M4 flame fuel thickening compound

M4 flame fuel thickening compound is a nonhygroscopic thickener, a di-acid aluminum soap of isooctanoic acids derived from isooctyl alcohol or isooctyl aldehyde, which are obtained from the oxidization of petroleum.[1] M4 is used in fire bombs and incendiary weapons. It is commonly referred to as isooctal, with incendiary oils obtained by the use of M4 being denoted Iso. It is used to prepare an Incendiary in the field.

Chemical structure of the major constituents of the M4.

Composed of 98% aluminum isooctanoic acids and 2% Attasorb clay or Santocel C as anti-caking agents. The M4 thickener has a higher density than the M1 or M2 thickeners. 2-Ethylhexanoic acid is used as a peptizer. A 2% solution in gasoline has the same thickening as the M1 and M2 thickener at 4%. It is not favorable to oxidation, unlike M1, which contains oleic acid.

Dissolve more faster than M1, M2 and M3. It is less favorable to agglomeration than the M1 and M2. The aluminum salt of 6-methylheptanoic acid is not the most active component of M4 and is sterically hindered.

This was developed in response to the series of deficiencies of the M1 thickener and of the M3 (octal), with all fillings having been remedied. M1 has a terrible tendency to absorb moisture from the air, this was reflected since its drying process, which was specified for below 1%, in immediate packaging and in an impermeable manner.

M1 grade napalm was obtained from critical sources, which required a military grade of logistics and could easily be harmed. M1 has a tendency to stay above the fuel, due to its low density and ease of agglomeration, this required rapid agitation and agglomerate breakage.

The main problem, without a doubt, was the high paraffinity of the components used in the manufacture of the M1, which gave it a poor compatibility with other fuels of similar paraffinity and the cost/benefit ratio of the thickener, requiring, in most cases, two 5 lb cans to prepare an incendiary bomb (it was common for more than one batch to be consumed in a raid).[2]

Unlike other thickeners, isooctal did not get a redesign during its experimentation, being considered satisfactory, being the fourth thickener experienced (E4R1).[2]