Reinforced PHA/CNC Biocomposites in Extrusion-Based Additive Manufacturing.

Polyhydroxyalkanoate (PHA) is a biopolymer that can be 3D printed using the material extrusion method. Nevertheless, their mechanical properties are inferior to those of petroleum-derived polymers, which restricts their broader application. Herein, nanobiocomposites comprising naturally sourced PHA and cellulose nanocrystals (CNC) as fillers were successfully synthesized. These nanobiocomposites were prepared with filler concentrations ranging from 0.5 to 2.5% by weight, in increments of 0.5 wt %. Filaments were produced from binary PHA/CNC mixtures and subsequently employed for 3D printing of the respective nanobiocomposite samples. They were subjected to mechanical, rheological, thermal, and structural analyses using analytical techniques and the respective standards. The integration of CNC into the pure PHA polymer matrix has been reported to enhance PHA's mechanical properties of PHA, with an increase in flexural strength by 23.3%, flexural modulus by 20.8%, and Young's modulus by 47.3%, although there was a reduction in impact strength and microhardness. Morphological characterization confirmed the homogeneous dispersion of CNC, whereas the thermal and rheological properties remained almost unchanged. The porosity and geometric accuracy of the 3D-printed samples, evaluated using micro-CT, were improved by incorporating CNC into the PHA matrix. The 0.5 wt % CNC concentration was the optimum one, improving mechanical and quality metrics. These findings highlight the potential of PHA/CNC nanocomposites as innovative high-performance biodegradable materials for 3D printing for biomedical, packaging, and structural engineering applications. Such nanobiocomposites can contribute to reducing the environmental impact of petroleum polymers through a cost-effective additive manufacturing method.