High-toughening modification of polylactic acid by long-chain hyperbranched polymers

The hyperbranched polyester synthesized by one-step method was grafted with stearic acid to obtain long-chain hyperbranched polymers (LCHBPs) with a large number of long stearic acid chains at the end. By means of FTIR and C-13-NMR characterization, it was proved that stearic acids were grafted onto hyperbranched polyesters (HBPE) to yield LCHBPs successfully. It was determined by GPC and hydroxyl value titration that the number average molecular weight of HBPE was 4.86 x 10(3) and the grafting rate of stearic acid was 47%. Polylactic acid (PLA)/LCHBPs blends were prepared by melt processing method. The results showed that comparing with neat PLA, the tensile strength of PLA/LCHBPs blends decreased slightly with the increase of LCHBPs, but still maintained a high level, while the elongation at break and the impact strength of the PLA with 3.0 phr LCHBPs were greatly improved by 1360.0% and 119.8%, respectively. In addition, the impacted fracture characteristics of PLA changed significantly from brittle fracture to ductile fracture after LCHBPs incorporation, with the formation of a large number of filamentous structures. Thus, LCHBPs was an excellent toughening modifier for PLA and the resulting blends with improved performance possess wider applications.

Automated summary

Long-chain hyperbranched polymers (LCHBPs) were successfully synthesized by grafting stearic acid onto hyperbranched polyesters (HBPE), leading to improved mechanical properties when blended with polylactic acid (PLA) at a certain ratio.