Fluorine-free Foams with Oleophobic Surfactants and Additives for Effective Pool Fire Suppression

Dr. Ramagopal Ananth | U.S. Naval Research Laboratory

WP-2739

Objective

The objective of this project is to develop a fluorine-free, firefighting surfactant formulation that meets the performance requirements of MIL-F-24385F and is an environmentally friendly drop-in replacement for the current environmentally hazardous Aqueous Film Forming Foam (AFFF).

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Technical Approach

This project will build on the research community’s understanding and the investigator’s own research experience on fire suppression mechanisms, laboratory experimental methods, and computational models at the U.S. Naval Research Laboratory (NRL), and on the toxicology and analytical capabilities of Oregon State University in a dual-track approach to identify and develop fluorine-free surfactants with both fire suppression effectiveness and low environmental impact. The investigators will choose oxyhydrocarbon and siloxane surfactants from commercial sources where available or synthesize at laboratory scale (10 ml of surfactant makes 10 liters of final firefighting solution needed for 28 ft2 fire extinction test) using existing methods with good yields. Investigators employ a tiered-approach, wherein the number of candidate surfactants taken forward will be reduced at each tier based on the results from modeling, measurements of fire suppression efficiency, and environmental acceptability. They will choose and modify surfactant structures to balance oleophobicity and amphiphilicity to improve suppression of fuel transport through foam and foam stability. They will use QSAR, molecular and continuum dynamics models to select, eliminate, and modify surfactant structures based on acute toxicity and fuel transport through a single lamella (bubble’s liquid wall). They will perform prescreening measurements of surfactant solution properties and lamella dynamics to down select promising surfactants. They will evaluate surfactants by quantifying long-term toxicity, biodegradability, and the fire suppression effectiveness of the foams at laboratory scale. Finally, investigators will perform the 28 ft2 pool fire suppression test and the aquatic toxicity test according to MIL-F- 24385F and the appropriate ASTM, EPA, OECD methods on the down-selected foam formulations.

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Benefits

A fluorine-free alternative to the current AFFF will eliminate the bio-accumulative, environmentally persistent, and toxic perfluorooctanyl sulfonate (PFOS) and any derivatives. This will be achieved by eliminating the presence of extremely stable carbon-fluorine chemical bonds from the surfactant molecules in the firefighting foam. The fluorine-free firefighting foam will be an improvement over the telomere-based fluoro-surfactant products, which still contain carbon-fluorine bonds to a varying degree. The fluorine-free firefighting foam will lead to an improved aquatic environment and benefit to human health. While it will be an improvement to the environment, to be a successful alternative to AFFF, it must maintain essential fire suppression performance critical to Depatment of Defense (DOD) applications. The challenge is to mimic the fire suppression effect of the fluorocarbon surfactant with a fluorine-free surfactant. Until now, the search for replacement Class B fire suppression agents has relied on empirical testing. In this proposal, a new approach is outlined based on applying understanding of the fire suppression properties of the fluoro-surfactant to develop fluorine-free surfactants. The investigators will utilize the relationships between surfactant’s molecular structure and its fire suppression performance as well as its impact on the environment.

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Points of Contact

Principal Investigator

Ramagopal Ananth

U.S. Naval Research Lab

Phone: 202-767-3197

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