Preparation of multifunctional flame-retardant coating based on lignocellulose and its flame-retardant performance on expandable polystyrene (EPS) foam

Expandable polystyrene (EPS) foam is widely used in external wall insulation, packaging, logistics, and other fields, but it is limited by high fire hazard. To enhance the flame retardancy of EPS foam, this study fabricated a green and efficient biomass-based multifunctional flame-retardant coating (PDA@xLC@yAPP) through dopamine (DA)-mediated combination of lignocellulose (LC) and ammonium polyphosphate (APP). Specifically, LC was functionally modified, and APP was anchored on its surface via DA; the resulting coating was then applied to the surface of EPS foam, successfully constructing an EPS composite material with excellent flame-retardant and smoke-suppressant properties as well as green and environmentally friendly characteristics. The results show that the limiting oxygen index (LOI) of E-PDA@6LC@6APP exceeds 60 vol%, and it achieves V-0 grade in the vertical burning (UL-94) test, effectively inhibiting melt dripping. In the cone calorimeter test, compared with pure EPS, the peak heat release rate (pHRR) is reduced by 50.71%, the peak smoke production rate (pSPR) is decreased by 14.29%, and the smoke release is delayed by approximately 170 s. Additionally, the fire growth index (FGI) is 1.29, and the fire performance index (FPI) is 0.1446. This biomass-based LC flame-retardant coating not only fills the research gap in the field of biomass-based LC for EPS flame retardancy but also exhibits broad application prospects.