Mechanical and barrier properties of nanocrystalline cellulose reinforced chitosan based nanocomposite films
Highlights
► NCC reinforced chitosan-based films were prepared by casting. ► Incorporation of only 5% (w/w) NCC improved the TS of the chitosan films by 24%. ► Favorable NCC–chitosan interaction and effective stress transfer. ► NCC incorporation enhanced the barrier properties of the films. ► SEM images revealed proper dispersion of NCC into chitosan matrix.
Introduction
Global environmental concern, regarding the use of non-biodegradable petroleum-based packaging materials, has been encouraging researchers, industries and governments in the quest for alternative materials made from natural biopolymers. Bio-based packaging is made from raw materials originating from natural sources, such as starch, cellulose, chitin or biodegradable synthetic polymers such as, polycaprolactone and polylactic acid (Arumugam et al., 1989, Chandra and Rustgi, 1998, Ciesla et al., 2006, Le Tien et al., 2000). Despite great improvements, the use of natural polymers for food packaging has been limited because of the poor barrier properties and weak mechanical properties of the film (Rhim & Perry, 2007). For these reasons natural polymers were either blended with other synthetic polymers or chemically modified to enhance these features (Giannelis, 1996, Khan et al., 2010a, Weber et al., 2002). Some of the limited mechanical and barrier properties (water vapor, oxygen permeability, etc.) of biopolymers can be significantly enhanced by the use of reinforcing fillers to create nanocomposite films. Nanocomposite films extend the food shelf-life, and also improve food quality as they can serve as carriers of some active substances, such as antioxidants and antimicrobials (Sorrentino & Gorrasi, 2007).
Chitosan, a natural linear polysaccharide consisting of 1,4-linked 2-amino-deoxy-β-d-glucan, is a partially deacetylated derivative of chitin, the second most abundant natural polysaccharide after cellulose. Chitosan is non-toxic, biodegradable, biofunctional, biocompatible and was reported by several researchers to have strong antimicrobial and antifungal activities (Darmadji and Izumimoto, 1994, Kim et al., 2011, No et al., 2007, Rabea et al., 2003). Chitosan films have been successfully used as a packaging material for the quality of preservation of foods (Jo, Lee, Lee, & Byun, 2001).
Cellulose, another natural linear carbohydrate polymer chain consisting of d-glucopyranose units joined together by β-1,4-glycosidic linkages, is the most abundant biopolymer and can be found in wood, cotton, hemp among other sources. Cellulose nanocrystals, also called nanocrystalline cellulose (NCC) can be extracted from cellulose sources after the cellulose fibers are digested by a controlled acid hydrolysis process. NCC is a highly crystalline nanometer sized rod-like particle that is obtained as a stable aqueous colloidal suspension. This NCC was extracted from softwood bleached kraft pulp with an acid hydrolysis process inspired from the literature (Beck-Candanedo, Roman, & Gray, 2005). This type of NCC was found to exhibit an average length of 110 nm long for a 5–10 nm width (Revol, Bradford, Giasson, Marchessault, & Gray, 1992). The use of sulfuric acid in the hydrolysis process, leads to a more stable dispersion than the one using hydrochloric acid due to the grafting of sulfate groups on the surface of the NCC that stabilizes the NCC suspensions by electrostatic repulsion (Beck-Candanedo et al., 2005). NCC was shown to reinforce polymers due to the formation of a percolation network that connects the well dispersed NCC by hydrogen bonds (Favier, Chanzy, & Cavaille, 1996). It was shown that the presence of NCC reinforcing fillers in the polymer matrix provides superior performances such as mechanical properties, barrier properties leading to the next generation of biodegradable materials (Azeredo et al., 2010, Cao et al., 2008, Dieter-Klemm et al., 2009).
The objective of the present research was to evaluate the effect of NCC incorporation on the mechanical, barrier, thermal and structural properties of chitosan-based biodegradable films. The mechanical properties of the films were measured to evaluate the films tensile strength (TS), tensile modulus (TM), and elongation at break (Eb). The barrier properties of the films were investigated by carrying out water vapor permeability tests and swelling properties were monitored by the water uptake of the nanocomposite films. Fourier Transform Infrared Spectroscopy (FTIR) was used analyze the interaction between chitosan and NCC. Surface morphology of the NCC reinforced chitosan films was investigated by scanning electron microscopy (SEM).
Section snippets
Materials
Chitosan (high mol. weight, degree of deacetylation: 88–89%) was purchased from Kitomer Biotech (Rivière-au-Renard, QC, Canada). NCC (prepared as a dry redispersible powder in water) was produced in the FPInnovations pilot plant NCC reactor (Pointe-Claire, QC, Canada) from a commercial bleached softwood kraft pulp according to a procedure modified from the literature (Dong, Revol, & Gray, 1998).
