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 H-1 NMR, C-13 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 mu m to 0.5 mu m 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.