Sintered PVC separator

1 Sintered PVC Separators The first synthetic separator is still in use 

Sintered PVC is not at all one uniform product large differences in properties and quality are possible. Experience has shown that premium quahties require significantly higher production costs. 

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. 

Whereas a maximum number of contact points between PVC grains is desired to achieve mechanical stability, this prevents higher porosities. Typical values for porosity are 30-35% therefore the electrical resistance is rather high, that is, 170 mS2 cm, despite thin 0.3mm backwebs for top qualities. As mentioned, the range is very wide - even considerably higher electrical resistances are sometimes acceptable, for example, in areas where cold crank performance is of no significant importance. 

Typical pore size distributions result in mean pore diameters of around 15 (xm. Even long and intensive efforts did not succeed in decreasing this value decisively 

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PVC and their low-cost industrial production process, sintered PVC separators have been used since around 1950 and some are still employed today. 

Sintered PVC separators are frequently produced only for captive consumption beyond that there are specialized producers for these separators [64,68,69] and for equipment for their production [64]. The data compiled in Table 6 comprise only premium products of independent producers. 

A thorough study (cf. Ref. [40]) of failure modes in practice has shown that with this form of separation also the cause of failure has not been the separator the usual failure modes for leaf-type separators, as they have been described for sintered PVC separators, apply here as well. 

Sintered PVC separators for open stationary batteries are produced in the same way as the corresponding starter battery version (Sec. 9.2.2.2). Their brittleness and thus difficult processability are disadvantages, as is their relatively low porosity the concerns about release of chloride ions and subsequent increased corrosion are to be considered here as well. On the other hand,... 

Polyethylene separators Phenol-Formal dehyde-resorcinol Separators Microporous PVC separators Sintered PVC separators Rubber separators... 

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

Microporous polypropylene film Microporous polypropylene film Microporous filled UHMW polyethylene separator Sintered PVC separator... 

SLI batteries use either phenolic/cellulosic separators, sintered PVC separators or more recently a trend toward microporous polyethylene in either leaf or envelope form. The average pore diameters are in the 5 to 30-/im range. Heavy-duty batteries usually have microporous rubber or polyolefin (mainly polyethylene) separators which have smaller pore sizes and give longer life at a higher cost. Glass liber scrim is added to some separator materials to improve acid retention. 

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