Toughening Modification of Polylactic Acid by Long-Chain Hyperbranched Polymers Containing Polycaprolactone end Groups

The hyperbranched polyester (HBPEs) were synthesized by the "one-step method" and grafted with caprolactone (ε-Cl) to obtain long-chain hyperbranched polymers (LCHBPs-Cl). In this study, LCHBPs-Cl with Cl long chain end groups were used for the first time to toughen and strengthen polylactic acid (PLA) by melt blending. Compared with pure PLA, the most significant toughening effect was obviously when the addition amount of LCHBPs-Cl was 2.0 phr. The tensile strength increased from 37.00 to 62.61 MPa. The impact strength was increased from 14.88 to 18.50 kJ. The elongation at break increased from 1.80% to 2.50%. The scanning electron microscope (SEM) images showed the impact section of the blends became rough, the brittle-ductile fracture transition occurred, and a large number of white wire drawing phenomena were produced. Due to the formation of topological entanglement and cohesive entanglement between the long-chain substituents of LCHBPs-Cl and PLA molecular chains, the plastic deformation of PLA was successfully improved, and the toughness of polylactic acid was highly improved.