Parichat Thipchai, Winita Punyodom, Kittisak Jantanasakulwong, Thomas Karbowiak, Jonghwan Suhr, Pornchai Rachtanapun
Converting agricultural waste into cellulose nanocrystals provides a sustainable route for producing biodegradable packaging materials. This study investigated how the crystalline polymorphism of CNCs from different agricultural residues influences the structure-property relationships of hydroxypropyl methylcellulose (HPMC) nanocomposite films. Cellulose I-rich CNCs from durian rind (CNC I) and cellulose II-rich CNCs from sugarcane bagasse (CNC II) were directly compared under identical HPMC film-forming conditions at a fixed CNC loading to clarify their effects on film structure and performance. CNC I and CNC II were characterized by extraction yields of 41.8% and 32.7%, crystallinity indices of 37.4% and 53.1%, and aspect ratios of 18.3 and 10.5, respectively. Dynamic light scattering revealed bimodal apparent hydrodynamic diameters for CNC I (30.8 and 139.8 nm), whereas CNC II showed a single apparent diameter of 102.4 nm. These differences in crystalline structure, morphology, size distribution, aspect ratio, crystallinity, and aggregation behavior contributed to distinct mechanical, barrier, and water-stability properties of the resulting HPMC-CNC films. Compared with neat HPMC, HPMC-CNC I exhibited improved mechanical properties, with tensile strength and Young's modulus increasing from 34.6 to 53.2 MPa and from 1097.9 to 3302.5 MPa, respectively. In contrast, HPMC-CNC II showed lower oxygen transmission rates of 76.0 and 142.4 cm3·m-2·day-1·bar-1 at 50% and 80% RH, respectively, together with reduced water solubility to 10.8-30.4%. These findings demonstrate that CNCs from agricultural residues can be strategically selected based on their source-dependent structural characteristics to tailor the mechanical, barrier, and water-stability properties of biodegradable HPMC films while supporting the value-added utilization of agricultural residues.