The objective of this project was to refine P N Solutions Inc. formulation and application to have an alternative to aqueous film forming foam (AFFF) for fuel fires that is ready for Military Specification testing. PNS Syrup (PNS) is an environmentally friendly, proprietary fire extinguishing agent made by P N Solutions Inc. PNS is found to react with the ions and radicals in the flames and stop the chain reaction, suppressing the smoke and the fire. PNS is an effective fire extinguishing agent for large gasoline fires. Large gasoline fires can be extinguished (28ft² and 50ft²) in less than 30 seconds by applying PNS in a mist. Despite excellent fire extinguishing characteristics, PNS is a non-foaming liquid and as such, does not have adequate burnback capability. The main objective of this project has been to develop approaches for dealing with this limitation. In the final report the project team discussed the efforts and outcomes with three approaches for adapting PNS to achieve good burnback. It is believed the resultant formulations may also be of use to other groups working to replace AFFF. 

The project team used three different technical approaches to add burn back capability to PNS.

1) Combine PNS with widely used surfactants to enable foaming. 

2) Combine PNS with commercially available Fluorine free foam (FFF). 

3) Chemically alter PNS to enable foaming while maintaining similar overall chemical structure and fire extinguishing properties. 

It has been discovered that sodium lauryl ether sulfate (SLES) reacts with the flame retardant PNS to form a viscous solution as the two compounds sequester each other without decomposition. This modified PNS/SLES can be made into a liquid foam concentrate by addition of glycol ether. The project team found that this new formulation has good fire extinguishing ability and burnback when applied as a mist compared to a commercially available FFF. 

PNS was added to the best performing FFF. PNS is a fire extinguishing agent that is self-intumescent and forms a light-weight foamy char which stops the chain reaction of free radicals and ions in a flame and associated heat release. This is expected to decrease fire extinguishing time and improve foam bubble stability in FFF. As PNS is not a foaming agent, extra surfactant may have to be added. Initial results are promising, however, PNS lowers the expansion ratio of FFF such that additional surfactants may need to be added. 

A family of modified PNS compounds have been discovered and produced that have foaming properties in addition to being flame retardants. When foams made with PNS-F are exposed to high heat, the modified PNS appear to convert to intumescent char that conducts heat poorly and does not become fuel. Initial experiments have demonstrated some very interesting and encouraging properties of this family of compounds. On testing, fire extinguishing ability appears similar to the original PNS. Most notably, PNS-F compounds create excellent foams with expansion ratios of between 6.5 and 10 and bubbles that are extremely long lasting. Burnback testing at Naval Research Labs exceeded 10 minutes. 

While the project team did not reach the initial objective of a drop-in replacement for AFFF, this project represents a large body of research and development and the contribution of a family of new fire extinguishing compounds. This work has resulted in the award of two additional grants (WP22-3287 and WP23-3875) and two patent applications (PCT US 20 52061 and PCT US 22 38529). Current commercialized FFF have improved dramatically over the past decade. Though they are still not as effective as AFFF, they will continue to improve. P N Solutions Inc. believes the fire extinguishing agents could be an important “piece of the puzzle” in the arsenal of agents which will eventually bring FFF up to the effectiveness of AFFF.