Poly(ε-caprolactone) blended with thermoplastic waxy starch matrix reinforced with cellulose nanocrystals from Macauba (Acrocomia spp.) Rachis

Aiming at a sustainable bionanocomposites, cellulose nanocrystals (CNCs) were extracted by acid hydrolysis from rachis fibers of macauba (Acrocomia spp.) palm trees natural of the Brazilian Pantanal. In a second step, CNCs were incorporated as reinforcement into thermoplastic waxy starch (TPS) phase blended with poly (epsilon-caprolactone) (PCL), 70/30 (w/w), by higher shear rate co-rotating extrusion. Nanocomposites were formulated with 3.25, 6.5 and 13 wt% CNCs in relation to TPS mass. The nanocomposite containing only 3.25 wt% CNCs improved the mechanical tensile strength by three times and the elastic modulus by more than six times in relation to the TPS/PCL matrix, reaching values close to 12 MPa and 1 GPa, respectively. In addition, the lower amount of CNCs guaranteed the thermal stability of the TPS/PCL nanocomposites (similar to 250 degrees C), showing an increase in T-onset of 20 degrees C in relation to the neat matrix. This effect may be associated with the interactions between TPS molecules and CNCs, as observed in the rheological measurements. Therefore, this study showed the potential of macauba as a renewable source for CNC extraction, bringing higher economic value to this plant and establishing its sustainable productive chain.

Automated summary

In this study, cellulose nanocrystals (CNCs) were extracted from macauba palm fibers and incorporated into a thermoplastic starch matrix. The nanocomposites showed improved mechanical properties and thermal stability, with the nanocomposite containing 3.25% CNCs exhibiting the best performance.