Films from multi-film laminates

The flat cell is illustrated in Fig. 8.5. In this construction, a duplex electrode is formed by coating a zinc plate with either a carbon-filled conductive paint or laminating it to a carbon-filled conductive plastic film. Either coating provides electrical contact to the zinc anode, isolates the zinc from the cathode of the next cell, and performs the function of cathode collector. The collector function is the same as that performed by the carbon rod in cylindrical cells. When the conductive paint method is used, an adhesive must be placed onto the painted side of the zinc prior to assembly to effectively seal the painted surface directly to the vinyl band to encapsulate the cell. No expansion chamber or carbon rod is used as in the cylindrical cell. The use of conductive polyisobutylene film laminated to the zinc instead of the conductive paint and adhesive usually results in improved sealing to the vinyl however, the film typically occupies more volume than the paint and adhesive design. These methods of construction readily lend themselves to the assembly of multi-cell batteries. 

The microstructure was realized by a dry-film photoresist technique and based on established techniques from printed circuit board technology [142], Dry resists are available as thin films, e.g. of thickness 50 or 100 pm. The resist films are encased in other polymer materials which are later removed. The resist films can be deposited on various base materials such as silicon or polymers giving mechanical stability. Lamination is carried out with a roller laminator. Then, exposure is made and spray development without any solvents follows. The process steps can be repeated at multi-laminated structures. Closed structures can be made in this way. 

Coextrusion produces a multi-ply material directly from the individual resins. The method is limited to thermoplastic materials such as polythene, polypropylene and nylons. Thin layers of extruded bonding resins are necessary to combine many of the resins. Coextrudates have to be surface printed and the outer film cannot be reverse printed as it is often used with more conventional laminates with a film outer ply. 

Table 4.3 provides a comparison between the helium permeation rates in two films, a laminate incorporating a 6 pm aluminium foil, PET 12 pm/Aluminium 6 pm/HDPE 50 pm (Film B) and a multi-layered barrier composed of four aluminium-sputtered PET sheets laminated onto a 50 pm PE (Film A). Tests were run at 24 °C. From the measurement of... 

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