Halogen-Free Flame Retarded Poly(Lactic Acid) with an Isosorbide-Derived Polyphosphonate

Fabrication of flame retardants from renewable biomass has aroused extensive interest over the past decade. This work reported a synthesis of isosorbide-derived polyphosphonate (PICPP) as an anti-flammable agent for poly (lactic acid) (PLA). The presence of PICPP notably declined the storage modulus of PLA/PICPP owing to the declined molecular weight of PLA catalyzed by the presence of PICPP. PLA and PLA/PICPP thermally degraded in one stage under either air or nitrogen atmosphere. With increasing the amount of PICPP, the onset thermal decomposition temperature of PLA/PICPP was decreased gradually, owing to the earlier decomposition of PICPP. With only 10 wt% of PICPP, PLA/PICPP-10 achieved a high limiting oxygen index of 30.0% and UL-94 V-0 clas-sification, manifesting that PICPP was an efficient anti-flammable agent for PLA. The inclusion of 15 wt% PICPP also caused 33% and 16% decline in PHRR and THR of PLA, respectively. TG-IR results clarified that PLA/PICPP produced the less typical pyrolysis products especially flammable carbonyls than PLA, which may account for the suppressed PHRR and THR values of PLA/PICPP.