Cellulose I and II nanocrystals produced by sulfuric acid hydrolysis of Tetra pak cellulose I.

Polymorphism is an important factor associated with the cellulose nanomaterial properties. In this study, cellulose fibers (CFs) were efficiently isolated from waste Tetra pak packages, and cellulose I and II nanocrystals were produced by treatment of CFs with 64% sulfuric acid and controlling the reaction time from 15 to 30 min. Cellulose I (CI) was partially converted to cellulose II (CII) within 15 min and the resulting cellulose nanocrystal product (i.e. CNC15) contained 93.2% CII. Further extending the hydrolysis time decreased the CII content of CNC20 to 25.5% and CNC30 was completely CI without CII. CNC15 (285.1 ± 120.7 nm long, 50.6 ± 16.5 nm wide, 0.64 at% sulfur) was much thicker, slightly longer, less thermal stable and contained more sulfate groups than CNC30 (207.2 ± 77.8 nm long, 23.2 ± 7.8 nm wide, 0.34 at% sulfur). CNCs with controllable allomorph may have potentially diverse applications.