Nanocellulose in Bioplastics for Sustainable Packaging

Packaging has become a critical concern due to the prevalence of single-use plastics from petrochemicals, leading to environmental issues. To address this, interest in bio-based materials for packaging has grown, offering biodegradability and a lower carbon footprint. However, bioplastics have limitations like weak mechanical properties and high permeability. To overcome these issues, there is a need for chemical compositions and processing methods that improve the barrier properties. One effective approach is incorporating nanomaterials, such as cellulose nanofibers, to enhance bioplastics' properties and contribute to sustainable development.
\nOne prominent bioplastic that has garnered significant attention is thermoplastic starch (TPS). Furthermore, the preparation of blends comprising polybutylene succinate (PBS) and TPS (at a ratio of 30%) has been explored as a means of producing cost-effective composite materials with desirable performance characteristics. The TPS and PBS blends were prepared through extrusion and hot pressing, and their morphological, mechanical, and barrier properties were assessed. The findings revealed that the presence of fibers in the composite acted as reinforcement within the matrix, thereby improving the mechanical properties and, to some extent, the barrier properties. Notably, the incorporation of citric acid as a compatibilizer further enhanced the composite's performance.
\nThe primary objective of this project is producing cellulose nanofibers (CNF) from industrial hemp and develop biodegradable nanocomposite films with excellent barrier properties for packaging applications. PBS is known for its favorable transparency, mechanical properties, and water resistance, but it is expensive and lacks adequate oxygen resistance. Hence, in this study, PBS was blended with CNF to increase the biobased content and reduce costs. The nanocomposites, comprising CNF and PBS, were prepared using an extruder and hot press. The microstructure, barrier properties, and mechanical properties of the nanocomposites were investigated.
\nScanning electron microscopy (SEM) analysis revealed that lower CNF contents (less than 15%) exhibited better dispersion of nanoparticles within the polymer matrix, while higher contents (30 and 50% wt) resulted in agglomeration of CNF, making the nanocomposites more brittle. The water vapor permeability (WVP) tests showed that the incorporation of nanofibers had no significant impact on film permeability. However, there was a notable improvement in oxygen permeability. The transparency of all the films was found to be satisfactory, particularly when the CNF content was below 15%. 
\nOther aspects of the research involved comparing CNF with and without bleaching processes, as well as utilizing different chemicals to enhance CNF dispersion in PBS and improve the properties. The effect of these chemicals on atomized droplet size and hydrogen bond retardation between CNFs was examined by analyzing product morphology, particle size distribution, and dispersion stability in aqueous systems. The results indicated that CNF suspensions treated with Sodium chloride (NaCl) could be atomized into smaller droplets during spray drying, leading to the production of CNF powder with reduced particle sizes. Therefore, drying with NaCl was considered a cost-effective and environmentally friendly method for obtaining highly dispersible dried CNFs suitable for large-scale industrial applications in composite industries. Additionally, NaCl salts are relatively inexpensive, and the process does not involve the use of organic solvents or hazardous chemicals. The intriguing aspect of this section pertained to the varying coloration observed between the CNF and the final film. The films incorporating bleached CNF exhibited a transparent and white appearance, while those created solely through mechanical means exhibited a slight yellowish hue while maintaining good transparency. Furthermore, all films demonstrated a consistent and homogeneous appearance without any surface particles.
\nOverall, the PBS/CNF nanocomposites demonstrated favorable properties for sustainable packaging, depending on the specific application requirements. However, further research and development are necessary to enhance and optimize the final properties of these materials.

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