Toughening of Poly(l-Lactide) with Branched Polycaprolactone: Effect of Chain Length

In this work, a series of branched polycaprolactone (BPCL) samples with different ε-caprolactone (CL) chain lengths were synthesized and used to toughen poly (lactic acid) (PLA). The spherical structure increased the free volume, facilitating the free movement of the PLA chain segment and increasing the ductility. In addition, the hydrogen bonds between the multi-terminal hydroxyl group of BPCL x and PLA improved the interaction between them. The glass-transition temperatures ( T g ) and crystallization temperatures ( T c ) of the blends were significantly lower than those of PLA, and these temperatures increased with the chain length of polycaprolactone. BPCL x increased the crystallization rate of PLA through heterogeneous nucleation. A longer chain length of CL increased the mutual entanglement in the blends, reduced the hydrogen bonding between BPCL x and PLA, and increased the entanglement of BPCL x chains. When the chain length of CL was 6, the impact strength and elongation at break of the PLA/BPCL blends exhibited an increase of 151.72 and 465.8%, respectively, as compared with PLA.