Rigid bonded seals

The various options for sealing and joining the ceramic and metal components in pSOFCs can be broadly classified into one of three categories rigid bonded seals, compressive seals, and bonded compliant seals. As outiined in Table 11.2, rigid... 

Bonded seals can be rigid or compliant. A hermetic seal is achieved through adhesive forces between the seal material and both surfaces against which the seal is to work. Naturally, the seal material must have good adhesive properties (good wettability of the material to be sealed). 

It is mainly used in the industrial production of rigid polyurethane foams. Many other uses are in the fields of coatings, adhesives, sealants and elastomers such as paints, adhesives, weather-resistant sealing materials and foohvear. There is use also in the production of particle board (bonding of wood) and mould cores for the foundry industry (European Union, 1999). 

Calix[4]arene provides a suitable semi-rigid concave scaffold for the construction of dimeric capsules. Both the upper and lower rim can be decorated with a wide variety of functional groups, in particular the urea moiety is known to provide a good combination of hydrogen bond donor and acceptor character implemented in the same functional group and this sequence of atoms have been extensively employed in the constructions of calix[4]arene dimeric molecular capsules (Fig. 9). Characteristic of these dimers is the presence of a cyclic seam of hydrogen bonds that seal the capsule and provides an internal molecular cavity that easily accommodates molecules as big as benzene. 

On the other hand, 1 3 dienes react with acyclic aliphatic mono-fluorophosphites in a sealed tube via the usual Arbuzov rearrangement eliminating the alkyl fluoride (267), and it has been suggested that in the cyclic esters the rigidity of the ring makes the P-0 bond less stable. 

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