Phosphate intercalated Mg/Al layered double hydroxide nanosheets as a novel flame retardant for leather: Synthesis, characterization, and application studies

Abstract

Ammonium polyphosphate (APP) modified Mg/Al layered double hydroxide (LDH) flame retardants (FR) were synthesized by varying the APP concentration between 5 and 15% (PLDH-5, PLDH-10, PLDH-15). Synthesized PLDH (APP modified LDH) were characterized for their microstructural, physicochemical, and thermal properties. FE-SEM images of the PLDH showed agglomerated nanosheets indicating the interaction of APP with the LDH. XRD studies of the PLDH confirmed the intercalation of phosphate ions into the interlayer gallery, leading to an increase in the interlayer distance from 0.76 to 1.07 nm. Emphasis was given to the thermogravimetric (TGA/DTG) and differential scanning calorimetric (DSC) examination of the PLDH, and PLDH treated leathers to understand their thermal insight. The PLDH-treated leathers showed an increase in the thermal stability of the collagen. The endothermic dehydroxylation and decomposition observed in the DSC studies indicated the suitability of the PLDH as flame-retardant material. Application of 3% PLDH during leather making improved the flammability degree of leather by 18.2%. The synthesized PLDH exhibited equivalent or better flame retardant performance as compared to the other flame retardant chemicals reported in the literature for leather applications. The flame retardant mechanism of PLDH was also discussed.