Toughening and thermal characteristics of plasticized polylactide and poly(butylene adipate-co-terephthalate) blend films: Influence of compatibilization

Bio-based polylactide (PLA) derived from fermented corn starch was blended with poly(butylene adipate-co-terephthalate) (PBAT) and triethyl citrate (TEC) plasticizer using a twin screw extruder. PLA-grafted-maleic anhydride (PLA-g-MA) synthesized via reactive maleation and toluene diisocyanate (TDI) were used as compatibilizers for these blends. Improvements in the toughness, phase morphology and thermal behavior of the PLA/PBAT/TEC (PBT) blend films were evaluated in terms of compatibilization effect. The compatibilized PBT blends showed noticeably superior tensile strength, elongation, and tensile-impact toughness compared with uncompatibilized ones due to the greater compatibility of PLA and PBAT phases. Well dispersed PBAT particles and many elongated fibrils were observed on the fracture surface of the film after compatibilization. Both TDI and PLA-g-MA were effective compatibilizers for the blend at an appropriate level. The addition of PLA-g-MA to the plasticized blends not only significantly enhanced mechanical properties and phase adhesion, but also accelerated cold crystallization and formed crystal perfection, a result of improvements in chain mobility and packing efficiency. Differential scanning calorimetry (DSC) results revealed changes in T_g and melting behavior of the blends from influences of compatibilization. The different types and levels of compatibilizer affected the thermal stability of the PLA phase but did not affect char remaining.