Why Fire Retardancy Matters

When it comes to building safty, fire retardancy plays a crucial role in protecting lives and reducing property damage. But how can we improve fire resistance in building insulation while also making it eco-friendly? This question lies at the heart of our research, which focuses on enhancing the fire retardancy of polyisocyanurate foam (PIR foam) using an innovative, sustainable fire retardant: basic magnesium sulfate (BMS).

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The Insulation Material: Polyisocyanurate Foam (PIR Foam)

PIR foam, a specialised type of polyurethane (PU) foam, is widely used for insulation in buildings. It stands out for its superior fire resistance thanks to its ring-like structure, which provides both thermal and structural stability.

A Greener Solution: Basic Magnesium Sulfate (BMS)

Our research focuses on replacing the harmful halogenated fire retardants with basic magnesium sulfate (BMS), a mineral fire retardant. Unlike halogenated additives that emit toxic substances during combustion, mineral fire retardants form a protective barrier that slows down fire spread and release only water vapour or inert gases when decomposed at high temperature, offering a safer and more environmentally friendly flame retardant solution.

How It Works: The Fire Retardant Mechanism

Mineral fire retardants operate through three key mechanisms:

• Heat Absorption: During endothermic decomposition, the mineral fire retardants absorb heat, therefore cooling the surrounding polymer.
• Production of inert gases: The release of inert gases, such as water, lowers the concentration of free radicals that help sustain the flame.
• Protective Barrier Formation: The inorganic residue integrates with the char to form a inert barrier. This layer prevents oxygen from reaching the flammable polymer and also prevents fuel from escaping.

These fire retardant action gives people more time to evacuate a burning building, potentially saving lives.

Testing and Results: Balancing Safety and Insulation

In our experiments, basic magnesium sulfate (BMS) was synthesised and added to PIR foam. The goals were to:

• Improve Thermal Conductivity: Enhance the thermal insulation properties.
• Improve Compression Strength: Enhance structural resilience.

Since BMS has not yet been studied in PU or PIR foams, we first reviewed existing literature on magnesium hydroxide (Mg(OH)₂) as a representative mineral fire retardant. Studies show that increasing Mg(OH)₂ content reduces cell size, enhancing structural integrity without compromising thermal insulation. These findings suggest mineral fire retardants can improve fire safety while preserving foam performance, supporting future exploration of BMS.

Real-World Application: Building Safer Homes

Our material is intended for use in steel lintels with an integrated thermal break, designed for cavity wall construction. It supports typical masonry, timber floor, and roof loads, and is suitable for fair-faced inner leaf masonry applications.

Picture this: a fire breaks out in your home, but instead of spreading rapidly, the insulation releases water vapour and forms a protective barrier, slowing the fire's progress. This delay gives you precious extra minutes to evacuate safely.

Beyond fire safety, using mineral fire retardant in PIR foam also promotes energy efficiency. Better insulation means buildings retain heat in winter and stay cool in summer, reducing energy consumption and lowering utility bills.

Why This Research Matters

Our work bridges the gap between sustainability and safety. By replacing toxic fire retardants with basic magnesium sulfate (BMS), we are contributing to a greener future without compromising on the essential need for fire protection. This innovative approach not only benefits individual households but also supports global efforts to create more sustainable cities.

References

• Xu, Q.; Hong, T.; Zhou, Z.; Gao, J.; Xue, L. The effect of the trimerization catalyst on the thermal stability and the fire performance of the polyisocyanurate‐polyurethane foam. Fire and Materials 2018, 42 (1), 119-127. DOI: 10.1002/fam.2463.
• Reignier, J.; Méchin, F.; Sarbu, A. Chemical gradients in PIR foams as probed by ATR-FTIR analysis and consequences on fire resistance. Polymer Testing 2021, 93, 106972. DOI: https://doi.org/10.1016/j.polymertesting.2020.106972.
• Liu, X.; Hao, J.; Gaan, S. Recent studies on the decomposition and strategies of smoke and toxicity suppression for polyurethane based materials. RSC Advances 2016, 6 (78), 74742-74756. DOI: 10.1039/c6ra14345h.
• Hewitt, F.; Hull, T. R. Mineral Filler Fire Retardants. Springer International Publishing, 2017; pp 329-354.
• Hejna, A. Clays as Inhibitors of Polyurethane Foams’ Flammability. Materials 2021, 14 (17), 4826. DOI: 10.3390/ma14174826.
• Hull, T. R.; Witkowski, A.; Hollingbery, L. Fire retardant action of mineral fillers. Polymer Degradation and Stability 2011, 96 (8), 1462-1469.
• Peng, H. K.; Wang, X.; Li, T. T.; Lou, C. W.; Wang, Y.; Lin, J. H. Mechanical properties, thermal stability, sound absorption, and flame retardancy of rigid PU foam composites containing a fire‐retarding agent: Effect of magnesium hydroxide and aluminum hydroxide. Polymers for Advanced Technologies 2019, 30 (8), 2045-2055.
• Yuvaraj, L.; Jeyanthi, S.; Kadam, D. D.; Ajai, R. G. Influence of Magnesium Hydroxide Fillers on Acoustic, Thermal, and Flame Retardant Properties of Pu Foam. Springer Singapore, 2021; pp 393-408.