Morphology, rheological and crystallization behavior in thermoplastic polyurethane toughed poly(l-lactide) with stereocomplex crystallites

Melt-blending poly( l -lactide) (PLLA) with elastomers has been well demonstrated to improve toughness of PLLA. Here, we show a poly( d -lactide) (PDLA) grafted thermoplastic polyurethane (TPU) (TPU-g-PDLA) toughed PLLA with simultaneous formation of few amount stereocomplex crystallites (SCs) which exhibited higher efficient toughening than that of PLLA with TPU. The TPU-g-PDLA was prepared by the in-situ melt-reaction of TPU and PDLA with 4, 4’-diphenylmethane diisocyanate (MDI). A comparative study on morphology, rheological and crystallization behavior was also carried in PLLA/TPU, PLLA/TPU-g-PDLA and PLLA/TPU/PDLA samples. The PLLA/TPU-g-PDLA samples show the highest crystallization rate, complex viscosity, impact strength and tensile strength among PLLA/TPU, PLLA/TPU-g-PDLA and PLLA/TPU/PDLA samples, indicating that the higher interfacial interaction between TPU-g-PDLA and PLLA. Furthermore, TPU chains in TPU-g-PDLA were thought to break the intermolecular interaction of PLLA and rapid its crystallization and increase crystallinity .