Document Type : Research Paper
Authors
Wood and Paper Science Department, Faculty of Natural Resources, Sari Agricultural Sciences and Natural Resource University Sari, Iran
Abstract
Background and objectives: The use of polymers with petroleum derivatives in the packaging industry has caused environmental problems due to their non-biodegradability. Development of active and biodegradable packaging is possible by coating biopolymers on packaging materials. In this research, we tried to use biodegradable materials that are easily decomposed after use in the environment. In this regard, the effect of different treatments with Carboxymethyl chitosan (CMCh), purified Guar gum (PGG) and Nanocrystalline cellulose (NCC) on resistance and barrier properties.
Methodology: Carboxymethyl chitosan powder and purified Guar gum were dissolved separately in distilled water along with glycerol (40% by weight of biopolymers) as softener. Then the bio composite solutions were heated on a magnetic stirrer for 120 and 90 minutes until the biopolymers were completely dissolved. At the end, they were kept in a static state for 30 minutes to cool down and remove the air bubbles completely. Also, Nanocrystal cellulose suspension (3, 6 and 9% compared to biopolymers) prepared by dissolving in distilled water by ultrasonic device for 3 minutes was added to bio composite solution with mixed ratios (30:70, 50:50 and 70:30) was added and the final suspension was heated on a magnetic stirrer for 120 minutes and it was completely dissolved. Then, in order to cool down and remove the air bubbles completely, it was put in a static state for 30 minutes. At the end, we centrifuged it and let it stand still for 2 minutes to completely remove the air bubbles. Finally, 25 grams of gel was poured into a polystyrene petri dish with a diameter of 10 cm and the petri dishes were placed in an oven at 50 °C for 24 hours. Also, the morphological tests of Carboxymethyl chitosan and bio Nano composite films and the resistance and barrier characteristics of the treatments were studied.
Results: The results of measuring the resistance characteristics of biopolymer films showed that with the increase of Nanocrystal cellulose up to the level of 6%, the tensile strength of the treatments increased significantly, and the highest amount was related to the films CMCh/PGG/NCC (50/50/6%). is Also, with the increase of cellulose Nanocrystals up to the level of 9% due to the accumulation of Nanocrystal particles in one area, the tensile strength of bio nano composites decreased. Also, due to the origin of its crystallinity, cellulose Nanocrystals led to the brittleness and reduced flexibility of the treatments to reduce the Elongation at break of bio nano composite films. The solubility of bio composite films has decreased by adding NCC to the biopolymer matrix due to the establishment of hydrogen interactions between the components of this matrix with nanoparticles at different levels, and the lowest water Solubility is related to the films CMCh/PGG/NCC (50/50/6%). The water vapor permeability of the treatments decreased by adding NCC to the CMCh/PGG matrix due to reasons such as the crystalline structure and the hydrophobic nature of cellulose fibers, the reduction of pores and the reduction of the diffusion coefficient of vapor molecules, and the best impermeability was obtained by films CMCh/PGG/NCC (50/50/6%) because of uniform dispersion of nanoparticles.
Conclusion: According to the results, by adding cellulose Nanocrystals to the composite suspension; Tensile strength, resistance to water solubility and impermeability to water vapor of the films increased and only their Elongation at break decreased and the best resistance and barrier properties of bio nano composites produced in the presence of 6% Nanocrystalline cellulose were obtained.
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