Abstract: In this work, the effects of temperature (0~40 ℃) on physicochemical properties (surface activity, foaming property and spreading property) of three surfactants with different fluorocarbon chain lengths were studied. The results show that with the increase of temperature, the critical micelle concentration (CMC) of the fluorocarbon surfactant increased, the surface tension (γCMC) decreased. And the longer the fluorocarbon chain of the surfactant, the stronger the micelle formation ability, in which the CMC of the FC8 surfactant solution was the smallest (0.23 mmol/L), and the γCMC value was the lowest (15.07 mN /m). At low temperature, the foaming ratio of fluorocarbon surfactant is the lowest (especially FC4 is only 3.70 times at 0 ℃), and the foaming ratio reaches the best (6.00~8.73 times) when the temperature rises to 20 ℃. The surfactants achieve the best foaming ratio at a temperature of 20 ℃, and further heating has little effect on the foaming ratio. At the same temperature, the longer the fluorocarbon chain, the larger the foaming ratio, and the foaming ratio of FC8 reached 8.73 times at 20 ℃. Moreover, the spreading coefficient (S) of fluorocarbon surfactant increases with the increase of temperature, and the change of S tends to be gentle when the temperature reaches 20 ℃, and the longer the fluorocarbon chain is conducive to reducing the consumption of surfactant per unit area and saving cost. It can be seen that low temperature has a great impact on the performance of short fluorocarbon chain surfactants, especially when the foaming ratio is too low to meet the use requirements. If it is used in aqueous film forming foam extinguishing agent, it needs to be compounded to improve its use performance.

Key words: fluorocarbon chains, surfactants, surface tension, foaming performance, spreading performance