Influence of cellulose nanocrystal aspect ratio on shear force aligned films: Physical and mechanical properties

The present study investigates the effect of cellulose nanocrystals (CNCs) aspect ratio on the shear force alignment. A molecular CNC exhibits anisotropic behavior because of its different chemical bonds in different directions, especially its different mechanical properties parallel and perpendicular to its axial direction. We used these shear-force aligned films to develop biodegradable and sustainable films in a sandwiched starch/chitosan system. According to the results from 2D-XRD on the CNC films, at lower initial CNC suspension (approximate to 1%), the calculated Hermans order parameters was much higher for the high AR (approximate to 63) tunicate CNC (TCNC) as compared to the low AR (approximate to 12) wood CNC (WCNC). Compared to the TCNC's Hermans order parameter, the hybrid CNC films (HCNC) (1:1 ratio of WCNC:TCNC) showed approximately similar order parameters. WCNC shear force aligned films were chiral nematically organized and did not show any alignment. Accordingly, alignment significantly affected the TCNC and HCNC's physical and mechanical properties, such as water vapor permeability, elastic modulus, and tensile strength. This paper reports the study results on the alignment of CNCs with different ARs and the hybrid configuration under shear force and its effect on the physical and mechanical properties of the polymeric nanocomposites.