Transparent Stretchable Film Through Physicochemical Interaction Between Hydroxypropylmethyl Cellulose and TEMPO‐Oxidized Nanocellulose

Bio‐based materials with high elongation are essential for applications requiring flexibility and durability, such as packaging, wearable sensors, or conformable biomedical films. Biobased films were produced by solvent casting from suspensions of Hydroxypropyl methylcellulose (HPMC) and TEMPO‐oxidized cellulose nanofibrils (CNFt). The rheological properties were investigated through flow curves and strain sweep measurements. Even with a small addition of nanocellulose, 6 wt%, the resulting blend exhibited strong shear‐thinning behavior characteristics of CNFt. CNFt contributes to structuring the suspension, even if the percolation threshold is not reached, proving reinforcing interactions between HPMC and CNFt. The films ensued from these suspensions were characterized by tensile testing. Increasing the nanocellulose content in the deformable HPMC films enhanced mechanical strength. However, further increasing the CNFt content resulted in very brittle films. A screening of potential plasticizers to enhance elongation property was then made. Incorporating 20 wt% of polyurethane diol increases strain at break by 58%, while 20 wt% of glycerol led to a 107% increase in comparison with the pristine HPMC/CNFt films. By adjusting the HPMC/CNFt ratio and adding an appropriate plasticizer, the mechanical properties of the films can be tailored to specific needs, leading to the production of transparent, homogeneous self‐standing films with improved mechanical deformation.