The layer-by-layer (LbL) assembly of chitosan (CH) and phosphorylated cellulose nanofibrils (P-CNF) is presented as a novel, sustainable and efficient fire protection system for polyurethane foams. The assembly yields a linearly growing coating where P-CNF is the main component and is embedded in a continuous CH matrix. This CH/P-CNF system homogenously coats the complex 3D structure of the foam producing a nano-exoskeleton that displays excellent mechanical properties increasing the modulus of the foam while maintaining its ability of being cyclically deformed. During combustion the CH/P-CNF exoskeleton efficiently prevents foam collapse and suppresses melt dripping while reducing the heat release rate peak by 31% with only 8% of added weight. The coating behavior during combustion is investigated and correlated to the observed performances. Physical and chemical mechanisms are identified and related to the unique composition and structure of the coating imparted by the LbL assembly.

壳聚糖（CH）和磷酸化纤维素纳米原纤维（P-CNF）的逐层组装（LbL）是一种新颖，可持续，高效的聚氨酯泡沫防火系统。该组件产生线性增长的涂层，其中P-CNF是主要成分，并嵌入连续的CH基体中。这种CH / P-CNF系统均匀地涂覆了泡沫的复杂3D结构，产生了纳米外骨骼，纳米外骨骼显示出出色的机械性能，从而提高了泡沫的模量，同时又保持了其周期性变形的能力。在燃烧过程中，CH / P-CNF外骨骼有效地防止了泡沫破裂并抑制了熔滴，同时仅增加了8％的重量就将放热率峰值降低了31％。研究了燃烧过程中的涂层行为，并将其与观察到的性能相关联。