Optimization of cellulose nanocrystal (CNC) concentration in polycaprolactone bio-composites for bio-plotting: a robust interpretation of the reinforcement mechanisms

Bioabsorbable and biodegradable composites have experienced rapid growth, owing to their high demand in the biomedical sector. Polymer-cellulose nanocrystal (CNC) compounds were developed using a medical-grade poly (ε-caprolactone) (PCL) matrix to improve the stiffness and load-bearing capacity of pure PCL. Five PCL/CNCs filament grades were melt-extruded, pelletized, and fed into an industrial bioplotter to fabricate specimens. To assess the effects of CNCs on pure PCL, 14 tests were conducted, including rheological, thermomechanical, and in situ micro-mechanical testing, among others. The porosity and dimensional accuracy of the samples were also documented using micro-computed tomography while scanning electron microscopy was employed for morphological characterization. Overall, the 4.0 wt % CNCs loading accomplished the optimum mechanical response, with an increase in its tensile (19.1%) and flexural strength (12.6%) compared to pure PCL. Concurrently, this grade exhibited the highest MFR, minimum porosity, and highest nominal-to-actual geometric accuracy, thereby convincingly interpreting the reinforcement mechanisms.