Grafting polycaprolactone onto alkaline lignin for improved compatibility and processability

Area of Science:

• Polymer Chemistry
• Materials Science
• Biomaterials Engineering

Background:

• Industrial lignin, a byproduct of pulping, exhibits poor compatibility and processability in composite materials.
• Valorization of industrial lignin is crucial for sustainable material development and waste reduction.

Purpose of the Study:

• To enhance the compatibility and processability of industrial lignin by grafting polycaprolactone (PCL).
• To investigate the effect of grafted PCL chain length on the properties of lignin-PCL composites.

Main Methods:

• Ring-opening polymerization of ε-caprolactone onto alkaline lignin using n-butyl titanate catalyst.
• Characterization of the lignin-g-polycaprolactone copolymer using FTIR, 31P NMR, and 1H NMR.
• Preparation and mechanical property evaluation of lignin-g-PCL/PCL composites via melt blending.

Main Results:

• Successful synthesis of lignin-g-polycaprolactone copolymer, confirming grafting and reaction mechanisms.
• Significant improvement in lignin compatibility and processability within PCL matrices.
• Mechanical properties, including tensile and bending strength, were optimized with an average PCL arm length of approximately 19 units.

Conclusions:

• Grafting modification effectively enhances lignin's suitability for composite applications.
• The length of grafted polycaprolactone arms critically influences the mechanical performance of the resulting composites.
• This approach offers a viable pathway for the broader application of lignin in advanced composites and biomaterials.