| Version | Summary | Created by | Modification | Content Size | Created at | Operation |
|---|---|---|---|---|---|---|
| 1 | Jack Zhong | -- | 187 | 2026-10-08 10:09:28 | | | |
| 2 | Jack Zhong | -11 word(s) | 176 | 2026-10-08 10:12:24 | | |
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].