Film preparation
Chitosan (1%, w/v) was dissolved in 2% aqueous acetic acid solution. A dilute aqueous NCC suspension
Mechanical properties of the NCC reinforced chitosan-based films
The effect on the tensile strength of NCC incorporated in chitosan-based films was observed as a function of the NCC loading ranging between 1 and 10% (w/w) of the final dry weight of the film (Fig. 1a). The TS of pure chitosan films was found to be 79 MPa and the reinforced films with addition of 1, 3, 5 and 10% (w/w) NCC increased the TS values up to 86, 92, 99 and 98 MPa respectively (P ≤ 0.05). The increase corresponds to a gain in TS of 8.8, 16.5, 25.3 and 24% compared to the control sample
Conclusions
It was observed that NCC acted as a good reinforcing agent in chitosan and only 3–5% of NCC loading gave the best TS values. Improvement of the mechanical properties was due to the formation of a percolating network and strong filler–matrix interaction. Incorporation of only 5% NCC increased the TM of the chitosan films by 87%. NCC also improved the barrier properties of the chitosan by reducing the WVP and swelling property. A 27% reduction of WVP was obtained due to only 5% NCC incorporation.
Acknowledgements
This research was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) and by FPInnovations (Pointe-Claire, Canada) through the RDC program. The authors highly appreciate SEM support from Mrs. Line Mongeon, Technician of the Biomedical Engineering Department and the Facility Electron Microscopy Research (FEMR) at McGill University.
References (55)
- et al.
Cellulose nanocrystals reinforced poly(oxyethylene)
Polymer
(2004) - et al.
Biodegradable polymers
Progress in Polymer Science
(1998) - et al.
Physical and mechanical properties of thermoplastic starch/montmorillonite nanocomposite films
Carbohydrate Polymers
(2008) - et al.
Effect of chitosan in meat preservation
Meat Science
(1994) - et al.
Oriented growth of V amylase n-butanol crystals on cellulose
Carbohydrate Polymers
(1994) - et al.
Quality properties of pork sausage prepared with water-soluble chitosan oligomer
Meat Science
(2001) - et al.
Mechanical properties of high density polyethylene/carbon nanotube composites
Composites Science and Technology
(2007) - et al.
Antimicrobial activity against foodborne pathogens of chitosan biopolymer films of different molecular weights
LWT – Food Science and Technology
(2011) - et al.
The assignment of IR absorption bands due to free hydroxyl groups in cellulose
Polymer
(1996) - et al.
Creep behavior and manufacturing parameters of wood flour filled polypropylene composites
Composite Structures
(2004)
Spectroscopic manifestation of stretching vibrations of glycosidic linkage in polysaccharides
Journal of Molecular Structure
Poly(vinyl alcohol)/cellulose nanocrystal barrier membranes
Journal of Membrane Science
Helicoidal self-ordering of cellulose microfibrils in aqueous suspension
International Journal of Biological Macromolecules
Effect of clay contents on mechanical and water vapor barrier properties of agar-based nanocomposite films
Carbohydrate Polymers
Template synthesis of porous titania using cellulose nanocrystals
Materials Letters
Molecular interactions in collagen and chitosan blends
Biomaterials
Potential perspectives of bio-nanocomposites for food packaging applications
Trends in Food Science & Technology
Reduced water vapour sorption in cellulose nanocomposites with starch matrix
Composites Science and Technology
Coconut-fiber reinforced rubber composites
Journal of Applied Polymer Science
Standard test method for tensile strength of plastics. Annual book of ASTM standards
Standard test method for water vapor transmission of materials
Nanocellulose reinforced chitosan composite films as affected by nanofiller loading & plasticizer content
Journal of Food Science
Nanocomposite edible films from mango puree reinforced with cellulose nanofibers
Journal of Food Science
Review of recent research into cellulosic whiskers, their properties and their application in nanocomposite field
Biomacromolecules
Effect of reaction conditions on the properties and behavior of wood cellulose nanocrystal suspensions
Biomacromolecules
Modification of nanocellulose with a xyloglucan–RGD conjugate enhances adhesion and proliferation of endothelial cells: Implications for tissue engineering
Biomacromolecules
Starch-based nanocomposites reinforced with flax cellulose nanocrystals
Polymer Letters
Cited by (546)
Valorization of non-edible fruit seeds into valuable products: A sustainable approach towards circular bioeconomy
2024, Science of the Total EnvironmentDevelopment of CO<inf>2</inf>-sensitive antimicrobial bilayer films based on gellan gum and sodium alginate/sodium carboxymethyl cellulose and its application in strawberries
2024, International Journal of Biological MacromoleculesImproving the optical, thermal, mechanical, electrical properties and antibacterial activity of PVA-chitosan by biosynthesized Ag nanoparticles: Eco-friendly nanocomposites for food packaging applications
2024, International Journal of Biological Macromolecules