EFFECT OF PARTICLE ALIGNMENT ON MECHANICAL PROPERTIES OF NEAT CELLULOSE NANOCRYSTAL FILMS

Shear-based film casting methods were used to cast neat films from wood-based cellulose nanocrystal (CNC) suspensions. The degree of CNC alignment in dried films was characterized using the Hermans order parameter (S), and the film elastic modulus (E), ultimate tensile strength (sigma(1)), elongation at failure (epsilon(1)), and work of fracture (WF) were measured with respect to casting direction and CNC alignment. The degree of CNC alignment in dried films was found to increase with higher casting shear rates (0, 10.s(-1), and 100.s(-1)) and at higher suspension pH (similar to 3 versus similar to 7). The maximum orientation (S=0.53) was achieved for CNC suspensions having a neutral pH and sheared at a rate of 100.s(-1). Elastic modulus of CNC films scaled with CNC alignment reached a maximum average of E=30 GPa in the direction of CNC alignment. sigma(1), epsilon(1), and WF did not scale with CNC alignment. Thermal treatments (85 degrees C for 24 h) to CNC films had minimal influence on E, sigma(1), epsilon(1), and WF.