PLA-PBAT-PLA tri-block copolymers: Effective compatibilizers for promotion of the mechanical and rheological properties of PLA/PBAT blends

Polylactide-poly(butylene adipate-co-terephthalate)-polylactide tri-block copolymers incorporating PLA blocks (LPB and HPB) with different chain lengths were synthesized as compatibilizers for PLA/PBAT blends. The structure of the tri-block copolymers could be adjusted by varying the feeding ratios of the monomer and macro-initiator, and the polymers were characterized by 1H NMR, 13C NMR, GPC, and DSC measurements. Compared to the short chains of the PLA blocks (LPB) in the copolymers, HPB was a more effective compatibilizer for two immiscible blends because the long chains achieve enhanced interpenetration of the relevant homopolymers. The elongation between the blocks of the PLA/PBAT blends with 5% HPB compatibilizer was seven times more than that of the pristine blends. The addition of compatibilizer reduced the particle size of the dispersed phase from 1.5 μm to 0.5 μm and improved the miscibility of PLA and PBAT, as confirmed by the thermal, morphological, and rheological properties. The experimental results established that tri-block copolymers improved the interfacial interaction and the miscibility between PLA and PBAT.