Separators resin-impregnated cellulose

The resins and the carbon-impregnated polyurethane foam were separately placed in cellulose thimbles and Soxhlet extracted successively for 24 h with HPLC-grade hexane, dichloromethane, acetone, and methanol. The final methanol extract from each adsorbent was concentrated and analyzed by GC by using the FID. 

The separation of FFAs using HPLC does not present a problem. A broad spectrum of stationary phases can be used SiOi phases, stationary phases impregnated with cations, reversed phases, ion-exchange resins, or cellulose. However, detection of underivatized aliphatic fatty acids may be difficult to perform because of a lack of suitable chromatopho-res, luminophores, or fluorophores in the molecule. 

In the meantime another development had decisively altered the outset situation plastics had been discovered and synthesized, among them also some acid-stable ones such as phenol-formaldehyde resin or poly(vinyl chloride) (PVC). These opened up new possibilities cellulose papers could be impregnated with phenol-formaldehyde resin solution and thus rendered sufficiently acid-stable, and sintered sheets from PVC powder were developed. Independent separators producers were founded, combining knowledge of the chemical industry with experience of the battery industry and thus accelerating the development process. 

The development of the starter battery in Japan has taken an independent course (see Sec. 9.2.1.2), visibly expressed by the separator s thick glass mat and its lack of spacing ribs (cf. Fig. 19). The cellulosic backweb impregnated with phenolic resin, generally in use until around 1980 and largely identical to the separator of the same type already mentioned has been completely replaced by thin ( 0.3 mm) fleece materials made of organic fibers. 

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