Effects of ternary potassium containing intumescent flame retardant coating on the combustion and thermal degradation properties of reconstituted tobacco sheet

•RTS was first modified by ternary intumescent coating.•The optimized coating proportion of APP, CS and PC was 1:1:5 (wt %).•PHRR and THR of MCC data decreased by 18.3% and 20.0%, respectively.•The synergism of potassium carbon complex and char produced less carbonyl compounds.•The coating reduced the cigarette burning temperature by 100.1 ℃.