Eucalyptus spp. cellulose nanocrystals obtained by acid hydrolysis and ultrasound processing for structural strengthening in paper packaging

The objective of the present study was to obtain and evaluate the conditions of acid hydrolysis for cellulose nanocrystals (CNC) production, as well as to characterize its chemical and morphological structure and finally to realize and evaluate its application potential on paper as a structural reinforcing agent. From bleached cellulose, CNC is obtained by the acid hydrolysis process at 35, 40 or 45 °C for 25, 30 and 35 min. Then, an ultrasonic disruptor was used to reduce the particle size of the samples. The average particle diameters ranged from 203.4 to 66.4 nm, with yields from 57.57% to 30.14%. To obtain the paper, the cellulose is homogenized by mechanical stirring and is incorporated with starch (5%) and CNC (6, 12 and 18%). This suspension was vacuum filtered and the papers formed are pressed in a hydraulic press (Carver®) for five minutes under 5000kgf. The addition of CNC showed to be a good option for increasing physical and mechanical properties as they improved the paper quality. Papers produced and incorporated with 12% and 18% CNC have superior characteristics in mechanical tensile testing (8.1 MPa) compared to paper without CNC added. Optical properties were not influenced after the incorporation of CNC .