Abstract: In this paper， a bio-based flame-retardant coating with different chitosan-sulfonated graphene layers was constructed on the surface of a RPUF by using a water-based layer-by-layer self-assembly method （LBL）. The influence of different layers on the flame retardancy and smoke suppression of the RPUF was intensively investigated. The results indicated that the RPUF coated with the flame-retardant coating exhibited excellent flame-retardant performance， high thermal stability， and good smoke suppression， which were also affecting by the numbers of coating layers. The 5-layer-self-assembly coated RPUF （RPU-5BL） reached a UL 94 V-0 rating in the vertical burning test along with a limiting oxygen index of 35.1 vol% and a char yield of 34.9 wt% at 800 ℃， which were increased by 78.2 % and 85.6 %， respectively， compared to the untreated RPUF. Moreover， the RPU-5BL exhibited a peak heat release rate of 163.9 kW/m2， a total smoke production of 9.1 m2， a maximum smoke density of 22.9 %， and a smoke density grade of 14.9， which decreased by 30.6%， 14.2%， 61.9%， and 120.1%， respectively， compared to the controlled sample.

Key words: polyurethane, foam, flame retardant, smoke suppression, sulfonated graphene, layer-by-layer self-assembly