Document Type : Research Paper
Authors
1 Cellulosic Industry, Department of Wood and Cellulosic Products Engineering, Sari Agricultural Sciences and Natural Resources University, Mazandaran, Iran
2 Department of Wood and Cellulosic Products Engineering, Sari Agricultural Sciences and Natural Resources University, Mazandaran, Iran
Abstract
Abstract
Background and Objective: The extensive use of petroleum-based polymers in the packaging industry, due to their non-biodegradable nature, has led to the accumulation of persistent waste, contamination of soil and surface waters, and ultimately the degradation of ecosystems. In this context, biopolymers - particularly pectin extracted from citrus peels as an agricultural by-product - have emerged as suitable alternatives to conventional synthetic polymers. The extraction of pectin using organic acids such as citric acid represents a green and sustainable approach, owing to its safety, environmental compatibility, and ability to produce materials of appropriate quality. However, films made from neat pectin generally exhibit limitations in mechanical strength and barrier performance. Cellulose nanofibrils, due to their high elastic modulus, favorable tensile strength, and biodegradability, can be effectively employed as reinforcing agents within pectin matrices. The aim of this study was to fabricate and characterize pectin/CNF bionanocomposite films with enhanced properties for biodegradable packaging applications.
Methodology: Pectin with a degree of esterification of 61.63% was extracted from lemon peel using citric acid, and cellulose nanofibrils (CNF) were supplied by NanoNovin Polymer Co. Films were prepared using the solution casting method. Briefly, pectin was dissolved in distilled water at 70 °C, glycerol was then added as a plasticizer, and the pH of the solution was adjusted to 4. Simultaneously, CNF was dispersed in distilled water at concentrations of 1, 3, and 5% (w/w) and subjected to ultrasonication for 30 min to ensure uniform dispersion. The CNF suspension was subsequently added to the pectin solution, and the mixture was homogenized for 25 min. After degassing in a vacuum oven, the film-forming solutions were cast into Petri dishes and dried for 48 h in a desiccator containing a saturated magnesium nitrate solution (52.8% relative humidity at 25 °C). The tensile properties, optical properties, thickness, water vapor permeability, and moisture absorption of the films were evaluated. Neat pectin films and films containing 5% CNF were selected for Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses. Statistical analysis of the data was performed using SPSS software.
Results: The results demonstrated that the incorporation of cellulose nanofibrils (CNF) had a significant effect on the properties of pectin-based films. The Young’s modulus increased from 3.12 MPa for the neat pectin film to 8.08 MPa for the film containing 5% CNF. Likewise, the tensile strength increased from 1.42 to 2.60 MPa, and the tensile energy absorption increased from 12.94 to 22.43 J, indicating a simultaneous improvement in stiffness, strength, and toughness of the system. The water vapor permeability decreased by approximately 51% upon the addition of 5% CNF, from 4.54 × 10⁻¹¹ to 2.22 × 10⁻¹¹ g/m·s·Pa, demonstrating a substantial enhancement in barrier performance comparable to that of cellophane. In addition, the moisture absorption of the films decreased to 25.35% at a CNF content of 5%. In contrast, increasing the CNF content resulted in a reduction in film transparency from 98.26% to 80.09%. FTIR analysis confirmed the formation of strong hydrogen bonds between CNF and the pectin matrix. XRD patterns revealed an approximately 73% increase in diffraction intensity, indicating an improvement in the degree of crystallinity. Furthermore, SEM micrographs confirmed the relatively uniform dispersion of cellulose nanofibrils and good interfacial compatibility between CNF and the pectin matrix.
Conclusion: The findings of this study demonstrated that pectin/cellulose nanofibril bionanocomposite films provide a favorable combination of mechanical and barrier properties. The enhanced performance of this system can be attributed to the formation of strong hydrogen bonds between the pectin matrix and CNF, an increased degree of crystallinity, and the development of a three-dimensional reinforcing network. Accordingly, pectin/cellulose nanofibril films represent a promising biodegradable alternative to conventional plastic packaging materials and can contribute effectively to reducing the environmental impacts of packaging waste within the framework of the circular economy and sustainable development.
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