Reactable versus soluble DOPO derivatives in poly(lactic acid)/poly(butylene adipate‐co‐terephthalate) composites: Flame retardance, mechanical properties and morphology

Abstract Flame retardant poly(lactic acid)/poly(butylene adipate‐co‐ terephthalate) (PLA/PBAT) composites containing 9,10‐dihydro‐9‐oxa‐10‐ phosphaphenanthrene‐10‐oxide (DOPO) derivatives (phosphorus‐containing diol compound of DOPO‐HQ, and bis DOPO phosphonates of DIDOPO) were systematically and comparatively investigated. Results showed that the different structures of the two derivatives with reactable or soluble characteristics display different effects. DIDOPO endows a higher limiting oxygen index and a better UL‐94 rating for PLA/PBAT composites compared with DOPO‐HQ. Compared with that of PLA/PBAT, the peak heat release rate of PLA/PBAT/DIDOPO‐12.5 is 8.4% lower and that of PLA/PBAT/DOPO‐HQ‐12.5 is 30.6% lower. The flame retardant mechanism of the main gaseous and minor condensed phases is evident for the flame retardant PLA/PBAT composites. In comparison, DIDOPO displays a greater flame inhibition effect, and DOPO‐HQ shows better barrier and protective functions in PLA/PBAT composites. Besides, the elongation at break of the composites with DOPO‐HQ is slightly superior to that of PLA/PBAT/DIDOPO. After the introduction of flame retardant, the blends show dispersed particles with size reduction relative to those of PLA/PBAT. This work provides a guidance to design PLA composites with simultaneously improved flame retardancy and toughness.