Investigation on molecular sieve 4A as synergist to improve thermal stability and flame retardancy of biodegradable PBS/PAPP composites

Abstract As a promising biodegradable polymer, poly(butylene succinate) (PBS) is limited by its inherent flammable and melt-dripping nature. In this study, the effect of molecular sieve 4A (MS4A) as synergist on thermal stability and flame retardancy of PBS/piperazine pyrophosphate (PAPP) composites was investigated. TGA results showed that the addition of MS4A could effectively improve the thermal stability of PBS/PAPP composites both in nitrogen and air atmospheres. Compared to PBS/20PAPP, PBS/17PAPP-3MS4A exhibited the optimal flame retardancy with limited oxygen index of 29.8%, V0 rating in UL-94 vertical burning test, and 86.6% reduction on the peak of heat release rate in cone calorimeter test. According to the analysis for char morphology and microstructure, the combination of PPAP/MS4A mainly imparted its flame retardancy through condensed phase. The enhancement mechanism was ascribed to their catalytic carbonization effect and the migration of MS4A to construct stronger char layer in out interface during combustion. This work provides a new intumescent flame-retardant system with high efficiency and low toxicity, which will greatly promote the widely applications of PBS composites. Graphical abstract