A soluble Salen-DOPO flame retardant for efficiently improving PBAT/PLLA film

Organic catalyst ligand Salen exhibits sound catalytic activity in ring-opening polymerization, but few flame retardations involve it. In the work, the Salen was synthesized and coupled with 9, 10-dihydro-9-oxa-10-phosphate-10-oxide (DOPO) to make a SD flame retardant that could dissolve in various organic solvents at room temperature. It was integrated into poly (butylene adipate phthalate)/poly(L-lactic acid) (PBAT/PLLA) film by solution casting. When the mass ratio of SD to polymers was 15 wt%, the composite film showed the ability to form carbon, the limiting oxygen index (LOI) was 27.5 %, and the UL-94 test reached the V-0 rating. The total heat release (THR) and total smoke production (TSP) decreased to 26.58 MJ/m2 and 7.57 m2, respectively. The multidimensional and biphasic action contributed to excellent suppression of flume and flame retardations. The tensile strength and elongation at the break increased to 26.95 MPa and 248.64 %, which were higher than those of PBAT/PLLA. SD also enhanced the hydrophobicity of PBAT/PLLA. The interesting work would open up a new scene for the flame retardation sciences and the development of biodegradable polymers.