Polyethylene pocket separators

The term polyethylene separator is somewhat misleading, since this separator consists mainly of agglomerates of precipitated silica, held within a network of extremely long-chained, ultrahigh-molecular weight polyethylene molecules. The raw materials, precipitated silica (SiOj — about 60 percent), ultrahigh- 

Filled polyethylene separators are the only pocket material that has been able to meet all requirements of a starter battery reliably [39-48]. It is flexible and weldable into three-sided closed pockets, making the previously usual mud room at the bottom 

The thin backweb, typically 0.2 mm thick with a porosity of 60 percent yields excellent electrical resistance values of 50 m Q cm, permitting further optimization of high-performance battery constructions. These require very thin electrodes due to the overproportionally increasing polarization effects at higher current densities and consequently also low distances most modern versions have separators only 0.6 mm thick. Such narrow spacings enforce microporous separation  

In this connection the remaining oil in the separator plays an important role. At the first glance, to increase the porosity a total extraction of the oil would be expedient, but certain oil components have been shown to exert a protective action on the polyethylene. Oil content and its distribution, as well as selection of the oil, thus gain particular significance [41, 52-54]. 

For problem-free processing, high tensile and puncture strengths are desirable. Especially when using expanded metal 

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Polyethylene pocket separators Sintered PVC/ Rubber separators Cellulosic/ Glass separators Synth, pulp / GM separators VRLA SLI Batteries Total... 

Polyethylene pocket separators Sintered PVC separators Cellulosic separators Cellulosic/ glass mix separators Glass fiber leaf separators... 

Polyethylene pocket separators Sintered PVC/rubber separators Cellulosic/glass separators Synthetic pulp/CM separators VRLASLI batteries Total... 

Separators for Starter Batteries 11.2.2.1 Polyethylene Pocket Separators... 

Practical experience has shown polyethylene pocket separators only in very exceptional cases to be considered as a cause of failure in starter batteries... 

Separators for Lead-Acid Storage Batteries 307 Table 11.5 Microporous polyethylene pocket separators. 

The microporous polyethylene pocket has succeeded worldwide more than 70 percent of all starter batteries use this form of separation. Whereas in the USA and Western Europe the transition is essentially complete, a similar development in the Asia-Pacific area and Latin America, and in the medium term also in Russia and China, is expected [3],... 

The production process is comparatively simple, even though — of course — the respective know-how is also decisive. The equipment for the production of sintered PVC separators is suitable in size and production capacity to be operated on its own by individual, medium-sized, starter battery plants, in contrast to the far larger units required for the production of polyethylene pocket material. 

Because of the increased shedding with these alloys, pure leaf separation is hardly suitable. Separations with supporting glass mats or fleeces as well as microfiber glass mats provide technical advantages, but are expensive and can be justified only in special cases. Also under these conditions of use the microporous polyethylene pocket offers the preferred solution [40]. Lower electrical properties at higher temperatures, especially decreased cold crank duration, are battery-related the choice of suitable alloys and expanders gains increased importance. 

Steel electrode frame. The pocket plate follows a similar process. Rectangular pockets of perforated nickel-plated iron strips are filled with active material, crimped, closed, and fixed/bolted in a nickel-plated steel frame. The assembled cells are placed in polyethylene containers and filled with KOH electrolyte. Spacing of the negative and positive electrodes is maintained by the internal assembly structure. There are no separators as are common in the lead acid battery structure. 

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