Page 353 - Handbook of Battery Materials

11.2 Separators for Lead–Acid Storage Batteries 323

Table 11.12 Separators for flooded lead–acid stationary batteries.

Polyethylene Phenol– Microporous Sintered Rubber
separators formaldehyde– PVC PVC separators
resorcinol separators separators
separators

Supplier Daramic, Inc. Daramic, Inc. AMER-SIL Jungfer AMERACE
[60, 61] a [60, 61] s.a. [86] GmbH [64] Microporous
Products [87]
Brand name DARAMIC DARAK 5005 AMER-SIL Sintered PVC Micropor-Sil
Industrial CL HP M3
Backweb 0.5 0.5 0.5 0.5 0.50
thickness
(mm)
Pore size 0.1 0.5 0.5 15 0.25
(average)
(µm)
Acid 280 200 220 350 n.a. c
displacement
3
–2
(cm m )
Electrical 240 110 150 300 150
resistance
2
(m cm )
Initial 0 ++ ++ 0 ++
capacity b
Handling ++ ++ + 0 +
properties b
Black deposits b + ++ ++ ++ ++

a
Polyethylene industrial separators are also available from ENTEK International 1621.
b Ranking: ++, very good; +, good; 0, acceptable; –, poor.
c
n.a.: not available.

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, they are unrivalled in low cost, even up to extreme overall
thickness (up to 5 mm). Since at these thicknesses electrical resistance and acid
displacement by the back-web have a relatively low impact, there is a remaining
niche for the application of sintered PVC separators.

11.2.3.2.5 Comparative Evaluation of Separators for Open Stationary Batteries
Table 11.12 shows the physicochemical data of separators used in open stationary
batteries. Since the emphasis is on low acid displacement, low electrical resistance,
and high chemical stability, the phenolic resin–resorcinol separator is under-
standably the preferred system, even though polyethylene separators, especially at
low backweb, are frequently used. For large electrode spacing and consequently