(124c) The Effects of Additives 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 containing polymer additives. Cellulose nanocrystals are being increasingly recognized for their potential in advanced materials applications due to their high strength, low density, and natural abundance. For this work, sulfuric acid hydrolyzed CNC (CNC-SA) from wood pulp were obtained from the US Forest Service’s Cellulose Nano-Materials Pilot Plant. Pure CNC-SA films with thicknesses on the order of 0.1 mm were produced by doctor blade coating of aqueous dispersions on a substrate that allows for easy removal after drying. However, these films tend to be very brittle and form cracks during drying. We show that the addition of polymers such as hydroxypropyl cellulose, and polyethylene oxide results in more ductile films with less tendency towards cracking. The effect of adding of hydrochloric acid (HCl) to the aqueous dispersion is also examined based on the flocculation  and film cracking  theories outlined in Sing et al. (Langmuir, 1999). Film properties were characterized by tensile testing, nanoindentation, and cross polarized microscopy.