PFA 55MB, the jet fuel anti-icing additive now in general U.S. military service use, has demonstrated biocidal effectiveness in service and in the laboratory on microbial growths representative of those known to exist in the field. The recent announcement of this effect by Phillips Petroleum Company, which developed and patented the product, has aroused interest in military and commercial aviation circles in the U. S. and abroad, partly because of the significance of the finding itself, but also because this product has already been tested, found compatible with materials of aircraft construction and approved for military use (specification MIL-I-27686A) and, by the FAA, for commercial use. Its biocidal feature can therefore be immediately utilized in service without further testing.
This paper is concerned solely with the biocidal feature of PFA 55MB, its anti-icing properties having been previously covered by other publications.
Within a few months after PFA 55MB entered general service use in military jet fuel (April, 1962), various reports were received that the water bottoms of field storage tanks had become sterile. While this appeared to verify earlier laboratory observations, it was recognized that other factors may have been involved and that the field observations would be more meaningful if the biocidal effect of PFA 55 MB could be repeatedly demonstrated in the laboratory under severe conditions which would insure prolific microbiological growth - using a large number of bacterial and fungi species representative of those found in the field. Twenty-eight cultures were obtained from Boeing which it had isolated from aircraft fuel tanks .rom various locations; two cultures were obtained from a major airlines fuel storage system; other cultures were obtained from the bottoms of other airport tanks, two diesel fuel tanks, and two refinery diesel fuel storage tanks. The investigation showed the following:
The components of PFA 55MB were individually and collectively biocidal to all the microbiological growths tested. Biocidal concentrations will exist in discrete water phases such as at the bottom of fuel tanks if the fuel has been treated with approximately 0.05 volume per cent PFA 55MB. Glycerol, the minor component, also improves the fuel tank topcoatings, by reducing the softening which such coatings normally experience in the presence of water, thereby improving the protection which such coatings provide against corrosion.
Once tank bottoms are sterilized with PFA 55MB, subsequent biological contamination will be sterilized if the concentration of additive in the water layer is not reduced.
By virtue of being already approved for and compatible with materials of aircraft construction, PFA 55MB provides a simple means for biocidal effectiveness in all elements of fuel handling and storage.