Lignin Particle Size Affects the Properties of PLA Composites Prepared by In Situ Ring-Opening Polymerization

Area of Science:

• Materials Science
• Polymer Chemistry
• Biocomposites

Background:

• Poly(lactic) acid (PLA) is a biodegradable polymer with limitations in mechanical strength and thermal stability.
• Biobased fillers like lignin offer a sustainable route to enhance polymer properties.

Purpose of the Study:

• To synthesize and characterize novel biobased lignin-poly(lactic) acid (PLA) composites.
• To investigate the effect of uniform lignin dispersion on composite properties.
• To evaluate the mechanical, thermal, antioxidant, and UV-blocking performance of these composites.

Main Methods:

• Organosolv lignin from beechwood was extracted and ultrasonicated to reduce particle size (~700 nm).
• PLA-lignin composites were prepared via in situ ring-opening polymerization (ROP) of L-lactide with varying lignin loadings (0.5, 1.0, 2.5 wt%).
• Characterization included FTIR, XPS, DSC, and Broadband Dielectric Spectroscopy (BDS).

Main Results:

• Uniform lignin dispersion was achieved through PLA chain grafting onto lignin particles.
• Mechanical properties significantly improved, with a two-fold increase in tensile strength and elongation at 1 wt% lignin.
• Antioxidant activity (DPPH• reduction) and UV-blocking capabilities increased with lignin content.

Conclusions:

• The in situ ROP method effectively creates well-dispersed lignin-PLA composites with enhanced functionalities.
• These biobased composites demonstrate improved mechanical performance, antioxidant properties, and UV protection.
• The study highlights the potential of lignin as a sustainable filler for advanced PLA materials.