Ballard Advanced Materials

There is ongoing work to investigate alternative membranes that not only exhibit durability and high performance, but also can be manufactured inexpensively at high volume. Work at Ballard Advanced Materials Corporation has concentrated on developing low-cost membranes using trifluorostyrene and substituted trifluorostyrene copolymeric compositions (17). 

Presently, two commercial (or semicommercial) PEMs are based on styrene or styrene-like monomers BAM from Ballard, and Dais Analytic s sul-fonated styrene—ethylene—butylene—styrene (SEBS) membrane. Ballard Advanced Materials Corporation introduced a styrenic membrane based on a novel family of sulfonated copolymers incorporating a,/3,l3-trifluorostyrene and substituted a,y3, -trifluoro-styrene comonomers. These are registered as BAM membranes, and their general formula is given in Figure 3. 

Ballard itself, via Ballard Advanced Materials (Lovell and Page, 1997), has been generating a possible Nafion alternative, namely... 

Styrenic polymers, which are easy to synthesize and modify, were studied extensively in the early literature. One example is BAM made by Ballard Advanced Materials (see chemical structure below). This membrane is 75 pm thick and has an ion exchange capacity of about 1.1 to 2.6 meg/g. Its chemical stability is not as good as PFSA even with its perfluorinated backbone. Ballard claimed that this membrane could last for several hundred hours under low RH operating conditions. It is no longer in production due to its high cost and the lack of availability of the monomer. 

Made by Ballard Advanced Materials, this membrane contains an aromatic ether (biphenol) segment that is common to poly(ether ketone). This aromatic backbone confers structural flexibility. The sulfone group is stable with respect to oxidation and reduction. 

Poly(a,(3,(3-Trihuorostyrene) and Copolymers Ballard Advanced Materials.797... 

Ballard Advanced Materials (BAM) ionomers are sulfonated copolymers of trifluorostyrene and substimted trifluorostyrene monomers. BAM, a subsidiary of Ballard Power Systems, investigated the conducting polymers based on polyphenylquinoxaline (PPQ). These can be sulfonated in a wide range and were referred to as BAMIG (Ballard first generation) membranes, but these membranes were found to have short durability. To overcome this problem, BAM developed a second generation of advanced membranes based on two distinct material types. The first material type consisted of a series of sulfonated poly(2,6-diphenyl 1,4-phenylene oxide). The second material type consisted of a series of sulfonated poly(arylether sulfone). But the durability of these membranes was also insufficient. Since the durability of previous membranes was limited, Ballard produced a novel family of sulfonated membranes based on a,p,p-ttifluorostyrene monomers and a series of substituted ttifluoro-comonomers... 

Poly(a, p, y-Trifluorostyrene) and Copolymers (Ballard Advanced Materials).594... 

Research has been actively conducted for the past 20 years in search of alternatives to perfluorinated membranes for PEMFC and DMFC applications. Partially fluorinated ionomers are of great interest among other various candidates in such efforts. Like perfluorinated membranes, partially fluorinated ionomers also have a PTFE-like polymer backbone as a main part to resist chemical attacks. However, ionic groups are attached to styrenic moieties instead of perfluorinated side chains. Due to its availability and easy sulfonation, styrene is a reasonable choice for ionomeric materials. In the late 1990s, Ballard Power Systems introduced a partially fluorinated low-cost membrane for fuel cell applications [24,47,48]. Ballard Advanced Materials (BAM) membrane is a family of sulfonated styrenic co-polymers of a,p,p-trifluorostyrene and substituted a,p,p-trifluorostyrene co-monomers by emulsion polymerization. The chemical structure of BAM membrane is shown in Fig. 13.9. 

The standard electrolyte material for PEMFC is Nafion, which is produced by E.I. Dupont de Nemours (Membrane No. 117 C20). The Dow Chemical Company has produced an electrolyte membrane (XUS 13204.10) that exhibits superior qualities over the Nafion membrane i.e., it has low electrical resistance and high current densities. But these membranes are relatively more expensive than the Nafion membranes. The Dow membrane is supplied at 2 mils whereas the Nafion is supplied for 7 mils. Ballard Advanced Material Corporation is working on developing trifluorostyrene copolymeric membranes for PEMFC. The membranes used currently are expensive and are available only in specific ranges and conductivity. So, the research is focused on developing low cost membranes with low resistivity. 

Based on the above work on sulphonated TFS membranes, a novel family of sulphonated copolymers incorporating TFS and a series of substituted TFS monomers provided the group of materials referred to as BAM3G (Ballard Advanced Materials 3rd Generation of membranes) (Savadogo et al, 1995 Savadogo and Roberge, 1997). 

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