Polyurethane foam is a cellular polymer formed by the reaction of a polyol with an isocyanate in which a blowing agent, whether produced by the reaction itself or added separately, expands the reacting mixture into a gas-filled structure. The properties follow from the cell size and from whether the cells are open or closed: closed-cell rigid foam carries load and insulates, while open-cell flexible foam recovers from compression. Both burn readily, and a large part of the literature concerns flame retardancy; a phosphorus-nitrogen intumescent system in rigid foam forms a char that shields the underlying polymer [1], and modifying the intumescent formulation changes how effective that char is [2]. Understanding how the intumescent layer works during a fire is what allows the formulation to be chosen rationally [3]. Building the flame-retardant moiety into the polymer backbone rather than adding it as a filler avoids the loss of mechanical properties that a high filler loading causes [4]. Surface coatings offer a way to keep the bulk formulation unchanged [5].
- rigid foam
- flexible foam
- isocyanate
- blowing agent
- flame retardant
- intumescent char
- closed cell
Polymer Foaming and Composites·Polymers and Plastics·Materials Science·Physical Sciences
References
- Wu, D.; Zhao, P.; Zhang, M.; Liu, Y. Preparation and properties of flame retardant rigid polyurethane foam with phosphorus–nitrogen intumescent flame retardant. High Performance Polymers 2013, 25, 868-875. [CrossRef]
- Dai, P.B.; Yang, L.Y.; Zheng, T.; Qin, C.; Tang, Q.C. Flame Retardant Effect of a Modified Intumescent Flame Retardant on a Rigid Polyurethane Foam. Key Engineering Materials 2017, 748, 51-54. [CrossRef]
- Lee, S.H.; Lee, S.G.; Lee, J.S.; Ma, B.C. Understanding the Flame Retardant Mechanism of Intumescent Flame Retardant on Improving the Fire Safety of Rigid Polyurethane Foam. Polymers 2022, 14, 4904. [CrossRef]
- Li, Y.; Zhang, A.; Wang, Y.; Fan, D.; Lin, Y.; Liu, J.; Tang, T. Intrinsic flame-retardant flexible polyurethane foam based on phosphorus-containing polyol with Si-O-C segment: Simultaneously improving fire safety and mechanical property. Chemical Engineering Journal 2025, 515, 163689. [CrossRef]
- Meng, D.; Liu, X.; Wang, S.; Sun, J.; Li, H.; Wang, Z.; Gu, X.; Zhang, S. Self-healing polyelectrolyte complex coating for flame retardant flexible polyurethane foam with enhanced mechanical property. Composites Part B: Engineering 2021, 219, 108886. [CrossRef]