Improved mechanical properties of biodegradable polycaprolactone nanocomposites prepared using cellulose nanocrystals

Polycaprolactone (PCL) is a biodegradable polymer showing excellent promise for application to environmentally sustainable materials. Among various biodegradable polymers, PCL comprises semicrystalline low-melting-point (similar to 60 degrees C) aliphatic polyesters, which simplify processing. However, disadvantageous mechanical properties limit the practical applications of PCL. In this study, cellulose nanocrystals (CNCs) and PCL were subjected to in-situ polymerization to synthesize a CNC-PCL nanocomposite with improved mechanical properties compared to those of PCL. Additionally, solvent exchange was used to optimize the hydrophilic-CNC dispersion in the hydrophobic PCL matrix and epsilon-caprolactone monomer for the ring-opening polymerization. This approach was used to prepare a homogeneously dispersed 0.3 wt% CNC-loaded nanocomposite exhibiting a 1.4-fold-higher ultimate tensile strength of 61 MPa and 1.2-fold-increased elongation at break of 1,340%. Moreover, the PCL/CNC nanocomposite exhibited a tear toughness 1.7-fold higher than that of neat PCL and could broaden the industrial-application range of reinforced bioplastics.