Chemical Composition
Chemically, FSII is an almost pure (99.9%) ethylene glycol monomethyl ether (EGMME, 2-methoxy ethanol, APISOLVE 76, CAS number ), or glycol monomethyl ether since 1994 diethylene glycol monomethyl ether (DEGMME, 2- (2-methoxy ethoxy) ethanol, APITOL 120, methyl carbitol, CAS number ). Prior to 1994, Prist was regulated under the MIL-I-27686E standard, which specified use of EGMME, but subsequently came under the MIL-DTL-85470B, with use of less hazardous DEGMME with higher flash point.
FSII retards the growth of microorganisms eventually present in the fuel, mostly Cladosporium resinae fungi and Pseudomonas aeruginosa bacteria, known as "hydrocarbon utilizing microorganisms" or "HUM bugs", which live in the water-fuel interface of the water droplets, form dark, gel-like mats, and cause microbial corrosion to plastic and rubber parts.
EGMME had been certified as a pesticide by the EPA, but as the requirement changes raised the certification costs, DEGMME has no official pesticide certification. DEGMME is a potent solvent, and at high concentrations can damage fuel bladders and filters. Long-term storage of FSII-fuel mixtures is therefore not recommended.
Anhydrous isopropyl alcohol is sometimes used as an alternative.
Read more about this topic: Fuel System Icing Inhibitor
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