Development of CNC-reinforced PBAT nanocomposites with reduced percolation threshold: a comparative study on the preparation method

Cellulose nanocrystal (CNC)-reinforced poly(butylene adipate-co-terephthalate) (PBAT) nanocomposites with CNC contents of 1, 3, and 5 wt% were prepared through either solution casting or dilution of a PBAT/CNC masterbatch through melt mixing. The efficiency of these preparation approaches on CNC dispersion quality was examined using transmission electron microscopy and rheological analysis. It was found that solution-casted nanocomposites possessed a much finer CNC dispersion, while melt mixing could cause the formation of CNC agglomerates. In the nanocomposites, the rheological percolation threshold through small-amplitude oscillatory shear experiments was determined to be around 2.18 and 3.15 wt% CNC, respectively. The PBAT melt crystallization was also promoted with CNC regardless of the preparation method. The oxygen permeability of PBAT remarkably reduced with the CNC incorporation, specifically in the solution-casted nanocomposites with finer CNC dispersion. The thermal degradation, thermomechanical, and mechanical properties of the nanocomposites were also compared although no significant differences were observed.