Synergistic Toughening of Polylactide by Layer Structure and Network Structure

This work demonstrates that environmental-friendly bio-based and biodegradable polylactide (PLA) can be significantly toughened by processing modification alone. The notched Izod impact strength of the prepared PLA increased from 3.4 kJ/m² to 89.9 kJ/m² without other components incorporated. We emphasized the changes in crystalline structure and traced the layer and network structures through etching experiment and dissolution experiment. The results manifested that the synergistic effect of layer structure formed by in-situ oriented crystallites and the network structure generated by stereocomplex crystallites (SCs) with stronger intermolecular force and high density tie chains was the dominant reason for the toughness enhancement. Moreover, the tensile strength and Vicat softening temperature of PLA was improved simultaneously, which reached 92.4 MPa and 167.6 °C, respectively. Notably, by comparing with the petroleum-based engineering plastics, the prepared PLA exhibits excellent comprehensive performance and can be used as a green engineering plastic to expand its potential applications.