Stretch-induced crystalline structural evolution and cavitation of poly (butylene adipate-ran-butylene terephthalate)/poly(lactic acid) immiscible blends

摘要

Semicrystalline polymer blends show much more complicated structural and morphological evolutions during stretching, due to the interplay between phase separation and polymer crystallization. Understanding the stretch-induced multilevel structural evolutions of semicrystalline polymer blends is of fundamental importance for their practical processing. Herein, we choose the poly(butylene adipate-ran-terephthalate) (PBAT)/poly(lactic acid) (PLA) pair as the immiscible semicrystalline blend and investigate the evolutions of crystal orientation, polymorphic crystalline structure, lamellar morphology, and the cavitation behavior of PBAT-rich PBAT/PLA blends under stretching. We find that the strength and modulus of PBAT are considerably improved after the incorporation of PLA. Crystal orientation of PLA is much slower than that of PBAT crystals in their blends under stretching. PBAT undergoes the a-to-p phase transition and melt recrystallization of lamellae upon stretching, which is seldom affected by the addition of PLA. Stretch-induced cavitation is observed during stretching the PBAT/PLA blends; the cavities are mainly formed around the PBAT/PLA interface due to the interfacial debonding and in the PLA phase by the fragmentation of crystal lamellae. The formation and development of cavities in PBAT/PLA blends are significantly influenced by the blend composition, crystallization and stretching temperatures (T-c, T-d). Cavitation of PBAT/PLA blends is suppressed as T-c is lowered or T-d is enhanced.