Eliminating the thermal degradation of polylactic acid by the modification of a macromolecular epoxy‐type chain extender

Abstract A novel macromolecular epoxy chain extender was synthesized and used to modify the PLA resin for developing conventional melt extrusion technology. Fourier‐transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and 1 H nuclear magnetic resonance ( 1 H NMR) characterized the successful synthesis. For the first time, the molecular weight plays a key role in preventing thermal degradation and chain extension were discussed experimentally. Macromolecular chain extender showed superior advantages in that the chain extender with higher molecular weight was easier to get the long chain branched (LCB) structure in the modification of PLA. The characterization by rotational rheometer, GPC, melt index, chemical titration, and differential scanning calorimeter (DSC), results demonstrate that the macromolecular epoxy chain extender could decrease the concentration of terminal carboxyl groups and increase with only 0.5% dosage. At a concentration ≥2%, there were a large number of long chain branched structures in the chain extension system for modified PLA. It showed better melt strength and would influence the crystallinity of PLA which would significantly improve the processability of PLA, especially in high‐temperature extrusion, blow molding, spinning, and other processing technologies and applications.