Encapsulated Water Imparts Unprecedented Flame Retardancy to Cross-Linked Polystyrene Foams

Area of Science:

• Materials Science
• Polymer Chemistry
• Fire Safety Engineering

Background:

• Water is an effective flame retardant due to its high heat capacity and vaporization.
• Integrating water into materials while ensuring its retention presents a significant challenge for flame retardant applications.

Purpose of the Study:

• To develop a novel flame-retardant material by incorporating water into cross-linked polystyrene foams (cPSs).
• To evaluate the flame retardancy performance and long-term stability of these water-containing composite foams.

Main Methods:

• Development of cross-linked polystyrene foams (cPSs) with water encapsulated in closed pores.
• Evaluation of flame retardancy using the UL-94 test and measurement of key parameters like peak heat release rate (PHRR), total heat release (THR), time to ignition (TTI), and flame performance index (FPI).
• Incorporation of flame-retardant coatings and salts to delay water evaporation and enhance material durability.

Main Results:

• Composite cPSs achieved a flame retardancy rating above V-0 in the UL-94 test at water volume fractions exceeding 33%.
• A representative composite (cPSs-M2) showed a 55.4% reduction in PHRR and a 31.1% reduction in THR.
• TTI and FPI were enhanced by over 10 and 25 times, respectively.
• Flame-retardant coating and salt incorporation significantly delayed water evaporation, projecting a service life exceeding eight years.

Conclusions:

• Cross-linked polystyrene foams containing water in closed pores offer excellent flame retardant properties.
• The developed composite materials demonstrate superior fire safety performance compared to conventional materials.
• The strategy of incorporating water with delayed evaporation mechanisms provides a durable and effective flame retardant solution.