As the fire protection industry transitions away from PFAS-containing firefighting foams, Synthetic Fluorine Free Foams (SFFF) are becoming increasingly important for Class B fire protection. However, beyond fire performance and environmental considerations, the stability of polymers used in some foam formulations, particularly the issue of 'hidden gum', requires attention.
What Is 'Hidden Gum' in SFFF Foams?
Natural polymers like xanthan gum and guar gum have been used in firefighting foam formulations for decades to enhance the foam blanket's strength and resistance. However, these polymers can also increase the viscosity of a foam concentrate, affecting its pumping and proportioning capabilities. According to Fomtec, some SFFF formulations use partially hydrated polymers to maintain manageable viscosity, which can later change, creating 'hidden gum'.
Why Does Foam Viscosity Matter?
Viscosity is crucial as it affects how a firefighting foam concentrate behaves within a suppression system. Significant changes in viscosity during storage or operation can influence the system's flow characteristics, potentially creating challenges for equipment designed for specific properties.
This is particularly important because foam systems are designed around specific flow characteristics. A concentrate that behaves differently from when it was originally installed can potentially create challenges for equipment that was selected according to its original properties.
How Can Water Affect Partially Hydrated Polymers?
Partially hydrated polymers can continue to hydrate when exposed to water, increasing viscosity. Fomtec's testing showed that several AR-SFFF products experienced significant viscosity increases when water was added, affecting pumping demands and system performance.
For example, increased viscosity could contribute to higher pumping demands, greater pressure losses or difficulties passing through filters and strainers. Changes in the concentrate’s physical characteristics could also affect proportioning and discharge performance.
The Importance of Long-Term Foam Stability
Firefighting foam concentrates must remain stable over years of storage. Factors like temperature fluctuations and humidity can influence their condition. Evaluating a foam's stability, viscosity changes, and compatibility with equipment is essential, especially when transitioning from PFAS-containing foams to SFFF alternatives.
This means that evaluating a foam should involve more than looking at its initial fire test results. Fire protection professionals should also consider questions such as: How stable is the concentrate during long-term storage? How does its viscosity change over time? How does it respond to water contamination? Is the concentrate compatible with existing proportioning equipment?
Understanding how these polymers behave is important for fire departments, airports, oil and gas facilities, petrochemical sites, marine applications and other high-hazard environments where firefighting foam systems must operate reliably when needed.
The transition to fluorine-free firefighting foam is not simply a matter of replacing one liquid with another. SFFF formulations can have different physical and performance characteristics, and the finished foam produced by a particular discharge device can have a major influence on fire suppression performance.
What Happens Next?
As SFFF technology continues to develop, greater transparency around formulation, polymer behaviour and long-term performance can help the industry make better-informed decisions and ensure that firefighting foam systems remain ready when they are needed most.
Manufacturers should be able to provide technical information covering viscosity, storage conditions, compatibility and relevant testing. Where a foam relies on polymers, understanding the polymer technology and its hydration state can also provide useful information when assessing long-term reliability.
Practical Takeaways for UK Fire Safety Professionals
Evaluate SFFF concentrates for long-term stability and compatibility with existing systems.
Consider the impact of viscosity changes on system performance.
Regularly inspect and test foam concentrates as per manufacturer recommendations.
Ensure transparency from manufacturers regarding polymer technology and hydration states.
