Composition Effects on the Optical and Mechanical Properties of Cellulose Nanocrystal Films

The objective of this research is to compare the optical and mechanical properties of cellulose nanocrystal (CNC) films with various compositions. CNC produced by the acid hydrolysis of natural cellulosic materials are increasingly being recognized for their potential in advanced materials applications. Sulfuric acid hydrolyzed CNC (CNC-SA) from wood pulp and acetic acid hydrolyzed CNC (CNC-AA) from cotton are the two types of CNC being used in this work. Aqueous dispersions of CNC can be sheared and dried to produce a solid film. However, CNC-SA films tend to be brittle. It was hypothesized that the addition of hydroxypropyl cellulose (HPC) or CNC-AA to CNC-SA dispersions could enable films with a broader range of mechanical properties. Aqueous dispersions containing a total of 12-13 wt% cellulosic material were prepared with ratios of 8:1, 9:1, and 10:1 CNC-SA to CNC-AA or HPC. Films were produced by doctor blade coating and characterized using cross-polarized optical microscopy and nanoindentation.