Objective Nanocellulose are renewable, green alternatives to petroleum-based food packaging materials. However, their single-component films often lack sufficient mechanical strength and gas barrier properties for commercial applications. Moreover, most existing studies rely on high aspect ratio cellulose, which involves complex preparation processes, high costs, and challenges in scaling up from laboratory to industrial production. This study starts with commercially available low aspect ratio nanocellulose and aims to enhance their mechanical and barrier properties through incorporation of layered double hydroxides (LDHs). Glycerol is introduced to improve LDHs dispersion, enabling the construction of high-strength, high-barrier composite films from low aspect ratio nanocellulose. This work seeks to provide a novel strategy for the scalable production of low-cost, biodegradable food packaging materials.
Methods Cellulose nanocrystals (CNCs) were selected as the research object in this study. CNCs were prepared via sulfuric acid hydrolysis, and Mg-Al-LDHs nanosheets were synthesized hydrothermally. LDHs content was systematically varied from 0% to 50%, and glycerol content from 0% to 10%, using a single-variable approach. Composite films were fabricated through simple solution blending followed by ambient drying. The resulting LDHs/CNCs films were characterized using UV-visible spectroscopy, tensile testing, oxygen transmission measurements, scanning electron microscopy (SEM), and X-ray diffraction (XRD) to evaluate optical transparency, mechanical performance, and oxygen barrier properties, thereby elucidating the intrinsic relationships among composition, structure, and performance.
Results The LDHs nanosheets were uniformly embedded within the 3D CNCs network, forming dense, defect-free composite structures. With increasing LDHs content, film transparency gradually decreased, while tensile strength initially increased and then declined. The elongation at break remained below 2.5% in all cases. A maximum tensile strength of 29.6 MPa was achieved at 1% LDHs loading; further increases led to nanoplatelet aggregation, creating stress concentration points and reducing strength. Upon addition of 5% glycerol, LDHs dispersion was significantly improved. The composite films maintained high tensile strength while achieving an elongation at break of up to 8%, and the oxygen transmission was reduced to a minimum of 0.03 cm3/(m2·d·0.1MPa) (at 25% LDHs and 5% glycerol), demonstrating effective balance between strength and toughness, along with dramatically enhanced barrier performance.
Conclusion Low aspect ratio nanocellulose can achieve high mechanical strength and excellent oxygen barrier properties with only a small amount of LDHs (1%). Glycerol plays a dual role in plasticization and dispersion, further optimizing the strength−toughness balance and significantly suppressing oxygen transmission. The proposed fabrication process operates under mild, aqueous conditions without organic solvents, making it compatible with existing papermaking and coating equipment. This approach offers a feasible pathway for the large-scale production of low-cost, high-performance, biodegradable food packaging films and provides general guidance for performance design in other nanocellulose-based systems.
DownLoad: