The effect of poly(D-lactide) on the properties of poly(butylene adipate-co-terephthalate)/poly(L-lactide) blends with stereocomplex crystallites formed in situ

In order to overcome the drawback of poor mechanical and rheological properties and potentially extend the poly(butylene adipate-co-butylene terephthalate) (PBAT) application market, in this work, we developed PBAT blend with excellent comprehensive performance through blending with biodegradable poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA). Two-step melt blending and constant polylactide (PLA) content were devised to prepared PBAT blend. The effect of PDLA on the crystallization properties, rheological properties, miscibility, morphological structure, and mechanical properties of blend was investigated. According to torque-time curve and DSC results, PLA stereocomplex (SC-PLA) crystallites were formed in blend system. DMA results confirmed that the compatibility between PBAT and PLLA was not changed when PDLA was introduced. SEM results showed that the phase morphology of PBAT/20PLLA/0PDLA blend displayed typical sea-island structure and the particle size of dispersed phase decreased accompanying by agglomeration when PDLA was added. Rheological results showed that percolation SC-PLA network structure had formed and a much denser crystallite network could be formed with high PDLA content, which significantly enhanced rheological properties of blend. The mechanical results demonstrated that the addition of PDLA could significantly enhance mechanical properties. The blend with 6 wt% PDLA presented yield strength, elongation at break, and modulus about 13.3 MPa, 307%, and 221.2 MPa, respectively, the yield strength and modulus increased by 141.7% and 54.7% compared with the pure PBAT.

Graphical abstract