Modification of brittle polylactide by novel hyperbranched polymer-based nanostructures

Area of Science:

• Polymer Science and Engineering
• Materials Science
• Nanotechnology

Background:

• Polylactide (PLA) is a biodegradable polymer with limited applications due to its inherent brittleness.
• Improving the mechanical properties of PLA, particularly toughness and ductility, is crucial for its broader industrial adoption.

Purpose of the Study:

• To develop an industrially viable method for creating a polylactide (PLA)-based nanoblend with an improved balance of stiffness and toughness.
• To investigate the effect of in-situ cross-linked hyperbranched polymer (HBP) particles within a PLA matrix on mechanical properties.

Main Methods:

• In-situ cross-linking of a hydroxyl-functional hyperbranched polymer (HBP) with a polyanhydride (PA) within a polylactide (PLA) matrix during melt processing.
• Characterization using Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), rheological data, Fourier Transform Infrared Spectroscopy (FTIR), and low-temperature dynamical mechanical thermal analysis (DMTA).

Main Results:

• Formation of a PLA-based nanoblend with a sea-island morphology, featuring cross-linked HBP particles (<100 nm) dispersed in the PLA matrix.
• Significant improvements in toughness (approx. 570%) and elongation at break (approx. 847%) compared to unmodified PLA.
• Enhanced ductility attributed to stress whitening and multiple crazing, with improved compatibility due to a networked interface.

Conclusions:

• The proposed in-situ cross-linking methodology effectively enhances the mechanical properties of polylactide (PLA).
• The developed PLA-based nanoblend offers a promising solution for applications requiring a combination of stiffness and toughness.
• The cross-linked hyperbranched polymer particles act as effective toughening agents, improving PLA's ductility and processability.