Apparatus for and method of forming seals in fuel cells and fuel stacks
View Patent ↗A sealing technique is provided for forming complex and multiple seal configurations for fuel cells and other electrochemical cells. To provide a seal, for sealing chambers for oxidant, fuel and/or coolant, a groove network is provided extending through the various elements of the fuel cell assembly. A source of seal material is then connected to an external filling port and injected into the groove network, and the seal material is then cured to form the seal. There is thus formed a “seal in place”, that is robust and can accommodate variations in tolerances and dimensions, and that can be bonded, where possible, to individual elements of the fuel cell assembly. This avoids the difficulty, labor intensive cost and complexity of manually assembling many individual gaskets into complex groove shapes and the like. The seal material can be selected to be comparable with a wide variety of gases, liquid coolants and the like.
1. A method of forming seals in an electrochemical cell assembly comprising a plurality of separate elements, the method comprising injecting a curable seal material into a groove network within the fuel cell assembly, the curable seal material comprising:
(a) 100 parts by weight of a polydiorganosiloxane containing two or more silicon-atom-bonded alkenyl groups in each molecule;
(b) 5–50 parts by weight of a reinforcing filler;
(c) 1–20 parts by weight of an oxide or hydroxide of an alkaline earth metal with an atomic weight of 40 or greater;
(d) an organohydrogensiloxane containing three or more silicon-atom-bonded hydrogen atoms in each molecule, the hydrogen atoms being present in an amount providing a molar ratio of silicon-atom-bonded hydrogen atoms in component (d) to silicon-atom-bonded alkenyl groups in component (a) which is in a range of 0.4:1 to 5:1; and
(e) a platinum-type metal catalyst in an amount providing 0.1–500 parts by weight of platinum-type metal per one million parts by weight of component (a);
wherein at least portions of the groove network within the electrochemical cell assembly are defined solely by the elements of the electrochemical cell assembly and the method comprises using the curable seal material to form a seal including a seal between at east two adjacent elements of the electrochemical cell assembly that define a chamber for a fluid for operation of the electrochemical cell assembly.
2. A method as claimed in claim 1 , wherein the seal material further comprises:
(a) 0.1–5.0 parts by weight of an organic peroxide in combination with component (e) or in place of component (e);
(b) 0.01–5.0 parts by weight of an inhibitor; and
(c) 0.01–100 parts by weight of a non-reinforcing extending filler.
3. A method as claimed in claim 1 , in which the polydiorganosiloxane of component (a) is a vinyl terminated polydimethylsiloxane having a viscosity of at least 55 Pa·s (55,000 cP) or a blend of lower and higher viscosity vinyl containing polydimethylsiloxanes such that the viscosity of the blend is at least 55 Pa·s (55,000 cP).
4. A method as claimed in claim 3 , wherein component (a) is a vinyl terminated trifluoropropylmethylsiloxane dimethylsiloxane copolymer in which the mole percent of methyltrifluoropropyl is 10–100 mole percent.
5. A method as claimed in claim 1 , wherein component (a) is a vinyl terminated diphenylsiloxane dimethylsiloxane copolymer in which the mole percent of diphenylsiloxane is 2–50 mole percent.
6. A method as claimed in claim 1 , in which component (e) is encapsulated in a thermoplastic organic polymer.
7. A method as claimed in claim 1 , in which component (e) is present in an amount to provide 5–50 parts by weight of platinum type metal per one million parts by weight of component (a), and the seal material is cured by heating it to a temperature of 30–120° C.
8. A method as claimed in claim 1 , in which component (e) is an organic peroxide, instead of the metal catalyst, present in an amount of 0.5–5.0 parts per 100 parts of the seal material, and the seal material is cured by heating it to a temperature of 100–200° C.
9. A method as claimed in claim 1 , in which the seal material further comprises:
(f) 0.1–20 parts by weight of an adhesion promoter which is an epoxy containing organosilicon compound, the adhesion promoter being added to the seal material before it is cured to improve bonding of the seal material during cure.
10. A method as claimed in claim 2 , in which the viscosity of the seal material is 1,000–1,500 Pa·s (100,000–150,000 cp).