Designing Next Generation Polymer-Based Surfactants for Fire Suppression

Dr. Timothy Long | Virginia Polytechnic Institute and State University

WP18-1559

Objective

The Aqueous Film Forming Foams (AFFFs) used by the military for Class B (liquid fuel) fire suppression contain fluorinated surfactants (perfluorinated compounds [PFCs]) that are linked to a number of serious environmental impacts. The Persistence, Bioaccumulation, and Toxicity (PBT) of these compounds have resulted in the appearance of fluorosurfactant chemicals in populations that were not directly exposed to the primary chemical but rather through indirect exposure by chemical migration within the ecosystem. Costly remediation efforts are already in process for treatment of PFCs in groundwater at or around military and civil aviation facilities. A new fluorine-free foam will be developed through this project that is capable of meeting the fire suppression and environmental performance in MIL-F-24385F (NAVSEA, 1992). Halogenated surfactants provide desirable thermal stability and flammability resistance; however, their environmental impact suggests a necessary design paradigm that completely removes halogenated sequences in conventional surfactants. This project describes a new modular family of sulfonated polyimides, containing flame-resistant aromatic sequences and imide linkages coupled with pendant or telechelic sulfonated units to impart water dispersibility/foaming and photo-crosslinkable sites to influence long-range flow. Testing will be conducted to assess the foam fire suppression performance and environmental impact.

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Technical Approach

This effort will develop a new fluorine-free foam that meets the fire qualification requirements, limits the environmental impact, and is compatible with existing AFFF equipment. This effort will build on the previous successful development of fluorine-free foams for commercial applications and utilize a new polymer additive to create a fluorine-free foam capable of meeting or exceeding the fire and environmental requirements in MIL-F-24385F. Aromatic polymers are known to inhibit flammability through the formation of a char that serves to extinguish burning, and in combination with latent crosslinking sites serves to further limit migration and flow, thus decreasing the propensity for molecules to effectively transport to the environment. This project takes advantage of the fire radiation to impart efficient crosslinking during application.

New formulations will be evaluated through a series of small-scale test to quantify different suppression aspects of foam. This includes tests on expansion ratio and drainage, foam sealibility, blanket degradation and ignition prevention under heat, foam flow over fuel and burnback resistance. These formulations will be compared with baseline performance of AFFF as well as commercially available RF6 foam solutions. The most promising formulation developed in this effort will be evaluated based on the 28ft two large-scale fire suppression/burn-back tests and environmental impact requirements described in MIL-F-24385F.

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Benefits

The primary benefit of this research is that a fluorine-free foam will be formulated that minimizes the impact on the environment. The new formulations will replace the PFCs with different polymer-based surfactants. The chemistry of these surfactants will also be developed to prevent the foam from draining into water sources. The new fluorine-free foam will also be available for commercial markets such as airports.

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Points of Contact

Principal Investigator

Dr. Timothy Long

Virginia Polytechnic Institute and State University

Phone: 540-231-2480

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