fuel cell (DMFC) applications were prepared from a graft-copolymer (PSF- g -PSSA) consisting of a polysulfone (PSF) main chain and poly(styrene sulfonic acid) (PSSA) side chains with various average distances between side chains ( L av) and side chain lengths ( L sc). The polymers were synthesized by grafting ethyl p -styrenesulfonate (EtSS) on macro-initiators of chloromethylated polysulfone with different contents of chloromethyl (CM) groups, and by changing EtSS content in the copolymers by using atom transfer radical polymerization (ATRP). The DMFC performance tests using membrane electrode assemblis (MEAs) with the three types of the PEMs revealed that: a PSF- g -PSSA PEM (SF-6) prepared from a graft copolymer with short average distances between side chains ( L av) and medium L sc had higher DMFC performance than PEMs with long L av and long L sc or with short L av and short L sc. SF-6 had about two times higher PD max (68.4 mW/cm 2 ) than Nafion ® 112 at 30 wt % of methanol concentration. Furthermore, it had 58.2 mW/cm 2 of PD max at 50 wt % of methanol concentration because of it has the highest proton selectivity during DMFC operation of all the PSF- g -PSSA PEMs and Nafion ® 112.
PEMs with high proton conductivity and excellent methanol resistance based on sulfonated poly (aryl ether ketone sulfone) containing comb-shaped structures for DMFCs applications
Abstract Sulfonated poly (aryl ether ketone sulfone) polymers (SPAEKS-PSA X) with the comb-shaped structure were prepared by grafting with 1, 3-propanesultone (PSA). The successful synthesis of SPAEKS-PSA X was confirmed by the FT-IR spectra. The morphology of the membrane was investigated by the small angle X-ray scattering and the transmission electron microscopy. The nanophase separation was brought in a comb-shaped structure between the main chains and the propyl sulfonic acid groups. The SPAEKS-PSA 15 membrane exhibited the highest conductivity of 101 mS cm−1 under 80 °C and 100% relative humidity conditions (100% RH). In addition, the methanol permeability coefficients of SPAEKS-PSA X membranes (7.56 × 10−7 to 9.44 × 10−7 cm2 s−1) were much lower compared to Nafion®117 (22.37 × 10−7 cm2 s−1). Meanwhile, the SPAEKS-PSA X membranes also displayed excellent mechanical properties (tensile modulus >30 MPa), thermal, oxidative stabilities and fuel cell performance. Considering the parameters above, especially the elevated proton conductivities as well as high methanol resistance, the comb-shaped structure is a promising design for DMFCs applications.
Development of polyamide curable modified epoxy novolac resins with improved adhesion and chemical resistance
Purpose – To prepare modified epoxy resins from resorcinol, cresol and phenol for improved adhesion and chemical resistance. To evaluate the properties of such modified epoxy resins.Design/methodology/approach – Epoxy novolac resins (ENRs) were synthesised by condensing epichlorohydrin with novolacs based on different types of substituted phenols for improving adhesion and chemical resistance. Various compositions were made by incorporating different proportions of polyamide resin. The chemical and adhesive strengths of the conventional epoxy and the modified epoxy resins were characterised.Findings – The modified ENR using substituted phenols showed significant enhancement of chemical and adhesive strengths over the conventional DGEBA resin. The modified ENR had an increased number of glycidyl groups (thus increased functionality) of resin, which was responsible for improved chemical and adhesive strengths over the conventional DGEBA resin.Research limitations/implications – The EPN resins used in the pr...