Development of an analytical AFFF formulation for the evaluation of alternative surfactants
K. Hinnant et al., presented at the 10th U.S. National Meeting of the Combustion Institute
Full paper available for download here: 10thCombustionMeetingPaper_Final-1spqpee
Abstract: Following criteria set by MIL-F-24385F for firefighting foams, we are developing an analytical aqueous firefighting foam (AFFF) formulation to be used for laboratory testing in place of proprietary commercial AFFF formulation. An aqueous reference foam solution containing 0.15% Capstone (fluorocarbon surfactant), 0.05% Triton X-100 (hydrocarbon surfactant), and 0.95% diethylene glycol butyl ether, by weight and was found to meet MilSpec criteria for aqueous film formation, which was inferred to be essential for improved fire extinction. However, the reference AFFF extinguished the 28 ft2 gasoline pool fire in 54 seconds, exceeding the maximum 30 second qualification standard. Despite similar surface tensions and spreading coefficients between the reference and commercial AFFF indicating adequate film formation, the fire extinction time criterion could not be met. However, we found that the reference AFFF and a commercial AFFF degraded in 30 and 45 minutes respectively when the foams were placed over 50°C n-heptane fuel at bench-scale consistent with burn-back Milspec test results. Differences in foam degradation may prove to be more valuable to fire extinction than the role of film formation.