The flame retardancy and mechanical properties of waste polyester fabric/hemp stalk composites modified with piperazine pyrophosphate and ammonium polyphosphate

Abstract

Abstract The piperazine pyrophosphate (PAPP) and ammonium polyphosphate (APP) were employed to enhance the flame retardancy of waste polyester/hemp stalk composites. And the impact of PAPP/APP flame retardants on the flame retardancy and mechanical properties of waste polyester/hemp stalk was investigated. The results indicated that the PAPP/APP combination offered superior flame retardancy, with minimal impact on the composites’ bending property. Notably, when the total addition of PAPP/APP was 25%, with a mass ratio of 1 to 1, the limiting oxygen index (LOI) value of the PAPP/APP/waste polyester/hemp stalk composite material increased significantly from 18.8% to 27.1%, achieving the flame retardant level. Correspondingly, the vertical combustion level attained V-0 level, and the charring rate at 600°C escalated from the initial 25.8% to 32.5%. Remarkably, both the bending strength and modulus of PAPP/APP/waste polyester/hemp stalk composites remained stable.