Cellulose Nanomaterial-based Films for Grease-resistance Food Packaging Application

Abstract

The common uses of plastic for food packaging are advantageous in many cases because of its easy processability, low cost, and excellent resistance to water, oil, and grease penetration. The per- and poly-fluoroalkyl substances (PFASs) treated paper using the conventional paper manufacturing process has also achieved similar functionalities to prevent oil, water, and grease passages. However, due to the health and environmental concerns of the two packaging systems mentioned above, food packaging industries are now open to more options. A sustainable and health-promoting paper-based food packaging system that can restrict oil, water, and grease from passing through is highly desirable to fulfill the increasing demand for convenience food products. Cellulose nanomaterials (CNs), such as cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs), are ideal alternatives. CNFs have excellent mechanical strength and gas barrier properties, but they have high hydrophilicity because of their amorphous structure and surface hydroxyl groups which decrease their properties whenever in contact with moisture or high humidity. On the other hand, CNCs are less chemically reactive to water due to their crystalline structure, but films prepared with only CNCs are very brittle. To overcome the limitations of each of these two CNs, this research studied films prepared by blending CNF and CNC suspensions at various ratios. Water-soluble polymer polyethylene oxide (PEO), widely known for coating applications, was added to the film formulation development process to optimize the film performance. This research aims to prepare standalone grease resistance films and/or coating materials for food packaging applications. The properties of the films were characterized by mechanical property tests, contact angle analysis, atomic force microscopy analysis, grease resistance test, pore size distribution iii measurement, and Fourier-transform infrared spectroscopy (FTIR) analysis. Films prepared with 100% CNF showed better tensile strength (103 ± 11 MPa), strain at break (13% ± 0.02), and tensile energy absorption (9059.8 ± 2076.8 J/m3) than all the other CNF/CNC composite films as well as commercially available parchment paper, butcher paper, pan liner, and copy paper. FTIR analysis reported that intermolecular hydrogen bonds of cellulose molecules were replaced by the hydrogen bonds between PEO and CNF in the films prepared with CNF/PEO. In addition, pore size distribution results reported that PEO helped reduce the overall pore size distribution of CNF film, which can be advantageous in grease resistance.